COMMITTEE DRAFT ISO/IEC 1539-1 September 23, 2002 13:08 This draft has line numbers to facilitate comments; they are not intended to be part of the published standard. SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 Contents 1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Processor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.3 Inclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.4 Exclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.5 Conformance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.6 Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.6.1 Fortran 95 compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.6.2 Fortran 90 compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.6.3 FORTRAN 77 compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.7 Notation used in this standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.7.1 Informative notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.7.2 Syntax rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.7.3 Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.7.4 Assumed syntax rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.7.5 Syntax conventions and characteristics . . . . . . . . . . . . . . . . . . . . . . . 6 1.7.6 Text conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.8 Deleted and obsolescent features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.8.1 Nature of deleted features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.8.2 Nature of obsolescent features . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.9 Normative references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2 Fortran terms and concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.1 High level syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.2 Program unit concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.2.1 Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.2.2 Main program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.2.3 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.2.4 Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.3 Execution concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.3.1 Executable/nonexecutable statements . . . . . . . . . . . . . . . . . . . . . . . . 13 2.3.2 Statement order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.3.3 The END statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.3.4 Execution sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.4 Data concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.4.1 Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.4.2 Data value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.4.3 Data entity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.4.4 Scalar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.4.5 Array . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2.4.6 Pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2.4.7 Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2.5 Fundamental terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2.5.1 Name and designator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.5.2 Keyword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.5.3 Association . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.5.4 Declaration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 SEP 2002 COMMITTEE DRAFT i ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 2.5.5 Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.5.6 Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.5.7 Intrinsic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.5.8 Operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.5.9 Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.5.10 Companion processors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3 Characters, lexical tokens, and source form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3.1 Processor character set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3.1.1 Letters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3.1.2 Digits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3.1.3 Underscore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3.1.4 Special characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3.1.5 Other characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3.2 Low-level syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3.2.1 Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.2.2 Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.2.3 Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.2.4 Statement labels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.2.5 Delimiters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.3 Source form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.3.1 Free source form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.3.2 Fixed source form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.4 Including source text . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 4 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 4.1 The concept of type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 4.1.1 Set of values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 4.1.2 Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 4.1.3 Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 4.2 Type parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 4.3 Relationship of types and values to objects . . . . . . . . . . . . . . . . . . . . . . . . . . 33 4.4 Intrinsic types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 4.4.1 Integer type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 4.4.2 Real type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 4.4.3 Complex type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 4.4.4 Character type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 4.4.5 Logical type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 4.5 Derived types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 4.5.1 Derived-type definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 4.5.2 Determination of derived types . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 4.5.3 Extensible types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 4.5.4 Component order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 4.5.5 Type parameter order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 4.5.6 Derived-type values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 4.5.7 Derived-type specifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 4.5.8 Construction of derived-type values . . . . . . . . . . . . . . . . . . . . . . . . . 57 4.5.9 Derived-type operations and assignment . . . . . . . . . . . . . . . . . . . . . . 59 4.5.10 The finalization process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4.6 Type aliases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 4.7 Enumerations and enumerators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 4.8 Construction of array values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 5 Data object declarations and specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 ii COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 5.1 Type declaration statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 5.1.1 Type specifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 5.1.2 Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 5.2 Attribute specification statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 5.2.1 Accessibility statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 5.2.2 ALLOCATABLE statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 5.2.3 ASYNCHRONOUS statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 5.2.4 BIND statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 5.2.5 DATA statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 5.2.6 DIMENSION statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 5.2.7 INTENT statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 5.2.8 OPTIONAL statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 5.2.9 PARAMETER statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 5.2.10 POINTER statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 5.2.11 PROTECTED statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 5.2.12 SAVE statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 5.2.13 TARGET statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 5.2.14 VALUE statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 5.2.15 VOLATILE statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 5.3 IMPLICIT statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 5.4 NAMELIST statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 5.5 Storage association of data objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 5.5.1 EQUIVALENCE statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 5.5.2 COMMON statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 6 Use of data objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 6.1 Scalars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 6.1.1 Substrings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 6.1.2 Structure components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 6.1.3 Type parameter inquiry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 6.2 Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 6.2.1 Whole arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 6.2.2 Array elements and array sections . . . . . . . . . . . . . . . . . . . . . . . . . . 105 6.3 Dynamic association . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 6.3.1 ALLOCATE statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 6.3.2 NULLIFY statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 6.3.3 DEALLOCATE statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 7 Expressions and assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 7.1 Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 7.1.1 Form of an expression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 7.1.2 Intrinsic operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 7.1.3 Defined operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 7.1.4 Type, type parameters, and shape of an expression . . . . . . . . . . . . . . . . 123 7.1.5 Conformability rules for elemental operations . . . . . . . . . . . . . . . . . . . 125 7.1.6 Specification expression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 7.1.7 Initialization expression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 7.1.8 Evaluation of operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 7.2 Interpretation of operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 7.2.1 Numeric intrinsic operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 7.2.2 Character intrinsic operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 7.2.3 Relational intrinsic operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 7.2.4 Logical intrinsic operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 7.3 Precedence of operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 SEP 2002 COMMITTEE DRAFT iii ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 7.4 Assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 7.4.1 Assignment statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 7.4.2 Pointer assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 7.4.3 Masked array assignment ­ WHERE . . . . . . . . . . . . . . . . . . . . . . . . 145 7.4.4 FORALL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 8 Execution control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 8.1 Executable constructs containing blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 8.1.1 Rules governing blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 8.1.2 IF construct . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 8.1.3 CASE construct . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 8.1.4 ASSOCIATE construct . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 8.1.5 SELECT TYPE construct . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 8.1.6 DO construct . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 8.2 Branching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 8.2.1 GO TO statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 8.2.2 Computed GO TO statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 8.2.3 Arithmetic IF statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 8.3 CONTINUE statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 8.4 STOP statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 9 Input/output statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 9.1 Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 9.1.1 Formatted record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 9.1.2 Unformatted record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 9.1.3 Endfile record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 9.2 External files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 9.2.1 File existence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 9.2.2 File access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 9.2.3 File position . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 9.2.4 File storage units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 9.3 Internal files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 9.4 File connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 9.4.1 Connection modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 9.4.2 Unit existence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 9.4.3 Connection of a file to a unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 9.4.4 Preconnection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 9.4.5 The OPEN statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 9.4.6 The CLOSE statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 9.5 Data transfer statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 9.5.1 Control information list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 9.5.2 Data transfer input/output list . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 9.5.3 Execution of a data transfer input/output statement . . . . . . . . . . . . . . . 193 9.5.4 Termination of data transfer statements . . . . . . . . . . . . . . . . . . . . . . 203 9.6 Waiting on pending data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 9.6.1 WAIT statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 9.6.2 Wait operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 9.7 File positioning statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 9.7.1 BACKSPACE statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 9.7.2 ENDFILE statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206 9.7.3 REWIND statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206 9.8 FLUSH statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206 9.9 File inquiry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207 9.9.1 Inquiry specifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 iv COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 9.9.2 Restrictions on inquiry specifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . 214 9.9.3 Inquire by output list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214 9.10 Error, end-of-record, and end-of-file conditions . . . . . . . . . . . . . . . . . . . . . . . . 214 9.10.1 Error conditions and the ERR= specifier . . . . . . . . . . . . . . . . . . . . . . 214 9.10.2 End-of-file conditions and the END= specifier . . . . . . . . . . . . . . . . . . . 215 9.10.3 End-of-record conditions and the EOR= specifier . . . . . . . . . . . . . . . . . 215 9.10.4 IOSTAT= specifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 9.10.5 IOMSG= specifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 9.11 Restrictions on input/output statements . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 10 Input/output editing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 10.1 Explicit format specification methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 10.1.1 FORMAT statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 10.1.2 Character format specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 10.2 Form of a format item list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 10.2.1 Edit descriptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 10.2.2 Fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 10.3 Interaction between input/output list and format . . . . . . . . . . . . . . . . . . . . . . 222 10.4 Positioning by format control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223 10.5 Decimal symbol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 10.6 Data edit descriptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 10.6.1 Numeric editing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 10.6.2 Logical editing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 10.6.3 Character editing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 10.6.4 Generalized editing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230 10.6.5 User-defined derived-type editing . . . . . . . . . . . . . . . . . . . . . . . . . . 231 10.7 Control edit descriptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232 10.7.1 Position editing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232 10.7.2 Slash editing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233 10.7.3 Colon editing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233 10.7.4 SS, SP, and S editing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233 10.7.5 P editing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234 10.7.6 BN and BZ editing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234 10.7.7 RU, RD, RZ, RN, RC, and RP editing . . . . . . . . . . . . . . . . . . . . . . . 234 10.7.8 DC and DP editing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234 10.8 Character string edit descriptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235 10.9 List-directed formatting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235 10.9.1 List-directed input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 10.9.2 List-directed output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238 10.10 Namelist formatting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 10.10.1 Namelist input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 10.10.2 Namelist output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 11 Program units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 11.1 Main program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 11.2 Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 11.2.1 Module reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 11.2.2 The USE statement and use association . . . . . . . . . . . . . . . . . . . . . . . 247 11.3 Block data program units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 12 Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 12.1 Procedure classifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 12.1.1 Procedure classification by reference . . . . . . . . . . . . . . . . . . . . . . . . . 251 12.1.2 Procedure classification by means of definition . . . . . . . . . . . . . . . . . . . 251 SEP 2002 COMMITTEE DRAFT v ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 12.2 Characteristics of procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252 12.2.1 Characteristics of dummy arguments . . . . . . . . . . . . . . . . . . . . . . . . 252 12.2.2 Characteristics of function results . . . . . . . . . . . . . . . . . . . . . . . . . . 253 12.3 Procedure interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 12.3.1 Implicit and explicit interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 12.3.2 Specification of the procedure interface . . . . . . . . . . . . . . . . . . . . . . . 254 12.4 Procedure reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262 12.4.1 Actual arguments, dummy arguments, and argument association . . . . . . . . . 264 12.4.2 Function reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272 12.4.3 Subroutine reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272 12.4.4 Resolving procedure references . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272 12.5 Procedure definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274 12.5.1 Intrinsic procedure definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274 12.5.2 Procedures defined by subprograms . . . . . . . . . . . . . . . . . . . . . . . . . 275 12.5.3 Definition and invocation of procedures by means other than Fortran . . . . . . 280 12.5.4 Statement function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281 12.6 Pure procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281 12.7 Elemental procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 12.7.1 Elemental procedure declaration and interface . . . . . . . . . . . . . . . . . . . 283 12.7.2 Elemental function actual arguments and results . . . . . . . . . . . . . . . . . . 284 12.7.3 Elemental subroutine actual arguments . . . . . . . . . . . . . . . . . . . . . . . 284 13 Intrinsic procedures and modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 13.1 Classes of intrinsic procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 13.2 Arguments to intrinsic procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 13.2.1 The shape of array arguments . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288 13.2.2 Mask arguments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288 13.3 Bit model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288 13.4 Numeric models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 13.5 Standard generic intrinsic procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290 13.5.1 Numeric functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290 13.5.2 Mathematical functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290 13.5.3 Character functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291 13.5.4 Kind functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291 13.5.5 Miscellaneous type conversion functions . . . . . . . . . . . . . . . . . . . . . . . 291 13.5.6 Numeric inquiry functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291 13.5.7 Array inquiry functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292 13.5.8 Other inquiry functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292 13.5.9 Bit manipulation procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292 13.5.10 Floating-point manipulation functions . . . . . . . . . . . . . . . . . . . . . . . . 292 13.5.11 Vector and matrix multiply functions . . . . . . . . . . . . . . . . . . . . . . . . 293 13.5.12 Array reduction functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 13.5.13 Array construction functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 13.5.14 Array location functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 13.5.15 Null function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 13.5.16 Random number subroutines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 13.5.17 System environment procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . 294 13.6 Specific names for standard intrinsic functions . . . . . . . . . . . . . . . . . . . . . . . . 294 13.7 Specifications of the standard intrinsic procedures . . . . . . . . . . . . . . . . . . . . . . 296 13.8 Standard intrinsic modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353 13.8.1 The ISO C BINDING module . . . . . . . . . . . . . . . . . . . . . . . . . . . 353 13.8.2 The IEEE modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353 13.8.3 The ISO FORTRAN ENV intrinsic module . . . . . . . . . . . . . . . . . . . . 353 vi COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 14 Exceptions and IEEE arithmetic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355 14.1 Derived types and constants defined in the modules . . . . . . . . . . . . . . . . . . . . . 356 14.2 The exceptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357 14.3 The rounding modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359 14.4 Halting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359 14.5 The floating point status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359 14.6 Exceptional values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360 14.7 IEEE arithmetic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360 14.8 Tables of the procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361 14.8.1 Inquiry functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361 14.8.2 Elemental functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362 14.8.3 Kind function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362 14.8.4 Elemental subroutines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362 14.8.5 Nonelemental subroutines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362 14.9 Specifications of the procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363 14.10 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376 15 Interoperability with C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381 15.1 The ISO C BINDING intrinsic module . . . . . . . . . . . . . . . . . . . . . . . . . . . 381 15.1.1 Named constants and derived types in the module . . . . . . . . . . . . . . . . . 381 15.1.2 Procedures in the module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 382 15.2 Interoperability between Fortran and C entities . . . . . . . . . . . . . . . . . . . . . . . 385 15.2.1 Interoperability of intrinsic types . . . . . . . . . . . . . . . . . . . . . . . . . . 385 15.2.2 Interoperability with C pointer types . . . . . . . . . . . . . . . . . . . . . . . . 386 15.2.3 Interoperability of derived types and C struct types . . . . . . . . . . . . . . . . 386 15.2.4 Interoperability of scalar variables . . . . . . . . . . . . . . . . . . . . . . . . . . 388 15.2.5 Interoperability of array variables . . . . . . . . . . . . . . . . . . . . . . . . . . 388 15.2.6 Interoperability of procedures and procedure interfaces . . . . . . . . . . . . . . 389 15.3 Interoperation with C global variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391 15.3.1 Binding labels for common blocks and variables . . . . . . . . . . . . . . . . . . 392 15.4 Interoperation with C functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392 15.4.1 Binding labels for procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392 16 Scope, association, and definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395 16.1 Scope of global entities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395 16.2 Scope of local entities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396 16.2.1 Local entities that have the same names as common blocks . . . . . . . . . . . . 397 16.2.2 Function results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397 16.2.3 Restrictions on generic declarations . . . . . . . . . . . . . . . . . . . . . . . . . 397 16.2.4 Components, type parameters, and bindings . . . . . . . . . . . . . . . . . . . . 398 16.2.5 Argument keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398 16.3 Statement and construct entities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399 16.4 Association . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400 16.4.1 Name association . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400 16.4.2 Pointer association . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403 16.4.3 Storage association . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405 16.4.4 Inheritance association . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408 16.4.5 Establishing associations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408 16.5 Definition and undefinition of variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409 16.5.1 Definition of objects and subobjects . . . . . . . . . . . . . . . . . . . . . . . . . 409 16.5.2 Variables that are always defined . . . . . . . . . . . . . . . . . . . . . . . . . . 409 16.5.3 Variables that are initially defined . . . . . . . . . . . . . . . . . . . . . . . . . . 409 16.5.4 Variables that are initially undefined . . . . . . . . . . . . . . . . . . . . . . . . 409 16.5.5 Events that cause variables to become defined . . . . . . . . . . . . . . . . . . . 410 SEP 2002 COMMITTEE DRAFT vii ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 16.5.6 Events that cause variables to become undefined . . . . . . . . . . . . . . . . . . 411 16.5.7 Variable definition context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413 A Glossary of technical terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415 B Decremental features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427 B.1 Deleted features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427 B.2 Obsolescent features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428 B.2.1 Alternate return . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428 B.2.2 Computed GO TO statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428 B.2.3 Statement functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428 B.2.4 DATA statements among executables . . . . . . . . . . . . . . . . . . . . . . . . 429 B.2.5 Assumed character length functions . . . . . . . . . . . . . . . . . . . . . . . . . 429 B.2.6 Fixed form source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429 B.2.7 CHARACTER* form of CHARACTER declaration . . . . . . . . . . . . . . . . 429 C Extended notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431 C.1 Section 4 notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431 C.1.1 Intrinsic and derived types (4.4, 4.5) . . . . . . . . . . . . . . . . . . . . . . . . 431 C.1.2 Selection of the approximation methods (4.4.2) . . . . . . . . . . . . . . . . . . 432 C.1.3 Extensible types (4.5.3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432 C.1.4 Pointers (4.5.1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433 C.1.5 Structure constructors and generic names . . . . . . . . . . . . . . . . . . . . . . 434 C.1.6 Final subroutines (4.5.1.7, 4.5.10, 4.5.10.1, 4.5.10.2) . . . . . . . . . . . . . . . . 436 C.2 Section 5 notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438 C.2.1 The POINTER attribute (5.1.2.11) . . . . . . . . . . . . . . . . . . . . . . . . . 438 C.2.2 The TARGET attribute (5.1.2.14) . . . . . . . . . . . . . . . . . . . . . . . . . . 439 C.2.3 The VOLATILE attribute (5.1.2.16) . . . . . . . . . . . . . . . . . . . . . . . . . 439 C.3 Section 6 notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 440 C.3.1 Structure components (6.1.2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 440 C.3.2 Allocation with dynamic type (6.3.1) . . . . . . . . . . . . . . . . . . . . . . . . 442 C.3.3 Pointer allocation and association . . . . . . . . . . . . . . . . . . . . . . . . . . 442 C.4 Section 7 notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443 C.4.1 Character assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443 C.4.2 Evaluation of function references . . . . . . . . . . . . . . . . . . . . . . . . . . 443 C.4.3 Pointers in expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444 C.4.4 Pointers on the left side of an assignment . . . . . . . . . . . . . . . . . . . . . . 444 C.4.5 An example of a FORALL construct containing a WHERE construct . . . . . . 445 C.4.6 Examples of FORALL statements . . . . . . . . . . . . . . . . . . . . . . . . . . 446 C.5 Section 8 notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446 C.5.1 Loop control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446 C.5.2 The CASE construct . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446 C.5.3 Examples of DO constructs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446 C.5.4 Examples of invalid DO constructs . . . . . . . . . . . . . . . . . . . . . . . . . 449 C.6 Section 9 notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 450 C.6.1 External files (9.2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 450 C.6.2 Nonadvancing input/output (9.2.3.1) . . . . . . . . . . . . . . . . . . . . . . . . 451 C.6.3 Asynchronous input/output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 452 C.6.4 OPEN statement (9.4.5) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 453 C.6.5 Connection properties (9.4.3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 454 C.6.6 CLOSE statement (9.4.6) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 455 C.7 Section 10 notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 455 C.7.1 Number of records (10.3, 10.4, 10.7.2) . . . . . . . . . . . . . . . . . . . . . . . . 455 C.7.2 List-directed input (10.9.1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 456 viii COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 C.8 Section 11 notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 457 C.8.1 Main program and block data program unit (11.1, 11.3) . . . . . . . . . . . . . 457 C.8.2 Dependent compilation (11.2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 457 C.8.3 Examples of the use of modules . . . . . . . . . . . . . . . . . . . . . . . . . . . 459 C.9 Section 12 notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 465 C.9.1 Portability problems with external procedures (12.3.2.2) . . . . . . . . . . . . . 465 C.9.2 Procedures defined by means other than Fortran (12.5.3) . . . . . . . . . . . . . 466 C.9.3 Procedure interfaces (12.3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 466 C.9.4 Argument association and evaluation (12.4.1.2) . . . . . . . . . . . . . . . . . . 466 C.9.5 Pointers and targets as arguments (12.4.1.2) . . . . . . . . . . . . . . . . . . . . 467 C.9.6 Polymorphic Argument Association (12.4.1.3) . . . . . . . . . . . . . . . . . . . 469 C.9.7 Generic resolution and dynamic dispatch (12.4.4) . . . . . . . . . . . . . . . . . 470 C.10 Section 15 notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 470 C.10.1 Runtime environments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 470 C.10.2 Examples of Interoperation between Fortran and C Functions . . . . . . . . . . 470 C.11 Section 16 notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476 C.11.1 Examples of host association (16.4.1.3) . . . . . . . . . . . . . . . . . . . . . . . 476 C.11.2 Rules ensuring unambiguous generics (16.2.3) . . . . . . . . . . . . . . . . . . . 477 C.12 Array feature notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482 C.12.1 Summary of features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482 C.12.2 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483 C.12.3 FORmula TRANslation and array processing . . . . . . . . . . . . . . . . . . . 488 C.12.4 Sum of squared residuals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489 C.12.5 Vector norms: infinity-norm and one-norm . . . . . . . . . . . . . . . . . . . . . 489 C.12.6 Matrix norms: infinity-norm and one-norm . . . . . . . . . . . . . . . . . . . . . 489 C.12.7 Logical queries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489 C.12.8 Parallel computations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490 C.12.9 Example of element-by-element computation . . . . . . . . . . . . . . . . . . . . 490 C.12.10 Bit manipulation and inquiry procedures . . . . . . . . . . . . . . . . . . . . . . 490 D Index of syntax rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493 E Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 533 SEP 2002 COMMITTEE DRAFT ix ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 x COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 List of Tables 2.1 Requirements on statement ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.2 Statements allowed in scoping units . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.1 Special characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 6.1 Subscript order value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 7.1 Type of operands and results for intrinsic operators . . . . . . . . . . . . . . . . . 121 7.2 Interpretation of the numeric intrinsic operators . . . . . . . . . . . . . . . . . . . 133 7.3 Interpretation of the character intrinsic operator // . . . . . . . . . . . . . . . . . 134 7.4 Interpretation of the relational intrinsic operators . . . . . . . . . . . . . . . . . . 135 7.5 Interpretation of the logical intrinsic operators . . . . . . . . . . . . . . . . . . . . 136 7.6 The values of operations involving logical intrinsic operators . . . . . . . . . . . . 136 7.7 Categories of operations and relative precedence . . . . . . . . . . . . . . . . . . . 136 7.8 Type conformance for the intrinsic assignment statement . . . . . . . . . . . . . . 139 7.9 Numeric conversion and the assignment statement . . . . . . . . . . . . . . . . . . 140 13.1 Characteristics of the result of NULL ( ) . . . . . . . . . . . . . . . . . . . . . . . . 335 15.1 Names of C characters with special semantics . . . . . . . . . . . . . . . . . . . . . 382 15.2 Interoperability between Fortran and C types . . . . . . . . . . . . . . . . . . . . . 385 SEP 2002 COMMITTEE DRAFT xi ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 Foreword ISO (the International Organization for Standardization) and IEC (the International Electrotechni- cal Commission) form the specialized system for worldwide standardization. National bodies that are members of ISO or IEC participate in the development of International Standards through technical committees established by the respective organization to deal with particular fields of technical activ- ity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international organizations, governmental and nongovernmental, in liaison with ISO and IEC, also take part in the work. In the field of information technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical committee are circu- lated to national bodies for voting. Publication of an International Standard requires approval by at least 75% of the national bodies casting a vote. International Standard ISO/IEC 1539-1 was prepared by Joint Technical Committee ISO/IEC/JTC1, Information technology, Subcommittee SC22, Programming languages, their environments and system software interfaces. This fourth edition cancels and replaces the third edition (ISO/IEC 1539-1:1997), which has been tech- nically revised. ISO/IEC 1539 consists of the following parts, under the general title Information technology -- Pro- gramming languages -- Fortran: -- Part 1: Base language -- Part 2: Varying length character strings -- Part 3: Conditional Compilation The annexes of this part of ISO/IEC 1539 are for information only. xii COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 Introduction Standard programming language Fortran This part of the international standard comprises the specification of the base Fortran language, infor- mally known as Fortran 2000. With the limitations noted in 1.6.2, the syntax and semantics of Fortran 95 are contained entirely within Fortran 2000. Therefore, any standard-conforming Fortran 95 program not affected by such limitations is a standard conforming Fortran 2000 program. New features of Fortran 2000 can be compatibly incorporated into such Fortran 95 programs, with any exceptions indicated in the text of this part of the standard. Fortran 2000 contains several extensions to Fortran 95; among them are: (1) Derived-type enhancements: parameterized derived types (allows the kind, length, or shape of a derived type's components to be chosen when the derived type is used), mixed compo- nent accessibility (allows different components to have different accessibility), public entities of private type, improved structure constructors, and finalizers. (2) Object oriented programming support: enhanced data abstraction (allows one type to ex- tend the definition of another type), polymorphism (allows the type of a variable to vary at runtime), dynamic type allocation, SELECT TYPE construct (allows a choice of execu- tion flow depending upon the type a polymorphic object currently has), and type-bound procedures. (3) The ASSOCIATE construct (allows a complex expression or object to be denoted by a simple symbol). (4) Data manipulation enhancements: allocatable components, deferred type parameters, VOL- ATILE attribute, explicit type specification in array constructors, INTENT specification of pointer arguments, specified lower bounds of pointer assignment and pointer rank remap- ping, extended initialization expressions, MAX and MIN intrinsics for character type, and enhanced complex constants. (5) Input/output enhancements: asynchronous transfer operations (allows a program to con- tinue to process data while an input/output transfer occurs), stream access (allows access to a file without reference to any record structure), user specified transfer operations for derived types, user specified control of rounding during format conversions, the FLUSH statement, named constants for preconnected units, regularization of input/output keywords, and ac- cess to input/output error messages. (6) Procedure pointers. (7) Scoping enhancements: the ability to rename defined operators (supports greater data ab- straction) and control of host association into interface bodies. (8) Support for IEC 60559 (IEEE 754) exceptions and arithmetic (to the extent a processor's arithmetic supports the IEC standard). (9) Interoperability with the C programming language (allows portable access to many libraries and the low-level facilities provided by C and allows the portable use of Fortran libraries by programs written in C). (10) Support for international usage: (ISO 10646) and choice of decimal or comma in numeric formatted input/output. (11) Enhanced integration with the host operating system: access to command line arguments and environment variables, and access to the processor's error messages (improves the ability to handle exceptional conditions). SEP 2002 COMMITTEE DRAFT xiii ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 Organization of this part of ISO/IEC 1539 This part of ISO/IEC 1539 is organized in 16 sections, dealing with 8 conceptual areas. These 8 areas, and the sections in which they are treated, are: High/low level concepts Sections 1, 2, 3 Data concepts Sections 4, 5, 6 Computations Sections 7, 13, 14 Execution control Section 8 Input/output Sections 9, 10 Program units Sections 11, 12 Interoperability with C Section 15 Scoping and association rules Section 16 It also contains the following nonnormative material: Glossary Annex A Decremental features Annex B Extended notes Annex C Index of syntax rules Annex D Index Annex E xiv COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 Information technology -- Programming languages -- 2 Fortran -- 3 Part 1: 4 Base Language 5 Section 1: Overview 6 1.1 Scope 7 ISO/IEC 1539 is a multipart International Standard; the parts are published separately. This publi- 8 cation, ISO/IEC 1539-1, which is the first part, specifies the form and establishes the interpretation 9 of programs expressed in the base Fortran language. The purpose of this part of ISO/IEC 1539 is to 10 promote portability, reliability, maintainability, and efficient execution of Fortran programs for use on 11 a variety of computing systems. The second part, ISO/IEC 1539-2, defines additional facilities for the 12 manipulation of character strings of variable length. The third part, ISO/IEC 1539-3, defines a stan- 13 dard conditional compilation facility for Fortran. A processor conforming to part 1 need not conform to 14 ISO/IEC 1539-2 or ISO/IEC 1539-3; however, conformance to either assumes conformance to this part. 15 Throughout this publication, the term "this standard" refers to ISO/IEC 1539-1. 16 1.2 Processor 17 The combination of a computing system and the mechanism by which programs are transformed for use 18 on that computing system is called a processor in this standard. 19 1.3 Inclusions 20 This standard specifies 21 (1) The forms that a program written in the Fortran language may take, 22 (2) The rules for interpreting the meaning of a program and its data, 23 (3) The form of the input data to be processed by such a program, and 24 (4) The form of the output data resulting from the use of such a program. 25 1.4 Exclusions 26 This standard does not specify 27 (1) The mechanism by which programs are transformed for use on computing systems, 28 (2) The operations required for setup and control of the use of programs on computing systems, 29 (3) The method of transcription of programs or their input or output data to or from a storage 30 medium, 31 (4) The program and processor behavior when this standard fails to establish an interpretation 32 except for the processor detection and reporting requirements in items (2) through (8) of SEP 2002 COMMITTEE DRAFT 1 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 1.5, 2 (5) The size or complexity of a program and its data that will exceed the capacity of any 3 particular computing system or the capability of a particular processor, 4 (6) The physical properties of the representation of quantities and the method of rounding, 5 approximating, or computing numeric values on a particular processor, 6 (7) The physical properties of input/output records, files, and units, or 7 (8) The physical properties and implementation of storage. 8 1.5 Conformance 9 A program (2.2.1) is a standard-conforming program if it uses only those forms and relationships 10 described herein and if the program has an interpretation according to this standard. A program unit 11 (2.2) conforms to this standard if it can be included in a program in a manner that allows the program 12 to be standard conforming. 13 A processor conforms to this standard if 14 (1) It executes any standard-conforming program in a manner that fulfills the interpretations 15 herein, subject to any limits that the processor may impose on the size and complexity of 16 the program; 17 (2) It contains the capability to detect and report the use within a submitted program unit of 18 a form designated herein as obsolescent, insofar as such use can be detected by reference to 19 the numbered syntax rules and constraints; 20 (3) It contains the capability to detect and report the use within a submitted program unit of 21 an additional form or relationship that is not permitted by the numbered syntax rules or 22 constraints, including the deleted features described in Annex B; 23 (4) It contains the capability to detect and report the use within a submitted program unit of 24 kind type parameter values (4.4) not supported by the processor; 25 (5) It contains the capability to detect and report the use within a submitted program unit of 26 source form or characters not permitted by Section 3; 27 (6) It contains the capability to detect and report the use within a submitted program of name 28 usage not consistent with the scope rules for names, labels, operators, and assignment 29 symbols in Section 16; 30 (7) It contains the capability to detect and report the use within a submitted program unit of 31 intrinsic procedures whose names are not defined in Section 13; and 32 (8) It contains the capability to detect and report the reason for rejecting a submitted program. 33 However, in a format specification that is not part of a FORMAT statement (10.1.1), a processor need not 34 detect or report the use of deleted or obsolescent features, or the use of additional forms or relationships. 35 A standard-conforming processor may allow additional forms and relationships provided that such ad- 36 ditions do not conflict with the standard forms and relationships. However, a standard-conforming 37 processor may allow additional intrinsic procedures even though this could cause a conflict with the 38 name of a procedure in a standard-conforming program. If such a conflict occurs and involves the name 39 of an external procedure, the processor is permitted to use the intrinsic procedure unless the name is 40 given the EXTERNAL attribute (5.1.2.6) in the scoping unit (16). A standard-conforming program 41 shall not use nonstandard intrinsic procedures or modules that have been added by the processor. 42 Because a standard-conforming program may place demands on a processor that are not within the 43 scope of this standard or may include standard items that are not portable, such as external procedures 44 defined by means other than Fortran, conformance to this standard does not ensure that a program will 45 execute consistently on all or any standard-conforming processors. 2 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 In some cases, this standard allows the provision of facilities that are not completely specified in the 2 standard. These facilities are identified as processor dependent. They shall be provided, with methods 3 or semantics determined by the processor. NOTE 1.1 The processor should be accompanied by documentation that specifies the limits it imposes on the size and complexity of a program and the means of reporting when these limits are exceeded, that defines the additional forms and relationships it allows, and that defines the means of reporting the use of additional forms and relationships and the use of deleted or obsolescent forms. In this context, the use of a deleted form is the use of an additional form. The processor should be accompanied by documentation that specifies the methods or semantics of processor-dependent facilities. 4 1.6 Compatibility 5 Each standard since ISO 1539:1980 (informally referred to as Fortran 77), defines more intrinsic 6 procedures than the previous one. Therefore, a Fortran program conforming to an older standard may 7 have a different interpretation under a newer standard if it invokes an external procedure having the 8 same name as one of the new standard intrinsic procedures, unless that procedure is specified to have 9 the EXTERNAL attribute. 10 1.6.1 Fortran 95 compatibility 11 Except as identified in this section, this standard is an upward compatible extension to the preceding 12 Fortran International Standard, ISO/IEC 1539:1997 (Fortran 95). Any standard-conforming Fortran 95 13 program remains standard-conforming under this standard. The following Fortran 95 features may have 14 different interpretations in this standard: 15 (1) Earlier Fortran standards had the concept of printing, meaning that column one of format- 16 ted output had special meaning for a processor-dependent (possibly empty) set of logical 17 units. This could be neither detected nor specified by a standard-specified means. The 18 interpretation of the first column is not specified by this standard. 19 (2) This standard specifies a different output format for real zero values in list-directed and 20 namelist output. 21 1.6.2 Fortran 90 compatibility 22 Except for the deleted features noted in Annex B.1, and except as identified in this section, this stan- 23 dard is an upward compatible extension to ISO/IEC 1539:1991 (Fortran 90). Any standard-conforming 24 Fortran 90 program that does not use one of the deleted features remains standard-conforming under 25 this standard. 26 The PAD= specifier in the INQUIRE statement in this standard returns the value UNDEFINED if there 27 is no connection or the connection is for unformatted input/output. Fortran 90 specified YES. 28 Fortran 90 specified that if the second argument to MOD or MODULO was zero, the result was processor 29 dependent. This standard specifies that the second argument shall not be zero. 30 1.6.3 FORTRAN 77 compatibility 31 Except for the deleted features noted in Annex B.1, and except as identified in this section, this standard 32 is an upward compatible extension to ISO 1539:1980 (Fortran 77). Any standard-conforming For- 33 tran 77 program that does not use one of the deleted features noted in Annex B.1 and that does not SEP 2002 COMMITTEE DRAFT 3 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 depend on the differences specified here remains standard conforming under this standard. This stan- 2 dard restricts the behavior for some features that were processor dependent in Fortran 77. Therefore, 3 a standard-conforming Fortran 77 program that uses one of these processor-dependent features may 4 have a different interpretation under this standard, yet remain a standard-conforming program. The 5 following Fortran 77 features may have different interpretations in this standard: 6 (1) Fortran 77 permitted a processor to supply more precision derived from a real constant 7 than can be represented in a real datum when the constant is used to initialize a data 8 object of type double precision real in a DATA statement. This standard does not permit 9 a processor this option. 10 (2) If a named variable that was not in a common block was initialized in a DATA statement and 11 did not have the SAVE attribute specified, Fortran 77 left its SAVE attribute processor 12 dependent. This standard specifies (5.2.5) that this named variable has the SAVE attribute. 13 (3) Fortran 77 specified that the number of characters required by the input list was to be 14 less than or equal to the number of characters in the record during formatted input. This 15 standard specifies (9.5.3.4.2) that the input record is logically padded with blanks if there 16 are not enough characters in the record, unless the PAD= specifier with the value 'NO' is 17 specified in an appropriate OPEN or READ statement. 18 (4) A value of 0 for a list item in a formatted output statement will be formatted in a differ- 19 ent form for some G edit descriptors. In addition, this standard specifies how rounding of 20 values will affect the output field form, but Fortran 77 did not address this issue. There- 21 fore, some Fortran 77 processors may produce an output form different from the output 22 form produced by Fortran 2000 processors for certain combinations of values and G edit 23 descriptors. 24 (5) If the processor can distinguish between positive and negative real zero, the behavior of the 25 SIGN intrinsic function when the second argument is negative real zero is changed by this 26 standard. 27 1.7 Notation used in this standard 28 In this standard, "shall" is to be interpreted as a requirement; conversely, "shall not" is to be interpreted 29 as a prohibition. Except where stated otherwise, such requirements and prohibitions apply to programs 30 rather than processors. 31 1.7.1 Informative notes 32 Informative notes of explanation, rationale, examples, and other material are interspersed with the 33 normative body of this publication. The informative material is nonnormative; it is identified by being 34 in shaded, framed boxes that have numbered headings beginning with "NOTE." 35 1.7.2 Syntax rules 36 Syntax rules describe the forms that Fortran lexical tokens, statements, and constructs may take. These 37 syntax rules are expressed in a variation of Backus-Naur form (BNF) in which: 38 (1) Characters from the Fortran character set (3.1) are interpreted literally as shown, except 39 where otherwise noted. 40 (2) Lower-case italicized letters and words (often hyphenated and abbreviated) represent gen- 41 eral syntactic classes for which particular syntactic entities shall be substituted in actual 42 statements. 4 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 Common abbreviations used in syntactic terms are: arg for argument attr for attribute decl for declaration def for definition desc for descriptor expr for expression int for integer op for operator spec for specifier stmt for statement 2 (3) The syntactic metasymbols used are: is introduces a syntactic class definition or introduces a syntactic class alternative [ ] encloses an optional item [ ] ... encloses an optionally repeated item that may occur zero or more times continues a syntax rule 3 (4) Each syntax rule is given a unique identifying number of the form Rsnn, where s is a one- 4 or two-digit section number and nn is a two-digit sequence number within that section. 5 The syntax rules are distributed as appropriate throughout the text, and are referenced by 6 number as needed. Some rules in Sections 2 and 3 are more fully described in later sections; 7 in such cases, the section number s is the number of the later section where the rule is 8 repeated. 9 (5) The syntax rules are not a complete and accurate syntax description of Fortran, and cannot 10 be used to generate a Fortran parser automatically; where a syntax rule is incomplete, it is 11 restricted by corresponding constraints and text. NOTE 1.2 An example of the use of the syntax rules is: digit-string is digit [ digit ] ... The following are examples of forms for a digit string allowed by the above rule: digit digit digit digit digit digit digit digit digit digit digit digit digit digit digit If particular entities are substituted for digit , actual digit strings might be: 4 67 1999 10243852 12 1.7.3 Constraints 13 Each constraint is given a unique identifying number of the form Csnn, where s is a one- or two-digit 14 section number and nn is a two-digit sequence number within that section. 15 Often a constraint is associated with a particular syntax rule. Where that is the case, the constraint is 16 annotated with the syntax rule number in parentheses. A constraint that is associated with a syntax 17 rule constitutes part of the definition of the syntax term defined by the rule. It thus applies in all places SEP 2002 COMMITTEE DRAFT 5 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 where the syntax term appears. 2 Some constraints are not associated with particular syntax rules. The effect of such a constraint is similar 3 to that of a restriction stated in the text, except that a processor is required to have the capability to 4 detect and report violations of constraints (1.5). In some cases, a broad requirement is stated in text 5 and a subset of the same requirement is also stated as a constraint. This indicates that a standard- 6 conforming program is required to adhere to the broad requirement, but that a standard-conforming 7 processor is required only to have the capability of diagnosing violations of the constraint. 8 1.7.4 Assumed syntax rules 9 In order to minimize the number of additional syntax rules and convey appropriate constraint informa- 10 tion, the following rules are assumed; an explicit syntax rule for a term overrides an assumed rule. The 11 letters "xyz " stand for any syntactic class phrase: 12 R101 xyz-list is xyz [ , xyz ] ... 13 R102 xyz-name is name 14 R103 scalar-xyz is xyz 15 C101 (R103) scalar-xyz shall be scalar. 16 1.7.5 Syntax conventions and characteristics 17 (1) Any syntactic class name ending in "-stmt " follows the source form statement rules: it shall 18 be delimited by end-of-line or semicolon, and may be labeled unless it forms part of another 19 statement (such as an IF or WHERE statement). Conversely, everything considered to be 20 a source form statement is given a "-stmt " ending in the syntax rules. 21 (2) The rules on statement ordering are described rigorously in the definition of program-unit 22 (R202). Expression hierarchy is described rigorously in the definition of expr (R722). 23 (3) The suffix "-spec" is used consistently for specifiers, such as input/output statement speci- 24 fiers. It also is used for type declaration attribute specifications (for example, "array-spec" 25 in R515), and in a few other cases. 26 (4) Where reference is made to a type parameter, including the surrounding parentheses, the 27 suffix "-selector " is used. See, for example, "kind-selector " (R507) and "length-selector " 28 (R511). 29 (5) The term "subscript " (for example, R618, R619, and R620) is used consistently in array 30 definitions. 31 1.7.6 Text conventions 32 In the descriptive text, an equivalent English word is frequently used in place of a syntactic term. 33 Particular statements and attributes are identified in the text by an upper-case keyword, e.g., "END 34 statement". Boldface words are used in the text where they are first defined with a specialized meaning. 35 The descriptions of obsolescent features appear in a smaller type size. NOTE 1.3 This sentence is an example of the type size used for obsolescent features. 36 1.8 Deleted and obsolescent features 37 This standard protects the users' investment in existing software by including all but five of the language 38 elements of Fortran 90 that are not processor dependent. This standard identifies two categories of 39 outmoded features. There are five in the first category, deleted features, which consists of features 40 considered to have been redundant in Fortran 77 and largely unused in Fortran 90. Those in the second 6 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 category, obsolescent features, are considered to have been redundant in Fortran 90 and Fortran 95, 2 but are still frequently used. 3 1.8.1 Nature of deleted features 4 (1) Better methods existed in Fortran 77. 5 (2) These features are not included in Fortran 95 or this revision of Fortran. 6 1.8.2 Nature of obsolescent features 7 (1) Better methods existed in Fortran 90 and Fortran 95. 8 (2) It is recommended that programmers use these better methods in new programs and convert 9 existing code to these methods. 10 (3) These features are identified in the text of this document by a distinguishing type font 11 (1.7.6). 12 (4) If the use of these features becomes insignificant, future Fortran standards committees should 13 consider deleting them. 14 (5) The next Fortran standards committee should consider for deletion only those language 15 features that appear in the list of obsolescent features. 16 (6) Processors supporting the Fortran language should support these features as long as they 17 continue to be used widely in Fortran programs. 18 1.9 Normative references 19 The following standards contain provisions which, through reference in this standard, constitute provi- 20 sions of this standard. At the time of publication, the editions indicated were valid. All standards are 21 subject to revision, and parties to agreements based on this standard are encouraged to investigate the 22 possibility of applying the most recent editions of the standards indicated below. Members of IEC and 23 ISO maintain registers of currently valid International Standards. 24 ISO/IEC 646:1991, Information technology--ISO 7-bit coded character set for information interchange. 25 ISO/IEC 646:1991 (International Reference Version) is the international equivalent of ANSI X3.4-1986, 26 commonly known as ASCII. This standard refers to it as the ASCII standard. 27 ISO 8601:1988, Data elements and interchange formats--Information interchange-- 28 Representation of dates and times. 29 ISO/IEC 9989:1999, Information technology--Programming languages--C. 30 This standard refers to ISO/IEC 9899:1999 as the C standard. 31 ISO/IEC 10646-1:2000, Information technology--Universal multiple-octet coded character set (UCS)-- 32 Part 1: Architecture and basic multilingual plane. 33 IEC 60559 (1989-01), Binary floating-point arithmetic for microprocessor systems. 34 Since IEC 60559 (1989-01) was originally IEEE 754-1985, Standard for binary floating-point arithmetic, 35 and is widely known by this name, this standard refers to it as the IEEE standard. SEP 2002 COMMITTEE DRAFT 7 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 8 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 Section 2: Fortran terms and concepts 2 2.1 High level syntax 3 This section introduces the terms associated with program units and other Fortran concepts above the 4 construct, statement, and expression levels and illustrates their relationships. The notation used in this 5 standard is described in 1.7. NOTE 2.1 Constraints and other information related to the rules that do not begin with R2 appear in the appropriate section. 6 R201 program is program-unit 7 [ program-unit ] ... 8 A program shall contain exactly one main-program program-unit or a main program defined by means 9 other than Fortran, but not both. 10 R202 program-unit is main-program 11 or external-subprogram 12 or module 13 or block-data 14 R1101 main-program is [ program-stmt ] 15 [ specification-part ] 16 [ execution-part ] 17 [ internal-subprogram-part ] 18 end-program-stmt 19 R203 external-subprogram is function-subprogram 20 or subroutine-subprogram 21 R1223 function-subprogram is function-stmt 22 [ specification-part ] 23 [ execution-part ] 24 [ internal-subprogram-part ] 25 end-function-stmt 26 R1230 subroutine-subprogram is subroutine-stmt 27 [ specification-part ] 28 [ execution-part ] 29 [ internal-subprogram-part ] 30 end-subroutine-stmt 31 R1104 module is module-stmt 32 [ specification-part ] 33 [ module-subprogram-part ] 34 end-module-stmt 35 R1116 block-data is block-data-stmt 36 [ specification-part ] 37 end-block-data-stmt 38 R204 specification-part is [ use-stmt ] ... 39 [ import-stmt ] ... 40 [ implicit-part ] 41 [ declaration-construct ] ... SEP 2002 COMMITTEE DRAFT 9 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 R205 implicit-part is [ implicit-part-stmt ] ... 2 implicit-stmt 3 R206 implicit-part-stmt is implicit-stmt 4 or parameter-stmt 5 or format-stmt 6 or entry-stmt 7 R207 declaration-construct is derived-type-def 8 or entry-stmt 9 or enum-alias-def 10 or format-stmt 11 or interface-block 12 or parameter-stmt 13 or procedure-declaration-stmt 14 or specification-stmt 15 or type-alias-stmt 16 or type-declaration-stmt 17 or stmt-function-stmt 18 R208 execution-part is executable-construct 19 [ execution-part-construct ] ... 20 R209 execution-part-construct is executable-construct 21 or format-stmt 22 or entry-stmt 23 or data-stmt 24 R210 internal-subprogram-part is contains-stmt 25 internal-subprogram 26 [ internal-subprogram ] ... 27 R211 internal-subprogram is function-subprogram 28 or subroutine-subprogram 29 R1107 module-subprogram-part is contains-stmt 30 module-subprogram 31 [ module-subprogram ] ... 32 R1108 module-subprogram is function-subprogram 33 or subroutine-subprogram 34 R212 specification-stmt is access-stmt 35 or allocatable-stmt 36 or asynchronous-stmt 37 or bind-stmt 38 or common-stmt 39 or data-stmt 40 or dimension-stmt 41 or equivalence-stmt 42 or external-stmt 43 or intent-stmt 44 or intrinsic-stmt 45 or namelist-stmt 46 or optional-stmt 47 or pointer-stmt 48 or protected-stmt 49 or save-stmt 50 or target-stmt 51 or volatile-stmt 52 or value-stmt 53 R213 executable-construct is action-stmt 54 or associate-construct 10 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 or case-construct 2 or do-construct 3 or forall-construct 4 or if-construct 5 or select-type-construct 6 or where-construct 7 R214 action-stmt is allocate-stmt 8 or assignment-stmt 9 or backspace-stmt 10 or call-stmt 11 or close-stmt 12 or continue-stmt 13 or cycle-stmt 14 or deallocate-stmt 15 or endfile-stmt 16 or end-function-stmt 17 or end-program-stmt 18 or end-subroutine-stmt 19 or exit-stmt 20 or flush-stmt 21 or forall-stmt 22 or goto-stmt 23 or if-stmt 24 or inquire-stmt 25 or nullify-stmt 26 or open-stmt 27 or pointer-assignment-stmt 28 or print-stmt 29 or read-stmt 30 or return-stmt 31 or rewind-stmt 32 or stop-stmt 33 or wait-stmt 34 or where-stmt 35 or write-stmt 36 or arithmetic-if-stmt 37 or computed-goto-stmt 38 C201 (R208) An execution-part shall not contain an end-function-stmt , end-program-stmt , or end- 39 subroutine-stmt . 40 2.2 Program unit concepts 41 Program units are the fundamental components of a Fortran program. A program unit may be 42 a main program, an external subprogram, a module, or a block data program unit. A subprogram 43 may be a function subprogram or a subroutine subprogram. A module contains definitions that are 44 to be made accessible to other program units. A block data program unit is used to specify initial 45 values for data objects in named common blocks. Each type of program unit is described in Section 46 11 or 12. An external subprogram is a subprogram that is not in a main program, a module, or 47 another subprogram. An internal subprogram is a subprogram that is in a main program or another 48 subprogram. A module subprogram is a subprogram that is in a module but is not an internal 49 subprogram. 50 A program unit consists of a set of nonoverlapping scoping units. A scoping unit is SEP 2002 COMMITTEE DRAFT 11 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 (1) A program unit or subprogram, excluding any scoping units in it, 2 (2) A derived-type definition (4.5.1), or 3 (3) An interface body, excluding any scoping units in it. 4 A scoping unit that immediately surrounds another scoping unit is called the host scoping unit (often 5 abbreviated to host). 6 2.2.1 Program 7 A program consists of exactly one main program, any number (including zero) of other kinds of program 8 units, and any number (including zero) of external procedures and other entities defined by means other 9 than Fortran. NOTE 2.2 There is a restriction that there shall be no more than one unnamed block data program unit (11.3). This standard places no ordering requirement on the program units that constitute a program, but since the public portions of a module are required to be available by the time a module reference (11.2.1) is processed, a processor may require a particular order of processing of the program units. 10 2.2.2 Main program 11 The Fortran main program is described in 11.1. 12 2.2.3 Procedure 13 A procedure encapsulates an arbitrary sequence of actions that may be invoked directly during program 14 execution. Procedures are either functions or subroutines. A function is a procedure that is invoked 15 in an expression; its invocation causes a value to be computed which is then used in evaluating the 16 expression. The variable that returns the value of a function is called the result variable. A subroutine 17 is a procedure that is invoked in a CALL statement, by a defined assignment statement, or by some 18 operations on derived-type entities. Unless it is a pure procedure, a subroutine may be used to change 19 the program state by changing the values of any of the data objects accessible to the subroutine; unless 20 it is a pure procedure, a function may do this in addition to computing the function value. 21 Procedures are described further in Section 12. 22 2.2.3.1 External procedure 23 An external procedure is a procedure that is defined by an external subprogram or by means other 24 than Fortran. An external procedure may be invoked by the main program or by any procedure of a 25 program. 26 2.2.3.2 Module procedure 27 A module procedure is a procedure that is defined by a module subprogram (R1108). A module 28 procedure may be invoked by another module subprogram in the module or by any scoping unit that 29 accesses the module procedure by use association (11.2.2). The module containing the subprogram is 30 the host scoping unit of the module procedure. 31 2.2.3.3 Internal procedure 32 An internal procedure is a procedure that is defined by an internal subprogram (R211). The containing 33 main program or subprogram is the host scoping unit of the internal procedure. An internal procedure 12 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 is local to its host in the sense that the internal procedure is accessible within the host scoping unit and 2 all its other internal procedures but is not accessible elsewhere. 3 2.2.3.4 Interface block 4 An interface body describes an abstract interface or the interface of a dummy procedure, external 5 procedure, procedure pointer, or type-bound procedure. 6 An interface block is a specific interface block, an abstract interface block, or a generic interface block. 7 A specific interface block is a collection of interface bodies. A generic interface block may also be used 8 to specify that procedures may be invoked 9 (1) By using a generic name, 10 (2) By using a defined operator, 11 (3) By using a defined assignment, or 12 (4) For derived-type input/output. 13 2.2.4 Module 14 A module contains (or accesses from other modules) definitions that are to be made accessible to other 15 program units. These definitions include data object declarations, type definitions, procedure definitions, 16 and interface blocks. A scoping unit in another program unit may access the definitions in a module. 17 Modules are further described in Section 11. 18 2.3 Execution concepts 19 Each Fortran statement is classified as either an executable statement or a nonexecutable statement. 20 There are restrictions on the order in which statements may appear in a program unit, and not all 21 executable statements may appear in all contexts. 22 2.3.1 Executable/nonexecutable statements 23 Program execution is a sequence, in time, of actions. An executable statement is an instruction to 24 perform or control one or more of these actions. Thus, the executable statements of a program unit 25 determine the behavior of the program unit. The executable statements are all of those that make up 26 the syntactic class executable-construct . 27 Nonexecutable statements do not specify actions; they are used to configure the program environment 28 in which actions take place. The nonexecutable statements are all those not classified as executable. 29 2.3.2 Statement order 30 The syntax rules of subclause 2.1 specify the statement order within program units and subprograms. 31 These rules are illustrated in Table 2.1 and Table 2.2. Table 2.1 shows the ordering rules for state- 32 ments and applies to all program units and subprograms. Vertical lines delineate varieties of statements 33 that may be interspersed and horizontal lines delineate varieties of statements that shall not be in- 34 terspersed. Internal or module subprograms shall follow a CONTAINS statement. Between USE and 35 CONTAINS statements in a subprogram, nonexecutable statements generally precede executable state- 36 ments, although the ENTRY statement, FORMAT statement, and DATA statement may appear among 37 the executable statements. Table 2.2 shows which statements are allowed in a scoping unit. SEP 2002 COMMITTEE DRAFT 13 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 Table 2.1: Requirements on statement ordering PROGRAM, FUNCTION, SUBROUTINE, MODULE, or BLOCK DATA statement USE statements IMPORT statements IMPLICIT NONE PARAMETER IMPLICIT statements statements Derived-type definitions, FORMAT interface blocks, and PARAMETER type declaration statements, ENTRY and DATA type alias definitions, statements statements enumeration declarations, procedure declarations, specification statements, and statement function statements DATA Executable statements constructs CONTAINS statement Internal subprograms or module subprograms END statement Table 2.2: Statements allowed in scoping units Kind of scoping unit: Main Module Block External Module Internal Interface program data subprog subprog subprog body USE statement Yes Yes Yes Yes Yes Yes Yes IMPORT statement No No No No No No Yes ENTRY statement No No No Yes Yes No No FORMAT statement Yes No No Yes Yes Yes No Misc. decls (see note) Yes Yes Yes Yes Yes Yes Yes DATA statement Yes Yes Yes Yes Yes Yes No Derived-type definition Yes Yes Yes Yes Yes Yes Yes Interface block Yes Yes No Yes Yes Yes Yes Executable statement Yes No No Yes Yes Yes No CONTAINS statement Yes Yes No Yes Yes No No Statement function statement Yes No No Yes Yes Yes No Notes for Table 2.2: 1) Misc. declarations are PARAMETER statements, IMPLICIT statements, type declaration statements, type alias statements, enum statements, procedure declara- tion statements, and specification statements. 2) The scoping unit of a module does not include any module subprograms that the module contains. 1 2.3.3 The END statement 2 An end-program-stmt , end-function-stmt , end-subroutine-stmt , end-module-stmt , or end-block-data-stmt 3 is an END statement. Each program unit, module subprogram, and internal subprogram shall have 4 exactly one END statement. The end-program-stmt , end-function-stmt , and end-subroutine-stmt state- 5 ments are executable, and may be branch target statements (8.2). Executing an end-program-stmt causes 14 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 normal termination of execution of the program. Executing an end-function-stmt or end-subroutine-stmt 2 is equivalent to executing a return-stmt with no scalar-int-expr. 3 The end-module-stmt and end-block-data-stmt statements are nonexecutable. 4 2.3.4 Execution sequence 5 If a program contains a Fortran main program, execution of the program begins with the first executable 6 construct of the main program. The execution of a main program or subprogram involves execution of 7 the executable constructs within its scoping unit. When a procedure is invoked, execution begins with 8 the first executable construct appearing after the invoked entry point. With the following exceptions, 9 the effect of execution is as if the executable constructs are executed in the order in which they appear 10 in the main program or subprogram until a STOP, RETURN, or END statement is executed. The 11 exceptions are the following: 12 (1) Execution of a branching statement (8.2) changes the execution sequence. These statements 13 explicitly specify a new starting place for the execution sequence. 14 (2) CASE constructs, DO constructs, IF constructs, and SELECT TYPE constructs contain 15 an internal statement structure and execution of these constructs involves implicit internal 16 branching. See Section 8 for the detailed semantics of each of these constructs. 17 (3) END=, ERR=, and EOR= specifiers may result in a branch. 18 (4) Alternate returns may result in a branch. 19 Internal subprograms may precede the END statement of a main program or a subprogram. The 20 execution sequence excludes all such definitions. 21 Normal termination of execution of the program occurs if a STOP statement or end-program-stmt is 22 executed. Normal termination of execution of a program also may occur during execution of a procedure 23 defined by a companion processor (C standard 5.1.2.2.3 and 7.20.4.3). If normal termination of execution 24 occurs within a Fortran program unit and the program incorporates procedures defined by a companion 25 processor, the process of execution termination shall include the effect of executing the C exit() function 26 (C standard 7.20.4.3). 27 2.4 Data concepts 28 Nonexecutable statements are used to specify the characteristics of the data environment. This includes 29 typing variables, declaring arrays, and defining new types. 30 2.4.1 Type 31 A type is a named category of data that is characterized by a set of values, a syntax for denoting 32 these values, and a set of operations that interpret and manipulate the values. This central concept is 33 described in 4.1. 34 A type may be parameterized, in which case the set of data values, the syntax for denoting them, and 35 the set of operations depend on the values of one or more parameters. Such a parameter is called a type 36 parameter (4.2). 37 There are two categories of types: intrinsic types and derived types. 38 2.4.1.1 Intrinsic type 39 An intrinsic type is a type that is defined by the language, along with operations, and is always 40 accessible. The intrinsic types are integer, real, complex, character, and logical. The properties of 41 intrinsic types are described in 4.4. The intrinsic type parameters are KIND and LEN. SEP 2002 COMMITTEE DRAFT 15 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 The kind type parameter indicates the decimal exponent range for the integer type (4.4.1), the 2 decimal precision and exponent range for the real and complex types (4.4.2, 4.4.3), and the representation 3 methods for the character and logical types (4.4.4, 4.4.5). The character length parameter specifies 4 the number of characters for the character type. 5 2.4.1.2 Derived type 6 A derived type is a type that is not defined by the language but requires a type definition to declare its 7 components. A scalar object of such a derived type is called a structure (5.1.1.7). Derived types may 8 be parameterized. Assignment of structures is defined intrinsically (7.4.1.3), but there are no intrinsic 9 operations for structures. For each derived type, a structure constructor is available to provide values 10 (4.5.8). In addition, data objects of derived type may be used as procedure arguments and function 11 results, and may appear in input/output lists. If additional operations are needed for a derived type, 12 they shall be supplied as procedure definitions. 13 Derived types are described further in 4.5. 14 2.4.2 Data value 15 Each intrinsic type has associated with it a set of values that a datum of that type may take, depending 16 on the values of the type parameters. The values for each intrinsic type are described in 4.4. The values 17 that objects of a derived type may assume are determined by the type definition, type parameter values, 18 and the sets of values of its components. 19 2.4.3 Data entity 20 A data entity is a data object, the result of the evaluation of an expression, or the result of the execution 21 of a function reference (called the function result). A data entity has a type and type parameters; it 22 may have a data value (an exception is an undefined variable). Every data entity has a rank and is thus 23 either a scalar or an array. 24 2.4.3.1 Data object 25 A data object (often abbreviated to object) is a constant (4.1.2), a variable (6), or a subobject of a 26 constant. The type and type parameters of a named data object may be specified explicitly (5.1) or 27 implicitly (5.3). 28 Subobjects are portions of certain objects that may be referenced and defined (variables only) inde- 29 pendently of the other portions. These include portions of arrays (array elements and array sections), 30 portions of character strings (substrings), portions of complex objects (real and imaginary parts), and 31 portions of structures (components). Subobjects are themselves data objects, but subobjects are refer- 32 enced only by object designators or intrinsic functions. In contexts where a structure component that is 33 a pointer refers to its target, the structure component is not a subobject of the structure. A subobject 34 of a variable is a variable. Subobjects are described in Section 6. 35 Objects referenced by a name are: a named scalar (a scalar object) 36 a named array (an array object) 37 Subobjects referenced by an object designator are: an array element (a scalar subobject) an array section (an array subobject) a structure component (a scalar or an array subobject) 38 a substring (a scalar subobject) 16 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 Subobjects of complex objects may also be referenced by intrinsic functions. 2 2.4.3.1.1 Variable 3 A variable may have a value and may be defined and redefined during execution of a program. 4 A named local variable of the scoping unit of a module, main program, or subprogram, is a named 5 variable that is a local entity of the scoping unit, is not a dummy argument, is not in COMMON, does 6 not have the BIND attribute, and is not accessed by use or host association. A subobject of a named 7 local variable is also a local variable. 8 2.4.3.1.2 Constant 9 A constant has a value and cannot become defined, redefined, or undefined during execution of a 10 program. A constant with a name is called a named constant and has the PARAMETER attribute 11 (5.1.2.10). A constant without a name is called a literal constant (4.4). 12 2.4.3.1.3 Subobject of a constant 13 A subobject of a constant is a portion of a constant. The portion referenced may depend on the 14 value of a variable. NOTE 2.3 For example, given: CHARACTER (LEN = 10), PARAMETER :: DIGITS = '0123456789' CHARACTER (LEN = 1) :: DIGIT INTEGER :: I ... DIGIT = DIGITS (I:I) DIGITS is a named constant and DIGITS (I:I) designates a subobject of the constant DIGITS. 15 2.4.3.2 Expression 16 An expression (7.1) produces a data entity when evaluated. An expression represents either a data 17 reference or a computation; it is formed from operands, operators, and parentheses. The type, type 18 parameters, value, and rank of an expression result are determined by the rules in Section 7. 19 2.4.3.3 Function reference 20 A function reference (12.4.2) produces a data entity when the function is executed during expression 21 evaluation. The type, type parameters, and rank of a function result are determined by the interface of 22 the function (12.2.2). The value of a function result is determined by execution of the function. 23 2.4.4 Scalar 24 A scalar is a datum that is not an array. Scalars may be of any intrinsic type or derived type. NOTE 2.4 A structure is scalar even if it has arrays as components. 25 The rank of a scalar is zero. The shape of a scalar is represented by a rank-one array of size zero. SEP 2002 COMMITTEE DRAFT 17 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 2.4.5 Array 2 An array is a set of scalar data, all of the same type and type parameters, whose individual elements 3 are arranged in a rectangular pattern. An array element is one of the individual elements in the array 4 and is a scalar. An array section is a subset of the elements of an array and is itself an array. 5 An array may have up to seven dimensions, and any extent (number of elements) in any dimension. 6 The rank of the array is the number of dimensions; its size is the total number of elements, which is 7 equal to the product of the extents. An array may have zero size. The shape of an array is determined 8 by its rank and its extent in each dimension, and may be represented as a rank-one array whose elements 9 are the extents. All named arrays shall be declared, and the rank of a named array is specified in its 10 declaration. The rank of a named array, once declared, is constant; the extents may be constant or may 11 vary during execution. 12 Two arrays are conformable if they have the same shape. A scalar is conformable with any array. Any 13 intrinsic operation defined for scalar objects may be applied to conformable objects. Such operations 14 are performed element-by-element to produce a resultant array conformable with the array operands. 15 Element-by-element operation means corresponding elements of the operand arrays are involved in a 16 scalar operation to produce the corresponding element in the result array, and all such element operations 17 may be performed in any order or simultaneously. Such an operation is described as elemental. 18 A rank-one array may be constructed from scalars and other arrays and may be reshaped into any 19 allowable array shape (4.8). 20 Arrays may be of any intrinsic type or derived type and are described further in 6.2. 21 2.4.6 Pointer 22 A data pointer is a data entity that has the POINTER attribute. A procedure pointer is a procedure 23 entity that has the POINTER attribute. A pointer is either a data pointer or a procedure pointer. 24 A pointer is associated with a target by pointer assignment (7.4.2). A data pointer may also be 25 associated with a target by allocation (6.3.1). A pointer is disassociated following execution of a 26 NULLIFY statement, following pointer assignment with a disassociated pointer, by default initialization, 27 or by explicit initialization. A data pointer may also be disassociated by execution of a DEALLOCATE 28 statement. A disassociated pointer is not associated with a target (16.4.2). 29 A pointer that is not associated shall not be referenced or defined. 30 If a data pointer is an array, the rank is declared, but the extents are determined when the pointer is 31 associated with a target. 32 2.4.7 Storage 33 Many of the facilities of this standard make no assumptions about the physical storage characteristics of 34 data objects. However, program units that include storage association dependent features shall observe 35 the storage restrictions described in 16.4.3. 36 2.5 Fundamental terms 37 The following terms are defined here and used throughout this standard. 18 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 2.5.1 Name and designator 2 A name is used to identify a program constituent, such as a program unit, named variable, named 3 constant, dummy argument, or derived type. The rules governing the construction of names are given 4 in 3.2.1. A designator is a name followed by zero or more component selectors, array section selectors, 5 array element selectors, and substring selectors. 6 An object designator is a designator for a data object. A procedure designator is a designator for 7 a procedure. NOTE 2.5 An object name is a special case of an object designator. 8 2.5.2 Keyword 9 The term keyword is used in two ways. 10 (1) It is used to describe a word that is part of the syntax of a statement. These keywords are 11 not reserved words; that is, names with the same spellings are allowed. In the syntax rules, 12 such keywords appear literally. In descriptive text, this meaning is denoted by the term 13 "keyword" without any modifier. Examples of statement keywords are: IF, READ, UNIT, 14 KIND, and INTEGER. 15 (2) It is used to denote names that identify items in a list. In actual argument lists, type 16 parameter lists, and structure constructors, items may be identified by a preceding keyword = 17 rather than their position within the list. An argument keyword is the name of a dummy 18 argument in the interface for the procedure being referenced, a type parameter keyword 19 is the name of a type parameter in the type being specified, and a component keyword 20 is the name of a component in a structure constructor. 21 R215 keyword is name NOTE 2.6 Use of keywords rather than position to identify items in a list can make such lists more readable and allows them to be reordered. This facilitates specification of a list in cases where optional items are omitted. 22 2.5.3 Association 23 Association may be name association (16.4.1), pointer association (16.4.2), storage association (16.4.3), 24 or inheritance association (16.4.4). Name association may be argument association, host association, 25 use association, linkage association, or construct association. 26 Storage association causes different entities to use the same storage. Any association permits an entity 27 to be identified by different names in the same scoping unit or by the same name or different names in 28 different scoping units. 29 2.5.4 Declaration 30 The term declaration refers to the specification of attributes for various program entities. Often this 31 involves specifying the type of a named data object or specifying the shape of a named array object. 32 2.5.5 Definition 33 The term definition is used in two ways. SEP 2002 COMMITTEE DRAFT 19 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 (1) It refers to the specification of derived types and procedures. 2 (2) When an object is given a valid value during program execution, it is said to become 3 defined. This is often accomplished by execution of an assignment or input statement. 4 When a variable does not have a predictable value, it is said to be undefined. Similarly, 5 when a pointer is associated with a target or nullified, its pointer association status is said 6 to become defined. When the association status of a pointer is not predictable, its pointer 7 association status is said to be undefined. 8 Section 16 describes the ways in which variables may become defined and undefined. 9 2.5.6 Reference 10 A data object reference is the appearance of the data object designator in a context requiring its 11 value at that point during execution. 12 A procedure reference is the appearance of the procedure designator, operator symbol, or assignment 13 symbol in a context requiring execution of the procedure at that point. An occurrence of user-defined 14 derived-type input/output (10.6.5) or derived-type finalization (4.5.10) is also a procedure reference. 15 The appearance of a data object designator or procedure designator in an actual argument list does not 16 constitute a reference to that data object or procedure unless such a reference is necessary to complete 17 the specification of the actual argument. 18 A module reference is the appearance of a module name in a USE statement (11.2.1). 19 2.5.7 Intrinsic 20 The qualifier intrinsic has two meanings. 21 (1) The qualifier signifies that the term to which it is applied is defined in this standard. In- 22 trinsic applies to types, procedures, modules, assignment statements, and operators. All 23 intrinsic types, procedures, assignments, and operators may be used in any scoping unit 24 without further definition or specification. Intrinsic modules may be accessed by use as- 25 sociation. Intrinsic procedures and modules defined in this standard are called standard 26 intrinsic procedures and standard intrinsic modules, respectively. 27 (2) The qualifier applies to procedures or modules that are provided by a processor but are not 28 defined in this standard (13, 14, 15.1). Such procedures and modules are called nonstandard 29 intrinsic procedures and nonstandard intrinsic modules, respectively. 30 2.5.8 Operator 31 An operator specifies a computation involving one (unary operator) or two (binary operator) data values 32 (operands). This standard specifies a number of intrinsic operators (e.g., the arithmetic operators +, ­, 33 *, /, and ** with numeric operands and the logical operators .AND., .OR., etc. with logical operands). 34 Additional operators may be defined within a program (7.1.3). 35 2.5.9 Sequence 36 A sequence is a set ordered by a one-to-one correspondence with the numbers 1, 2, through n. The 37 number of elements in the sequence is n. A sequence may be empty, in which case it contains no elements. 38 The elements of a nonempty sequence are referred to as the first element, second element, etc. The 39 nth element, where n is the number of elements in the sequence, is called the last element. An empty 40 sequence has no first or last element. 20 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 2.5.10 Companion processors 2 A processor has one or more companion processors. A companion processor is a processor-dependent 3 mechanism by which global data and procedures may be referenced or defined. A companion processor 4 may be a mechanism that references and defines such entities by a means other than Fortran (12.5.3), 5 it may be the Fortran processor itself, or it may be another Fortran processor. If there is more than 6 one companion processor, the means by which the Fortran processor selects among them are processor 7 dependent. 8 If a procedure is defined by means of a companion processor that is not the Fortran processor itself, 9 this standard refers to the C function that defines the procedure, although the procedure need not be 10 defined by means of the C programming language. NOTE 2.7 A companion processor might or might not be a mechanism that conforms to the requirements of the C standard. For example, a processor may allow a procedure defined by some language other than Fortran or C to be linked (12.5.3) with a Fortran procedure if it can be described by a C prototype as defined in 6.5.5.3 of the C standard. SEP 2002 COMMITTEE DRAFT 21 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 22 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 Section 3: Characters, lexical tokens, and source form 2 This section describes the Fortran character set and the various lexical tokens such as names and oper- 3 ators. This section also describes the rules for the forms that Fortran programs may take. 4 3.1 Processor character set 5 The processor character set is processor dependent. The structure of a processor character set is: 6 (1) Control characters ("newline", for example) 7 (2) Graphic characters 8 (a) Letters (3.1.1) 9 (b) Digits (3.1.2) 10 (c) Underscore (3.1.3) 11 (d) Special characters (3.1.4) 12 (e) Other characters (3.1.5) 13 The letters, digits, underscore, and special characters make up the Fortran character set. 14 R301 character is alphanumeric-character 15 or special-character 16 R302 alphanumeric-character is letter 17 or digit 18 or underscore 19 Except for the currency symbol, the graphics used for the characters shall be as given in 3.1.1, 3.1.2, 20 3.1.3, and 3.1.4. However, the style of any graphic is not specified. 21 3.1.1 Letters 22 The twenty-six letters are: 23 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 24 The set of letters defines the syntactic class letter . The processor character set shall include lower- 25 case and upper-case letters. A lower-case letter is equivalent to the corresponding upper-case letter in 26 program units except in a character context (3.3). NOTE 3.1 The following statements are equivalent: CALL BIG_COMPLEX_OPERATION (NDATE) call big_complex_operation (ndate) Call Big_Complex_Operation (NDate) 27 3.1.2 Digits 28 The ten digits are: SEP 2002 COMMITTEE DRAFT 23 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 0 1 2 3 4 5 6 7 8 9 2 The ten digits define the syntactic class digit . 3 3.1.3 Underscore 4 R303 underscore is 5 The underscore may be used as a significant character in a name. 6 3.1.4 Special characters 7 The special characters are shown in Table 3.1. Table 3.1: Special characters Character Name of character Character Name of character Blank ; Semicolon = Equals ! Exclamation point + Plus " Quotation mark or quote - Minus % Percent * Asterisk & Ampersand / Slash ~ Tilde \ Backslash < Less than ( Left parenthesis > Greater than ) Right parenthesis ? Question mark [ Left square bracket ' Apostrophe ] Right square bracket ` Grave accent { Left curly bracket ^ Circumflex accent } Right curly bracket | Vertical bar , Comma $ Currency symbol . Decimal point or period # Number sign : Colon @ Commercial at 8 The special characters define the syntactic class special-character . Some of the special characters are 9 used for operator symbols, bracketing, and various forms of separating and delimiting other lexical 10 tokens. 11 3.1.5 Other characters 12 Additional characters may be representable in the processor, but may appear only in comments (3.3.1.1, 13 3.3.2.1), character constants (4.4.4), input/output records (9.1.1), and character string edit descriptors 14 (10.2.1). 15 The default character type shall support a character set that includes the Fortran character set. By 16 supplying nondefault character types, the processor may support additional character sets. The char- 17 acters available in the nondefault character types are not specified, except that one character in each 18 nondefault character type shall be designated as a blank character to be used as a padding character. 19 3.2 Low-level syntax 20 The low-level syntax describes the fundamental lexical tokens of a program unit. Lexical tokens are 21 sequences of characters that constitute the building blocks of a program. They are keywords, names, 24 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 literal constants other than complex literal constants, operators, labels, delimiters, comma, =, =>, :, ::, 2 ;, and %. 3 3.2.1 Names 4 Names are used for various entities such as variables, program units, dummy arguments, named con- 5 stants, and derived types. 6 R304 name is letter [ alphanumeric-character ] ... 7 C301 (R304) The maximum length of a name is 63 characters. NOTE 3.2 Examples of names: A1 NAME LENGTH (single underscore) S P R E A D O U T (two consecutive underscores) TRAILER (trailing underscore) NOTE 3.3 The word "name" always denotes this particular syntactic form. The word "identifier" is used where entities may be identified by other syntactic forms or by values; its particular meaning depends on the context in which it is used. 8 3.2.2 Constants 9 R305 constant is literal-constant 10 or named-constant 11 R306 literal-constant is int-literal-constant 12 or real-literal-constant 13 or complex-literal-constant 14 or logical-literal-constant 15 or char-literal-constant 16 or boz-literal-constant 17 R307 named-constant is name 18 R308 int-constant is constant 19 C302 (R308)int-constant shall be of type integer. 20 R309 char-constant is constant 21 C303 (R309) char-constant shall be of type character. 22 3.2.3 Operators 23 R310 intrinsic-operator is power-op 24 or mult-op 25 or add-op 26 or concat-op 27 or rel-op 28 or not-op 29 or and-op 30 or or-op SEP 2002 COMMITTEE DRAFT 25 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 or equiv-op 2 R707 power-op is ** 3 R708 mult-op is * 4 or / 5 R709 add-op is + 6 or ­ 7 R711 concat-op is // 8 R713 rel-op is .EQ. 9 or .NE. 10 or .LT. 11 or .LE. 12 or .GT. 13 or .GE. 14 or == 15 or /= 16 or < 17 or <= 18 or > 19 or >= 20 R718 not-op is .NOT. 21 R719 and-op is .AND. 22 R720 or-op is .OR. 23 R721 equiv-op is .EQV. 24 or .NEQV. 25 R311 defined-operator is defined-unary-op 26 or defined-binary-op 27 or extended-intrinsic-op 28 R703 defined-unary-op is . letter [ letter ] ... . 29 R723 defined-binary-op is . letter [ letter ] ... . 30 R312 extended-intrinsic-op is intrinsic-operator 31 3.2.4 Statement labels 32 A statement label provides a means of referring to an individual statement. 33 R313 label is digit [ digit [ digit [ digit [ digit ] ] ] ] 34 C304 (R313) At least one digit in a label shall be nonzero. 35 If a statement is labeled, the statement shall contain a nonblank character. The same statement label 36 shall not be given to more than one statement in a scoping unit. Leading zeros are not significant in 37 distinguishing between statement labels. NOTE 3.4 For example: 99999 10 010 are all statement labels. The last two are equivalent. There are 99999 unique statement labels and a processor shall accept any of them as a statement 26 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 3.4 (cont.) label. However, a processor may have an implementation limit on the total number of unique statement labels in one program unit. 1 Any statement may have a statement label, but the labels are used only in the following ways: 2 (1) The label on a branch target statement (8.2) is used to identify that statement as the 3 possible destination of a branch. 4 (2) The label on a FORMAT statement (10.1.1) is used to identify that statement as the format 5 specification for a data transfer statement (9.5). 6 (3) In some forms of the DO construct (8.1.6), the range of the DO construct is identified by 7 the label on the last statement in that range. 8 3.2.5 Delimiters 9 Delimiters are used to enclose syntactic lists. The following pairs are delimiters: 10 ( ... ) 11 / ... / 12 [ ... ] 13 (/ ... /) 14 3.3 Source form 15 A Fortran program unit is a sequence of one or more lines, organized as Fortran statements, comments, 16 and INCLUDE lines. A line is a sequence of zero or more characters. Lines following a program unit 17 END statement are not part of that program unit. A Fortran statement is a sequence of one or more 18 complete or partial lines. 19 A character context means characters within a character literal constant (4.4.4) or within a character 20 string edit descriptor (10.2.1). 21 A comment may contain any character that may occur in any character context. 22 There are two source forms: free and fixed. Free form and fixed form shall not be mixed in the same program unit. 23 The means for specifying the source form of a program unit are processor dependent. 24 3.3.1 Free source form 25 In free source form there are no restrictions on where a statement (or portion of a statement) may 26 appear within a line. A line may contain zero characters. If a line consists entirely of characters of 27 default kind (4.4.4), it may contain at most 132 characters. If a line contains any character that is not 28 of default kind, the maximum number of characters allowed on the line is processor dependent. 29 Blank characters shall not appear within lexical tokens other than in a character context or in a format 30 specification. Blanks may be inserted freely between tokens to improve readability; for example, blanks 31 may occur between the tokens that form a complex literal constant. A sequence of blank characters 32 outside of a character context is equivalent to a single blank character. 33 A blank shall be used to separate names, constants, or labels from adjacent keywords, names, constants, 34 or labels. SEP 2002 COMMITTEE DRAFT 27 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 3.5 For example, the blanks after REAL, READ, 30, and DO are required in the following: REAL X READ 10 30 DO K=1,3 1 One or more blanks shall be used to separate adjacent keywords except in the following cases, where 2 blanks are optional: Adjacent keywords where separating blanks are optional BLOCK DATA DOUBLE PRECISION ELSE IF ELSE WHERE END ASSOCIATE END BLOCK DATA END DO END ENUM END FILE END FORALL END FUNCTION END IF END INTERFACE END MODULE END PROGRAM END SELECT END SUBROUTINE END TYPE END WHERE GO TO IN OUT SELECT CASE SELECT TYPE 3 3.3.1.1 Free form commentary 4 The character "!" initiates a comment except where it appears within a character context. The 5 comment extends to the end of the line. If the first nonblank character on a line is an "!", the line 6 is a comment line. Lines containing only blanks or containing no characters are also comment lines. 7 Comments may appear anywhere in a program unit and may precede the first statement of a program 8 unit. Comments have no effect on the interpretation of the program unit. NOTE 3.6 The standard does not restrict the number of consecutive comment lines. 9 3.3.1.2 Free form statement continuation 10 The character "&" is used to indicate that the current statement is continued on the next line that is not 11 a comment line. Comment lines cannot be continued; an "&" in a comment has no effect. Comments may 12 occur within a continued statement. When used for continuation, the "&" is not part of the statement. 13 No line shall contain a single "&" as the only nonblank character or as the only nonblank character 14 before an "!" that initiates a comment. 15 If a noncharacter context is to be continued, an "&" shall be the last nonblank character on the line, 16 or the last nonblank character before an "!". There shall be a later line that is not a comment; the 17 statement is continued on the next such line. If the first nonblank character on that line is an "&", the 18 statement continues at the next character position following that "&"; otherwise, it continues with the 19 first character position of that line. 20 If a lexical token is split across the end of a line, the first nonblank character on the first following 21 noncomment line shall be an "&" immediately followed by the successive characters of the split token. 22 If a character context is to be continued, an "&" shall be the last nonblank character on the line and 28 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 shall not be followed by commentary. There shall be a later line that is not a comment; an "&" shall be 2 the first nonblank character on the next such line and the statement continues with the next character 3 following that "&". 4 3.3.1.3 Free form statement termination 5 If a statement is not continued, a comment or the end of the line terminates the statement. 6 A statement may alternatively be terminated by a ";" character that appears other than in a character 7 context or in a comment. The ";" is not part of the statement. After a ";" terminator, another statement 8 may appear on the same line, or begin on that line and be continued. A ";" shall not appear as the first 9 nonblank character on a line. A sequence consisting only of zero or more blanks and one or more ";" 10 terminators, in any order, is equivalent to a single ";" terminator. 11 3.3.1.4 Free form statements 12 A label may precede any statement not forming part of another statement. NOTE 3.7 No Fortran statement begins with a digit. 13 A statement shall not have more than 255 continuation lines. 14 3.3.2 Fixed source form 15 In fixed source form, there are restrictions on where a statement may appear within a line. If a source line contains only 16 default kind characters, it shall contain exactly 72 characters; otherwise, its maximum number of characters is processor 17 dependent. 18 Except in a character context, blanks are insignificant and may be used freely throughout the program. 19 3.3.2.1 Fixed form commentary 20 The character "!" initiates a comment except where it appears within a character context or in character position 6. The 21 comment extends to the end of the line. If the first nonblank character on a line is an "!" in any character position other 22 than character position 6, the line is a comment line. Lines beginning with a "C" or "*" in character position 1 and lines 23 containing only blanks are also comment lines. Comments may appear anywhere in a program unit and may precede the 24 first statement of the program unit. Comments have no effect on the interpretation of the program unit. NOTE 3.8 The standard does not restrict the number of consecutive comment lines. 25 3.3.2.2 Fixed form statement continuation 26 Except within commentary, character position 6 is used to indicate continuation. If character position 6 contains a blank 27 or zero, the line is the initial line of a new statement, which begins in character position 7. If character position 6 contains 28 any character other than blank or zero, character positions 7­72 of the line constitute a continuation of the preceding 29 noncomment line. NOTE 3.9 An "!" or ";" in character position 6 is interpreted as a continuation indicator unless it appears within commentary indicated by a "C" or "*" in character position 1 or by an "!" in character positions 1­5. 30 Comment lines cannot be continued. Comment lines may occur within a continued statement. 31 3.3.2.3 Fixed form statement termination 32 If a statement is not continued, a comment or the end of the line terminates the statement. SEP 2002 COMMITTEE DRAFT 29 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 A statement may alternatively be terminated by a ";" character that appears other than in a character context, in a 2 comment, or in character position 6. The ";" is not part of the statement. After a ";" terminator, another statement may 3 begin on the same line, or begin on that line and be continued. A ";" shall not appear as the first nonblank character on 4 a line, except in character position 6. A sequence consisting only of zero or more blanks and one or more ";" terminators, 5 in any order, is equivalent to a single ";" terminator. 6 3.3.2.4 Fixed form statements 7 A label, if present, shall occur in character positions 1 through 5 of the first line of a statement; otherwise, positions 1 8 through 5 shall be blank. Blanks may appear anywhere within a label. A statement following a ";" on the same line shall 9 not be labeled. Character positions 1 through 5 of any continuation lines shall be blank. A statement shall not have more 10 than 255 continuation lines. The program unit END statement shall not be continued. A statement whose initial line 11 appears to be a program unit END statement shall not be continued. 12 3.4 Including source text 13 Additional text may be incorporated into the source text of a program unit during processing. This is 14 accomplished with the INCLUDE line, which has the form 15 INCLUDE char-literal-constant 16 The char-literal-constant shall not have a kind type parameter value that is a named-constant . 17 An INCLUDE line is not a Fortran statement. 18 An INCLUDE line shall appear on a single source line where a statement may appear; it shall be the 19 only nonblank text on this line other than an optional trailing comment. Thus, a statement label is not 20 allowed. 21 The effect of the INCLUDE line is as if the referenced source text physically replaced the INCLUDE line 22 prior to program processing. Included text may contain any source text, including additional INCLUDE 23 lines; such nested INCLUDE lines are similarly replaced with the specified source text. The maximum 24 depth of nesting of any nested INCLUDE lines is processor dependent. Inclusion of the source text 25 referenced by an INCLUDE line shall not, at any level of nesting, result in inclusion of the same source 26 text. 27 When an INCLUDE line is resolved, the first included statement line shall not be a continuation line 28 and the last included statement line shall not be continued. 29 The interpretation of char-literal-constant is processor dependent. An example of a possible valid inter- 30 pretation is that char-literal-constant is the name of a file that contains the source text to be included. NOTE 3.10 In some circumstances, for example where source code is maintained in an INCLUDE file for use in programs whose source form might be either fixed or free, observing the following rules allows the code to be used with either source form: (1) Confine statement labels to character positions 1 to 5 and statements to character positions 7 to 72; (2) Treat blanks as being significant; (3) Use only the exclamation mark (!) to indicate a comment, but do not start the comment in character position 6; (4) For continued statements, place an ampersand (&) in both character position 73 of a continued line and character position 6 of a continuing line. 30 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 Section 4: Types 2 Fortran provides an abstract means whereby data may be categorized without relying on a particular 3 physical representation. This abstract means is the concept of type. 4 An intrinsic type is one that is defined by the language. The intrinsic types are integer, real, complex, 5 character, and logical. 6 A derived type is one that is defined by a derived-type definition ((4.5.1)). 7 A derived type may be used only where its definition is accessible (4.5.1.8). An intrinsic type is always 8 accessible. 9 4.1 The concept of type 10 A type has a name, a set of valid values, a means to denote such values (constants), and a set of 11 operations to manipulate the values. NOTE 4.1 For example, the logical type has a set of two values, denoted by the lexical tokens .TRUE. and .FALSE., which are manipulated by logical operations. An example of a less restricted type is the integer type. This type has a processor-dependent set of integer numeric values, each of which is denoted by an optional sign followed by a string of digits, and which may be manipulated by integer arithmetic operations and relational operations. 12 4.1.1 Set of values 13 For each type, there is a set of valid values. The set of valid values may be completely determined, as is 14 the case for logical, or may be determined by a processor-dependent method, as is the case for integer, 15 character, and real. For complex or derived types, the set of valid values consists of the set of all the 16 combinations of the values of the individual components. 17 4.1.2 Constants 18 The syntax for literal constants of each intrinsic type is specified in 4.4. 19 The syntax for denoting a value indicates the type, type parameters, and the particular value. 20 A constant value may be given a name (5.1.2.10, 5.2.9). 21 A structure constructor (4.5.8) may be used to construct a constant value of derived type from an 22 appropriate sequence of initialization expressions (7.1.7). Such a constant value is considered to be a 23 scalar even though the value may have components that are arrays. 24 4.1.3 Operations 25 For each of the intrinsic types, a set of operations and corresponding operators is defined intrinsically. 26 These are described in Section 7. The intrinsic set may be augmented with operations and operators 27 defined by functions with the OPERATOR interface (12.3.2.1). Operator definitions are described in 28 Sections 7 and 12. SEP 2002 COMMITTEE DRAFT 31 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 For derived types, there are no intrinsic operations. Operations on derived types may be defined by the 2 program (4.5.9). 3 4.2 Type parameters 4 A type may be parameterized. In this case, the set of values, the syntax for denoting the values, and 5 the set of operations on the values of the type depend on the values of the parameters. 6 The intrinsic types are all parameterized. Derived types may be defined to be parameterized. 7 A type parameter is either a kind type parameter or a nonkind type parameter. 8 A kind type parameter may be used in initialization and specification expressions within the derived-type 9 definition (4.5.1) for the type; it participates in generic resolution (16.2.3). Each of the intrinsic types 10 has a kind type parameter named KIND, which is used to distinguish multiple representations of the 11 intrinsic type. NOTE 4.2 By design, the value of a kind type parameter is known at compile time. Some parameterizations that involve multiple representation forms need to be distinguished at compile time for practical implementation and performance. Examples include the multiple precisions of the intrinsic real type and the possible multiple character sets of the intrinsic character type. A type parameter of a derived type may be specified to be a kind type parameter in order to allow generic resolution based on the parameter; that is to allow a single generic to include two specific procedures that have interfaces distinguished only by the value of a kind type parameter of a dummy argument. Generics are designed to be resolvable at compile time. 12 A nonkind type parameter may be used in specification expressions within the derived-type definition 13 for the type, but it may not be used in initialization expressions. The intrinsic character type has a 14 nonkind type parameter named LEN, which is the length of the string. NOTE 4.3 A typical use of a nonkind type parameter is to specify a size. An example is the length of an entity of intrinsic character type. 15 A type parameter value may be specified with a type specification (5.1, 4.5.7). 16 R401 type-param-value is scalar-int-expr 17 or * 18 or : 19 C401 (R401) The type-param-value for a kind type parameter shall be an initialization expression. 20 C402 (R401) A colon may be used as a type-param-value only in the declaration of an entity or 21 component that has the POINTER or ALLOCATABLE attribute. 22 A deferred type parameter is a nonkind type parameter whose value can change during execution of 23 the program. A colon as a type-param-value specifies a deferred type parameter. 24 The values of the deferred type parameters of an object are determined by successful execution of an 25 ALLOCATE statement (6.3.1), execution of a derived-type intrinsic assignment statement (7.4.1.2), 26 execution of a pointer assignment statement (7.4.2), or by argument association (12.4.1.2). 32 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 4.4 Deferred type parameters of functions, including function procedure pointers, have no values. Instead, they indicate that those type parameters of the function result will be determined by execution of the function, if it returns an allocated allocatable result or an associated pointer result. 1 An assumed type parameter is a nonkind type parameter for a dummy argument that assumes 2 the type parameter value from the corresponding actual argument. An asterisk as a type-param-value 3 specifies an assumed type parameter. 4 4.3 Relationship of types and values to objects 5 The name of a type serves as a type specifier and may be used to declare objects of that type. A 6 declaration specifies the type of a named object. A data object may be declared explicitly or implicitly. 7 Data objects may have attributes in addition to their types. Section 5 describes the way in which a data 8 object is declared and how its type and other attributes are specified. 9 Scalar data of any intrinsic or derived type may be shaped in a rectangular pattern to compose an array 10 of the same type and type parameters. An array object has a type and type parameters just as a scalar 11 object does. 12 Variables may be objects or subobjects. The type and type parameters of a variable determine which 13 values that variable may take. Assignment provides one means of defining or redefining the value of a 14 variable of any type. Assignment is defined intrinsically for all types where the type, type parameters, 15 and shape of both the variable and the value to be assigned to it are identical. Assignment between 16 objects of certain differing intrinsic types, type parameters, and shapes is described in Section 7. A 17 subroutine and a generic interface (4.5.1, 12.3.2.1) whose generic specifier is ASSIGNMENT (=) define 18 an assignment that is not defined intrinsically or redefine an intrinsic derived-type assignment (7.4.1.4). NOTE 4.5 For example, assignment of a real value to an integer variable is defined intrinsically. 19 The type of a variable determines the operations that may be used to manipulate the variable. 20 4.4 Intrinsic types 21 The intrinsic types are: numeric types: integer, real, and complex 22 nonnumeric types: character and logical 23 The numeric types are provided for numerical computation. The normal operations of arithmetic, 24 addition (+), subtraction (­), multiplication (*), division (/), exponentiation (**), identity (unary +), 25 and negation (unary ­), are defined intrinsically for the numeric types. 26 4.4.1 Integer type 27 The set of values for the integer type is a subset of the mathematical integers. A processor shall 28 provide one or more representation methods that define sets of values for data of type integer. Each 29 such method is characterized by a value for a type parameter called the kind type parameter. The kind 30 type parameter of a representation method is returned by the intrinsic inquiry function KIND (13.7.57). 31 The decimal exponent range of a representation method is returned by the intrinsic function RANGE 32 (13.7.92). The intrinsic function SELECTED INT KIND (13.7.101) returns a kind value based on a SEP 2002 COMMITTEE DRAFT 33 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 specified decimal range requirement. The integer type includes a zero value, which is considered neither 2 negative nor positive. The value of a signed integer zero is the same as the value of an unsigned integer 3 zero. 4 The type specifier for the integer type uses the keyword INTEGER (R503). 5 If the kind type parameter is not specified, the default kind value is KIND (0) and the data entity is of 6 type default integer. 7 Any integer value may be represented as a signed-int-literal-constant . 8 R402 signed-int-literal-constant is [ sign ] int-literal-constant 9 R403 int-literal-constant is digit-string [ kind-param ] 10 R404 kind-param is digit-string 11 or scalar-int-constant-name 12 R405 signed-digit-string is [ sign ] digit-string 13 R406 digit-string is digit [ digit ] ... 14 R407 sign is + 15 or ­ 16 C403 (R404) A scalar-int-constant-name shall be a named constant of type integer. 17 C404 (R404) The value of kind-param shall be nonnegative. 18 C405 (R403) The value of kind-param shall specify a representation method that exists on the pro- 19 cessor. 20 The optional kind type parameter following digit-string specifies the kind type parameter of the integer 21 constant; if it is not present, the constant is of type default integer. 22 An integer constant is interpreted as a decimal value. NOTE 4.6 Examples of signed integer literal constants are: 473 +56 -101 21_2 21_SHORT 1976354279568241_8 where SHORT is a scalar integer named constant. 23 R408 boz-literal-constant is binary-constant 24 or octal-constant 25 or hex-constant 26 R409 binary-constant is B ' digit [ digit ] ... ' 27 or B " digit [ digit ] ... " 28 C406 (R409) digit shall have one of the values 0 or 1. 29 R410 octal-constant is O ' digit [ digit ] ... ' 30 or O " digit [ digit ] ... " 31 C407 (R410) digit shall have one of the values 0 through 7. 34 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 R411 hex-constant is Z ' hex-digit [ hex-digit ] ... ' 2 or Z " hex-digit [ hex-digit ] ... " 3 R412 hex-digit is digit 4 or A 5 or B 6 or C 7 or D 8 or E 9 or F 10 Binary, octal and hexadecimal constants are interpreted according to their respective number systems. 11 The hex-digit s A through F represent the numbers ten through fifteen, respectively; they may be repre- 12 sented by their lower-case equivalents. 13 C408 (R408) A boz-literal-constant shall appear only as a data-stmt-constant in a DATA statement, as 14 the actual argument associated with the dummy argument A of the numeric intrinsic functions 15 DBLE, REAL or INT, or as the actual argument associated with the X or Y dummy argument 16 of the intrinsic CMPLX function. 17 4.4.2 Real type 18 The real type has values that approximate the mathematical real numbers. A processor shall provide 19 two or more approximation methods that define sets of values for data of type real. Each such method 20 has a representation method and is characterized by a value for a type parameter called the kind type 21 parameter. The kind type parameter of an approximation method is returned by the intrinsic inquiry 22 function KIND (13.7.57). The decimal precision and decimal exponent range of an approximation 23 method are returned by the intrinsic functions PRECISION (13.7.86) and RANGE (13.7.92). The 24 intrinsic function SELECTED REAL KIND (13.7.102) returns a kind value based on specified precision 25 and decimal range requirements. NOTE 4.7 See C.1.2 for remarks concerning selection of approximation methods. 26 The real type includes a zero value. Processors that distinguish between positive and negative zeros 27 shall treat them as equivalent 28 (1) in all relational operations, 29 (2) as actual arguments to intrinsic procedures other than those for which it is explicitly specified 30 that negative zero is distinguished, and 31 (3) as the scalar-numeric-expr in an arithmetic IF. NOTE 4.8 On a processor that can distinguish between 0.0 and -0.0, ( X >= 0.0 ) evaluates to true if X = 0.0 or if X = -0.0, ( X < 0.0 ) evaluates to false for X = -0.0, and SEP 2002 COMMITTEE DRAFT 35 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 4.8 (cont.) IF (X) 1,2,3 causes a transfer of control to the branch target statement with the statement label "2" for both X = 0.0 and X = -0.0. In order to distinguish between 0.0 and -0.0, a program should use the SIGN function. SIGN(1.0,X) will return -1.0 if X < 0.0 or if the processor distinguishes between 0.0 and -0.0 and X has the value -0.0. NOTE 4.9 Historically some systems had a distinct negative zero value that presented some difficulties. For- tran standards were specified such that these difficulties had to be handled by the processor and not the user. The IEEE standard introduced a negative zero with particular properties. For example, when the exact result of an operation is negative but rounding produces a zero, the value specified by the IEEE standard is -0.0. This standard includes adjustments intended to permit IEEE-compliant processors to behave in accordance with that standard without violating this standard. 1 The type specifier for the real type uses the keyword REAL (R503). The keyword DOUBLE PRECISION 2 (R503) is an alternate specifier for one kind of real type. 3 If the type keyword REAL is specified and the kind type parameter is not specified, the default kind value 4 is KIND (0.0) and the data entity is of type default real. If the type keyword DOUBLE PRECISION is 5 specified, a kind type parameter shall not be specified and the data entity is of type double precision 6 real. The kind type parameter of such an entity has the value KIND (0.0D0). The decimal precision of 7 the double precision real approximation method shall be greater than that of the default real method. 8 R413 signed-real-literal-constant is [ sign ] real-literal-constant 9 R414 real-literal-constant is significand [ exponent-letter exponent ] [ kind-param ] 10 or digit-string exponent-letter exponent [ kind-param ] 11 R415 significand is digit-string . [ digit-string ] 12 or . digit-string 13 R416 exponent-letter is E 14 or D 15 R417 exponent is signed-digit-string 16 C409 (R414) If both kind-param and exponent-letter are present, exponent-letter shall be E. 17 C410 (R414) The value of kind-param shall specify an approximation method that exists on the 18 processor. 19 A real literal constant without a kind type parameter is a default real constant if it is without an 20 exponent part or has exponent letter E, and is a double precision real constant if it has exponent letter 21 D. A real literal constant written with a kind type parameter is a real constant with the specified kind 22 type parameter. 23 The exponent represents the power of ten scaling to be applied to the significand or digit string. The 24 meaning of these constants is as in decimal scientific notation. 25 The significand may be written with more digits than a processor will use to approximate the value of 26 the constant. 36 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 4.10 Examples of signed real literal constants are: -12.78 +1.6E3 2.1 -16.E4_8 0.45D-4 10.93E7_QUAD .123 3E4 where QUAD is a scalar integer named constant. 1 4.4.3 Complex type 2 The complex type has values that approximate the mathematical complex numbers. The values of a 3 complex type are ordered pairs of real values. The first real value is called the real part, and the second 4 real value is called the imaginary part. 5 Each approximation method used to represent data entities of type real shall be available for both the 6 real and imaginary parts of a data entity of type complex. A kind type parameter may be specified for 7 a complex entity and selects for both parts the real approximation method characterized by this kind 8 type parameter value. The kind type parameter of an approximation method is returned by the intrinsic 9 inquiry function KIND (13.7.57). 10 The type specifier for the complex type uses the keyword COMPLEX (R503). There is no keyword for 11 double precision complex. If the type keyword COMPLEX is specified and the kind type parameter is 12 not specified, the default kind value is the same as that for default real, the type of both parts is default 13 real, and the data entity is of type default complex. 14 R418 complex-literal-constant is ( real-part , imag-part ) 15 R419 real-part is signed-int-literal-constant 16 or signed-real-literal-constant 17 or named-constant 18 R420 imag-part is signed-int-literal-constant 19 or signed-real-literal-constant 20 or named-constant 21 C411 (R418) Each named constant in a complex literal constant shall be of type integer or real. 22 If the real part and the imaginary part of a complex literal constant are both real, the kind type 23 parameter value of the complex literal constant is the kind type parameter value of the part with the 24 greater decimal precision; if the precisions are the same, it is the kind type parameter value of one of the 25 parts as determined by the processor. If a part has a kind type parameter value different from that of 26 the complex literal constant, the part is converted to the approximation method of the complex literal 27 constant. 28 If both the real and imaginary parts are integer, they are converted to the default real approximation 29 method and the constant is of type default complex. If only one of the parts is an integer, it is converted 30 to the approximation method selected for the part that is real and the kind type parameter value of the 31 complex literal constant is that of the part that is real. SEP 2002 COMMITTEE DRAFT 37 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 4.11 Examples of complex literal constants are: (1.0, -1.0) (3, 3.1E6) (4.0_4, 3.6E7_8) ( 0., PI) where PI is a previously declared named real constant. 1 4.4.4 Character type 2 The character type has a set of values composed of character strings. A character string is a sequence 3 of characters, numbered from left to right 1, 2, 3, ... up to the number of characters in the string. The 4 number of characters in the string is called the length of the string. The length is a type parameter; its 5 value is greater than or equal to zero. Strings of different lengths are all of type character. 6 A processor shall provide one or more representation methods that define sets of values for data of 7 type character. Each such method is characterized by a value for a type parameter called the kind type 8 parameter. The kind type parameter of a representation method is returned by the intrinsic inquiry 9 function KIND (13.7.57). The intrinsic function SELECTED CHAR KIND (13.7.100) returns a kind 10 value based on the name of a character type. Any character of a particular representation method 11 representable in the processor may occur in a character string of that representation method. 12 The character set defined by ISO/IEC 646:1991 is referred to as the ASCII character set or the 13 ASCII character type. The character set defined by ISO/IEC 10646-1:2000 UCS-4 is referred to as 14 the ISO 10646 character set or the ISO 10646 character type. 15 The type specifier for the character type uses the keyword CHARACTER (R503). 16 If the kind type parameter is not specified, the default kind value is KIND ('A') and the data entity is 17 of type default character. 18 A character literal constant is written as a sequence of characters, delimited by either apostrophes 19 or quotation marks. 20 R421 char-literal-constant is [ kind-param ] ' [ rep-char ] ... ' 21 or [ kind-param ] " [ rep-char ] ... " 22 C412 (R421) The value of kind-param shall specify a representation method that exists on the pro- 23 cessor. 24 The optional kind type parameter preceding the leading delimiter specifies the kind type parameter of 25 the character constant; if it is not present, the constant is of type default character. 26 For the type character with kind kind-param, if present, and for type default character otherwise, a 27 representable character, rep-char , is defined as follows: 28 (1) In free source form, it is any graphic character in the processor-dependent character set. 29 (2) In fixed source form, it is any character in the processor-dependent character set. A processor may restrict 30 the occurrence of some or all of the control characters. NOTE 4.12 Fortran 77 allowed any character to occur in a character context. This standard allows a source 38 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 4.12 (cont.) program to contain characters of more than one kind. Some processors may identify characters of nondefault kinds by control characters (called "escape" or "shift" characters). It is difficult, if not impossible, to process, edit, and print files where some instances of control characters have their intended meaning and some instances may not. Almost all control characters have uses or effects that effectively preclude their use in character contexts and this is why free source form allows only graphic characters as representable characters. Nevertheless, for compatibility with Fortran 77, control characters remain permitted in principle in fixed source form. 1 The delimiting apostrophes or quotation marks are not part of the value of the character literal constant. 2 An apostrophe character within a character constant delimited by apostrophes is represented by two 3 consecutive apostrophes (without intervening blanks); in this case, the two apostrophes are counted as 4 one character. Similarly, a quotation mark character within a character constant delimited by quotation 5 marks is represented by two consecutive quotation marks (without intervening blanks) and the two 6 quotation marks are counted as one character. 7 A zero-length character literal constant is represented by two consecutive apostrophes (without inter- 8 vening blanks) or two consecutive quotation marks (without intervening blanks) outside of a character 9 context. 10 The intrinsic operation concatenation (//) is defined between two data entities of type character (7.2.2) 11 with the same kind type parameter. NOTE 4.13 Examples of character literal constants are: "DON'T" 'DON''T' both of which have the value DON'T and '' which has the zero-length character string as its value. NOTE 4.14 Examples of nondefault character literal constants, where the processor supports the corresponding character sets, are: BOLD FACE 'This is in bold face' ITALICS 'This is in italics' where BOLD FACE and ITALICS are named constants whose values are the kind type parameters for bold face and italic characters, respectively. 12 4.4.4.1 Collating sequence 13 Each implementation defines a collating sequence for the character set of each kind of character. A 14 collating sequence is a one-to-one mapping of the characters into the nonnegative integers such that 15 each character corresponds to a different nonnegative integer. The intrinsic functions CHAR (13.7.19) 16 and ICHAR (13.7.50) provide conversions between the characters and the integers according to this 17 mapping. SEP 2002 COMMITTEE DRAFT 39 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 4.15 For example: ICHAR ( 'X' ) returns the integer value of the character 'X' according to the collating sequence of the processor. 1 For the default character type, the only constraints on the collating sequence are the following: 2 (1) ICHAR ('A') < ICHAR ('B') < ... < ICHAR ('Z') for the twenty-six upper-case letters. 3 (2) ICHAR ('0') < ICHAR ('1') < ... < ICHAR ('9') for the ten digits. 4 (3) ICHAR (' ') < ICHAR ('0') < ICHAR ('9') < ICHAR ('A') or 5 ICHAR (' ') < ICHAR ('A') < ICHAR ('Z') < ICHAR ('0'). 6 (4) ICHAR ('a') < ICHAR ('b') < ... < ICHAR ('z') for the twenty-six lower-case letters. 7 (5) ICHAR (' ') < ICHAR ('0') < ICHAR ('9') < ICHAR ('a') or 8 ICHAR (' ') < ICHAR ('a') < ICHAR ('z') < ICHAR ('0'). 9 Except for blank, there are no constraints on the location of the special characters and underscore in 10 the collating sequence, nor is there any specified collating sequence relationship between the upper-case 11 and lower-case letters. 12 The sequence of numerical codes defined by the ASCII standard is called the ASCII collating sequence 13 in this standard. NOTE 4.16 The intrinsic functions ACHAR (13.7.2) and IACHAR (13.7.45) provide conversions between these characters and the integers according to the ASCII collating sequence. 14 The intrinsic functions LGT, LGE, LLE, and LLT (13.7.61-13.7.64) provide comparisons between strings 15 based on the ASCII collating sequence. International portability is guaranteed if the set of characters 16 used is limited to the letters, digits, underscore, and special characters. 17 4.4.5 Logical type 18 The logical type has two values, which represent true and false. 19 A processor shall provide one or more representation methods for data of type logical. Each such 20 method is characterized by a value for a type parameter called the kind type parameter. The kind type 21 parameter of a representation method is returned by the intrinsic inquiry function KIND (13.7.57). 22 The type specifier for the logical type uses the keyword LOGICAL (R503). 23 If the kind type parameter is not specified, the default kind value is KIND (.FALSE.) and the data entity 24 is of type default logical. 25 R422 logical-literal-constant is .TRUE. [ kind-param ] 26 or .FALSE. [ kind-param ] 27 C413 (R422) The value of kind-param shall specify a representation method that exists on the pro- 28 cessor. 29 The optional kind type parameter following the trailing delimiter specifies the kind type parameter of 30 the logical constant; if it is not present, the constant is of type default logical. 31 The intrinsic operations defined for data entities of logical type are: negation (.NOT.), conjunction 40 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 (.AND.), inclusive disjunction (.OR.), logical equivalence (.EQV.), and logical nonequivalence (.NEQV.) 2 as described in 7.2.4. There is also a set of intrinsically defined relational operators that compare the 3 values of data entities of other types and yield a value of type default logical. These operations are 4 described in 7.2.3. 5 4.5 Derived types 6 Additional types may be derived from the intrinsic types and other derived types. A type definition is 7 required to define the name of the type and the names and attributes of its components. 8 The type specifier for a derived type uses the keyword TYPE followed by the name of the type in 9 parentheses (R503). 10 A derived type may be parameterized by multiple type parameters, each of which is defined to be either 11 a kind or nonkind type parameter. There is no concept of a default value for a type parameter of a 12 derived type; it is required to explicitly specify, assume, or defer the values of all type parameters of a 13 derived-type entity. 14 The ultimate components of an object of derived type are the components that are of intrinsic type 15 or have the POINTER or ALLOCATABLE attribute, plus the ultimate components of the components 16 of the object that are of derived type and have neither the ALLOCATABLE nor POINTER attribute. NOTE 4.17 The ultimate components of objects of the derived type kids defined below are name, age, and other kids. type :: person character(len=20) :: name integer :: age end type person type :: kids type(person) :: oldest_child type(person), allocatable, dimension(:) :: other_kids end type kids 17 By default, no storage sequence is implied by the order of the component definitions. However, a storage 18 order is implied for a sequence type (4.5.1.9). If the derived type has the BIND attribute, the storage 19 sequence is that required by the companion processor (2.5.10, 15.2.3). 20 A derived type may have procedures bound to it. A type-bound procedure is accessible when an object 21 of the type is accessible. 22 4.5.1 Derived-type definition 23 R423 derived-type-def is derived-type-stmt 24 [ type-param-def-stmt ] ... 25 [ data-component-part ] 26 [ type-bound-procedure-part ] 27 end-type-stmt 28 R424 derived-type-stmt is TYPE [ [ , type-attr-spec-list ] :: ] type-name 29 [ ( type-param-name-list ) ] 30 R425 type-attr-spec is access-spec 31 or EXTENSIBLE SEP 2002 COMMITTEE DRAFT 41 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 or EXTENDS ( [ access-spec :: ] parent-type-name 2 [ = initialization-expr ] ) 3 or BIND (C) 4 C414 (R424) A derived type type-name shall not be the same as the name of any intrinsic type defined 5 in this standard. 6 C415 (R424) The same type-attr-spec shall not appear more than once in a given derived-type-stmt . 7 C416 (R424) EXTENSIBLE and EXTENDS shall not both appear. 8 C417 (R425) A parent-type-name shall be the name of an accessible extensible type (4.5.3). 9 C418 (R423) If EXTENDS or EXTENSIBLE appears, neither BIND(C) nor SEQUENCE shall appear. 10 R426 type-param-def-stmt is INTEGER [ kind-selector ] , type-param-attr-spec :: 11 type-param-name-list 12 C419 (R426) A type-param-name in a type-param-def-stmt in a derived-type-def shall be one of the 13 type-param-names in the derived-type-stmt of that derived-type-def . 14 C420 (R426) Each type-param-name in the derived-type-stmt in a derived-type-def shall appear as a 15 type-param-name in a type-param-def-stmt in that derived-type-def . 16 R427 type-param-attr-spec is KIND 17 or NONKIND 18 R428 data-component-part is [ private-sequence-stmt ] ... 19 [ component-def-stmt ] ... 20 R429 private-sequence-stmt is PRIVATE 21 or SEQUENCE 22 C421 (R429) A PRIVATE statement is permitted only if the type definition is within the specification 23 part of a module. 24 C422 (R428) The same private-sequence-stmt shall not appear more than once in a given derived-type- 25 def . 26 C423 (R428) If SEQUENCE appears, all derived types specified in component definitions shall be 27 sequence types. 28 C424 (R423) If SEQUENCE appears, a type-bound-procedure-part shall not appear. 29 R430 component-def-stmt is data-component-def-stmt 30 or proc-component-def-stmt 31 R431 data-component-def-stmt is declaration-type-spec [ [ , component-attr-spec-list ] :: ] 32 component-decl -list 33 R432 component-attr-spec is POINTER 34 or DIMENSION ( component-array-spec ) 35 or ALLOCATABLE 36 or access-spec 37 R433 component-decl is component-name [ ( component-array-spec ) ] 38 [ * char-length ] [ component-initialization ] 39 R434 component-array-spec is explicit-shape-spec-list 40 or deferred-shape-spec-list 41 R435 component-initialization is = initialization-expr 42 or => null-init 43 C425 (R431) No component-attr-spec shall appear more than once in a given component-def-stmt . 42 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 C426 (R431) A component declared with the CLASS keyword (5.1.1.8) shall have the ALLOCATABLE 2 or POINTER attribute. 3 C427 (R431) If the POINTER attribute is not specified for a component, the declaration-type-spec in 4 the component-def-stmt shall specify an intrinsic type or a previously defined derived type. 5 C428 (R431) If the POINTER attribute is specified for a component, the declaration-type-spec in the 6 component-def-stmt shall specify an intrinsic type or any accessible derived type including the 7 type being defined. 8 C429 (R431) If the POINTER or ALLOCATABLE attribute is specified, each component-array-spec 9 shall be a deferred-shape-spec-list. 10 C430 (R431) If neither the POINTER attribute nor the ALLOCATABLE attribute is specified, each 11 component-array-spec shall be an explicit-shape-spec-list. 12 C431 (R434) Each bound in the explicit-shape-spec shall either be an initialization expression or be a 13 specification expression that does not contain references to specification functions or any object 14 designators other than named constants or subobjects thereof. 15 C432 (R431) A component shall not have both the ALLOCATABLE and the POINTER attribute. 16 C433 (R433) The * char-length option is permitted only if the type specified is character. 17 C434 (R430) Each type-param-value within a component-def-stmt shall either be a colon, be an ini- 18 tialization expression, or be a specification expression that contains neither references to speci- 19 fication functions nor any object designators other than named constants or subobjects thereof. NOTE 4.18 Since a type parameter is not an object, a bound for an explicit-shape-spec or a type-param-value may contain a type-param-name. 20 C435 (R431) If component-initialization appears, a double-colon separator shall appear before the 21 component-decl -list. 22 C436 (R431) If => appears in component-initialization, POINTER shall appear in the component- 23 attr-spec-list. If = appears in component-initialization, POINTER or ALLOCATABLE shall 24 not appear in the component-attr-spec-list. 25 R436 proc-component-def-stmt is PROCEDURE ( [ proc-interface ] ) , 26 proc-component-attr-spec-list :: proc-decl -list NOTE 4.19 See 12.3.2.3 for definitions of proc-interface and proc-decl . 27 R437 proc-component-attr-spec is POINTER 28 or PASS [ (arg-name) ] 29 or NOPASS 30 or access-spec 31 C437 (R436) The same proc-component-attr-spec shall not appear more than once in a given proc- 32 component-def-stmt . 33 C438 (R436) POINTER shall appear in each proc-component-attr-spec-list. 34 C439 (R436) If the procedure pointer component has an implicit interface or has no arguments, SEP 2002 COMMITTEE DRAFT 43 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 NOPASS shall be specified. 2 C440 (R436) If PASS (arg-name) appears, the interface shall have a dummy argument named arg- 3 name. 4 C441 (R436) PASS and NOPASS shall not both appear in the same proc-component-attr-spec-list. 5 R438 type-bound-procedure-part is contains-stmt 6 [ binding-private-stmt ] 7 proc-binding-stmt 8 [ proc-binding-stmt ] ... 9 R439 binding-private-stmt is PRIVATE 10 C442 (R438) A binding-private-stmt is permitted only if the type definition is within the specification 11 part of a module. 12 R440 proc-binding-stmt is specific-binding 13 or generic-binding 14 or final-binding 15 C443 (R440) No proc-binding-stmt shall specify a binding that overrides (4.5.3.2) one that is inherited 16 (4.5.3.1) from the parent type and has the NON OVERRIDABLE binding attribute. 17 R441 specific-binding is PROCEDURE 18 [ [ , binding-attr -list ] :: ] binding-name [ => binding ] 19 C444 (R441) If => binding appears, the double-colon separator shall appear. 20 If => binding does not appear, it is as though it had appeared with a procedure name the same as the 21 binding name. 22 R442 generic-binding is GENERIC 23 [, binding-attr -list ] :: generic-spec => binding-list 24 C445 (R442) If generic-spec is generic-name, generic-name shall not be the name of a nongeneric 25 binding of the type. 26 C446 (R442) If generic-spec is OPERATOR ( defined-operator ), the interface of each binding shall 27 be as specified in 12.3.2.1.1. 28 C447 (R442) If generic-spec is ASSIGNMENT ( = ), the interface of each binding shall be as specified 29 in 12.3.2.1.2. 30 C448 (R442) If generic-spec is dtio-generic-spec, the interface of each binding shall be as specified in 31 9.5.3.7. The type of the dtv argument shall be type-name. 32 R443 final-binding is FINAL [ :: ] final-subroutine-name-list 33 C449 (R443) A final-subroutine-name shall be the name of a module procedure with exactly one 34 dummy argument. That argument shall be nonoptional and shall be a nonpointer, nonallocat- 35 able, nonpolymorphic variable of the derived type being defined. All nonkind type parameters 36 of the dummy argument shall be assumed. The dummy argument shall not be INTENT(OUT). 37 C450 (R443) A final-subroutine-name shall not be one previously specified as a final subroutine for 38 that type. 39 C451 (R443) A final subroutine shall not have a dummy argument with the same kind type parameters 40 and rank as the dummy argument of another final subroutine of that type. 44 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 R444 binding-attr is PASS [ (arg-name) ] 2 or NOPASS 3 or NON OVERRIDABLE 4 or access-spec 5 C452 (R444) The same binding-attr shall not appear more than once in a given binding-attr -list. 6 C453 (R441, R442) If the interface of the binding has no dummy argument of the type being defined, 7 NOPASS shall appear. 8 C454 (R441, R442) If PASS (arg-name) appears, the interface of the binding shall have a dummy 9 argument named arg-name. 10 C455 (R440) PASS and NOPASS shall not both appear in the same binding-attr -list. 11 C456 (R442) A generic-binding for which generic-spec is not generic-name shall have a passed-object 12 dummy argument (4.5.1.6). 13 C457 (R442) An overriding binding shall have a passed-object dummy argument if and only if the 14 binding that it overrides has a passed-object dummy argument. 15 C458 (R442) Within the specification-part of a module, each generic-binding shall specify, either 16 implicitly or explicitly, the same accessibility as every other generic-binding in the same derived- 17 type-def that has the same generic-spec. 18 R445 binding is procedure-name 19 C459 (R445) The procedure-name shall be the name of an accessible module procedure or an external 20 procedure that has an explicit interface. 21 R446 end-type-stmt is END TYPE [ type-name ] 22 C460 (R446) If END TYPE is followed by a type-name, the type-name shall be the same as that in 23 the corresponding derived-type-stmt . 24 Derived types with the BIND attribute are subject to additional constraints as specified in 15.2.3. NOTE 4.20 An example of a derived-type definition is: TYPE PERSON INTEGER AGE CHARACTER (LEN = 50) NAME END TYPE PERSON An example of declaring a variable CHAIRMAN of type PERSON is: TYPE (PERSON) :: CHAIRMAN 25 4.5.1.1 Derived-type parameters 26 The derived type is parameterized if the derived-type-stmt has any type-param-names. 27 Each type parameter is itself of type integer. 28 A type parameter is either a kind type parameter or a nonkind type parameter (4.2). If it is a kind 29 parameter it is said to have the KIND attribute. Its type-param-attr-spec explicitly specifies whether a SEP 2002 COMMITTEE DRAFT 45 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 type parameter is kind or nonkind. 2 A type parameter may be used as a primary in a specification expression (7.1.6) in the derived-type- 3 def . A kind type parameter may also be used as a primary in an initialization expression (7.1.7) in the 4 derived-type-def . NOTE 4.21 The following example uses derived-type parameters. TYPE humongous_matrix(k, d) INTEGER, KIND :: k INTEGER(selected_int_kind(12)), NONKIND :: d !-- Specify a nondefault kind for d. REAL(k) :: element(d,d) END TYPE In the following example, dim is declared to be a kind parameter, allowing generic overloading of procedures distinguished only by dim. TYPE general_point(dim) INTEGER, KIND :: dim REAL :: coordinates(dim) END TYPE 5 4.5.1.2 Default initialization for components 6 Default initialization provides a means of automatically initializing pointer components to be disas- 7 sociated (4.5.1.4), and nonpointer nonallocatable components to have a particular value. Allocatable 8 components are always initialized to not allocated. 9 If initialization-expr appears for a nonpointer component, that component in any object of the type 10 is initially defined (16.5.3) or becomes defined as specified in 16.5.5 with the value determined from 11 initialization-expr . An initialization-expr in the EXTENDS type-attr-spec is for the parent component 12 (4.5.3.1). If necessary, the value is converted according to the rules of intrinsic assignment (7.4.1.3) to 13 a value that agrees in type, type parameters, and shape with the component. If the component is of a 14 type for which default initialization is specified for a component, the default initialization specified by 15 initialization-expr overrides the default initialization specified for that component. When one initializa- 16 tion overrides another it is as if only the overriding initialization were specified (see Note 4.23). Explicit 17 initialization in a type declaration statement (5.1) overrides default initialization (see Note 4.22). Unlike 18 explicit initialization, default initialization does not imply that the object has the SAVE attribute. 19 A subcomponent (6.1.2) is default-initialized if the type of the object of which it is a component 20 specifies default initialization for that component, and the subcomponent is not a subobject of an object 21 that is default-initialized or explicitly initialized. NOTE 4.22 It is not required that initialization be specified for each component of a derived type. For example: TYPE DATE INTEGER DAY CHARACTER (LEN = 5) MONTH 46 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 4.22 (cont.) INTEGER :: YEAR = 1994 ! Partial default initialization END TYPE DATE In the following example, the default initial value for the YEAR component of TODAY is overridden by explicit initialization in the type declaration statement: TYPE (DATE), PARAMETER :: TODAY = DATE (21, "Feb.", 1995) NOTE 4.23 The default initial value of a component of derived type may be overridden by default initialization specified in the definition of the type. Continuing the example of Note 4.22: TYPE SINGLE_SCORE TYPE(DATE) :: PLAY_DAY = TODAY INTEGER SCORE TYPE(SINGLE_SCORE), POINTER :: NEXT => NULL ( ) END TYPE SINGLE_SCORE TYPE(SINGLE_SCORE) SETUP The PLAY DAY component of SETUP receives its initial value from TODAY, overriding the initialization for the YEAR component. NOTE 4.24 Arrays of structures may be declared with elements that are partially or totally initialized by default. Continuing the example of Note 4.23 : TYPE MEMBER (NAME_LEN) INTEGER, NONKIND :: NAME_LEN CHARACTER (LEN = NAME_LEN) NAME = '' INTEGER :: TEAM_NO, HANDICAP = 0 TYPE (SINGLE_SCORE), POINTER :: HISTORY => NULL ( ) END TYPE MEMBER TYPE (MEMBER) LEAGUE (36) ! Array of partially initialized elements TYPE (MEMBER) :: ORGANIZER = MEMBER ("I. Manage",1,5,NULL ( )) ORGANIZER is explicitly initialized, overriding the default initialization for an object of type MEMBER. Allocated objects may also be initialized partially or totally. For example: ALLOCATE (ORGANIZER % HISTORY) ! A partially initialized object of type ! SINGLE_SCORE is created. 1 4.5.1.3 Array components 2 A data component is an array if its component-decl contains a component-array-spec or its data-component- 3 def-stmt contains the DIMENSION attribute. If the component-decl contains a component-array-spec, 4 it specifies the array rank, and if the array is explicit shape (5.1.2.5.1), the array bounds; otherwise, the 5 component-array-spec in the DIMENSION attribute specifies the array rank, and if the array is explicit 6 shape, the array bounds. SEP 2002 COMMITTEE DRAFT 47 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 4.25 A type definition may have a component that is an array. For example: TYPE LINE REAL, DIMENSION (2, 2) :: COORD ! ! COORD(:,1) has the value of (/X1, Y1/) ! COORD(:,2) has the value of (/X2, Y2/) REAL :: WIDTH ! Line width in centimeters INTEGER :: PATTERN ! 1 for solid, 2 for dash, 3 for dot END TYPE LINE An example of declaring a variable LINE SEGMENT to be of the type LINE is: TYPE (LINE) :: LINE_SEGMENT The scalar variable LINE SEGMENT has a component that is an array. In this case, the array is a subobject of a scalar. The double colon in the definition for COORD is required; the double colon in the definition for WIDTH and PATTERN is optional. NOTE 4.26 A derived type may have a component that is allocatable. For example: TYPE STACK INTEGER :: INDEX INTEGER, ALLOCATABLE :: CONTENTS (:) END TYPE STACK For each scalar variable of type STACK, the shape of the component CONTENTS is determined by execution of an ALLOCATE statement or assignment statement, or by argument association. NOTE 4.27 Default initialization of an explicit-shape array component may be specified by an initialization expression consisting of an array constructor (4.8), or of a single scalar that becomes the value of each array element. 1 4.5.1.4 Pointer components 2 A component is a pointer if its component-attr-spec-list contains the POINTER attribute. Pointers have 3 an association status of associated, disassociated, or undefined. If no default initialization is specified, the 4 initial association status is undefined. To specify that the default initial status of a pointer component is 5 to be disassociated, the pointer assignment symbol (=>) shall be followed by a reference to the intrinsic 6 function NULL ( ) with no argument. No mechanism is provided to specify a default initial status of 7 associated. NOTE 4.28 A derived type may have a component that is a pointer. For example: TYPE REFERENCE INTEGER :: VOLUME, YEAR, PAGE CHARACTER (LEN = 50) :: TITLE 48 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 4.28 (cont.) CHARACTER, DIMENSION (:), POINTER :: ABSTRACT => NULL() END TYPE REFERENCE Any object of type REFERENCE will have the four nonpointer components VOLUME, YEAR, PAGE, and TITLE, plus a pointer to an array of characters holding ABSTRACT. The size of this target array will be determined by the length of the abstract. The space for the target may be allocated (6.3.1) or the pointer component may be associated with a target by a pointer assignment statement (7.4.2). NOTE 4.29 A pointer component of a derived type may have as its target an object of that derived type. The type definition may specify that in objects declared to be of this type, such a pointer is default initialized to disassociated. For example: TYPE NODE INTEGER :: VALUE = 0 TYPE (NODE), POINTER :: NEXT_NODE => NULL ( ) END TYPE A type such as this may be used to construct linked lists of objects of type NODE. See C.1.4 for an example. 1 4.5.1.5 Type-bound procedures 2 Each binding in a proc-binding-stmt specifies a type-bound procedure. A generic-binding specifies a 3 type-bound generic interface. 4 The interface of a binding is that of the procedure specified by procedure-name. NOTE 4.30 An example of a type and a type-bound procedure is: TYPE, EXTENSIBLE :: POINT REAL :: X, Y CONTAINS PROCEDURE, PASS :: LENGTH => POINT_LENGTH END TYPE POINT ... and in the module-subprogram-part of the same module: REAL FUNCTION POINT_LENGTH (A, B) CLASS (POINT), INTENT (IN) :: A, B POINT_LENGTH = SQRT ( (A%X - B%X)**2 + (A%Y - B%Y)**2 ) END FUNCTION POINT_LENGTH 5 The same generic-spec may be used in several generic-bindings within a single derived-type definition. SEP 2002 COMMITTEE DRAFT 49 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 4.5.1.6 The passed-object dummy argument 2 A passed-object dummy argument is a distinguished dummy argument of a procedure pointer 3 component or type-bound procedure. It affects procedure overriding (4.5.3.2) and argument association 4 (12.4.1.1). 5 If NOPASS is specified, the procedure pointer component or type-bound procedure has no passed-object 6 dummy argument. 7 If neither PASS nor NOPASS is specified or PASS is specified without arg-name, the first dummy argu- 8 ment of a procedure pointer component or type-bound procedure is its passed-object dummy argument. 9 If PASS (arg-name) is specified, the dummy argument named arg-name is the passed-object dummy 10 argument of the procedure pointer component or named type-bound procedure. 11 C461 The passed-object dummy argument shall be a scalar, nonpointer, nonallocatable dummy data 12 object with the same declared type as the type being defined; all of its nonkind type parameters 13 shall be assumed; it shall be polymorphic if and only if the type being defined is extensible. NOTE 4.31 If a procedure is bound to several types as a type-bound procedure, different dummy arguments might be the passed-object dummy argument in different contexts. 14 4.5.1.7 Final subroutines 15 The FINAL keyword specifies a list of final subroutines. A final subroutine might be executed when 16 a data entity of that type is finalized (4.5.10). 17 A derived type is finalizable if it has any final subroutines or if it has any nonpointer, nonallocatable 18 component whose type is finalizable. A nonpointer data entity is finalizable if its type is finalizable. NOTE 4.32 Final subroutines are effectively always "accessible". They are called for entity finalization regard- less of the accessibility of the type, its other type-bound procedure bindings, or the subroutine name itself. NOTE 4.33 Final subroutines are not inherited through type extension and cannot be overridden. The final subroutines of the parent type are called after calling any additional final subroutines of an extended type. 19 4.5.1.8 Accessibility 20 By default, the names of derived types defined in the specification part of a module are accessible 21 (5.1.2.1, 5.2.1) in any scoping unit that accesses the module. This default may be changed to restrict 22 the accessibility of such type names to the host module itself. The name of a particular derived type 23 may be declared to be public or private regardless of the default accessibility declared for the module. 24 In addition, a type name may be accessible while some or all of its components are private. 25 The accessibility of a derived type name may be declared explicitly by an access-spec in its derived-type- 26 stmt or in an access-stmt (5.2.1). The accessibility is the default if it is not declared explicitly. If a type 27 definition is private, then the type name, and thus the structure constructor (4.5.8) for the type, are 28 accessible only within the module containing the definition. 29 The default accessibility for the components of a type is private if the data-component-part contains a 50 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 PRIVATE statement, and public otherwise. The default accessibility for the procedure bindings of a 2 type is private if the type-bound-procedure-part contains a PRIVATE statement, and public otherwise. 3 The accessibility of a component or procedure binding may be explicitly declared by an access-spec; 4 otherwise its accessibility is the default for the type definition in which it is declared. 5 If a component is private, that component name is accessible only within the module containing the 6 definition. NOTE 4.34 Type parameters are not components. They are effectively always public. 7 A public type-bound procedure is accessible via any accessible object of the type. A private type-bound 8 procedure is accessible only within the module containing the type definition. NOTE 4.35 The accessibility of a type-bound procedure is not affected by a PRIVATE statement in the data- component-part ; the accessibility of a data component is not affected by a PRIVATE statement in the type-bound-procedure-part . NOTE 4.36 The accessibility of the components of a type is independent of the accessibility of the type name. It is possible to have all four combinations: a public type name with a public component, a private type name with a private component, a public type name with a private component, and a private type name with a public component. NOTE 4.37 An example of a type with private components is: MODULE DEFINITIONS TYPE POINT PRIVATE REAL :: X, Y END TYPE POINT END MODULE DEFINITIONS Such a type definition is accessible in any scoping unit accessing the module via a USE statement; however, the components X and Y are accessible only within the module. NOTE 4.38 An example of a type with a private name is: TYPE, PRIVATE :: AUXILIARY LOGICAL :: DIAGNOSTIC CHARACTER (LEN = 20) :: MESSAGE END TYPE AUXILIARY Such a type would be accessible only within the module in which it is defined. SEP 2002 COMMITTEE DRAFT 51 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 4.39 The following example illustrates the use of an individual component access-spec to override the default accessibility: TYPE MIXED PRIVATE INTEGER :: I INTEGER, PUBLIC :: J END TYPE MIXED TYPE (MIXED) :: M The component M%J is accessible in any scoping unit where M is accessible; M%I is accessible only within the module containing the TYPE MIXED definition. 1 4.5.1.9 Sequence type 2 If the SEQUENCE statement is present, the type is a sequence type. The order of the component 3 definitions in a sequence type specifies a storage sequence for objects of that type. If there are no type 4 parameters and all of the ultimate components of objects of the type are of type default integer, default 5 real, double precision real, default complex, or default logical and are not pointers or allocatable, the 6 type is a numeric sequence type. If there are no type parameters and all of the ultimate components 7 of objects of the type are of type default character and are not pointers or allocatable, the type is a 8 character sequence type. NOTE 4.40 An example of a numeric sequence type is: TYPE NUMERIC_SEQ SEQUENCE INTEGER :: INT_VAL REAL :: REAL_VAL LOGICAL :: LOG_VAL END TYPE NUMERIC_SEQ NOTE 4.41 A structure resolves into a sequence of components. Unless the structure includes a SEQUENCE statement, the use of this terminology in no way implies that these components are stored in this, or any other, order. Nor is there any requirement that contiguous storage be used. The sequence merely refers to the fact that in writing the definitions there will necessarily be an order in which the components appear, and this will define a sequence of components. This order is of limited significance since a component of an object of derived type will always be accessed by a component name except in the following contexts: the sequence of expressions in a derived-type value constructor, intrinsic assignment, the data values in namelist input data, and the inclusion of the structure in an input/output list of a formatted data transfer, where it is expanded to this sequence of components. Provided the processor adheres to the defined order in these cases, it is otherwise free to organize the storage of the components for any nonsequence structure in memory as best suited to the particular architecture. 52 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 4.5.2 Determination of derived types 2 Derived-type definitions with the same type name may appear in different scoping units, in which case 3 they may be independent and describe different derived types or they may describe the same type. 4 Two data entities have the same type if they are declared with reference to the same derived-type 5 definition. The definition may be accessed from a module or from a host scoping unit. Data entities in 6 different scoping units also have the same type if they are declared with reference to different derived-type 7 definitions that specify the same type name, all have the SEQUENCE property or all have the BIND 8 attribute, have no components with PRIVATE accessibility, and have type parameters and components 9 that agree in order, name, and attributes. Otherwise, they are of different derived types. A data entity 10 declared using a type with the SEQUENCE property or with the BIND attribute is not of the same type 11 as an entity of a type declared to be PRIVATE or that has any components that are PRIVATE. NOTE 4.42 An example of declaring two entities with reference to the same derived-type definition is: TYPE POINT REAL X, Y END TYPE POINT TYPE (POINT) :: X1 CALL SUB (X1) ... CONTAINS SUBROUTINE SUB (A) TYPE (POINT) :: A ... END SUBROUTINE SUB The definition of derived type POINT is known in subroutine SUB by host association. Because the declarations of X1 and A both reference the same derived-type definition, X1 and A have the same type. X1 and A also would have the same type if the derived-type definition were in a module and both SUB and its containing program unit accessed the module. NOTE 4.43 An example of data entities in different scoping units having the same type is: PROGRAM PGM TYPE EMPLOYEE SEQUENCE INTEGER ID_NUMBER CHARACTER (50) NAME END TYPE EMPLOYEE TYPE (EMPLOYEE) PROGRAMMER CALL SUB (PROGRAMMER) ... END PROGRAM PGM SUBROUTINE SUB (POSITION) TYPE EMPLOYEE SEQUENCE INTEGER ID_NUMBER CHARACTER (50) NAME SEP 2002 COMMITTEE DRAFT 53 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 4.43 (cont.) END TYPE EMPLOYEE TYPE (EMPLOYEE) POSITION ... END SUBROUTINE SUB The actual argument PROGRAMMER and the dummy argument POSITION have the same type because they are declared with reference to a derived-type definition with the same name, the SEQUENCE property, and components that agree in order, name, and attributes. Suppose the component name ID NUMBER was ID NUM in the subroutine. Because all the component names are not identical to the component names in derived type EMPLOYEE in the main program, the actual argument PROGRAMMER would not be of the same type as the dummy argument POSITION. Thus, the program would not be standard conforming. NOTE 4.44 The requirement that the two types have the same name applies to the type-names of the respective derived-type-stmt s, not to type-alias names or to local names introduced via renaming in USE statements. 1 4.5.3 Extensible types 2 A derived type that has the EXTENSIBLE or EXTENDS attribute is an extensible type. 3 A type that has the EXTENSIBLE attribute is a base type. A type that has the EXTENDS attribute 4 is an extended type. The parent type of an extended type is the type named in the EXTENDS 5 attribute specification. NOTE 4.45 The name of the parent type might be a type-alias name or a local name introduced via renaming in a USE statement. 6 A base type is an extension type of itself only. An extended type is an extension of itself and of all 7 types for which its parent type is an extension. 8 4.5.3.1 Inheritance 9 An extended type includes all of the type parameters, components, and nonfinal procedure bindings of 10 its parent type. These are said to be inherited by the extended type from the parent type. They retain 11 all of the attributes that they had in the parent type. Additional type parameters, components, and 12 procedure bindings may be declared in the derived-type definition of the extended type. NOTE 4.46 Inaccessible components and bindings of the parent type are also inherited, but they remain inac- cessible in the extended type. Inaccessible entities occur if the type being extended is accessed via use association and has a private entity. NOTE 4.47 A base type is not required to have any components, bindings, or parameters; an extended type is not required to have more components, bindings, or parameters than its parent type. 13 An object of extended type has a scalar, nonpointer, nonallocatable, parent component with the 54 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 type and type parameters of the parent type. The name of this component is the parent type name. 2 Components of the parent component are inheritance associated (16.4.4) with the corresponding 3 components inherited from the parent type. NOTE 4.48 A component or type parameter declared in an extended type shall not have the same name as any accessible component or type parameter of its parent type. NOTE 4.49 Examples: TYPE, EXTENSIBLE :: POINT ! A base type REAL :: X, Y END TYPE POINT TYPE, EXTENDS(POINT) :: COLOR_POINT ! An extension of TYPE(POINT) ! Components X and Y, and component name POINT, inherited from parent INTEGER :: COLOR END TYPE COLOR_POINT 4 4.5.3.2 Type-bound procedure overriding 5 If a specific binding specified in a type definition has the same binding name as a binding inherited from 6 the parent type then the binding specified in the type definition overrides the one inherited from the 7 parent type. 8 The overriding binding and the inherited binding shall satisfy the following conditions: 9 (1) Either both shall have a passed-object dummy argument or neither shall. 10 (2) If the inherited binding is pure then the overriding binding shall also be pure. 11 (3) Either both shall be elemental or neither shall. 12 (4) They shall have the same number of dummy arguments. 13 (5) Passed-object dummy arguments, if any, shall correspond by name and position. 14 (6) Dummy arguments that correspond by position shall have the same names and characteris- 15 tics, except for the type of the passed-object dummy arguments. 16 (7) Either both shall be subroutines or both shall be functions having the same result charac- 17 teristics (12.2.2). 18 (8) If the inherited binding is PUBLIC then the overriding binding shall not be PRIVATE. NOTE 4.50 The following is an example of procedure overriding, expanding on the example in Note 4.30. TYPE, EXTENDS (POINT) :: POINT_3D REAL :: Z CONTAINS PROCEDURE, PASS :: LENGTH => POINT_3D_LENGTH END TYPE POINT_3D ... and in the module-subprogram-part of the same module: SEP 2002 COMMITTEE DRAFT 55 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 4.50 (cont.) REAL FUNCTION POINT_3D_LENGTH ( A, B ) CLASS (POINT_3D), INTENT (IN) :: A CLASS (POINT), INTENT (IN) :: B IF ( EXTENDS_TYPE_OF(B, A) ) THEN POINT_3D_LENGTH = SQRT( (A%X-B%X)**2 + (A%Y-B%Y)**2 + (A%Z-B%Z)**2 ) RETURN END IF PRINT *, 'In POINT_3D_LENGTH, dynamic type of argument is incorrect.' STOP END FUNCTION POINT_3D 1 A generic binding overrides an inherited binding if they both have the same generic-spec and satisfy the 2 above conditions for overriding. A generic binding with the same generic-spec that does not satisfy the 3 conditions extends the generic interface; it shall satisfy the requirements specified in 16.2.3. 4 If a generic binding in a type definition has the same dtio-generic-spec as one inherited from the parent, 5 and the dtv argument of the procedure it specifies has the same kind type parameters as the dtv argument 6 of one inherited from the parent type, then the binding specified in the type overrides the one inherited 7 from the parent type. Otherwise, it extends the type-bound generic interface for the dtio-generic-spec. 8 A binding of a type and a binding of an extension of that type are said to correspond if the latter binding 9 is the same binding as the former, overrides a corresponding binding, or is an inherited corresponding 10 binding. 11 A binding that has the NON OVERRIDABLE attribute in the parent type shall not be overridden. 12 4.5.4 Component order 13 Component order is an ordering of the nonparent components of a derived type; it is used for intrinsic 14 formatted input/output and structure constructors (where component keywords are not used). Parent 15 components are excluded from the component order of an extensible type. 16 The component order of a nonextended type is the order of the declarations of the components in the 17 derived-type definition. The component order of an extended type consists of the component order of 18 its parent type followed by any additional components in the order of their declarations in the extended 19 derived-type definition. 20 4.5.5 Type parameter order 21 Type parameter order is an ordering of the type parameters of a derived type; it is used for derived- 22 type specifiers. 23 The type parameter order of a nonextended type is the order of the type parameter list in the derived- 24 type definition. The type parameter order of an extended type consists of the type parameter order of 25 its parent type followed by any additional type parameters in the order of the type parameter list in the 26 derived-type definition. 27 4.5.6 Derived-type values 28 The set of values of a particular derived type consists of all possible sequences of component values 29 consistent with the definition of that derived type. 56 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 4.5.7 Derived-type specifier 2 A derived-type specifier is used in several contexts to specify a particular derived type and type param- 3 eters. 4 R447 derived-type-spec is type-name [ ( type-param-spec-list ) ] 5 or type-alias-name 6 R448 type-param-spec is [ keyword = ] type-param-value 7 C462 (R447) type-name shall be the name of an accessible derived type. 8 C463 (R447) type-alias-name shall be the name of an accessible type alias that is an alias for a derived 9 type. 10 C464 (R447) type-param-spec-list shall appear if and only if the type is parameterized. 11 C465 (R447) There shall be exactly one type-param-spec corresponding to each parameter of the type. 12 C466 (R448) The keyword = may be omitted from a type-param-spec only if the keyword = has been 13 omitted from each preceding type-param-spec in the type-param-spec-list. 14 C467 (R448) Each keyword shall be the name of a parameter of the type. 15 C468 (R448) An asterisk may be used as a type-param-value in a type-param-spec only in the decla- 16 ration or allocation of a dummy argument. 17 Type parameter values that do not have type parameter keywords specified correspond to type param- 18 eters in type parameter order (4.5.5). If a type parameter keyword is present, the value is assigned to 19 the type parameter named by the keyword. If necessary, the value is converted according to the rules of 20 intrinsic assignment (7.4.1.3) to a value of the same kind as the type parameter. 21 4.5.8 Construction of derived-type values 22 A derived-type definition implicitly defines a corresponding structure constructor that allows con- 23 struction of values of that derived type. The type and type parameters of a constructed value are 24 specified by a derived type specifier. 25 R449 structure-constructor is derived-type-spec ( [ component-spec-list ] ) 26 R450 component-spec is [ keyword = ] component-data-source 27 R451 component-data-source is expr 28 or data-target 29 or proc-target 30 C469 (R449) At most one component-spec shall be provided for a component. 31 C470 (R449) If a component-spec is be provided for a component, no component-spec shall be provided 32 for any component with which it is inheritance associated. 33 C471 (R449) A component-spec shall be provided for a component unless it has default initialization 34 or is inheritance associated with another component for which a component-spec is provided or 35 that has default initialization. 36 C472 (R450) The keyword = may be omitted from a component-spec only if the keyword = has been 37 omitted from each preceding component-spec in the constructor. 38 C473 (R450) Each keyword shall be the name of a component of the type. 39 C474 (R449) The type name and all components of the type for which a component-spec appears shall SEP 2002 COMMITTEE DRAFT 57 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 be accessible in the scoping unit containing the structure constructor. 2 C475 (R449) If derived-type-spec is a type name that is the same as a generic name, the component- 3 spec-list shall not be a valid actual-arg-spec-list for a function reference that is resolvable as a 4 generic reference (12.4.4.1). 5 C476 (R451) A data-target shall correspond to a nonprocedure pointer component; a proc-target shall 6 correspond to a procedure pointer component. 7 C477 (R451) A data-target shall have the same rank as its corresponding component. NOTE 4.51 The form 'name(...)' is interpreted as a generic function-reference if possible; it is interpreted as a structure-constructor only if it cannot be interpreted as a generic function-reference. 8 In the absence of a component keyword, each component-data-source is assigned to the corresponding 9 component in component order (4.5.4). If a component keyword is present, the expr is assigned to 10 the component named by the keyword. If necessary, each value is converted according to the rules of 11 intrinsic assignment (7.4.1.3) to a value that agrees in type and type parameters with the corresponding 12 component of the derived type. For nonpointer nonallocatable components, the shape of the expression 13 shall conform with the shape of the component. 14 If a component with default initialization has no corresponding component-data-source, then the default 15 initialization is applied to that component. NOTE 4.52 Because no parent components appear in the defined component ordering, a value for a parent component may be specified only with a component keyword. Examples of equivalent values using types defined in Note 4.49: ! Create values with components x = 1.0, y = 2.0, color = 3. TYPE(POINT) :: PV = POINT(1.0, 2.0) ! Assume components of TYPE(POINT) ! are accessible here. ... COLOR_POINT( point=point(1,2), color=3) ! Value for parent component COLOR_POINT( point=PV, color=3) ! Available even if TYPE(point) ! has private components COLOR_POINT( 1, 2, 3) ! All components of TYPE(point) ! need to be accessible. 16 A structure constructor shall not appear before the referenced type is defined. NOTE 4.53 This example illustrates a derived-type constant expression using a derived type defined in Note 4.20: PERSON (21, 'JOHN SMITH') This could also be written as PERSON (NAME = 'JOHN SMITH', AGE = 21) 58 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 4.54 An example constructor using the derived type GENERAL POINT defined in Note 4.21 is general_point(dim=3) ( (/ 1., 2., 3. /) ) 1 A derived-type definition may have a component that is an array. Also, an object may be an array of 2 derived type. Such arrays may be constructed using an array constructor (4.8). 3 Where a component in the derived type is a pointer, the corresponding component-data-source shall be 4 an allowable data-target or proc-target for such a pointer in a pointer assignment statement (7.4.2). NOTE 4.55 For example, if the variable TEXT were declared (5.1) to be CHARACTER, DIMENSION (1:400), TARGET :: TEXT and BIBLIO were declared using the derived-type definition REFERENCE in Note 4.28 TYPE (REFERENCE) :: BIBLIO the statement BIBLIO = REFERENCE (1, 1987, 1, "This is the title of the referenced & &paper", TEXT) is valid and associates the pointer component ABSTRACT of the object BIBLIO with the target object TEXT. 5 If a component of a derived type is allocatable, the corresponding constructor expression shall either be a 6 reference to the intrinsic function NULL with no arguments, an allocatable entity, or shall evaluate to an 7 entity of the same rank. If the expression is a reference to the intrinsic function NULL, the corresponding 8 component of the constructor has a status of unallocated. If the expression is an allocatable entity, the 9 corresponding component of the constructor has the same allocation status as that allocatable entity 10 and, if it is allocated, the same bounds (if any) and value. Otherwise the corresponding component of 11 the constructor has an allocation status of allocated and has the same bounds (if any) and value as the 12 expression. NOTE 4.56 When the constructor is an actual argument, the allocation status of the allocatable component is available through the associated dummy argument. 13 4.5.9 Derived-type operations and assignment 14 Intrinsic assignment of derived-type entities is described in 7.4.1. This standard does not specify any 15 intrinsic operations on derived-type entities. Any operation on derived-type entities or defined assign- 16 ment (7.4.1.4) for derived-type entities shall be defined explicitly by a function or a subroutine, and a 17 generic interface (4.5.1, 12.3.2.1). 18 4.5.10 The finalization process 19 Only finalizable entities are finalized. When an entity is finalized, the following steps are carried out 20 in sequence: SEP 2002 COMMITTEE DRAFT 59 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 (1) If the dynamic type of the entity has a final subroutine whose dummy argument has the 2 same kind type parameters and rank as the entity being finalized, it is called with the entity 3 as an actual argument. Otherwise, if there is an elemental final subroutine whose dummy 4 argument has the same kind type parameters as the entity being finalized, it is called with 5 the entity as an actual argument. Otherwise, no subroutine is called at this point. 6 (2) Each finalizable component that appears in the type definition is finalized. If the entity 7 being finalized is an array, each finalizable component of each element of that entity is 8 finalized separately. 9 (3) If the entity is of extended type and the parent type is finalizable, the parent component is 10 finalized. 11 If several entities are to be finalized as a consequence of an event specified in 4.5.10.1, the order in which 12 they are finalized is processor-dependent. A final subroutine shall not reference or define an object that 13 has already been finalized. 14 4.5.10.1 When finalization occurs 15 The target of a pointer is finalized when the pointer is deallocated. An allocatable entity is finalized 16 when it is deallocated. 17 A nonpointer, nonallocatable object that is not a dummy argument or function result is finalized im- 18 mediately before it would become undefined due to execution of a RETURN or END statement (16.5.6, 19 item (3)). If the object is defined in a module and there are no longer any active procedures referencing 20 the module, it is processor-dependent whether it is finalized. If the object is not finalized, it retains its 21 definition status and does not become undefined. 22 If an executable construct references a function, the result is finalized after execution of the innermost 23 executable construct containing the reference. 24 If an executable construct references a structure constructor, the entity created by the structure con- 25 structor is finalized after execution of the innermost executable construct containing the reference. 26 If a specification expression in a scoping unit references a function, the result is finalized before execution 27 of the first executable statement in the scoping unit. 28 When a procedure is invoked, a nonpointer, nonallocatable object that is an actual argument associated 29 with an INTENT(OUT) dummy argument is finalized. 30 When an intrinsic assignment statement is executed, variable is finalized after evaluation of expr and 31 before the definition of variable. NOTE 4.57 If finalization is used for storage management, it often needs to be combined with defined assign- ment. 32 If an object is allocated via pointer allocation and later becomes unreachable due to all pointers to that 33 object having their pointer association status changed, it is processor dependent whether it is finalized. 34 If it is finalized, it is processor dependent as to when the final subroutines are called. 35 4.5.10.2 Entities that are not finalized 36 If program execution is terminated, either by an error (e.g. an allocation failure) or by execution of 37 a STOP or END PROGRAM statement, entities existing immediately prior to termination are not 38 finalized. 60 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 4.58 A nonpointer, nonallocatable object that has the SAVE attribute or which occurs in the main pro- gram is never finalized as a direct consequence of the execution of a RETURN or END statement. A variable in a module is not finalized if it retains its definition status and value, even when there is no active procedure referencing the module. 1 4.6 Type aliases 2 Type aliasing provides a method of data abstraction. A type alias is an entity that may be used to 3 declare entities of an existing type; it is not a new type. The name of a type alias for a derived type 4 may also be used in the derived-type-spec of a structure-constructor . 5 R452 type-alias-stmt is TYPEALIAS :: type-alias-list 6 R453 type-alias is type-alias-name => declaration-type-spec 7 C478 (R453) A type-alias-name shall not be the same as the name of any intrinsic type defined in this 8 standard. 9 C479 (R453) A declaration-type-spec in a type-alias shall not use the CLASS keyword. 10 C480 (R453) A declaration-type-spec shall specify an intrinsic type or a previously defined derived 11 type. Each type-param-value shall be an initialization expression. 12 Explicit or implicit declaration of an entity or component using a type alias name has the same effect 13 as using the declaration-type-spec for which it is an alias. NOTE 4.59 The declarations for X, Y, and S TYPEALIAS :: DOUBLECOMPLEX => COMPLEX(KIND(1.0D0)), & NEWTYPE => TYPE(DERIVED), & ANOTHERTYPE => TYPE(NEWTYPE) TYPE(DOUBLECOMPLEX) :: X, Y TYPE(NEWTYPE) :: S TYPE(ANOTHERTYPE) :: T are equivalent to the declarations COMPLEX(KIND(1.0D0)) :: X, Y TYPE(DERIVED) :: S, T 14 4.7 Enumerations and enumerators 15 An enumeration is a type alias for an integer type. An enumerator is a named integer constant. An 16 enumeration definition specifies the enumeration and a set of enumerators of the corresponding integer 17 kind. 18 R454 enum-alias-def is enum-def-stmt 19 enumerator-def-stmt 20 [ enumerator-def-stmt ] ... 21 end-enum-stmt 22 R455 enum-def-stmt is ENUM, BIND(C) :: type-alias-name SEP 2002 COMMITTEE DRAFT 61 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 or ENUM [ kind-selector ] [ :: ] type-alias-name 2 R456 enumerator-def-stmt is ENUMERATOR [ :: ] enumerator -list 3 R457 enumerator is named-constant [ = scalar-int-initialization-expr ] 4 R458 end-enum-stmt is END ENUM [ type-alias-name ] 5 C481 (R456) If = appears in an enumerator , a double-colon separator shall appear before the enu- 6 merator -list. 7 C482 (R458) If END ENUM is followed by a type-alias-name, the type-alias-name shall be the same 8 as that in the corresponding enum-def-stmt . 9 The type-alias-name of an enumeration is treated as if it were explicitly declared in a type alias statement 10 as a type alias for an integer whose kind parameter is determined as follows: 11 (1) If BIND(C) is specified, the kind is selected such that an integer type with that kind is 12 interoperable (15.2.1) with the corresponding C enumeration type. The corresponding C 13 enumeration type is the type that would be declared by a C enumeration specifier (6.7.2.2 14 of the C standard) that specified C enumeration constants with the same values as those 15 specified by the enum-alias-def , in the same order as specified by the enum-alias-def . 16 The companion processor (2.5.10) shall be one that uses the same representation for the 17 types declared by all C enumeration specifiers that specify the same values in the same 18 order. NOTE 4.60 If a companion processor uses an unsigned type to represent a given enumeration type, the Fortran processor will use the signed integer type of the same width for the enumeration, even though some of the values of the enumerators cannot be represented in this signed integer type. The values of any such enumerators will be interoperable with the values declared in the C enumeration. NOTE 4.61 The C standard guarantees the enumeration constants fit in a C int (6.7.2.2 of the C standard). Therefore, the Fortran processor can evaluate all enumerator values using the integer type with kind parameter C INT, and then determine the kind parameter of the integer type that is interoperable with the corresponding C enumerated type. 19 (2) If kind-selector is specified, the kind is that specified by the kind-selector . 20 (3) If neither BIND(C) nor kind-selector is specified, the kind is that of default integer. NOTE 4.62 The C standard specifies that two enumeration types are compatible only if they specify enumer- ation constants with the same names and same values in the same order. This standard further requires that a C processor that is to be a companion processor of a Fortran processor use the same representation for two enumeration types if they both specify enumeration constants with the same values in the same order, even if the names are different. 21 An enumerator is treated as if it were explicitly declared with type type-alias-name and with the PA- 22 RAMETER attribute. The enumerator is defined in accordance with the rules of intrinsic assignment 23 (7.4) with the value determined as follows: 24 (1) If scalar-int-initialization-expr is specified, the value of the enumerator is the result of 25 scalar-int-initialization-expr . 26 (2) If scalar-int-initialization-expr is not specified and the enumerator is the first enumerator 27 in enum-alias-def , the enumerator has the value 0. 28 (3) If scalar-int-initialization-expr is not present and the enumerator is not the first enumerator 29 in enum-alias-def , its value is the result of adding 1 to the value of the enumerator that 62 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 immediately precedes it in the enum-alias-def . NOTE 4.63 The declarations ENUM (SELECTED_INT_KIND (1)) :: DIGITS ENUMERATOR :: ZERO, ONE, TWO END ENUM DIGITS ENUM, BIND(C) :: PRIMARY_COLORS ENUMERATOR :: RED = 4, BLUE = 9 ENUMERATOR YELLOW END ENUM TYPE (DIGITS) :: X are equivalent to the declarations TYPEALIAS :: DIGITS => INTEGER (SELECTED_INT_KIND(1)) TYPE (DIGITS), PARAMETER :: ZERO = 0, ONE = 1, TWO = 2 TYPE (DIGITS) :: X ! The kind type parameter for PRIMARY_COLORS is processor dependent, but the ! processor is required to select a kind sufficient to represent the values ! 4, 9, and 10, which are the values of its enumerators. ! The following declaration is one possibility for PRIMARY_COLORS. TYPEALIAS :: PRIMARY_COLORS => INTEGER (SELECTED_INT_KIND (2)) TYPE (PRIMARY_COLORS), PARAMETER :: RED = 4, BLUE = 9, YELLOW = 10 NOTE 4.64 There is no difference in the effect of declaring the enumerators in multiple ENUMERATOR statements or in a single ENUMERATOR statement. The order in which the enumerators in an enumeration definition are declared is significant, but the number of ENUMERATOR statements is not. 2 4.8 Construction of array values 3 An array constructor is defined as a sequence of scalar values and is interpreted as a rank-one array 4 where the element values are those specified in the sequence. 5 R459 array-constructor is (/ ac-spec /) 6 or left-square-bracket ac-spec right-square-bracket 7 R460 ac-spec is type-spec :: 8 or [type-spec ::] ac-value-list 9 R461 left-square-bracket is [ 10 R462 right-square-bracket is ] 11 R463 ac-value is expr 12 or ac-implied-do 13 R464 ac-implied-do is ( ac-value-list , ac-implied-do-control ) 14 R465 ac-implied-do-control is ac-do-variable = scalar-int-expr , scalar-int-expr 15 [ , scalar-int-expr ] 16 R466 ac-do-variable is scalar-int-variable SEP 2002 COMMITTEE DRAFT 63 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 C483 (R466) ac-do-variable shall be a named variable. 2 C484 (R460) If type-spec is omitted, each ac-value expression in the array-constructor shall have the 3 same type and kind type parameters. 4 C485 (R460) If type-spec specifies an intrinsic type, each ac-value expression in the array-constructor 5 shall be of an intrinsic type that is in type conformance with a variable of type type-spec as 6 specified in Table 7.8. 7 C486 (R460) If type-spec specifies a derived type, all ac-value expressions in the array-constructor 8 shall be of that derived type and shall have the same kind type parameter values as specified by 9 type-spec. 10 C487 (R464) The ac-do-variable of an ac-implied-do that is in another ac-implied-do shall not appear 11 as the ac-do-variable of the containing ac-implied-do. 12 If type-spec is omitted, the type and type parameters of the array constructor are those of the ac-value 13 expressions. 14 If type-spec appears, it specifies the type and type parameters of the array constructor. Each ac-value 15 expression in the array-constructor shall be compatible with intrinsic assignment to a variable of this 16 type and type parameters. Each value is converted to the type parameters of the array-constructor in 17 accordance with the rules of intrinsic assignment (7.4.1.3). 18 The character length of an ac-value in an ac-implied-do whose iteration count is zero shall not depend 19 on the value of the implied DO variable and shall not depend on the value of an expression that is not 20 an initialization expression. 21 If an ac-value is a scalar expression, its value specifies an element of the array constructor. If an ac- 22 value is an array expression, the values of the elements of the expression, in array element order (6.2.2.2), 23 specify the corresponding sequence of elements of the array constructor. If an ac-value is an ac-implied- 24 do, it is expanded to form a sequence of elements under the control of the ac-do-variable, as in the DO 25 construct (8.1.6.4). 26 For an ac-implied-do, the loop initialization and execution is the same as for a DO construct. 27 An empty sequence forms a zero-sized rank-one array. NOTE 4.65 A one-dimensional array may be reshaped into any allowable array shape using the RESHAPE intrinsic function (13.7.95). An example is: X = (/ 3.2, 4.01, 6.5 /) Y = RESHAPE (SOURCE = [ 2.0, [ 4.5, 4.5 ], X ], SHAPE = [ 3, 2 ]) This results in Y having the 3 × 2 array of values: 2.0 3.2 4.5 4.01 4.5 6.5 NOTE 4.66 Examples of array constructors containing an implied-DO are: 64 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 4.66 (cont.) (/ (I, I = 1, 1075) /) and [ 3.6, (3.6 / I, I = 1, N) ] NOTE 4.67 Using the type definition for PERSON in Note 4.20, an example of the construction of a derived- type array value is: (/ PERSON (40, 'SMITH'), PERSON (20, 'JONES') /) NOTE 4.68 Using the type definition for LINE in Note 4.25, an example of the construction of a derived-type scalar value with a rank-2 array component is: LINE (RESHAPE ( (/ 0.0, 0.0, 1.0, 2.0 /), (/ 2, 2 /) ), 0.1, 1) The RESHAPE intrinsic function is used to construct a value that represents a solid line from (0, 0) to (1, 2) of width 0.1 centimeters. NOTE 4.69 Examples of zero-size array constructors are: (/ INTEGER :: /) (/ ( I, I = 1, 0) /) NOTE 4.70 An example of an array constructor that specifies a nonkind type parameter: (/ CHARACTER(LEN=7) :: 'Takata', 'Tanaka', 'Hayashi' /) In this constructor, without the type specification, it would have been necessary to specify all of the constants with the same character length. SEP 2002 COMMITTEE DRAFT 65 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 66 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 Section 5: Data object declarations and specifications 2 Every data object has a type and rank and may have type parameters and other attributes that determine 3 the uses of the object. Collectively, these properties are the attributes of the object. The type of a 4 named data object is either specified explicitly in a type declaration statement or determined implicitly 5 by the first letter of its name (5.3). All of its attributes may be included in a type declaration statement 6 or may be specified individually in separate specification statements. NOTE 5.1 For example: INTEGER :: INCOME, EXPENDITURE declares the two data objects named INCOME and EXPENDITURE to have the type integer. REAL, DIMENSION (-5:+5) :: X, Y, Z declares three data objects with names X, Y, and Z. These all have default real type and are explicit-shape rank-one arrays with a lower bound of ­5, an upper bound of +5, and therefore a size of 11. 7 5.1 Type declaration statements 8 R501 type-declaration-stmt is declaration-type-spec [ [ , attr-spec ] ... :: ] entity-decl -list 9 R502 declaration-type-spec is type-spec 10 or CLASS ( derived-type-spec ) 11 or CLASS ( * ) 12 C501 (R502) In a declaration-type-spec, every type-param-value that is not a colon or an asterisk shall 13 be a specification-expr . 14 C502 (R502) In a declaration-type-spec that uses the CLASS keyword, derived-type-spec shall specify 15 an extensible type. NOTE 5.2 A declaration-type-spec is used in a nonexecutable statement; a type-spec is used in an array constructor or an ALLOCATE statement. 16 R503 type-spec is INTEGER [ kind-selector ] 17 or REAL [ kind-selector ] 18 or DOUBLE PRECISION 19 or COMPLEX [ kind-selector ] 20 or CHARACTER [ char-selector ] 21 or LOGICAL [ kind-selector ] 22 or TYPE ( derived-type-spec ) 23 or TYPE ( type-alias-name ) 24 C503 (R503) A type-alias-name shall be the name of a type alias. 25 R504 attr-spec is access-spec SEP 2002 COMMITTEE DRAFT 67 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 or ALLOCATABLE 2 or ASYNCHRONOUS 3 or DIMENSION ( array-spec ) 4 or EXTERNAL 5 or INTENT ( intent-spec ) 6 or INTRINSIC 7 or language-binding-spec 8 or OPTIONAL 9 or PARAMETER 10 or POINTER 11 or PROTECTED 12 or SAVE 13 or TARGET 14 or VALUE 15 or VOLATILE 16 R505 entity-decl is object-name [( array-spec )] [ * char-length ] [ initialization ] 17 or function-name [ * char-length ] 18 C504 (R505) If a type-param-value in a char-length in an entity-decl is not a colon or an asterisk, it 19 shall be a specification-expr . 20 R506 object-name is name 21 C505 (R506) The object-name shall be the name of a data object. 22 R507 kind-selector is ( [ KIND = ] scalar-int-initialization-expr ) 23 R508 initialization is = initialization-expr 24 or => null-init 25 R509 null-init is function-reference 26 C506 (R509) The function-reference shall be a reference to the NULL intrinsic function with no 27 arguments. 28 C507 (R501) The same attr-spec shall not appear more than once in a given type-declaration-stmt . 29 C508 An entity shall not be explicitly given any attribute more than once in a scoping unit. 30 C509 (R501) An entity declared with the CLASS keyword shall be a dummy argument or have the 31 ALLOCATABLE or POINTER attribute. 32 C510 (R501) An array that has the POINTER or ALLOCATABLE attribute shall be specified with 33 an array-spec that is a deferred-shape-spec-list (5.1.2.5.3). 34 C511 (R501) An array-spec for an object-name that is a function result that does not have the AL- 35 LOCATABLE or POINTER attribute shall be an explicit-shape-spec-list. 36 C512 (R501) If the POINTER attribute is specified, the ALLOCATABLE, TARGET, EXTERNAL, 37 or INTRINSIC attribute shall not be specified. 38 C513 (R501) If the TARGET attribute is specified, the POINTER, EXTERNAL, INTRINSIC, or 39 PARAMETER attribute shall not be specified. 40 C514 (R501) The PARAMETER attribute shall not be specified for a dummy argument, a pointer, 41 an allocatable entity, a function, or an object in a common block. 42 C515 (R501) The INTENT, VALUE, and OPTIONAL attributes may be specified only for dummy 43 arguments. 68 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 C516 (R501) The INTENT attribute shall not be specified for a dummy argument that is a dummy 2 procedure. NOTE 5.3 A dummy procedure pointer is not a dummy procedure. Therefore, INTENT may be specified for a dummy procedure pointer. 3 C517 (R501) The SAVE attribute shall not be specified for an object that is in a common block, a 4 dummy argument, a procedure, a function result, an automatic data object, or an object with 5 the PARAMETER attribute. 6 C518 An entity shall not have both the EXTERNAL attribute and the INTRINSIC attribute. 7 C519 (R501) An entity in an entity-decl -list shall not have the EXTERNAL or INTRINSIC attribute 8 specified unless it is a function. 9 C520 (R505) The * char-length option is permitted only if the type specified is character. 10 C521 (R505) The function-name shall be the name of an external function, an intrinsic function, a 11 function dummy procedure, or a statement function. 12 C522 (R501) The initialization shall appear if the statement contains a PARAMETER attribute 13 (5.1.2.10). 14 C523 (R501) If initialization appears, a double-colon separator shall appear before the entity-decl -list. 15 C524 (R505)initialization shall not appear if object-name is a dummy argument, a function result, an 16 object in a named common block unless the type declaration is in a block data program unit, 17 an object in blank common, an allocatable variable, an external name, an intrinsic name, or an 18 automatic object. 19 C525 (R505) If => appears in initialization, the object shall have the POINTER attribute. If = 20 appears in initialization, the object shall not have the POINTER attribute. 21 C526 (R503) The value of scalar-int-initialization-expr in kind-selector shall be nonnegative and shall 22 specify a representation method that exists on the processor. 23 C527 (R501) If the VOLATILE attribute is specified, the PARAMETER, INTRINSIC, EXTERNAL, 24 or INTENT(IN) attribute shall not be specified. 25 C528 (R501) If the VALUE attribute is specified, the PARAMETER, EXTERNAL, POINTER, 26 ALLOCATABLE, DIMENSION, VOLATILE, INTENT(INOUT), or INTENT(OUT) attribute 27 shall not be specified. 28 C529 (R501) If the VALUE attribute is specified for a dummy argument of type character, the length 29 parameter shall be omitted or shall be specified by an initialization expression with the value 30 one. 31 C530 (R501) The ALLOCATABLE, POINTER, or OPTIONAL attribute shall not be specified for a 32 dummy argument of a procedure that has a proc-language-binding-spec. 33 C531 (R504) A language-binding-spec shall appear only in the specification part of a module. 34 C532 (R501) If a language-binding-spec is specified, the entity declared shall be an interoperable 35 variable (15.2). 36 C533 (R501) If a language-binding-spec with a NAME= specifier appears, the entity-decl -list shall SEP 2002 COMMITTEE DRAFT 69 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 consist of a single entity-decl . 2 C534 (R504) The PROTECTED attribute is permitted only in the specification part of a module. 3 C535 (R501) The PROTECTED attribute is permitted only for a procedure pointer or named variable 4 that is not in a common block. 5 C536 (R501) If the PROTECTED attribute is specified, the EXTERNAL, INTRINSIC, or PARAM- 6 ETER attribute shall not be specified. 7 C537 A nonpointer object that has the PROTECTED attribute and is accessed by use association 8 shall not appear in a variable definition context (16.5.7) or as the data-target or proc-target in 9 a pointer-assignment-stmt . 10 C538 A pointer object that has the PROTECTED attribute and is accessed by use association shall 11 not appear as 12 (1) A pointer-object in a pointer-assignment-stmt or nullify-stmt , 13 (2) An allocate-object in an allocate-stmt or deallocate-stmt , or 14 (3) An actual argument in a reference to a procedure if the associated dummy argument is a 15 pointer with the INTENT(OUT) or INTENT(INOUT) attribute. 16 A name that identifies a specific intrinsic function in a scoping unit has a type as specified in 13.6. An 17 explicit type declaration statement is not required; however, it is permitted. Specifying a type for a 18 generic intrinsic function name in a type declaration statement is not sufficient, by itself, to remove the 19 generic properties from that function. 20 A function result may be declared to have the POINTER or ALLOCATABLE attribute. 21 A specification-expr in an array-spec, in a type-param-value in a declaration-type-spec corresponding to a 22 nonkind type parameter, or in a char-length in an entity-decl shall be an initialization expression unless 23 it is in an interface body (12.3.2.1), the specification part of a subprogram, or the declaration-type-spec 24 of a FUNCTION statement (12.5.2.1). If the data object being declared depends on the value of a 25 specification-expr that is not an initialization expression, and it is not a dummy argument, such an 26 object is called an automatic data object. NOTE 5.4 An automatic object shall neither appear in a SAVE or DATA statement nor be declared with a SAVE attribute nor be initially defined by an initialization. 27 If a type parameter in a declaration-type-spec or in a char-length in an entity-decl is defined by an 28 expression that is not an initialization expression, the type parameter value is established on entry to 29 the procedure and is not affected by any redefinition or undefinition of the variables in the specification 30 expression during execution of the procedure. 31 If an entity-decl contains initialization and the object-name does not have the PARAMETER attribute, 32 the entity is a variable with explicit initialization. Explicit initialization alternatively may be specified 33 in a DATA statement unless the variable is of a derived type for which default initialization is specified. 34 If initialization is =initialization-expr , the object-name is initially defined with the value specified by 35 the initialization-expr ; if necessary, the value is converted according to the rules of intrinsic assignment 36 (7.4.1.3) to a value that agrees in type, type parameters, and shape with the object-name. A variable, 37 or part of a variable, shall not be explicitly initialized more than once in a program. If the variable is an 38 array, it shall have its shape specified in either the type declaration statement or a previous attribute 39 specification statement in the same scoping unit. 40 If initialization is =>null-init , object-name shall be a pointer, and its initial association status is disas- 70 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 sociated. 2 The presence of initialization implies that object-name is saved, except for an object-name in a named 3 common block or an object-name with the PARAMETER attribute. The implied SAVE attribute may 4 be reaffirmed by explicit use of the SAVE attribute in the type declaration statement, by inclusion of 5 the object-name in a SAVE statement (5.2.12), or by the appearance of a SAVE statement without a 6 saved-entity-list in the same scoping unit. NOTE 5.5 Examples of type declaration statements are: REAL A (10) LOGICAL, DIMENSION (5, 5) :: MASK1, MASK2 COMPLEX :: CUBE_ROOT = (-0.5, 0.866) INTEGER, PARAMETER :: SHORT = SELECTED_INT_KIND (4) INTEGER (SHORT) K ! Range at least -9999 to 9999. REAL (KIND (0.0D0)) A REAL (KIND = 2) B COMPLEX (KIND = KIND (0.0D0)) :: C TYPE (PERSON) :: CHAIRMAN TYPE(NODE), POINTER :: HEAD => NULL ( ) TYPE (matrix (k=8, d=1000)) :: mat (The last line above uses a type definition from Note 4.21.) 7 5.1.1 Type specifiers 8 The type specifier in a type declaration statement specifies the type of the entities in the entity 9 declaration list. This explicit type declaration may override or confirm the implicit type that could 10 otherwise be indicated by the first letter of an entity name (5.3). 11 5.1.1.1 INTEGER 12 The INTEGER type specifier is used to declare entities of intrinsic type integer (4.4.1). The kind 13 selector, if present, specifies the integer representation method. If the kind selector is absent, the kind 14 type parameter is KIND (0) and the entities declared are of type default integer. 15 5.1.1.2 REAL 16 The REAL type specifier is used to declare entities of intrinsic type real (4.4.2). The kind selector, if 17 present, specifies the real approximation method. If the kind selector is absent, the kind type parameter 18 is KIND (0.0) and the entities declared are of type default real. 19 5.1.1.3 DOUBLE PRECISION 20 The DOUBLE PRECISION type specifier is used to declare entities of intrinsic type double precision 21 real (4.4.2). The kind parameter value is KIND (0.0D0). An entity declared with a type specifier 22 REAL (KIND (0.0D0)) is of the same kind as one declared with the type specifier DOUBLE PRECISION. 23 5.1.1.4 COMPLEX 24 The COMPLEX type specifier is used to declare entities of intrinsic type complex (4.4.3). The kind 25 selector, if present, specifies the real approximation method of the two real values making up the real SEP 2002 COMMITTEE DRAFT 71 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 and imaginary parts of the complex value. If the kind selector is absent, the kind type parameter is 2 KIND (0.0) and the entities declared are of type default complex. 3 5.1.1.5 CHARACTER 4 The CHARACTER type specifier is used to declare entities of intrinsic type character (4.4.4). 5 R510 char-selector is length-selector 6 or ( LEN = type-param-value , 7 KIND = scalar-int-initialization-expr ) 8 or ( type-param-value , 9 [ KIND = ] scalar-int-initialization-expr ) 10 or ( KIND = scalar-int-initialization-expr 11 [ , LEN =type-param-value ] ) 12 R511 length-selector is ( [ LEN = ] type-param-value ) 13 or * char-length [ , ] 14 R512 char-length is ( type-param-value ) 15 or scalar-int-literal-constant 16 C539 (R510) The value of scalar-int-initialization-expr shall be nonnegative and shall specify a rep- 17 resentation method that exists on the processor. 18 C540 (R512) The scalar-int-literal-constant shall not include a kind-param. 19 C541 (R510 R511 R512) A type-param-value of * may be used only in the following ways: 20 (1) to declare a dummy argument, 21 (2) to declare a named constant, 22 (3) in the type-spec of an ALLOCATE statement wherein each allocate-object is a dummy 23 argument of type CHARACTER with an assumed character length, or 24 (4) in an external function, to declare the character length parameter of the function result. 25 C542 A function name shall not be declared with an asterisk type-param-value unless it is of type CHAR- 26 ACTER and is the name of the result of an external function or the name of a dummy function. 27 C543 A function name declared with an asterisk type-param-value shall not be an array, a pointer, recursive, or pure. 28 C544 (R511) The optional comma in a length-selector is permitted only in a declaration-type-spec in a type-declaration- 29 stmt . 30 C545 (R511) The optional comma in a length-selector is permitted only if no double-colon separator appears in the 31 type-declaration-stmt . 32 C546 (R510) The length specified for a character statement function or for a statement function dummy argument of 33 type character shall be an initialization expression. 34 The char-selector in a CHARACTER type-spec and the * char-length in an entity-decl or in a component- 35 decl of a type definition specify character length. The * char-length in an entity-decl or a component-decl 36 specifies an individual length and overrides the length specified in the char-selector , if any. If a * char- 37 length is not specified in an entity-decl or a component-decl , the length-selector or type-param-value 38 specified in the char-selector is the character length. If the length is not specified in a char-selector or 39 a * char-length, the length is 1. 40 If the character length parameter value evaluates to a negative value, the length of character entities 41 declared is zero. A character length parameter value of : indicates a deferred type parameter (4.2). A 42 char-length type parameter value of * has the following meaning: 72 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 (1) If used to declare a dummy argument of a procedure, the dummy argument assumes the 2 length of the associated actual argument. 3 (2) If used to declare a named constant, the length is that of the constant value. 4 (3) If used in the type-spec of an ALLOCATE statement, each allocate-object assumes its length 5 from the associated actual argument. 6 (4) If used to specify the character length parameter of a function result, any scoping unit invoking the function 7 shall declare the function name with a character length parameter value other than * or access such a 8 definition by host or use association. When the function is invoked, the length of the result variable in the 9 function is assumed from the value of this type parameter. 10 The kind selector, if present, specifies the character representation method. If the kind selector is absent, 11 the kind type parameter is KIND ('A') and the entities declared are of type default character. NOTE 5.6 Examples of character type declaration statements are: CHARACTER (LEN = 10, KIND = 2) A CHARACTER B, C *20 12 5.1.1.6 LOGICAL 13 The LOGICAL type specifier is used to declare entities of intrinsic type logical (4.4.5). 14 The kind selector, if present, specifies the representation method. If the kind selector is absent, the kind 15 type parameter is KIND (.FALSE.) and the entities declared are of type default logical. 16 5.1.1.7 Derived type 17 A TYPE type specifier is used to declare entities of the derived type specified by the type-name of 18 the derived-type-spec. The components of each such entity are declared to be of the types specified by 19 the corresponding component-def-stmt s of the derived-type-def (4.5.1). When a data entity is declared 20 explicitly to be of a derived type, the derived type shall have been defined previously in the scoping unit 21 or be accessible there by use or host association. If the data entity is a function result, the derived type 22 may be specified in the FUNCTION statement provided the derived type is defined within the body of 23 the function or is accessible there by use or host association. 24 A scalar entity of derived type is a structure. If a derived type has the SEQUENCE property, a scalar 25 entity of the type is a sequence structure. 26 5.1.1.8 Polymorphic entities 27 A polymorphic entity is a data entity that is able to be of differing types during program execution. 28 The type of a data entity at a particular point during execution of a program is its dynamic type. The 29 declared type of a data entity is the type that it is declared to have, either explicitly or implicitly. 30 A CLASS type specifier is used to declare polymorphic objects. The declared type of a polymorphic 31 object is the specified type if the CLASS type specifier contains a type name. 32 An object declared with the CLASS(*) specifier is an unlimited polymorphic object. An unlimited 33 polymorphic entity is not declared to have a type. It is not considered to have the same declared type 34 as any other entity, including another unlimited polymorphic entity. 35 A nonpolymorphic entity is type compatible only with entities of the same type. For a polymorphic 36 entity, type compatibility is based on its declared type. A polymorphic entity that is not an unlimited 37 polymorphic entity is type compatible with entities of the same type or any of its extensions. Even SEP 2002 COMMITTEE DRAFT 73 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 though an unlimited polymorphic entity is not considered to have a declared type, it is type compatible 2 with all entities of extensible type. An entity is said to be type compatible with a type if it is type 3 compatible with entities of that type. 4 Two entities are type incompatible if neither is type compatible with the other. 5 An entity is type, kind, and rank compatible, or TKR compatible, with another entity if the first 6 entity is type compatible with the second, the kind type parameters of the first entity have the same 7 values as corresponding kind type parameters of the second, and both entities have the same rank. 8 Two entities are TKR incompatible if neither is TKR compatible with the other. 9 A polymorphic allocatable object may be allocated to be of any type with which it is type compatible. 10 A polymorphic pointer or dummy argument may, during program execution, be associated with objects 11 with which it is type compatible. 12 The dynamic type of an allocated allocatable polymorphic object is the type with which it was allocated. 13 The dynamic type of an associated polymorphic pointer is the dynamic type of its target. The dynamic 14 type of a nonallocatable nonpointer polymorphic dummy argument is the dynamic type of its associated 15 actual argument. The dynamic type of an unallocated allocatable or a disassociated pointer is the same 16 as its declared type. The dynamic type of an entity identified by an associate name (8.1.4) is the dynamic 17 type of the selector with which it is associated. The dynamic type of an object that is not polymorphic 18 is its declared type. NOTE 5.7 Only components of the declared type of a polymorphic object may be designated by component selection (6.1.2). 19 5.1.2 Attributes 20 The additional attributes that may appear in the attribute specification of a type declaration statement 21 further specify the nature of the entities being declared or specify restrictions on their use in the program. 22 5.1.2.1 Accessibility attribute 23 The accessibility attribute specifies the accessibility of an entity via a particular identifier. 24 R513 access-spec is PUBLIC 25 or PRIVATE 26 C547 (R513) An access-spec shall appear only in the specification-part of a module. 27 Identifiers that are specified in a module or accessible in that module by use association have either 28 the PUBLIC or PRIVATE attribute. Identifiers for which an access-spec is not explicitly specified in 29 that module have the default accessibility attribute for that module. The default accessibility attribute 30 for a module is PUBLIC unless it has been changed by a PRIVATE statement (5.2.1). Only identifiers 31 that have the PUBLIC attribute in that module are available to be accessed from that module by USE 32 association. NOTE 5.8 In order for an identifier to be accessed by use association, it must have the PUBLIC attribute in the module from which it is accessed. It can nonetheless have the PRIVATE attribute in a module in which it is accessed by use association, and therefore not be available for use association from a module where it is PRIVATE. 74 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 5.9 An example of an accessibility specification is: REAL, PRIVATE :: X, Y, Z 1 5.1.2.2 ALLOCATABLE attribute 2 An object with the ALLOCATABLE attribute is one for which space is allocated by an ALLOCATE 3 statement (6.3.1) or by a derived-type intrinsic assignment statement (7.4.1.3). 4 5.1.2.3 ASYNCHRONOUS attribute 5 The base object of a variable shall have the ASYNCHRONOUS attribute in a scoping unit if: 6 (1) the variable appears in an executable statement or specification expression in that scoping 7 unit and 8 (2) any statement of the scoping unit is executed while the variable is a pending I/O storage 9 sequence affector (9.5.1.4) 10 The ASYNCHRONOUS attribute may be conferred implicitly by the use of a variable in an asynchronous 11 input/output statement (9.5.1.4). 12 An object may have the ASYNCHRONOUS attribute in a particular scoping unit without necessarily 13 having it in other scoping units. If an object has the ASYNCHRONOUS attribute then all of its 14 subobjects also have the ASYNCHRONOUS attribute. NOTE 5.10 The ASYNCHRONOUS attribute specifies the variables that might be associated with a pending input/output storage sequence (the actual memory locations on which asynchronous input/output is being performed) while the scoping unit is in execution. This information could be used by the compiler to disable certain code motion optimizations. The ASYNCHRONOUS attribute is similar to the VOLATILE attribute. It is intended to facilitate traditional code motion optimizations in the presence of asynchronous input/output. 15 5.1.2.4 BIND attribute for data entities 16 The BIND attribute for a variable or common block specifies that it is capable of interoperating with a 17 C variable that has external linkage (15.3). 18 R514 language-binding-spec is BIND (C [, NAME = scalar-char-initialization-expr ]) 19 C548 (R514) The scalar-char-initialization-expr shall be of default character kind. NOTE 5.11 The C standard provides a facility for creating C identifiers whose characters are not restricted to the C basic character set. Such a C identifier is referred to as a universal character name (6.4.3 of the C standard). The name of such a C identifier may include characters that are not part of the representation method used by the processor for type default character. If so, the C entity cannot be linked (12.5.3, 15.3.1) with a Fortran entity. This standard does not require a processor to provide a means of linking Fortran entities with C entities whose names are specified using the universal character name facility. 20 The BIND attribute implies the SAVE attribute, which may be confirmed by explicit specification. SEP 2002 COMMITTEE DRAFT 75 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 5.12 Specifying the BIND attribute for an entity might have no discernable effect for a processor that is its own companion processor. 1 5.1.2.5 DIMENSION attribute 2 The DIMENSION attribute specifies entities that are arrays. The rank or shape is specified by 3 the array-spec, if there is one, in the entity-decl , or by the array-spec in the DIMENSION attr-spec 4 otherwise. An array-spec in an entity-decl specifies either the rank or the rank and shape for a single 5 array and overrides the array-spec in the DIMENSION attr-spec. To declare an array in a type declaration 6 statement, either the DIMENSION attr-spec shall appear, or an array-spec shall appear in the entity-decl . 7 The appearance of an array-spec in an entity-decl specifies the DIMENSION attribute for the entity. 8 The DIMENSION attribute alternatively may be specified in the specification statements DIMENSION, 9 ALLOCATABLE, POINTER, TARGET, or COMMON. 10 R515 array-spec is explicit-shape-spec-list 11 or assumed-shape-spec-list 12 or deferred-shape-spec-list 13 or assumed-size-spec 14 C549 (R515)The maximum rank is seven. NOTE 5.13 Examples of DIMENSION attribute specifications are: SUBROUTINE EX (N, A, B) REAL, DIMENSION (N, 10) :: W ! Automatic explicit-shape array REAL A (:), B (0:) ! Assumed-shape arrays REAL, POINTER :: D (:, :) ! Array pointer REAL, DIMENSION (:), POINTER :: P ! Array pointer REAL, ALLOCATABLE, DIMENSION (:) :: E ! Allocatable array 15 5.1.2.5.1 Explicit-shape array 16 An explicit-shape array is a named array that is declared with an explicit-shape-spec-list. This specifies 17 explicit values for the bounds in each dimension of the array. 18 R516 explicit-shape-spec is [ lower-bound : ] upper-bound 19 R517 lower-bound is specification-expr 20 R518 upper-bound is specification-expr 21 C550 (R516) An explicit-shape array whose bounds are not initialization expressions shall be a dummy 22 argument, a function result, or an automatic array of a procedure. 23 An automatic array is an explicit-shape array that is declared in a subprogram, is not a dummy 24 argument, and has bounds that are not initialization expressions. 25 If an explicit-shape array has bounds that are not initialization expressions, the bounds, and hence 26 shape, are determined at entry to the procedure by evaluating the bounds expressions. The bounds of 27 such an array are unaffected by the redefinition or undefinition of any variable during execution of the 28 procedure. 29 The values of each lower-bound and upper-bound determine the bounds of the array along a particular 30 dimension and hence the extent of the array in that dimension. The value of a lower bound or an upper 76 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 bound may be positive, negative, or zero. The subscript range of the array in that dimension is the set 2 of integer values between and including the lower and upper bounds, provided the upper bound is not 3 less than the lower bound. If the upper bound is less than the lower bound, the range is empty, the 4 extent in that dimension is zero, and the array is of zero size. If the lower-bound is omitted, the default 5 value is 1. The number of sets of bounds specified is the rank. 6 5.1.2.5.2 Assumed-shape array 7 An assumed-shape array is a nonpointer dummy argument array that takes its shape from the asso- 8 ciated actual argument array. 9 R519 assumed-shape-spec is [ lower-bound ] : 10 The rank is equal to the number of colons in the assumed-shape-spec-list. 11 The extent of a dimension of an assumed-shape array dummy argument is the extent of the corresponding 12 dimension of the associated actual argument array. If the lower bound value is d and the extent of the 13 corresponding dimension of the associated actual argument array is s, then the value of the upper bound 14 is s + d - 1. The lower bound is lower-bound , if present, and 1 otherwise. 15 5.1.2.5.3 Deferred-shape array 16 A deferred-shape array is an allocatable array or an array pointer. 17 An allocatable array is an array that has the ALLOCATABLE attribute and a specified rank, but its 18 bounds, and hence shape, are determined by allocation or argument association. 19 An array with the ALLOCATABLE attribute shall be declared with a deferred-shape-spec-list. Nonkind 20 type parameters may be deferred. 21 An array pointer is an array with the POINTER attribute and a specified rank. Its bounds, and hence 22 shape, are determined when it is associated with a target. An array with the POINTER attribute shall 23 be declared with a deferred-shape-spec-list. Nonkind type parameters may be deferred. 24 R520 deferred-shape-spec is : 25 The rank is equal to the number of colons in the deferred-shape-spec-list. 26 The size, bounds, and shape of an unallocated allocatable array or a disassociated array pointer are 27 undefined. No part of such an array shall be referenced or defined; however, the array may appear as an 28 argument to an intrinsic inquiry function as specified in 13.1. 29 The bounds of each dimension of an allocatable array are those specified when the array is allocated. 30 The bounds of each dimension of an array pointer may be specified in two ways: 31 (1) in an ALLOCATE statement (6.3.1) when the target is allocated, or 32 (2) by pointer assignment (7.4.2). 33 The bounds of the array target or allocatable array are unaffected by any subsequent redefinition or 34 undefinition of variables involved in the bounds' specification expressions. 35 5.1.2.5.4 Assumed-size array 36 An assumed-size array is a dummy argument array whose size is assumed from that of an associated 37 actual argument. The rank and extents may differ for the actual and dummy arrays; only the size of the 38 actual array is assumed by the dummy array. An assumed-size array is declared with an assumed-size- 39 spec. SEP 2002 COMMITTEE DRAFT 77 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 R521 assumed-size-spec is [ explicit-shape-spec-list , ] [ lower-bound : ] * 2 C551 An assumed-size-spec shall not appear except as the declaration of the array bounds of a dummy 3 data argument. 4 C552 An assumed-size array with INTENT (OUT) shall not be of a type for which default initialization 5 is specified. 6 The size of an assumed-size array is determined as follows: 7 (1) If the actual argument associated with the assumed-size dummy array is an array of any 8 type other than default character, the size is that of the actual array. 9 (2) If the actual argument associated with the assumed-size dummy array is an array element 10 of any type other than default character with a subscript order value of r (6.2.2.2) in an 11 array of size x, the size of the dummy array is x - r + 1. 12 (3) If the actual argument is a default character array, default character array element, or a 13 default character array element substring (6.1.1), and if it begins at character storage unit t 14 of an array with c character storage units, the size of the dummy array is MAX (INT ((c - 15 t + 1)/e), 0), where e is the length of an element in the dummy character array. 16 (4) If the actual argument is of type default character and is a scalar that is not an array element 17 or array element substring designator, the size of the dummy array is MAX (INT (l/e), 0), 18 where e is the length of an element in the dummy character array and l is the length of the 19 actual argument. 20 The rank equals one plus the number of explicit-shape-specs. 21 An assumed-size array has no upper bound in its last dimension and therefore has no extent in its last 22 dimension and no shape. An assumed-size array name shall not be written as a whole array reference 23 except as an actual argument in a procedure reference for which the shape is not required. 24 The bounds of the first n - 1 dimensions are those specified by the explicit-shape-spec-list, if present, in 25 the assumed-size-spec. The lower bound of the last dimension is lower-bound , if present, and 1 otherwise. 26 An assumed-size array may be subscripted or sectioned (6.2.2.3). The upper bound shall not be omitted 27 from a subscript triplet in the last dimension. 28 If an assumed-size array has bounds that are not initialization expressions, the bounds are determined 29 at entry to the procedure. The bounds of such an array are unaffected by the redefinition or undefinition 30 of any variable during execution of the procedure. 31 5.1.2.6 EXTERNAL attribute 32 The EXTERNAL attribute specifies that an entity is an external procedure, dummy procedure, 33 procedure pointer, or block data subprogram. This attribute may also be specified by an EXTER- 34 NAL statement (12.3.2.2), a procedure-declaration-stmt (12.3.2.3) or an interface body that is not in an 35 interface block (12.3.2.1). 36 If an external procedure or dummy procedure is used as an actual argument or is the target of a procedure 37 pointer assignment, it shall be declared to have the EXTERNAL attribute. 38 A procedure that has both the EXTERNAL and POINTER attributes is a procedure pointer. 39 5.1.2.7 INTENT attribute 40 The INTENT attribute specifies the intended use of a dummy argument. 41 R522 intent-spec is IN 42 or OUT 78 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 or INOUT 2 C553 (R522) A nonpointer object with the INTENT (IN) attribute shall not appear in a variable 3 definition context (16.5.7). 4 C554 (R522) A pointer object with the INTENT (IN) attribute shall not appear as 5 (1) A pointer-object in a pointer-assignment-stmt or nullify-stmt , 6 (2) An allocate-object in an allocate-stmt or deallocate-stmt , or 7 (3) An actual argument in a reference to a procedure if the associated dummy argument is a 8 pointer with the INTENT (OUT) or INTENT (INOUT) attribute. 9 The INTENT (IN) attribute for a nonpointer dummy argument specifies that it shall neither be de- 10 fined nor become undefined during the execution of the procedure. The INTENT (IN) attribute for a 11 pointer dummy argument specifies that during the execution of the procedure its association shall not 12 be changed except that it may become undefined if the target is deallocated other than through the 13 pointer (16.4.2.1.3). 14 The INTENT (OUT) attribute for a nonpointer dummy argument specifies that it shall be defined 15 before a reference to the dummy argument is made within the procedure and any actual argument that 16 becomes associated with such a dummy argument shall be definable. On invocation of the procedure, 17 such a dummy argument becomes undefined except for components of an object of derived type for 18 which default initialization has been specified. The INTENT (OUT) attribute for a pointer dummy 19 argument specifies that on invocation of the procedure the pointer association status of the dummy 20 argument becomes undefined. Any actual argument associated with such a pointer dummy shall be a 21 pointer variable. 22 The INTENT (INOUT) attribute for a nonpointer dummy argument specifies that it is intended for use 23 both to receive data from and to return data to the invoking scoping unit. Such a dummy argument may 24 be referenced or defined. Any actual argument that becomes associated with such a dummy argument 25 shall be definable. The INTENT (INOUT) attribute for a pointer dummy argument specifies that it is 26 intended for use both to receive a pointer association from and to return a pointer association to the 27 invoking scoping unit. Any actual argument associated with such a pointer dummy shall be a pointer 28 variable. 29 If no INTENT attribute is specified for a dummy argument, its use is subject to the limitations of the 30 associated actual argument (12.4.1.2, 12.4.1.3, 12.4.1.4). NOTE 5.14 An example of INTENT specification is: SUBROUTINE MOVE (FROM, TO) USE PERSON_MODULE TYPE (PERSON), INTENT (IN) :: FROM TYPE (PERSON), INTENT (OUT) :: TO 31 If an object has an INTENT attribute, then all of its subobjects have the same INTENT attribute. NOTE 5.15 If a dummy argument is a derived-type object with a pointer component, then the pointer as a pointer is a subobject of the dummy argument, but the target of the pointer is not. Therefore, the restrictions on subobjects of the dummy object apply to the pointer in contexts where it is used as a pointer, but not in contexts where it is dereferenced to indicate its target. For example, if X is a SEP 2002 COMMITTEE DRAFT 79 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 5.15 (cont.) dummy argument of derived type with an integer pointer component P, and X has INTENT(IN), then the statement X%P => NEW_TARGET is prohibited, but X%P = 0 is allowed (provided that X%P is associated with a definable target). Similarly, the INTENT restrictions on pointer dummy arguments apply only to the association of the dummy argument; they do not restrict the operations allowed on its target. NOTE 5.16 Argument intent specifications serve several purposes in addition to documenting the intended use of dummy arguments. A processor can check whether an INTENT (IN) dummy argument is used in a way that could redefine it. A slightly more sophisticated processor could check to see whether an INTENT (OUT) dummy argument could possibly be referenced before it is defined. If the procedure's interface is explicit, the processor can also verify that actual arguments corresponding to INTENT (OUT) or INTENT (INOUT) dummy arguments are definable. A more sophisticated processor could use this information to optimize the translation of the referencing scoping unit by taking advantage of the fact that actual arguments corresponding to INTENT (IN) dummy arguments will not be changed and that any prior value of an actual argument corresponding to an INTENT (OUT) dummy argument will not be referenced and could thus be discarded. INTENT (OUT) means that the value of the argument after invoking the procedure is entirely the result of executing that procedure. If there is any possibility that an argument should retain its current value rather than being redefined, INTENT (INOUT) should be used rather than INTENT (OUT), even if there is no explicit reference to the value of the dummy argument. Because an INTENT(OUT) variable is considered undefined on entry to the procedure, any default initialization specified for its type will be applied. INTENT (INOUT) is not equivalent to omitting the INTENT attribute. The argument corre- sponding to an INTENT (INOUT) dummy argument always shall be definable, while an argument corresponding to a dummy argument without an INTENT attribute need be definable only if the dummy argument is actually redefined. 1 5.1.2.8 INTRINSIC attribute 2 The INTRINSIC attribute confirms that a name is the specific name (13.6) or generic name (13.5) 3 of an intrinsic procedure. The INTRINSIC attribute allows the specific name of an intrinsic procedure 4 that is listed in 13.6 and not marked with a bullet (·) to be used as an actual argument (12.4). 5 Declaring explicitly that a generic intrinsic procedure name has the INTRINSIC attribute does not cause 6 that name to lose its generic property. 7 If the specific name of an intrinsic procedure (13.6) is used as an actual argument, the name shall be 8 explicitly specified to have the INTRINSIC attribute. 9 C555 (R504) (R1216) If the name of a generic intrinsic procedure is explicitly declared to have the 10 INTRINSIC attribute, and it is also the generic name in one or more generic interfaces (12.3.2.1) 11 accessible in the same scoping unit, the procedures in the interfaces and the specific intrinsic 80 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 procedures shall all be functions or all be subroutines, and the characteristics of the specific 2 intrinsic procedures and the procedures in the interfaces shall differ as specified in 16.2.3. 3 5.1.2.9 OPTIONAL attribute 4 The OPTIONAL attribute specifies that the dummy argument need not be associated with an actual 5 argument in a reference to the procedure (12.4.1.6). The PRESENT intrinsic function may be used 6 to determine whether an actual argument has been associated with a dummy argument having the 7 OPTIONAL attribute. 8 5.1.2.10 PARAMETER attribute 9 The PARAMETER attribute specifies entities that are named constants. The object-name has the 10 value specified by the initialization-expr that appears on the right of the equals; if necessary, the value 11 is converted according to the rules of intrinsic assignment (7.4.1.3) to a value that agrees in type, type 12 parameters, and shape with the object-name. 13 A named constant shall not be referenced unless it has been defined previously in the same statement, 14 defined in a prior statement, or made accessible by use or host association. NOTE 5.17 Examples of declarations with a PARAMETER attribute are: REAL, PARAMETER :: ONE = 1.0, Y = 4.1 / 3.0 INTEGER, DIMENSION (3), PARAMETER :: ORDER = (/ 1, 2, 3 /) TYPE(NODE), PARAMETER :: DEFAULT = NODE(0, NULL ( )) 15 5.1.2.11 POINTER attribute 16 Entities with the POINTER attribute can be associated with different data objects or procedures 17 during execution of a program. A pointer is either a data pointer or a procedure pointer. Procedure 18 pointers are described in 12.3.2.3. 19 A data pointer shall neither be referenced nor defined unless it is pointer associated with a target object 20 that may be referenced or defined. 21 If a data pointer is associated, the values of its deferred type parameters are the same as the values of 22 the corresponding type parameters of its target. 23 A procedure pointer shall not be referenced unless it is pointer associated with a target procedure. NOTE 5.18 Examples of POINTER attribute specifications are: TYPE (NODE), POINTER :: CURRENT, TAIL REAL, DIMENSION (:, :), POINTER :: IN, OUT, SWAP For a more elaborate example see C.2.1. 24 5.1.2.12 PROTECTED attribute 25 The PROTECTED attribute imposes limitations on the usage of module entities. 26 Other than within the module in which an entity is given the PROTECTED attribute, SEP 2002 COMMITTEE DRAFT 81 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 (1) if it is a nonpointer object, it is not definable, and 2 (2) if it is a pointer, it shall not appear in a context that causes its association status to change. 3 If an object has the PROTECTED attribute, all of its subobjects have the PROTECTED attribute. NOTE 5.19 An example of the PROTECTED attribute: MODULE temperature REAL, PROTECTED :: temp_c, temp_f CONTAINS SUBROUTINE set_temperature_c(c) REAL, INTENT(IN) :: c temp_c = c temp_f = temp_c*(9.0/5.0) + 32 END SUBROUTINE END MODULE The PROTECTED attribute ensures that the variables temp c and temp f cannot be modified other than via the set temperature c procedure, thus keeping them consistent with each other. 4 5.1.2.13 SAVE attribute 5 An entity with the SAVE attribute, in the scoping unit of a subprogram, retains its association status, 6 allocation status, definition status, and value after execution of a RETURN or END statement unless it 7 is a pointer and its target becomes undefined (16.4.2.1.3(3)). It is shared by all instances (12.5.2.3) of 8 the subprogram. 9 An entity with the SAVE attribute, declared in the scoping unit of a module, retains its association 10 status, allocation status, definition status, and value after a RETURN or END statement is executed in 11 a procedure that accesses the module unless it is a pointer and its target becomes undefined. 12 A saved entity is an entity that has the SAVE attribute. An unsaved entity is an entity that does not 13 have the SAVE attribute. 14 The SAVE attribute may appear in declarations in a main program and has no effect. 15 5.1.2.14 TARGET attribute 16 An object with the TARGET attribute may have a pointer associated with it (7.4.2). An object 17 without the TARGET attribute shall not have an accessible pointer associated with it. NOTE 5.20 In addition to variables explicitly declared to have the TARGET attribute, the objects created by allocation of pointers (6.3.1.2) have the TARGET attribute. 18 If an object has the TARGET attribute, then all of its nonpointer subobjects also have the TARGET 19 attribute. NOTE 5.21 Examples of TARGET attribute specifications are: 82 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 5.21 (cont.) TYPE (NODE), TARGET :: HEAD REAL, DIMENSION (1000, 1000), TARGET :: A, B For a more elaborate example see C.2.2. NOTE 5.22 Every object designator that starts from a target object will have either the TARGET or POINTER attribute. If pointers are involved, the designator might not necessarily be a subobject of the original target object, but because pointers may point only to targets, there is no way to end up at a nonpointer that is not a target. 1 5.1.2.15 VALUE attribute 2 The VALUE attribute specifies a type of argument association (12.4.1.2) for a dummy argument. 3 5.1.2.16 VOLATILE attribute 4 An object shall have the VOLATILE attribute if there is a reference to or definition of the object, or 5 the object becomes undefined, by means not specified in this standard. 6 An object may have the VOLATILE attribute in a particular scoping unit without necessarily having 7 it in other scoping units. If an object has the VOLATILE attribute then all of its subobjects also have 8 the VOLATILE attribute. NOTE 5.23 The Fortran processor should use the most recent definition of a volatile object when a value is required. Likewise, it should make the most recent Fortran definition available. It is the programmer's responsibility to manage the interactions with the non-Fortran processes. 9 If the POINTER and VOLATILE attributes are both specified, then the volatility applies to the pointer 10 association. NOTE 5.24 If the value of the target of a pointer can change by means outside of Fortran, while a pointer is associated with a target, then the pointer shall have the VOLATILE attribute. Usually a pointer should have the VOLATILE attribute if its target has the VOLATILE attribute. Similarly, all members of an EQUIVALENCE group should have the VOLATILE attribute if one member has the VOLATILE attribute. NOTE 5.25 If a pointer has the VOLATILE attribute, its target does not necessarily need the VOLATILE attribute. In such a case, if the target is accessed through the pointer, the most recent association status of the pointer needs to be loaded from memory and used in order to get the correct object. This has the effect of treating the object as volatile when it is accessed through the pointer, while access to the object that does not occur through the pointer is nonvolatile and can be optimized. 11 If the ALLOCATABLE and VOLATILE attributes are both specified, then the volatility applies to the 12 allocation status, bounds, and definition status. SEP 2002 COMMITTEE DRAFT 83 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 5.2 Attribute specification statements 2 All attributes (other than type) may be specified for entities, independently of type, by separate at- 3 tribute specification statements. The combination of attributes that may be specified for a particular 4 entity is subject to the same restrictions as for type declaration statements regardless of the method of 5 specification. This also applies to PROCEDURE, EXTERNAL, and INTRINSIC statements. 6 5.2.1 Accessibility statements 7 R523 access-stmt is access-spec [ [ :: ] access-id -list ] 8 R524 access-id is use-name 9 or generic-spec 10 C556 (R523) An access-stmt shall appear only in the specification-part of a module. Only one ac- 11 cessibility statement with an omitted access-id -list is permitted in the specification-part of a 12 module. 13 C557 (R524) Each use-name shall be the name of a named variable, procedure, derived type, named 14 constant, or namelist group. 15 An access-stmt with an access-id -list specifies the accessibility attribute (5.1.2.1), PUBLIC or PRIVATE, 16 of each access-id in the list. An access-stmt without an access-id list specifies the default accessibility 17 that applies to all potentially accessible identifiers in the specification-part of the module. The 18 statement 19 PUBLIC 20 specifies a default of public accessibility. The statement 21 PRIVATE 22 specifies a default of private accessibility. If no such statement appears in a module, the default is public 23 accessibility. NOTE 5.26 Examples of accessibility statements are: MODULE EX PRIVATE PUBLIC :: A, B, C, ASSIGNMENT (=), OPERATOR (+) 24 5.2.2 ALLOCATABLE statement 25 R525 allocatable-stmt is ALLOCATABLE [ :: ] 26 object-name [ ( deferred-shape-spec-list ) ] 27 [ , object-name [ ( deferred-shape-spec-list ) ] ] ... 28 This statement specifies the ALLOCATABLE attribute (5.1.2.2) for a list of objects. NOTE 5.27 An example of an ALLOCATABLE statement is: REAL A, B (:), SCALAR ALLOCATABLE :: A (:, :), B, SCALAR 84 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 5.2.3 ASYNCHRONOUS statement 2 R526 asynchronous-stmt is ASYNCHRONOUS [ :: ] object-name-list 3 The ASYNCHRONOUS statement specifies the ASYNCHRONOUS attribute (5.1.2.3) for a list of ob- 4 jects. 5 5.2.4 BIND statement 6 R527 bind-stmt is language-binding-spec [ :: ] bind-entity-list 7 R528 bind-entity is entity-name 8 or / common-block-name / 9 C558 (R527) If any bind-entity in a bind-stmt is an entity-name, the bind-stmt shall appear in the 10 specification part of a module and the entity shall be an interoperable variable (15.2.4, 15.2.5). 11 C559 (R527) If the language-binding-spec has a NAME= specifier, the bind-entity-list shall consist of 12 a single bind-entity. 13 C560 (R527) If a bind-entity is a common block, each variable of the common block shall be interop- 14 erable (15.2.4, 15.2.5). 15 The BIND statement specifies the BIND attribute (5.1.2.4) for a list of variables and common blocks. 16 5.2.5 DATA statement 17 R529 data-stmt is DATA data-stmt-set [ [ , ] data-stmt-set ] ... 18 This statement is used to specify explicit initialization (5.1). 19 A variable, or part of a variable, shall not be explicitly initialized more than once in a program. If a 20 nonpointer object has been specified with default initialization in a type definition, it shall not appear 21 in a data-stmt-object -list. 22 A variable that appears in a DATA statement and has not been typed previously may appear in a 23 subsequent type declaration only if that declaration confirms the implicit typing. An array name, 24 array section, or array element that appears in a DATA statement shall have had its array properties 25 established by a previous specification statement. 26 Except for variables in named common blocks, a named variable has the SAVE attribute if any part 27 of it is initialized in a DATA statement, and this may be confirmed by a SAVE statement or a type 28 declaration statement containing the SAVE attribute. 29 R530 data-stmt-set is data-stmt-object -list / data-stmt-value-list / 30 R531 data-stmt-object is variable 31 or data-implied-do 32 R532 data-implied-do is ( data-i-do-object -list , data-i-do-variable = 33 scalar-int-expr , scalar-int-expr [ , scalar-int-expr ] ) 34 R533 data-i-do-object is array-element 35 or scalar-structure-component 36 or data-implied-do 37 R534 data-i-do-variable is scalar-int-variable 38 C561 (R531) In a variable that is a data-stmt-object , any subscript, section subscript, substring start- 39 ing point, and substring ending point shall be an initialization expression. 40 C562 (R531) A variable whose designator is included in a data-stmt-object -list or a data-i-do-object - SEP 2002 COMMITTEE DRAFT 85 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 list shall not be: a dummy argument, made accessible by use association or host association, in 2 a named common block unless the DATA statement is in a block data program unit, in a blank 3 common block, a function name, a function result name, an automatic object, or an allocatable 4 variable. 5 C563 (R531) A data-i-do-object or a variable that appears as a data-stmt-object shall not be an object 6 designator in which a pointer appears other than as the entire rightmost part-ref . 7 C564 (R534)data-i-do-variable shall be a named variable. 8 C565 (R532) A scalar-int-expr of a data-implied-do shall involve as primaries only constants, subob- 9 jects of constants, or DO variables of the containing data-implied-dos, and each operation shall 10 be intrinsic. 11 C566 (R533) The array-element shall be a variable. 12 C567 (R533) The scalar-structure-component shall be a variable. 13 C568 (R533) The scalar-structure-component shall contain at least one part-ref that contains a sub- 14 script -list. 15 C569 (R533) In an array-element or a scalar-structure-component that is a data-i-do-object , any sub- 16 script shall be an expression whose primaries are either constants, subobjects of constants, or 17 DO variables of this data-implied-do or the containing data-implied-dos, and each operation shall 18 be intrinsic. 19 R535 data-stmt-value is [ data-stmt-repeat * ] data-stmt-constant 20 R536 data-stmt-repeat is scalar-int-constant 21 or scalar-int-constant-subobject 22 C570 (R536) The data-stmt-repeat shall be positive or zero. If the data-stmt-repeat is a named con- 23 stant, it shall have been declared previously in the scoping unit or made accessible by use 24 association or host association. 25 R537 data-stmt-constant is scalar-constant 26 or scalar-constant-subobject 27 or signed-int-literal-constant 28 or signed-real-literal-constant 29 or null-init 30 or structure-constructor 31 C571 (R537) If a DATA statement constant value is a named constant or a structure constructor, the 32 named constant or derived type shall have been declared previously in the scoping unit or made 33 accessible by use or host association. 34 C572 (R537) If a data-stmt-constant is a structure-constructor , it shall be an initialization expression. 35 R538 int-constant-subobject is constant-subobject 36 C573 (R538) int-constant-subobject shall be of type integer. 37 R539 constant-subobject is designator 38 C574 (R539) constant-subobject shall be a subobject of a constant. 39 C575 (R539) Any subscript, substring starting point, or substring ending point shall be an initializa- 40 tion expression. 86 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 The data-stmt-object -list is expanded to form a sequence of pointers and scalar variables, referred to as 2 "sequence of variables" in subsequent text. A nonpointer array whose unqualified name appears in a 3 data-stmt-object -list is equivalent to a complete sequence of its array elements in array element order 4 (6.2.2.2). An array section is equivalent to the sequence of its array elements in array element order. A 5 data-implied-do is expanded to form a sequence of array elements and structure components, under the 6 control of the implied-DO variable, as in the DO construct (8.1.6.4). 7 The data-stmt-value-list is expanded to form a sequence of data-stmt-constant s. A data-stmt-repeat 8 indicates the number of times the following data-stmt-constant is to be included in the sequence; omission 9 of a data-stmt-repeat has the effect of a repeat factor of 1. 10 A zero-sized array or an implied-DO list with an iteration count of zero contributes no variables to the 11 expanded sequence of variables, but a zero-length scalar character variable does contribute a variable 12 to the expanded sequence. A data-stmt-constant with a repeat factor of zero contributes no data-stmt- 13 constant s to the expanded sequence of scalar data-stmt-constant s. 14 The expanded sequences of variables and data-stmt-constant s are in one-to-one correspondence. Each 15 data-stmt-constant specifies the initial value or null-init for the corresponding variable. The lengths of 16 the two expanded sequences shall be the same. 17 A data-stmt-constant shall be null-init if and only if the corresponding data-stmt-object has the POINT- 18 ER attribute. The initial association status of a pointer data-stmt-object is disassociated. 19 A data-stmt-constant other than null-init shall be compatible with its corresponding variable according 20 to the rules of intrinsic assignment (7.4.1.2). The variable is initially defined with the value specified by 21 the data-stmt-constant ; if necessary, the value is converted according to the rules of intrinsic assignment 22 (7.4.1.3) to a value that agrees in type, type parameters, and shape with the variable. 23 If a data-stmt-constant is a boz-literal-constant , the corresponding variable shall be of type integer. The 24 boz-literal-constant is treated as if it were an int-literal-constant with a kind-param that specifies the 25 representation method with the largest decimal exponent range supported by the processor. NOTE 5.28 Examples of DATA statements are: CHARACTER (LEN = 10) NAME INTEGER, DIMENSION (0:9) :: MILES REAL, DIMENSION (100, 100) :: SKEW TYPE (NODE), POINTER :: HEAD_OF_LIST TYPE (PERSON) MYNAME, YOURNAME DATA NAME / 'JOHN DOE' /, MILES / 10 * 0 / DATA ((SKEW (K, J), J = 1, K), K = 1, 100) / 5050 * 0.0 / DATA ((SKEW (K, J), J = K + 1, 100), K = 1, 99) / 4950 * 1.0 / DATA HEAD_OF_LIST / NULL() / DATA MYNAME / PERSON (21, 'JOHN SMITH') / DATA YOURNAME % AGE, YOURNAME % NAME / 35, 'FRED BROWN' / The character variable NAME is initialized with the value JOHN DOE with padding on the right because the length of the constant is less than the length of the variable. All ten elements of the integer array MILES are initialized to zero. The two-dimensional array SKEW is initialized so that the lower triangle of SKEW is zero and the strict upper triangle is one. The structures MYNAME and YOURNAME are declared using the derived type PERSON from Note 4.20. The pointer HEAD OF LIST is declared using the derived type NODE from Note 4.29; it is initially disassociated. MYNAME is initialized by a structure constructor. YOURNAME is initialized by supplying a separate value for each component. SEP 2002 COMMITTEE DRAFT 87 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 5.2.6 DIMENSION statement 2 R540 dimension-stmt is DIMENSION [ :: ] array-name ( array-spec ) 3 [ , array-name ( array-spec ) ] ... 4 This statement specifies the DIMENSION attribute (5.1.2.5) and the array properties for each object 5 named. NOTE 5.29 An example of a DIMENSION statement is: DIMENSION A (10), B (10, 70), C (:) 6 5.2.7 INTENT statement 7 R541 intent-stmt is INTENT ( intent-spec ) [ :: ] dummy-arg-name-list 8 This statement specifies the INTENT attribute (5.1.2.7) for the dummy arguments in the list. NOTE 5.30 An example of an INTENT statement is: SUBROUTINE EX (A, B) INTENT (INOUT) :: A, B 9 5.2.8 OPTIONAL statement 10 R542 optional-stmt is OPTIONAL [ :: ] dummy-arg-name-list 11 This statement specifies the OPTIONAL attribute (5.1.2.9) for the dummy arguments in the list. NOTE 5.31 An example of an OPTIONAL statement is: SUBROUTINE EX (A, B) OPTIONAL :: B 12 5.2.9 PARAMETER statement 13 The PARAMETER statement specifies the PARAMETER attribute (5.1.2.10) and the values for 14 the named constants in the list. 15 R543 parameter-stmt is PARAMETER ( named-constant-def -list ) 16 R544 named-constant-def is named-constant = initialization-expr 17 The named constant shall have its type, type parameters, and shape specified in a prior specification of 18 the specification-part or declared implicitly (5.3). If the named constant is typed by the implicit typing 19 rules, its appearance in any subsequent specification of the specification-part shall confirm this implied 20 type and the values of any implied type parameters. 21 The value of each named constant is that specified by the corresponding initialization expression; if 22 necessary, the value is converted according to the rules of intrinsic assignment (7.4.1.3) to a value that 23 agrees in type, type parameters, and shape with the named constant. 88 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 5.32 An example of a PARAMETER statement is: PARAMETER (MODULUS = MOD (28, 3), NUMBER_OF_SENATORS = 100) 1 5.2.10 POINTER statement 2 R545 pointer-stmt is POINTER [ :: ] pointer-decl -list 3 R546 pointer-decl is object-name [ ( deferred-shape-spec-list ) ] 4 or proc-entity-name 5 C576 (R546) A proc-entity-name shall also be declared in a procedure-declaration-stmt . 6 This statement specifies the POINTER attribute (5.1.2.11) for a list of objects and procedure entities. NOTE 5.33 An example of a POINTER statement is: TYPE (NODE) :: CURRENT POINTER :: CURRENT, A (:, :) 7 5.2.11 PROTECTED statement 8 R547 protected-stmt is PROTECTED [ :: ] entity-name-list 9 The PROTECTED statement specifies the PROTECTED attribute (5.1.2.12) for a list of entities. 10 5.2.12 SAVE statement 11 R548 save-stmt is SAVE [ [ :: ] saved-entity-list ] 12 R549 saved-entity is object-name 13 or proc-pointer-name 14 or / common-block-name / 15 R550 proc-pointer-name is name 16 C577 (R550) A proc-pointer-name shall be the name of a procedure pointer. 17 C578 (R548) If a SAVE statement with an omitted saved entity list occurs in a scoping unit, no other 18 explicit occurrence of the SAVE attribute or SAVE statement is permitted in the same scoping 19 unit. 20 A SAVE statement with a saved entity list specifies the SAVE attribute (5.1.2.13) for all entities named 21 in the list or included within a common block named in the list. A SAVE statement without a saved 22 entity list is treated as though it contained the names of all allowed items in the same scoping unit. 23 If a particular common block name is specified in a SAVE statement in any scoping unit of a program 24 other than the main program, it shall be specified in a SAVE statement in every scoping unit in which 25 that common block appears except in the scoping unit of the main program. For a common block 26 declared in a SAVE statement, the values in the common block storage sequence (5.5.2.1) at the time a 27 RETURN or END statement is executed are made available to the next scoping unit in the execution 28 sequence of the program that specifies the common block name or accesses the common block. If a 29 named common block is specified in the scoping unit of the main program, the current values of the 30 common block storage sequence are made available to each scoping unit that specifies the named common 31 block. The definition status of each object in the named common block storage sequence depends on SEP 2002 COMMITTEE DRAFT 89 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 the association that has been established for the common block storage sequence. 2 A SAVE statement may appear in the specification part of a main program and has no effect. NOTE 5.34 An example of a SAVE statement is: SAVE A, B, C, / BLOCKA /, D 3 5.2.13 TARGET statement 4 R551 target-stmt is TARGET [ :: ] object-name [ ( array-spec ) ] 5 [ , object-name [ ( array-spec ) ] ] ... 6 This statement specifies the TARGET attribute (5.1.2.14) for a list of objects. NOTE 5.35 An example of a TARGET statement is: TARGET :: A (1000, 1000), B 7 5.2.14 VALUE statement 8 R552 value-stmt is VALUE [ :: ] dummy-arg-name-list 9 The VALUE statement specifies the VALUE attribute (5.1.2.15) for a list of dummy arguments. 10 5.2.15 VOLATILE statement 11 R553 volatile-stmt is VOLATILE [ :: ] object-name-list 12 The VOLATILE statement specifies the VOLATILE attribute (5.1.2.16) for a list of objects. 13 5.3 IMPLICIT statement 14 In a scoping unit, an IMPLICIT statement specifies a type, and possibly type parameters, for all 15 implicitly typed data entities whose names begin with one of the letters specified in the statement. 16 Alternatively, it may indicate that no implicit typing rules are to apply in a particular scoping unit. 17 R554 implicit-stmt is IMPLICIT implicit-spec-list 18 or IMPLICIT NONE 19 R555 implicit-spec is declaration-type-spec ( letter-spec-list ) 20 R556 letter-spec is letter [ ­ letter ] 21 C579 (R554) If IMPLICIT NONE is specified in a scoping unit, it shall precede any PARAMETER 22 statements that appear in the scoping unit and there shall be no other IMPLICIT statements 23 in the scoping unit. 24 C580 (R556) If the minus and second letter appear, the second letter shall follow the first letter 25 alphabetically. 26 A letter-spec consisting of two letters separated by a minus is equivalent to writing a list containing all 27 of the letters in alphabetical order in the alphabetic sequence from the first letter through the second 28 letter. For example, A­C is equivalent to A, B, C. The same letter shall not appear as a single letter, or 90 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 be included in a range of letters, more than once in all of the IMPLICIT statements in a scoping unit. 2 In each scoping unit, there is a mapping, which may be null, between each of the letters A, B, ..., Z 3 and a type (and type parameters). An IMPLICIT statement specifies the mapping for the letters in 4 its letter-spec-list. IMPLICIT NONE specifies the null mapping for all the letters. If a mapping is not 5 specified for a letter, the default for a program unit or an interface body is default integer if the letter 6 is I, J, ..., or N and default real otherwise, and the default for an internal or module procedure is the 7 mapping in the host scoping unit. 8 Any data entity that is not explicitly declared by a type declaration statement, is not an intrinsic 9 function, and is not made accessible by use association or host association is declared implicitly to be of 10 the type (and type parameters) mapped from the first letter of its name, provided the mapping is not 11 null. The mapping for the first letter of the data entity shall either have been established by a prior 12 IMPLICIT statement or be the default mapping for the letter. The mapping may be to a derived type 13 that is inaccessible in the local scope if the derived type is accessible to the host scope. The data entity 14 is treated as if it were declared in an explicit type declaration in the outermost scoping unit in which it 15 appears. An explicit type specification in a FUNCTION statement overrides an IMPLICIT statement 16 for the name of the result variable of that function subprogram. NOTE 5.36 The following are examples of the use of IMPLICIT statements: MODULE EXAMPLE_MODULE IMPLICIT NONE ... INTERFACE FUNCTION FUN (I) ! Not all data entities need INTEGER FUN ! be declared explicitly END FUNCTION FUN END INTERFACE CONTAINS FUNCTION JFUN (J) ! All data entities need to INTEGER JFUN, J ! be declared explicitly. ... END FUNCTION JFUN END MODULE EXAMPLE_MODULE SUBROUTINE SUB IMPLICIT COMPLEX (C) C = (3.0, 2.0) ! C is implicitly declared COMPLEX ... CONTAINS SUBROUTINE SUB1 IMPLICIT INTEGER (A, C) C = (0.0, 0.0) ! C is host associated and of ! type complex Z = 1.0 ! Z is implicitly declared REAL A = 2 ! A is implicitly declared INTEGER CC = 1 ! CC is implicitly declared INTEGER ... END SUBROUTINE SUB1 SUBROUTINE SUB2 Z = 2.0 ! Z is implicitly declared REAL and ! is different from the variable of SEP 2002 COMMITTEE DRAFT 91 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 5.36 (cont.) ! the same name in SUB1 ... END SUBROUTINE SUB2 SUBROUTINE SUB3 USE EXAMPLE_MODULE ! Accesses integer function FUN ! by use association Q = FUN (K) ! Q is implicitly declared REAL and ... ! K is implicitly declared INTEGER END SUBROUTINE SUB3 END SUBROUTINE SUB NOTE 5.37 An IMPLICIT statement may specify a declaration-type-spec of derived type. For example, given an IMPLICIT statement and a type defined as follows: IMPLICIT TYPE (POSN) (A-B, W-Z), INTEGER (C-V) TYPE POSN REAL X, Y INTEGER Z END TYPE POSN variables beginning with the letters A, B, W, X, Y, and Z are implicitly typed with the type POSN and the remaining variables are implicitly typed with type INTEGER. NOTE 5.38 The following is an example of a mapping to a derived type that is inaccessible in the local scope: PROGRAM MAIN IMPLICIT TYPE(BLOB) (A) TYPE BLOB INTEGER :: I END TYPE BLOB TYPE(BLOB) :: B CALL STEVE CONTAINS SUBROUTINE STEVE INTEGER :: BLOB .. AA = B .. END SUBROUTINE STEVE END PROGRAM MAIN In the subroutine STEVE, it is not possible to explicitly declare a variable to be of type BLOB because BLOB has been given a different meaning, but implicit mapping for the letter A still maps to type BLOB, so AA is of type BLOB. 92 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 5.4 NAMELIST statement 2 A NAMELIST statement specifies a group of named data objects, which may be referred to by a 3 single name for the purpose of data transfer (9.5, 10.10). 4 R557 namelist-stmt is NAMELIST 5 / namelist-group-name / namelist-group-object -list 6 [ [ , ] / namelist-group-name / 7 namelist-group-object -list ] . . . 8 C581 (R557) The namelist-group-name shall not be a name made accessible by use association. 9 R558 namelist-group-object is variable-name 10 C582 (R558) A namelist-group-object shall not be an assumed-size array. 11 C583 (R557) A namelist-group-object shall not have the PRIVATE attribute if the namelist-group- 12 name has the PUBLIC attribute. 13 The order in which the variables are specified in the NAMELIST statement determines the order in 14 which the values appear on output. 15 Any namelist-group-name may occur more than once in the NAMELIST statements in a scoping unit. 16 The namelist-group-object -list following each successive appearance of the same namelist-group-name in 17 a scoping unit is treated as a continuation of the list for that namelist-group-name. 18 A namelist group object may be a member of more than one namelist group. 19 A namelist group object shall either be accessed by use or host association or shall have its type, type 20 parameters, and shape specified by previous specification statements or the procedure heading in the 21 same scoping unit or by the implicit typing rules in effect for the scoping unit. If a namelist group object 22 is typed by the implicit typing rules, its appearance in any subsequent type declaration statement shall 23 confirm the implied type and type parameters. NOTE 5.39 An example of a NAMELIST statement is: NAMELIST /NLIST/ A, B, C 24 5.5 Storage association of data objects 25 In general, the physical storage units or storage order for data objects is not specifiable. However, 26 the EQUIVALENCE, COMMON, and SEQUENCE statements and the BIND(C) type-attr-spec provide 27 for control of the order and layout of storage units. The general mechanism of storage association is 28 described in 16.4.3. 29 5.5.1 EQUIVALENCE statement 30 An EQUIVALENCE statement is used to specify the sharing of storage units by two or more objects 31 in a scoping unit. This causes storage association of the objects that share the storage units. 32 If the equivalenced objects have differing type or type parameters, the EQUIVALENCE statement does 33 not cause type conversion or imply mathematical equivalence. If a scalar and an array are equivalenced, 34 the scalar does not have array properties and the array does not have the properties of a scalar. SEP 2002 COMMITTEE DRAFT 93 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 R559 equivalence-stmt is EQUIVALENCE equivalence-set -list 2 R560 equivalence-set is ( equivalence-object , equivalence-object -list ) 3 R561 equivalence-object is variable-name 4 or array-element 5 or substring 6 C584 (R561) An equivalence-object shall not be a designator with a base object that is a dummy 7 argument, a pointer, an allocatable variable, a derived-type object that has an allocatable ulti- 8 mate component, an object of a nonsequence derived type, an object of a derived type that has 9 a pointer at any level of component selection, an automatic object, a function name, an entry 10 name, a result name, a variable with the BIND attribute, a variable in a common block that 11 has the BIND attribute, or a named constant. 12 C585 (R561) An equivalence-object shall not be a designator that has more than one part-ref . 13 C586 (R561) An equivalence-object shall not have the TARGET attribute. 14 C587 (R561) Each subscript or substring range expression in an equivalence-object shall be an integer 15 initialization expression (7.1.7). 16 C588 (R560) If an equivalence-object is of type default integer, default real, double precision real, 17 default complex, default logical, or numeric sequence type, all of the objects in the equivalence 18 set shall be of these types. 19 C589 (R560) If an equivalence-object is of type default character or character sequence type, all of the 20 objects in the equivalence set shall be of these types. 21 C590 (R560) If an equivalence-object is of a sequence derived type that is not a numeric sequence or 22 character sequence type, all of the objects in the equivalence set shall be of the same type with 23 the same type parameter values. 24 C591 (R560) If an equivalence-object is of an intrinsic type other than default integer, default real, 25 double precision real, default complex, default logical, or default character, all of the objects in 26 the equivalence set shall be of the same type with the same kind type parameter value. 27 C592 (R561) If an equivalence-object has the PROTECTED attribute, all of the objects in the equiv- 28 alence set shall have the PROTECTED attribute. 29 C593 (R561) The name of an equivalence-object shall not be a name made accessible by use association. 30 C594 (R561) A substring shall not have length zero. NOTE 5.40 The EQUIVALENCE statement allows the equivalencing of sequence structures and the equiv- alencing of objects of intrinsic type with nondefault type parameters, but there are strict rules regarding the appearance of these objects in an EQUIVALENCE statement. A structure that appears in an EQUIVALENCE statement shall be a sequence structure. If a sequence structure is not of numeric sequence type or of character sequence type, it shall be equivalenced only to objects of the same type with the same type parameter values. A structure of a numeric sequence type may be equivalenced to another structure of a numeric sequence type, an object of default integer type, default real type, double precision real type, default complex type, or default logical type such that components of the structure ultimately become associated only with objects of these types. 94 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 5.40 (cont.) A structure of a character sequence type may be equivalenced to an object of default character type or another structure of a character sequence type. An object of intrinsic type with nondefault kind type parameters may be equivalenced only to objects of the same type and kind type parameters. Further rules on the interaction of EQUIVALENCE statements and default initialization are given in 16.4.3.3. 1 5.5.1.1 Equivalence association 2 An EQUIVALENCE statement specifies that the storage sequences (16.4.3.1) of the data objects specified 3 in an equivalence-set are storage associated. All of the nonzero-sized sequences in the equivalence-set , if 4 any, have the same first storage unit, and all of the zero-sized sequences in the equivalence-set , if any, 5 are storage associated with one another and with the first storage unit of any nonzero-sized sequences. 6 This causes the storage association of the data objects in the equivalence-set and may cause storage 7 association of other data objects. 8 5.5.1.2 Equivalence of default character objects 9 A data object of type default character may be equivalenced only with other objects of type default 10 character. The lengths of the equivalenced objects need not be the same. 11 An EQUIVALENCE statement specifies that the storage sequences of all the default character data 12 objects specified in an equivalence-set are storage associated. All of the nonzero-sized sequences in the 13 equivalence-set , if any, have the same first character storage unit, and all of the zero-sized sequences in 14 the equivalence-set , if any, are storage associated with one another and with the first character storage 15 unit of any nonzero-sized sequences. This causes the storage association of the data objects in the 16 equivalence-set and may cause storage association of other data objects. NOTE 5.41 For example, using the declarations: CHARACTER (LEN = 4) :: A, B CHARACTER (LEN = 3) :: C (2) EQUIVALENCE (A, C (1)), (B, C (2)) the association of A, B, and C can be illustrated graphically as: 1 2 3 4 5 6 7 |--- --- A --- ---| |--- --- B --- ---| |--- C(1) ---| |--- C(2) ---| 17 5.5.1.3 Array names and array element designators 18 For a nonzero-sized array, the use of the array name unqualified by a subscript list in an EQUIVALENCE 19 statement has the same effect as using an array element designator that identifies the first element of 20 the array. SEP 2002 COMMITTEE DRAFT 95 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 5.5.1.4 Restrictions on EQUIVALENCE statements 2 An EQUIVALENCE statement shall not specify that the same storage unit is to occur more than once 3 in a storage sequence. NOTE 5.42 For example: REAL, DIMENSION (2) :: A REAL :: B EQUIVALENCE (A (1), B), (A (2), B) ! Not standard conforming is prohibited, because it would specify the same storage unit for A (1) and A (2). 4 An EQUIVALENCE statement shall not specify that consecutive storage units are to be nonconsecutive. 5 NOTE 5.43 For example, the following is prohibited: REAL A (2) DOUBLE PRECISION D (2) EQUIVALENCE (A (1), D (1)), (A (2), D (2)) ! Not standard conforming 6 5.5.2 COMMON statement 7 The COMMON statement specifies blocks of physical storage, called common blocks, that may be 8 accessed by any of the scoping units in a program. Thus, the COMMON statement provides a global 9 data facility based on storage association (16.4.3). 10 The common blocks specified by the COMMON statement may be named and are called named com- 11 mon blocks, or may be unnamed and are called blank common. 12 R562 common-stmt is COMMON 13 [ / [ common-block-name ] / ] common-block-object -list 14 [ [ , ] / [ common-block-name ] / 15 common-block-object -list ] ... 16 R563 common-block-object is variable-name [ ( explicit-shape-spec-list ) ] 17 or proc-pointer-name 18 C595 (R563) Only one appearance of a given variable-name or proc-pointer-name is permitted in all 19 common-block-object -list s within a scoping unit. 20 C596 (R563) A common-block-object shall not be a dummy argument, an allocatable variable, a 21 derived-type object with an ultimate component that is allocatable, an automatic object, a 22 function name, an entry name, a variable with the BIND attribute, or a result name. 23 C597 (R563) If a common-block-object is of a derived type, it shall be a sequence type (4.5.1) with no 24 default initialization. 25 C598 (R563) A variable-name or proc-pointer-name shall not be a name made accessible by use 26 association. 27 In each COMMON statement, the data objects whose names appear in a common block object list 28 following a common block name are declared to be in that common block. If the first common block 96 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 name is omitted, all data objects whose names appear in the first common block object list are specified to 2 be in blank common. Alternatively, the appearance of two slashes with no common block name between 3 them declares the data objects whose names appear in the common block object list that follows to be 4 in blank common. 5 Any common block name or an omitted common block name for blank common may occur more than 6 once in one or more COMMON statements in a scoping unit. The common block list following each 7 successive appearance of the same common block name in a scoping unit is treated as a continuation of 8 the list for that common block name. Similarly, each blank common block object list in a scoping unit 9 is treated as a continuation of blank common. 10 The form variable-name (explicit-shape-spec-list ) declares variable-name to have the DIMENSION at- 11 tribute and specifies the array properties that apply. If derived-type objects of numeric sequence type 12 (4.5.1) or character sequence type (4.5.1) appear in common, it is as if the individual components were 13 enumerated directly in the common list. NOTE 5.44 Examples of COMMON statements are: COMMON /BLOCKA/ A, B, D (10, 30) COMMON I, J, K 14 5.5.2.1 Common block storage sequence 15 For each common block in a scoping unit, a common block storage sequence is formed as follows: 16 (1) A storage sequence is formed consisting of the sequence of storage units in the storage 17 sequences (16.4.3.1) of all data objects in the common block object lists for the common 18 block. The order of the storage sequences is the same as the order of the appearance of the 19 common block object lists in the scoping unit. 20 (2) The storage sequence formed in (1) is extended to include all storage units of any storage 21 sequence associated with it by equivalence association. The sequence may be extended only 22 by adding storage units beyond the last storage unit. Data objects associated with an entity 23 in a common block are considered to be in that common block. 24 Only COMMON statements and EQUIVALENCE statements appearing in the scoping unit contribute 25 to common block storage sequences formed in that unit. 26 5.5.2.2 Size of a common block 27 The size of a common block is the size of its common block storage sequence, including any extensions 28 of the sequence resulting from equivalence association. 29 5.5.2.3 Common association 30 Within a program, the common block storage sequences of all nonzero-sized common blocks with the 31 same name have the same first storage unit, and the common block storage sequences of all zero-sized 32 common blocks with the same name are storage associated with one another. Within a program, the 33 common block storage sequences of all nonzero-sized blank common blocks have the same first storage 34 unit and the storage sequences of all zero-sized blank common blocks are associated with one another and 35 with the first storage unit of any nonzero-sized blank common blocks. This results in the association of 36 objects in different scoping units. Use association or host association may cause these associated objects 37 to be accessible in the same scoping unit. 38 A nonpointer object of default integer type, default real type, double precision real type, default complex SEP 2002 COMMITTEE DRAFT 97 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 type, default logical type, or numeric sequence type shall become associated only with nonpointer objects 2 of these types. 3 A nonpointer object of type default character or character sequence type shall become associated only 4 with nonpointer objects of these types. 5 A nonpointer object of a derived type that is not a numeric sequence or character sequence type shall 6 become associated only with nonpointer objects of the same type with the same type parameter values. 7 A nonpointer object of intrinsic type other than default integer, default real, double precision real, default 8 complex, default logical, or default character shall become associated only with nonpointer objects of 9 the same type and type parameters. 10 A data pointer shall become storage associated only with data pointers of the same type and rank. 11 Data pointers that are storage associated shall have deferred the same type parameters; corresponding 12 nondeferred type parameters shall have the same value. A procedure pointer shall become storage 13 associated only with another procedure pointer; either both interfaces shall be explicit or both interfaces 14 shall be implicit. If the interfaces are explicit, the characteristics shall be the same. If the interfaces 15 are implicit, either both shall be subroutines or both shall be functions with the same type and type 16 parameters. 17 An object with the TARGET attribute may become storage associated only with another object that 18 has the TARGET attribute and the same type and type parameters. NOTE 5.45 A common block is permitted to contain sequences of different storage units, provided each scoping unit that accesses the common block specifies an identical sequence of storage units for the common block. For example, this allows a single common block to contain both numeric and character storage units. Association in different scoping units between objects of default type, objects of double precision real type, and sequence structures is permitted according to the rules for equivalence objects (5.5.1). 19 5.5.2.4 Differences between named common and blank common 20 A blank common block has the same properties as a named common block, except for the following: 21 (1) Execution of a RETURN or END statement may cause data objects in a named common 22 block to become undefined unless the common block name has been declared in a SAVE 23 statement, but never causes data objects in blank common to become undefined (16.5.6). 24 (2) Named common blocks of the same name shall be of the same size in all scoping units of a 25 program in which they appear, but blank common blocks may be of different sizes. 26 (3) A data object in a named common block may be initially defined by means of a DATA 27 statement or type declaration statement in a block data program unit (11.3), but objects in 28 blank common shall not be initially defined. 29 5.5.2.5 Restrictions on common and equivalence 30 An EQUIVALENCE statement shall not cause the storage sequences of two different common blocks to 31 be associated. 32 Equivalence association shall not cause a common block storage sequence to be extended by adding 33 storage units preceding the first storage unit of the first object specified in a COMMON statement for 34 the common block. 98 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 5.46 For example, the following is not permitted: COMMON /X/ A REAL B (2) EQUIVALENCE (A, B (2)) ! Not standard conforming 1 Equivalence association shall not cause a derived-type object with default initialization to be associated 2 with an object in a common block. SEP 2002 COMMITTEE DRAFT 99 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 100 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 Section 6: Use of data objects 2 The appearance of a data object designator in a context that requires its value is termed a reference. A 3 reference is permitted only if the data object is defined. A reference to a pointer is permitted only if the 4 pointer is associated with a target object that is defined. A data object becomes defined with a value 5 when events described in 16.5.5 occur. 6 R601 variable is designator 7 C601 (R601) designator shall not be a constant or a subobject of a constant. 8 R602 variable-name is name 9 C602 (R602) A variable-name shall be the name of a variable. 10 R603 designator is object-name 11 or array-element 12 or array-section 13 or structure-component 14 or substring 15 R604 logical-variable is variable 16 C603 (R604) logical-variable shall be of type logical. 17 R605 default-logical-variable is variable 18 C604 (R605) default-logical-variable shall be of type default logical. 19 R606 char-variable is variable 20 C605 (R606) char-variable shall be of type character. 21 R607 default-char-variable is variable 22 C606 (R607) default-char-variable shall be of type default character. 23 R608 int-variable is variable 24 C607 (R608) int-variable shall be of type integer. NOTE 6.1 For example, given the declarations: CHARACTER (10) A, B (10) TYPE (PERSON) P ! See Note 4.20 then A, B, B (1), B (1:5), P % AGE, and A (1:1) are all variables. 25 A constant (3.2.2) is a literal constant or a named constant. A literal constant is a scalar denoted by a 26 syntactic form, which indicates its type, type parameters, and value. A named constant is a constant 27 that has a name; the name has the PARAMETER attribute (5.1.2.10, 5.2.9). A reference to a constant 28 is always permitted; redefinition of a constant is never permitted. SEP 2002 COMMITTEE DRAFT 101 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 6.1 Scalars 2 A scalar (2.4.4) is a data entity that can be represented by a single value of the type and that is not an 3 array (6.2). Its value, if defined, is a single element from the set of values that characterize its type. NOTE 6.2 A scalar object of derived type has a single value that consists of the values of its components (4.5.6). 4 A scalar has rank zero. 5 6.1.1 Substrings 6 A substring is a contiguous portion of a character string (4.4.4). The following rules define the forms 7 of a substring: 8 R609 substring is parent-string ( substring-range ) 9 R610 parent-string is scalar-variable-name 10 or array-element 11 or scalar-structure-component 12 or scalar-constant 13 R611 substring-range is [ scalar-int-expr ] : [ scalar-int-expr ] 14 C608 (R610) parent-string shall be of type character. 15 The first scalar-int-expr in substring-range is called the starting point and the second one is called 16 the ending point. The length of a substring is the number of characters in the substring and is 17 MAX (l-f +1, 0), where f and l are the values of the starting and ending point expressions, respectively. 18 Let the characters in the parent string be numbered 1, 2, 3, ..., n, where n is the length of the parent 19 string. Then the characters in the substring are those from the parent string from the starting point and 20 proceeding in sequence up to and including the ending point. Both the starting point and the ending 21 point shall be within the range 1, 2, ..., n unless the starting point exceeds the ending point, in which 22 case the substring has length zero. If the starting point is not specified, the default value is 1. If the 23 ending point is not specified, the default value is n. 24 If the parent is a variable, the substring is also a variable. NOTE 6.3 Examples of character substrings are: B(1)(1:5) array element as parent string P%NAME(1:1) structure component as parent string ID(4:9) scalar variable name as parent string '0123456789'(N:N) character constant as parent string 25 6.1.2 Structure components 26 A structure component is part of an object of derived type; it may be referenced by an object 27 designator. A structure component may be a scalar or an array. 28 R612 data-ref is part-ref [ % part-ref ] ... 29 R613 part-ref is part-name [ ( section-subscript -list ) ] 102 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 C609 (R612) In a data-ref , each part-name except the rightmost shall be of derived type. 2 C610 (R612) In a data-ref , each part-name except the leftmost shall be the name of a component of 3 the derived-type definition of the declared type of the preceding part-name. 4 C611 (R612) The leftmost part-name shall be the name of a data object. 5 C612 (R613) In a part-ref containing a section-subscript -list, the number of section-subscript s shall 6 equal the rank of part-name. 7 The rank of a part-ref of the form part-name is the rank of part-name. The rank of a part-ref that has 8 a section subscript list is the number of subscript triplets and vector subscripts in the list. 9 C613 (R612) In a data-ref , there shall not be more than one part-ref with nonzero rank. A part-name 10 to the right of a part-ref with nonzero rank shall not have the ALLOCATABLE or POINTER 11 attribute. 12 The rank of a data-ref is the rank of the part-ref with nonzero rank, if any; otherwise, the rank is zero. 13 The base object of a data-ref is the data object whose name is the leftmost part name. 14 The type and type parameters, if any, of a data-ref are those of the rightmost part name. 15 A data-ref with more than one part-ref is a subobject of its base object if none of the part-names, 16 except for possibly the rightmost, are pointers. If the rightmost part-name is the only pointer, then the 17 data-ref is a subobject of its base object in contexts that pertain to its pointer association status but 18 not in any other contexts. NOTE 6.4 If X is an object of derived type with a pointer component P, then the pointer X%P is a subobject of X when considered as a pointer ­ that is in contexts where it is not dereferenced. However the target of X%P is not a subobject of X. Thus, in contexts where X%P is dereferenced to refer to the target, it is not a subobject of X. 19 R614 structure-component is data-ref 20 C614 (R614) In a structure-component , there shall be more than one part-ref and the rightmost 21 part-ref shall be of the form part-name. 22 A structure component shall be neither referenced nor defined before the declaration of the base object. 23 A structure component is a pointer only if the rightmost part name is defined to have the POINTER 24 attribute. NOTE 6.5 Examples of structure components are: SCALAR_PARENT%SCALAR_FIELD scalar component of scalar parent ARRAY_PARENT(J)%SCALAR_FIELD component of array element parent ARRAY_PARENT(1:N)%SCALAR_FIELD component of array section parent For a more elaborate example see C.3.1. NOTE 6.6 The syntax rules are structured such that a data-ref that ends in a component name without a SEP 2002 COMMITTEE DRAFT 103 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 6.6 (cont.) following subscript list is a structure component, even when other component names in the data- ref are followed by a subscript list. A data-ref that ends in a component name with a following subscript list is either an array element or an array section. A data-ref of nonzero rank that ends with a substring-range is an array section. A data-ref of zero rank that ends with a substring-range is a substring. 1 A subcomponent of an object of derived type is a component of that object or of a subobject of that 2 object. 3 6.1.3 Type parameter inquiry 4 A type parameter inquiry is used to inquire about a type parameter of a data object. It applies to 5 both intrinsic and derived types. 6 R615 type-param-inquiry is designator % type-param-name 7 C615 (R615) The type-param-name shall be the name of a type parameter of the declared type of the 8 object designated by the designator . 9 A deferred type parameter of a pointer that is not associated or of an unallocated allocatable variable 10 shall not be inquired about. NOTE 6.7 A type-param-inquiry has a syntax like that of a structure component reference, but it does not have the same semantics. It is not a variable and thus can never be assigned to. It may be used only as a primary in an expression. It is scalar even if designator is an array. The intrinsic type parameters can also be inquired about by using the intrinsic functions KIND and LEN. NOTE 6.8 The following are examples of type parameter inquiries: a%kind !-- A is real. Same value as KIND(a). s%len !-- S is character. Same value as LEN(s). b(10)%kind !-- Inquiry about an array element. p%dim !-- P is of the derived type general_point. See Note 4.21 for the definition of the general point type used in the last example above. 11 6.2 Arrays 12 An array is a set of scalar data, all of the same type and type parameters, whose individual elements 13 are arranged in a rectangular pattern. The scalar data that make up an array are the array elements. 14 No order of reference to the elements of an array is indicated by the appearance of the array designator, 15 except where array element ordering (6.2.2.2) is specified. 16 6.2.1 Whole arrays 17 A whole array is a named array, which may be either a named constant (5.1.2.10, 5.2.9) or a variable; 18 no subscript list is appended to the name. 104 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 The appearance of a whole array variable in an executable construct specifies all the elements of the 2 array (2.4.5). An assumed-size array is permitted to appear as a whole array in an executable construct 3 only as an actual argument in a procedure reference that does not require the shape. 4 The appearance of a whole array name in a nonexecutable statement specifies the entire array except 5 for the appearance of a whole array name in an equivalence set (5.5.1.3). 6 6.2.2 Array elements and array sections 7 R616 array-element is data-ref 8 C616 (R616) In an array-element , every part-ref shall have rank zero and the last part-ref shall 9 contain a subscript -list. 10 R617 array-section is data-ref [ ( substring-range ) ] 11 C617 (R617) In an array-section, exactly one part-ref shall have nonzero rank, and either the final 12 part-ref shall have a section-subscript -list with nonzero rank or another part-ref shall have 13 nonzero rank. 14 C618 (R617) In an array-section with a substring-range, the rightmost part-name shall be of type 15 character. 16 R618 subscript is scalar-int-expr 17 R619 section-subscript is subscript 18 or subscript-triplet 19 or vector-subscript 20 R620 subscript-triplet is [ subscript ] : [ subscript ] [ : stride ] 21 R621 stride is scalar-int-expr 22 R622 vector-subscript is int-expr 23 C619 (R622) A vector-subscript shall be an integer array expression of rank one. 24 C620 (R620) The second subscript shall not be omitted from a subscript-triplet in the last dimension 25 of an assumed-size array. 26 An array element is a scalar. An array section is an array. If a substring-range is present in an array- 27 section, each element is the designated substring of the corresponding element of the array section. NOTE 6.9 For example, with the declarations: REAL A (10, 10) CHARACTER (LEN = 10) B (5, 5, 5) A (1, 2) is an array element, A (1:N:2, M) is a rank-one array section, and B (:, :, :) (2:3) is an array of shape (5, 5, 5) whose elements are substrings of length 2 of the corresponding elements of B. 28 An array element or an array section never has the POINTER attribute. NOTE 6.10 Examples of array elements and array sections are: SEP 2002 COMMITTEE DRAFT 105 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 6.10 (cont.) ARRAY_A(1:N:2)%ARRAY_B(I, J)%STRING(K)(:) array section SCALAR_PARENT%ARRAY_FIELD(J) array element SCALAR_PARENT%ARRAY_FIELD(1:N) array section SCALAR_PARENT%ARRAY_FIELD(1:N)%SCALAR_FIELD array section 1 6.2.2.1 Array elements 2 The value of a subscript in an array element shall be within the bounds for that dimension. 3 6.2.2.2 Array element order 4 The elements of an array form a sequence known as the array element order. The position of an array 5 element in this sequence is determined by the subscript order value of the subscript list designating the 6 element. The subscript order value is computed from the formulas in Table 6.1. Table 6.1: Subscript order value Rank Subscript bounds Subscript list Subscript order value 1 j1:k1 s1 1 + (s1 - j1) 1 + (s 2 j 1 - j1) 1:k1,j2:k2 s1, s2 + (s2 - j2) × d1 1 + (s1 - j1) 3 j1:k1, j2:k2, j3:k3 s1, s2, s3 + (s2 - j2) × d1 + (s3 - j3) × d2 × d1 · · · · · · · · · · · · 1 + (s1 - j1) + (s2 - j2) × d1 + (s 7 j 3 - j3) × d2 × d1 1:k1, . . . , j7:k7 s1, . . . , s7 + . . . + (s7 - j7) × d6 × d5 × . . . × d1 Notes for Table 6.1: 1) di = max (ki - ji + 1, 0) is the size of the ith dimension. 2) If the size of the array is nonzero, ji si ki for all i = 1, 2, ..., 7. 7 6.2.2.3 Array sections 8 An array section is an array subobject optionally followed by a substring range. 9 In an array-section having a section-subscript -list, each subscript-triplet and vector-subscript in the 10 section subscript list indicates a sequence of subscripts, which may be empty. Each subscript in such a 11 sequence shall be within the bounds for its dimension unless the sequence is empty. The array section is 12 the set of elements from the array determined by all possible subscript lists obtainable from the single 13 subscripts or sequences of subscripts specified by each section subscript. 14 In an array-section with no section-subscript -list, the rank and shape of the array is the rank and shape 15 of the part-ref with nonzero rank; otherwise, the rank of the array section is the number of subscript 16 triplets and vector subscripts in the section subscript list. The shape is the rank-one array whose ith 17 element is the number of integer values in the sequence indicated by the ith subscript triplet or vector 18 subscript. If any of these sequences is empty, the array section has size zero. The subscript order of the 106 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 elements of an array section is that of the array data object that the array section represents. 2 6.2.2.3.1 Subscript triplet 3 A subscript triplet designates a regular sequence of subscripts consisting of zero or more subscript values. 4 The third expression in the subscript triplet is the increment between the subscript values and is called 5 the stride. The subscripts and stride of a subscript triplet are optional. An omitted first subscript in a 6 subscript triplet is equivalent to a subscript whose value is the lower bound for the array and an omitted 7 second subscript is equivalent to the upper bound. An omitted stride is equivalent to a stride of 1. 8 The stride shall not be zero. 9 When the stride is positive, the subscripts specified by a triplet form a regularly spaced sequence of 10 integers beginning with the first subscript and proceeding in increments of the stride to the largest such 11 integer not greater than the second subscript; the sequence is empty if the first subscript is greater than 12 the second. NOTE 6.11 For example, suppose an array is declared as A (5, 4, 3). The section A (3 : 5, 2, 1 : 2) is the array of shape (3, 2): A (3, 2, 1) A (3, 2, 2) A (4, 2, 1) A (4, 2, 2) A (5, 2, 1) A (5, 2, 2) 13 When the stride is negative, the sequence begins with the first subscript and proceeds in increments of 14 the stride down to the smallest such integer equal to or greater than the second subscript; the sequence 15 is empty if the second subscript is greater than the first. NOTE 6.12 For example, if an array is declared B (10), the section B (9 : 1 : ­2) is the array of shape (5) whose elements are B (9), B (7), B (5), B (3), and B (1), in that order. NOTE 6.13 A subscript in a subscript triplet need not be within the declared bounds for that dimension if all values used in selecting the array elements are within the declared bounds. For example, if an array is declared as B (10), the array section B (3 : 11 : 7) is the array of shape (2) consisting of the elements B (3) and B (10), in that order. 16 6.2.2.3.2 Vector subscript 17 A vector subscript designates a sequence of subscripts corresponding to the values of the elements 18 of the expression. Each element of the expression shall be defined. A many-one array section is an 19 array section with a vector subscript having two or more elements with the same value. A many-one 20 array section shall appear neither on the left of the equals in an assignment statement nor as an input 21 item in a READ statement. 22 An array section with a vector subscript shall not be argument associated with a dummy array that 23 is defined or redefined. An array section with a vector subscript shall not be the target in a pointer 24 assignment statement. An array section with a vector subscript shall not be an internal file. SEP 2002 COMMITTEE DRAFT 107 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 6.14 For example, suppose Z is a two-dimensional array of shape (5, 7) and U and V are one-dimensional arrays of shape (3) and (4), respectively. Assume the values of U and V are: U = (/ 1, 3, 2 /) V = (/ 2, 1, 1, 3 /) Then Z (3, V) consists of elements from the third row of Z in the order: Z (3, 2) Z (3, 1) Z (3, 1) Z (3, 3) and Z (U, 2) consists of the column elements: Z (1, 2) Z (3, 2) Z (2, 2) and Z (U, V) consists of the elements: Z (1, 2) Z (1, 1) Z (1, 1) Z (1, 3) Z (3, 2) Z (3, 1) Z (3, 1) Z (3, 3) Z (2, 2) Z (2, 1) Z (2, 1) Z (2, 3) Because Z (3, V) and Z (U, V) contain duplicate elements from Z, the sections Z (3, V) and Z (U, V) shall not be redefined as sections. 1 6.3 Dynamic association 2 Dynamic control over the allocation, association, and deallocation of pointer targets is provided by 3 the ALLOCATE, NULLIFY, and DEALLOCATE statements and pointer assignment. ALLOCATE 4 (6.3.1) creates targets for pointers; pointer assignment (7.4.2) associates pointers with existing targets; 5 NULLIFY (6.3.2) disassociates pointers from targets, and DEALLOCATE (6.3.3) deallocates targets. 6 Dynamic association applies to scalars and arrays of any type. 7 The ALLOCATE and DEALLOCATE statements also are used to create and deallocate variables with 8 the ALLOCATABLE attribute. NOTE 6.15 Detailed remarks regarding pointers and dynamic association are in C.3.3. 9 6.3.1 ALLOCATE statement 10 The ALLOCATE statement dynamically creates pointer targets and allocatable variables. 11 R623 allocate-stmt is ALLOCATE ( [ type-spec :: ] allocation-list 12 [, alloc-opt -list ] ) 13 R624 alloc-opt is STAT = stat-variable 14 or ERRMSG = errmsg-variable 15 or SOURCE = source-variable 16 R625 stat-variable is scalar-int-variable 17 R626 errmsg-variable is scalar-default-char-variable 18 R627 allocation is allocate-object [ ( allocate-shape-spec-list ) ] 19 R628 allocate-object is variable-name 20 or structure-component 108 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 R629 allocate-shape-spec is [ allocate-lower-bound : ] allocate-upper-bound 2 R630 allocate-lower-bound is scalar-int-expr 3 R631 allocate-upper-bound is scalar-int-expr 4 R632 source-variable is variable 5 C621 (R628) Each allocate-object shall be a nonprocedure pointer or an allocatable variable. 6 C622 (R623) If any allocate-object in the statement has a deferred type parameter, either type-spec or 7 SOURCE= shall appear. 8 C623 (R623) If a type-spec appears, it shall specify a type with which each allocate-object is type 9 compatible. 10 C624 (R623) If any allocate-object is unlimited polymorphic, either type-spec or SOURCE= shall 11 appear. 12 C625 (R623) A type-param-value in a type-spec shall be an asterisk if and only if each allocate-object 13 is a dummy argument for which the corresponding type parameter is assumed. 14 C626 (R623) If a type-spec appears, the kind type parameter values of each allocate-object shall be 15 the same as the corresponding type parameter values of the type-spec. 16 C627 (R627) An allocate-shape-spec-list shall appear if and only if the allocate-object is an array. 17 C628 (R627) The number of allocate-shape-specs in an allocate-shape-spec-list shall be the same as 18 the rank of the allocate-object . 19 C629 (R624) No alloc-opt shall appear more than once in a given alloc-opt -list. 20 C630 (R623) If SOURCE= appears, type-spec shall not appear and allocation-list shall contain only 21 one allocate-object , which shall be type compatible (5.1.1.8) with source-variable. 22 C631 (R623) The source-variable shall be a scalar or have the same rank as allocate-object . 23 C632 (R623) Corresponding kind type parameters of allocate-object and source-variable shall have the 24 same values. 25 An allocate-object or a bound or type parameter of an allocate-object shall not depend on stat-variable, 26 errmsg-variable, or on the value, bounds, allocation status, or association status of any allocate-object 27 in the same ALLOCATE statement. 28 Neither stat-variable, source-variable, nor errmsg-variable shall be allocated within the ALLOCATE 29 statement in which it appears; nor shall they depend on the value, bounds, allocation status, or associ- 30 ation status of any allocate-object in the same ALLOCATE statement. 31 The optional type-spec specifies the dynamic type and type parameters of the objects to be allocated. If 32 a type-spec is specified, allocation of a polymorphic object allocates an object with the specified dynamic 33 type; if a source-variable is specified, the allocation allocates an object whose dynamic type and type 34 parameters are the same as those of the source-variable; otherwise it allocates an object with a dynamic 35 type the same as its declared type. 36 When an ALLOCATE statement having a type-spec is executed, any type-param-values in the type-spec 37 specify the type parameters. If the value specified for a type parameter differs from a corresponding 38 nondeferred value specified in the declaration of any of the allocate-object s then an error condition occurs. 39 If a type-param-value in a type-spec in an ALLOCATE statement is an asterisk, it denotes the current 40 value of that assumed type parameter. If it is an expression, subsequent redefinition or undefinition of 41 any entity in the expression does not affect the type parameter value. SEP 2002 COMMITTEE DRAFT 109 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 6.16 An example of an ALLOCATE statement is: ALLOCATE (X (N), B (-3 : M, 0:9), STAT = IERR_ALLOC) 1 When an ALLOCATE statement is executed for an array, the values of the lower bound and upper 2 bound expressions determine the bounds of the array. Subsequent redefinition or undefinition of any 3 entities in the bound expressions do not affect the array bounds. If the lower bound is omitted, the 4 default value is 1. If the upper bound is less than the lower bound, the extent in that dimension is zero 5 and the array has zero size. NOTE 6.17 An allocate-object may be of type character with zero character length. 6 If SOURCE= appears, source-variable shall be conformable (2.4.5) with allocation. If the value of a 7 nondeferred nonkind type parameter of allocate-object is different from the value of the corresponding 8 type parameter of source-variable, an error condition occurs. If the allocation is successful, source- 9 variable is then assigned to allocate-object by intrinsic assignment for objects whose declared type is the 10 dynamic type of source-variable. NOTE 6.18 An example of an ALLOCATE statement in which the value and dynamic type are determined by reference to another object is: CLASS(*), ALLOCATABLE :: NEW CLASS(*), POINTER :: OLD ! ... ALLOCATE (NEW, SOURCE=OLD) ! Allocate NEW with the value and dynamic type of OLD A more extensive example is given in C.3.2. 11 If the STAT= specifier appears, successful execution of the ALLOCATE statement causes the stat- 12 variable to become defined with a value of zero. If an error condition occurs during the execution 13 of the ALLOCATE statement, the stat-variable becomes defined with a processor-dependent positive 14 integer value and each allocate-object will have a processor-dependent status; each allocate-object that 15 was successfully allocated shall have an allocation status of allocated or a pointer association status of 16 associated; each allocate-object that was not successfully allocated shall retain its previous allocation 17 status or pointer association status. 18 If an error condition occurs during execution of an ALLOCATE statement that does not contain the 19 STAT= specifier, execution of the program is terminated. 20 The ERRMSG= specifier is described in 6.3.1.3. 21 6.3.1.1 Allocation of allocatable variables 22 The allocation status of an allocatable entity is one of the following at any time during the execution of 23 a program: 24 (1) An allocatable variable has a status of allocated if it has been allocated by an ALLOCATE 25 statement and has not been subsequently deallocated (6.3.3). An allocatable variable with 26 this status may be referenced, defined, or deallocated; allocating it causes an error condition 27 in the ALLOCATE statement. The intrinsic function ALLOCATED (13.7.9) returns true 110 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 for such a variable. 2 (2) An allocatable variable has a status of unallocated if it is not allocated. An allocatable 3 variable with this status shall not be referenced or defined. It shall not be supplied as an 4 actual argument except to certain intrinsic inquiry functions. It may be allocated with the 5 ALLOCATE statement. Deallocating it causes an error condition in the DEALLOCATE 6 statement. The intrinsic function ALLOCATED (13.7.9) returns false for such a variable. 7 At the beginning of execution of a program, allocatable variables are unallocated. 8 A saved allocatable object has an initial status of unallocated. If the object is allocated, its status 9 changes to allocated. The status remains allocated until the object is deallocated. 10 When the allocation status of an allocatable variable changes, the allocation status of any associated 11 allocatable variable changes accordingly. Allocation of an allocatable variable establishes values for the 12 deferred type parameters of all associated allocatable variables. 13 An unsaved allocatable object that is a local variable of a procedure has a status of unallocated at the 14 beginning of each invocation of the procedure. The status may change during execution of the procedure. 15 An unsaved allocatable object that is a local variable of a module or a subobject thereof has an initial 16 status of unallocated. The status may change during execution of the program. 17 When an object of derived type is created by an ALLOCATE statement, any allocatable ultimate 18 components have an allocation status of unallocated. 19 6.3.1.2 Allocation of pointer targets 20 Allocation of a pointer creates an object that implicitly has the TARGET attribute. Following successful 21 execution of an ALLOCATE statement for a pointer, the pointer is associated with the target and may 22 be used to reference or define the target. Additional pointers may become associated with the pointer 23 target or a part of the pointer target by pointer assignment. It is not an error to allocate a pointer 24 that is already associated with a target. In this case, a new pointer target is created as required by the 25 attributes of the pointer and any array bounds, type, and type parameters specified by the ALLOCATE 26 statement. The pointer is then associated with this new target. Any previous association of the pointer 27 with a target is broken. If the previous target had been created by allocation, it becomes inaccessible 28 unless other pointers are associated with it. The ASSOCIATED intrinsic function (13.7.13) may be used 29 to determine whether a pointer that does not have undefined association status is associated. 30 At the beginning of execution of a function whose result is a pointer, the association status of the result 31 pointer is undefined. Before such a function returns, it shall either associate a target with this pointer 32 or cause the association status of this pointer to become defined as disassociated. 33 6.3.1.3 ERRMSG= specifier 34 If an error condition occurs during execution of an ALLOCATE or DEALLOCATE statement, the 35 processor shall assign an explanatory message to errmsg-variable. If no such condition occurs, the 36 processor shall not change the value of errmsg-variable. 37 6.3.2 NULLIFY statement 38 The NULLIFY statement causes pointers to be disassociated. 39 R633 nullify-stmt is NULLIFY ( pointer-object -list ) 40 R634 pointer-object is variable-name 41 or structure-component 42 or proc-pointer-name SEP 2002 COMMITTEE DRAFT 111 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 C633 (R634) Each pointer-object shall have the POINTER attribute. 2 A pointer-object shall not depend on the value, bounds, or association status of another pointer-object 3 in the same NULLIFY statement. NOTE 6.19 When a NULLIFY statement is applied to a polymorphic pointer (5.1.1.8), its dynamic type becomes the declared type. 4 6.3.3 DEALLOCATE statement 5 The DEALLOCATE statement causes allocatable variables to be deallocated; it causes pointer tar- 6 gets to be deallocated and the pointers to be disassociated. 7 R635 deallocate-stmt is DEALLOCATE ( allocate-object -list [ , dealloc-opt -list ] ) 8 C634 (R635) Each allocate-object shall be a nonprocedure pointer or an allocatable variable. 9 R636 dealloc-opt is STAT = stat-variable 10 or ERRMSG = errmsg-variable 11 C635 (R636) No dealloc-opt shall appear more than once in a given dealloc-opt -list. 12 An allocate-object shall not depend on the value, bounds, allocation status, or association status of 13 another allocate-object in the same DEALLOCATE statement; it also shall not depend on the value of 14 the stat-variable or errmsg-variable in the same DEALLOCATE statement. 15 Neither stat-variable nor errmsg-variable shall be deallocated within the same DEALLOCATE state- 16 ment; they also shall not depend on the value, bounds, allocation status, or association status of any 17 allocate-object in the same DEALLOCATE statement. 18 If the STAT= specifier appears, successful execution of the DEALLOCATE statement causes the stat- 19 variable to become defined with a value of zero. If an error condition occurs during the execution of 20 the DEALLOCATE statement, the stat-variable becomes defined with a processor-dependent positive 21 integer value and each allocate-object that was successfully deallocated shall have an allocation status of 22 unallocated or a pointer association status of disassociated. Each allocate-object that was not successfully 23 deallocated shall retain its previous allocation status or pointer association status. NOTE 6.20 The status of objects that were not successfully deallocated can be individually checked with the ALLOCATED or ASSOCIATED intrinsic functions. 24 If an error condition occurs during execution of a DEALLOCATE statement that does not contain the 25 STAT= specifier, execution of the program is terminated. 26 The ERRMSG= specifier is described in 6.3.1.3. NOTE 6.21 An example of a DEALLOCATE statement is: DEALLOCATE (X, B) 112 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 6.3.3.1 Deallocation of allocatable variables 2 Deallocating an unallocated allocatable variable causes an error condition in the DEALLOCATE state- 3 ment. Deallocating an allocatable variable with the TARGET attribute causes the pointer association 4 status of any pointer associated with it to become undefined. 5 When the execution of a procedure is terminated by execution of a RETURN or END statement, an 6 allocatable variable that is a named local variable of the procedure retains its allocation and definition 7 status if it has the SAVE attribute or is a function result variable or a subobject thereof; otherwise, it 8 is deallocated. NOTE 6.22 The ALLOCATED intrinsic function may be used to determine whether a variable is allocated or unallocated. 9 If an unsaved allocatable object is a local variable of a module, and it is allocated when execution 10 of a RETURN or END statement results in no active scoping unit having access to the module, it is 11 processor-dependent whether the object retains its allocation status or is deallocated. NOTE 6.23 The following example illustrates the effects of SAVE on allocation status. MODULE MOD1 TYPE INITIALIZED_TYPE INTEGER :: I = 1 ! Default initialization END TYPE INITIALIZED_TYPE SAVE :: SAVED1, SAVED2 INTEGER :: SAVED1, UNSAVED1 TYPE(INITIALIZED_TYPE) :: SAVED2, UNSAVED2 ALLOCATABLE :: SAVED1(:), SAVED2(:), UNSAVED1(:), UNSAVED2(:) END MODULE MOD1 PROGRAM MAIN CALL SUB1 ! The values returned by the ALLOCATED intrinsic calls ! in the PRINT statement are: ! .FALSE., .FALSE., .FALSE., and .FALSE. ! Module MOD1 is used, and its variables are allocated. ! After return from the subroutine, whether the variables ! which were not specified with the SAVE attribute ! retain their allocation status is processor dependent. CALL SUB1 ! The values returned by the first two ALLOCATED intrinsic ! calls in the PRINT statement are: ! .TRUE., .TRUE. ! The values returned by the second two ALLOCATED ! intrinsic calls in the PRINT statement are ! processor dependent and each could be either ! .TRUE. or .FALSE. CONTAINS SUBROUTINE SUB1 USE MOD1 ! Brings in saved and unsaved variables. PRINT *, ALLOCATED(SAVED1), ALLOCATED(SAVED2), & ALLOCATED(UNSAVED1), ALLOCATED(UNSAVED2) IF (.NOT. ALLOCATED(SAVED1)) ALLOCATE(SAVED1(10)) SEP 2002 COMMITTEE DRAFT 113 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 6.23 (cont.) IF (.NOT. ALLOCATED(SAVED2)) ALLOCATE(SAVED2(10)) IF (.NOT. ALLOCATED(UNSAVED1)) ALLOCATE(UNSAVED1(10)) IF (.NOT. ALLOCATED(UNSAVED2)) ALLOCATE(UNSAVED2(10)) END SUBROUTINE SUB1 END PROGRAM MAIN 1 If an executable construct references a function whose result is either allocatable or a structure with 2 a subobject that is allocatable, and the function reference is executed, an allocatable result and any 3 subobject that is an allocated allocatable entity in the result returned by the function is deallocated 4 after execution of the innermost executable construct containing the reference. 5 If a specification expression in a scoping unit references a function whose result is either allocatable or 6 a structure with a subobject that is allocatable, and the function reference is executed, an allocatable 7 result and any subobject that is an allocated allocatable entity in the result returned by the function is 8 deallocated before execution of the first executable statement in the scoping unit. 9 When a procedure is invoked, an allocated allocatable object that is an actual argument associated with 10 an INTENT(OUT) allocatable dummy argument is deallocated; an allocated allocatable object that is 11 a subobject of an actual argument associated with an INTENT(OUT) dummy argument is deallocated. 12 When an intrinsic assignment statement (7.4.1.3) is executed, any allocated allocatable subobject of the 13 variable is deallocated before the assignment takes place. 14 When a variable of derived type is deallocated, any allocated allocatable subobject is deallocated. 15 If an allocatable component is a subobject of a finalizable object, that object is finalized before the 16 component is automatically deallocated. 17 The effect of automatic deallocation is the same as that of a DEALLOCATE statement without a 18 dealloc-opt -list. NOTE 6.24 In the following example: SUBROUTINE PROCESS REAL, ALLOCATABLE :: TEMP(:) REAL, ALLOCATABLE, SAVE :: X(:) ... END SUBROUTINE PROCESS on return from subroutine PROCESS, the allocation status of X is preserved because X has the SAVE attribute. TEMP does not have the SAVE attribute, so it will be deallocated. On the next invocation of PROCESS, TEMP will have an allocation status of unallocated. 19 6.3.3.2 Deallocation of pointer targets 20 If a pointer appears in a DEALLOCATE statement, its association status shall be defined. Deallocating 21 a pointer that is disassociated or whose target was not created by an ALLOCATE statement causes an 22 error condition in the DEALLOCATE statement. If a pointer is associated with an allocatable entity, 23 the pointer shall not be deallocated. 24 If a pointer appears in a DEALLOCATE statement, it shall be associated with the whole of an object 25 or subobject that was created by allocation. Deallocating a pointer target causes the pointer association 114 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 status of any other pointer that is associated with the target or a portion of the target to become 2 undefined. 3 When the execution of a procedure is terminated by execution of a RETURN or END statement, the 4 pointer association status of a pointer declared or accessed in the subprogram that defines the procedure 5 becomes undefined unless it is one of the following: 6 (1) A pointer with the SAVE attribute, 7 (2) A pointer in blank common, 8 (3) A pointer in a named common block that appears in at least one other scoping unit that is 9 in execution, 10 (4) A pointer declared in the scoping unit of a module if the module also is accessed by another 11 scoping unit that is in execution, 12 (5) A pointer accessed by host association, or 13 (6) A pointer that is the return value of a function declared to have the POINTER attribute. 14 When a pointer target becomes undefined by execution of a RETURN or END statement, the pointer 15 association status (16.4.2.1) becomes undefined. SEP 2002 COMMITTEE DRAFT 115 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 116 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 Section 7: Expressions and assignment 2 This section describes the formation, interpretation, and evaluation rules for expressions, intrinsic and 3 defined assignment, pointer assignment, masked array assignment (WHERE), and FORALL. 4 7.1 Expressions 5 An expression represents either a data reference or a computation, and its value is either a scalar or 6 an array. An expression is formed from operands, operators, and parentheses. 7 An operand is either a scalar or an array. An operation is either intrinsic or defined (7.2). More 8 complicated expressions can be formed using operands which are themselves expressions. 9 Evaluation of an expression produces a value, which has a type, type parameters (if appropriate), and a 10 shape (7.1.4). 11 7.1.1 Form of an expression 12 An expression is defined in terms of several categories: primary, level-1 expression, level-2 expression, 13 level-3 expression, level-4 expression, and level-5 expression. 14 These categories are related to the different operator precedence levels and, in general, are defined in 15 terms of other categories. The simplest form of each expression category is a primary. The rules given 16 below specify the syntax of an expression. The semantics are specified in 7.2. 17 7.1.1.1 Primary 18 R701 primary is constant 19 or designator 20 or array-constructor 21 or structure-constructor 22 or function-reference 23 or type-param-inquiry 24 or type-param-name 25 or ( expr ) 26 C701 (R701) The type-param-name shall be the name of a type parameter. 27 C702 (R701) The designator shall not be a whole assumed-size array. NOTE 7.1 Examples of a primary are: Example Syntactic class 1.0 constant 'ABCDEFGHIJKLMNOPQRSTUVWXYZ' (I:I) constant-subobject A variable (/ 1.0, 2.0 /) array-constructor PERSON (12, 'Jones') structure-constructor F (X, Y) function-reference SEP 2002 COMMITTEE DRAFT 117 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 7.1 (cont.) (S + T) (expr ) 1 7.1.1.2 Level-1 expressions 2 Defined unary operators have the highest operator precedence (Table 7.7). Level-1 expressions are 3 primaries optionally operated on by defined unary operators: 4 R702 level-1-expr is [ defined-unary-op ] primary 5 R703 defined-unary-op is . letter [ letter ] ... . 6 C703 (R703) A defined-unary-op shall not contain more than 63 letters and shall not be the same as 7 any intrinsic-operator or logical-literal-constant . NOTE 7.2 Simple examples of a level-1 expression are: Example Syntactic class A primary (R701) .INVERSE. B level-1-expr (R702) A more complicated example of a level-1 expression is: .INVERSE. (A + B) 8 7.1.1.3 Level-2 expressions 9 Level-2 expressions are level-1 expressions optionally involving the numeric operators power-op, mult-op, 10 and add-op. 11 R704 mult-operand is level-1-expr [ power-op mult-operand ] 12 R705 add-operand is [ add-operand mult-op ] mult-operand 13 R706 level-2-expr is [ [ level-2-expr ] add-op ] add-operand 14 R707 power-op is ** 15 R708 mult-op is * 16 or / 17 R709 add-op is + 18 or ­ NOTE 7.3 Simple examples of a level-2 expression are: Example Syntactic class Remarks A level-1-expr A is a primary. (R702) B ** C mult-operand B is a level-1-expr , ** is a power-op, and C is a mult-operand . (R704) D * E add-operand D is an add-operand , * is a mult-op, and E is a mult-operand . (R705) +1 level-2-expr + is an add-op and 1 is an add-operand . (R706) F - I level-2-expr F is a level-2-expr , ­ is an add-op, and I is an add-operand . (R706) 118 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 7.3 (cont.) A more complicated example of a level-2 expression is: - A + D * E + B ** C 1 7.1.1.4 Level-3 expressions 2 Level-3 expressions are level-2 expressions optionally involving the character operator concat-op. 3 R710 level-3-expr is [ level-3-expr concat-op ] level-2-expr 4 R711 concat-op is // NOTE 7.4 Simple examples of a level-3 expression are: Example Syntactic class A level-2-expr (R706) B // C level-3-expr (R710) A more complicated example of a level-3 expression is: X // Y // 'ABCD' 5 7.1.1.5 Level-4 expressions 6 Level-4 expressions are level-3 expressions optionally involving the relational operators rel-op. 7 R712 level-4-expr is [ level-3-expr rel-op ] level-3-expr 8 R713 rel-op is .EQ. 9 or .NE. 10 or .LT. 11 or .LE. 12 or .GT. 13 or .GE. 14 or == 15 or /= 16 or < 17 or <= 18 or > 19 or >= NOTE 7.5 Simple examples of a level-4 expression are: Example Syntactic class A level-3-expr (R710) B == C level-4-expr (R712) D < E level-4-expr (R712) A more complicated example of a level-4 expression is: (A + B) /= C SEP 2002 COMMITTEE DRAFT 119 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 7.1.1.6 Level-5 expressions 2 Level-5 expressions are level-4 expressions optionally involving the logical operators not-op, and-op, 3 or-op, and equiv-op. 4 R714 and-operand is [ not-op ] level-4-expr 5 R715 or-operand is [ or-operand and-op ] and-operand 6 R716 equiv-operand is [ equiv-operand or-op ] or-operand 7 R717 level-5-expr is [ level-5-expr equiv-op ] equiv-operand 8 R718 not-op is .NOT. 9 R719 and-op is .AND. 10 R720 or-op is .OR. 11 R721 equiv-op is .EQV. 12 or .NEQV. NOTE 7.6 Simple examples of a level-5 expression are: Example Syntactic class A level-4-expr (R712) .NOT. B and-operand (R714) C .AND. D or-operand (R715) E .OR. F equiv-operand (R716) G .EQV. H level-5-expr (R717) S .NEQV. T level-5-expr (R717) A more complicated example of a level-5 expression is: A .AND. B .EQV. .NOT. C 13 7.1.1.7 General form of an expression 14 Expressions are level-5 expressions optionally involving defined binary operators. Defined binary oper- 15 ators have the lowest operator precedence (Table 7.7). 16 R722 expr is [ expr defined-binary-op ] level-5-expr 17 R723 defined-binary-op is . letter [ letter ] ... . 18 C704 (R723) A defined-binary-op shall not contain more than 63 letters and shall not be the same as 19 any intrinsic-operator or logical-literal-constant . NOTE 7.7 Simple examples of an expression are: Example Syntactic class A level-5-expr (R717) B.UNION.C expr (R722) More complicated examples of an expression are: (B .INTERSECT. C) .UNION. (X - Y) A + B == C * D .INVERSE. (A + B) A + B .AND. C * D E // G == H (1:10) 120 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 7.1.2 Intrinsic operations 2 An intrinsic operation is either an intrinsic unary operation or an intrinsic binary operation. An 3 intrinsic unary operation is an operation of the form intrinsic-operator x2 where x2 is of an intrinsic 4 type (4.4) listed in Table 7.1 for the unary intrinsic operator. 5 An intrinsic binary operation is an operation of the form x1 intrinsic-operator x2 where x1 and 6 x2 are of the intrinsic types (4.4) listed in Table 7.1 for the binary intrinsic operator and are in shape 7 conformance (7.1.5). Table 7.1: Type of operands and results for intrinsic operators Intrinsic operator Type of Type of Type of op x1 x2 [x1] op x2 Unary +, ­ I, R, Z I, R, Z I I, R, Z I, R, Z Binary +, ­, *, /, ** R I, R, Z R, R, Z Z I, R, Z Z, Z, Z // C C C I I, R, Z L, L, L .EQ., .NE., R I, R, Z L, L, L ==, /= Z I, R, Z L, L, L C C L I I, R L, L .GT., .GE., .LT., .LE. R I, R L, L >, >=, <, <= C I, R L, L .NOT. L L .AND., .OR., .EQV., .NEQV. L L L Note: The symbols I, R, Z, C, and L stand for the types integer, real, complex, character, and logical, respectively. Where more than one type for x2 is given, the type of the result of the operation is given in the same relative position in the next column. For the intrinsic operators with operands of type character, the kind type parameters of the operands shall be the same. 8 A numeric intrinsic operation is an intrinsic operation for which the intrinsic-operator is a numeric 9 operator (+, ­, *, /, or **). A numeric intrinsic operator is the operator in a numeric intrinsic 10 operation. 11 For numeric intrinsic binary operations, the two operands may be of different numeric types or different 12 kind type parameters. Except for a value raised to an integer power, if the operands have different types 13 or kind type parameters, the effect is as if each operand that differs in type or kind type parameter from 14 those of the result is converted to the type and kind type parameter of the result before the operation 15 is performed. When a value of type real or complex is raised to an integer power, the integer operand 16 need not be converted. 17 A character intrinsic operation, relational intrinsic operation, and logical intrinsic operation 18 are similarly defined in terms of a character intrinsic operator (//), relational intrinsic operator 19 (.EQ., .NE., .GT., .GE., .LT., .LE., ==, /=, >, >=, <, and <=), and logical intrinsic operator 20 (.AND., .OR., .NOT., .EQV., and .NEQV.), respectively. For the character intrinsic operator //, the 21 kind type parameters shall be the same. For the relational intrinsic operators with character operands, 22 the kind type parameters shall be the same. 23 A numeric relational intrinsic operation is a relational intrinsic operation where the operands are 24 of numeric type. A character relational intrinsic operation is a relational intrinsic operation where 25 the operands are of type character. SEP 2002 COMMITTEE DRAFT 121 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 7.1.3 Defined operations 2 A defined operation is either a defined unary operation or a defined binary operation. A defined 3 unary operation is an operation that has the form defined-unary-op x2 and that is defined by a 4 function and a generic interface (4.5.1, 12.3.2.1) or that has the form intrinsic-operator x2 where the 5 type of x2 is not that required for the unary intrinsic operation (7.1.2), and that is defined by a function 6 and a generic interface. 7 A function defines the unary operation op x2 if 8 (1) The function is specified with a FUNCTION (12.5.2.1) or ENTRY (12.5.2.4) statement that 9 specifies one dummy argument d2, 10 (2) Either 11 (a) A generic interface (12.3.2.1) provides the function with a generic-spec of OPERA- 12 TOR (op), or 13 (b) There is a type-bound generic binding (4.5.1) in the declared type of x2 with a generic- 14 spec of OPERATOR (op) and there is a corresponding binding to the function in the 15 dynamic type of x2, 16 (3) The type of d2 is compatible with the dynamic type of x2, 17 (4) The type parameters, if any, of d2 match the corresponding type parameters of x2, and 18 (5) Either 19 (a) The rank of x2 matches that of d2 or 20 (b) The function is elemental and there is no other function that defines the operation. 21 If d2 is an array, the shape of x2 shall match the shape of d2. 22 A defined binary operation is an operation that has the form x1 defined-binary-op x2 and that is 23 defined by a function and a generic interface or that has the form x1 intrinsic-operator x2 where the 24 types or ranks of either x1 or x2 or both are not those required for the intrinsic binary operation (7.1.2), 25 and that is defined by a function and a generic interface. 26 A function defines the binary operation x1 op x2 if 27 (1) The function is specified with a FUNCTION (12.5.2.1) or ENTRY (12.5.2.4) statement that 28 specifies two dummy arguments, d1 and d2, 29 (2) Either 30 (a) A generic interface (12.3.2.1) provides the function with a generic-spec of OPERA- 31 TOR (op), or 32 (b) There is a type-bound generic binding (4.5.1) in the declared type of x1 or x2 with a 33 generic-spec of OPERATOR (op) and there is a corresponding binding to the function 34 in the dynamic type of x1 or x2, respectively, 35 (3) The types of d1 and d2 are compatible with the dynamic types of x1 and x2, respectively, 36 (4) The type parameters, if any, of d1 and d2 match the corresponding type parameters of x1 37 and x2, respectively, and 38 (5) Either 39 (a) The ranks of x1 and x2 match those of d1 and d2 or 40 (b) The function is elemental, x1 and x2 are conformable, and there is no other function 41 that defines the operation. 42 If d1 or d2 is an array, the shapes of x1 and x2 shall match the shapes of d1 and d2, respectively. 122 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 7.8 An intrinsic operator may be used as the operator in a defined operation. In such a case, the generic properties of the operator are extended. 1 An extension operation is a defined operation in which the operator is of the form defined-unary-op 2 or defined-binary-op. Such an operator is called an extension operator. The operator used in an 3 extension operation may be such that a generic interface for the operator may specify more than one 4 function. 5 A defined elemental operation is a defined operation for which the function is elemental (12.7). 6 7.1.4 Type, type parameters, and shape of an expression 7 The type, type parameters, and shape of an expression depend on the operators and on the types, type 8 parameters, and shapes of the primaries used in the expression, and are determined recursively from 9 the syntactic form of the expression. The type of an expression is one of the intrinsic types (4.4) or a 10 derived type (4.5). 11 If an expression is a polymorphic primary or defined operation, the type parameters and the declared and 12 dynamic types of the expression are the same as those of the primary or defined operation. Otherwise 13 the type parameters and dynamic type of the expression are the same as its declared type and type 14 parameters; they are referred to simply as the type and type parameters of the expression. 15 R724 logical-expr is expr 16 C705 (R724) logical-expr shall be of type logical. 17 R725 char-expr is expr 18 C706 (R725) char-expr shall be of type character. 19 R726 default-char-expr is expr 20 C707 (R726) default-char-expr shall be of type default character. 21 R727 int-expr is expr 22 C708 (R727) int-expr shall be of type integer. 23 R728 numeric-expr is expr 24 C709 (R728) numeric-expr shall be of type integer, real, or complex. 25 7.1.4.1 Type, type parameters, and shape of a primary 26 The type, type parameters, and shape of a primary are determined according to whether the primary is a 27 constant, variable, array constructor, structure constructor, function reference, type parameter inquiry, 28 type parameter name, or parenthesized expression. If a primary is a constant, its type, type parameters, 29 and shape are those of the constant. If it is a structure constructor, it is scalar and its type and type 30 parameters are as described in 4.5.8. If it is an array constructor, its type, type parameters, and shape 31 are as described in 4.8. If it is a variable or function reference, its type, type parameters, and shape are 32 those of the variable (5.1.1, 5.1.2) or the function reference (12.4.2), respectively. If the function reference 33 is generic (12.3.2.1, 13.5) then its type, type parameters, and shape are those of the specific function 34 referenced, which is determined by the types, type parameters, and ranks of its actual arguments as 35 specified in 16.2.3. If it is a type parameter inquiry or type parameter name, it is a scalar integer with 36 the kind of the type parameter. SEP 2002 COMMITTEE DRAFT 123 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 If a primary is a parenthesized expression, its type, type parameters, and shape are those of the expres- 2 sion. 3 If a pointer appears as one of the following, the associated target object is referenced: 4 (1) A primary in an intrinsic or defined operation, 5 (2) The expr of a parenthesized primary, or 6 (3) The only primary on the right-hand side of an intrinsic assignment statement. 7 The type, type parameters, and shape of the primary are those of the current target. If the pointer is 8 not associated with a target, it may appear as a primary only as an actual argument in a reference to 9 a procedure whose corresponding dummy argument is declared to be a pointer, or as the target in a 10 pointer assignment statement. 11 A disassociated array pointer or an unallocated allocatable array has no shape but does have rank. The 12 type, type parameters, and rank of the result of the NULL intrinsic function depend on context (13.7.84). 13 7.1.4.2 Type, type parameters, and shape of the result of an operation 14 The type of the result of an intrinsic operation [x1] op x2 is specified by Table 7.1. The shape of the 15 result of an intrinsic operation is the shape of x2 if op is unary or if x1 is scalar, and is the shape of x1 16 otherwise. 17 The type, type parameters, and shape of the result of a defined operation [x1] op x2 is specified by the 18 function defining the operation (7.2). 19 An expression of an intrinsic type has a kind type parameter. An expression of type character also has 20 a character length parameter. 21 The type parameters of the result of an intrinsic operation are as follows: 22 (1) For an expression x1 // x2 where // is the character intrinsic operator and x1 and x2 are 23 of type character, the character length parameter is the sum of the lengths of the operands 24 and the kind type parameter is the kind type parameter of x1, which shall be the same as 25 the kind type parameter of x2. 26 (2) For an expression op x2 where op is an intrinsic unary operator and x2 is of type integer, 27 real, complex, or logical, the kind type parameter of the expression is that of the operand. 28 (3) For an expression x1 op x2 where op is a numeric intrinsic binary operator with one operand 29 of type integer and the other of type real or complex, the kind type parameter of the 30 expression is that of the real or complex operand. 31 (4) For an expression x1 op x2 where op is a numeric intrinsic binary operator with both 32 operands of the same type and kind type parameters, or with one real and one complex 33 with the same kind type parameters, the kind type parameter of the expression is identical 34 to that of each operand. In the case where both operands are integer with different kind type 35 parameters, the kind type parameter of the expression is that of the operand with the greater 36 decimal exponent range if the decimal exponent ranges are different; if the decimal exponent 37 ranges are the same, the kind type parameter of the expression is processor dependent, but 38 it is the same as that of one of the operands. In the case where both operands are any 39 of type real or complex with different kind type parameters, the kind type parameter of 40 the expression is that of the operand with the greater decimal precision if the decimal 41 precisions are different; if the decimal precisions are the same, the kind type parameter of 42 the expression is processor dependent, but it is the same as that of one of the operands. 43 (5) For an expression x1 op x2 where op is a logical intrinsic binary operator with both operands 44 of the same kind type parameter, the kind type parameter of the expression is identical to 45 that of each operand. In the case where both operands are of type logical with different 124 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 kind type parameters, the kind type parameter of the expression is processor dependent, 2 but it is the same as that of one of the operands. 3 (6) For an expression x1 op x2 where op is a relational intrinsic operator, the expression has 4 the default logical kind type parameter. 5 7.1.5 Conformability rules for elemental operations 6 An elemental operation is an intrinsic operation or a defined elemental operation. Two entities are 7 in shape conformance if both are arrays of the same shape, or one or both are scalars. 8 For all elemental binary operations, the two operands shall be in shape conformance. In the case where 9 one is a scalar and the other an array, the scalar is treated as if it were an array of the same shape as 10 the array operand with every element, if any, of the array equal to the value of the scalar. 11 7.1.6 Specification expression 12 A specification expression is an expression with limitations that make it suitable for use in specifi- 13 cations such as nonkind type parameters (R502) and array bounds (R517, R518). 14 R729 specification-expr is scalar-int-expr 15 C710 (R729) The scalar-int-expr shall be a restricted expression. 16 A restricted expression is an expression in which each operation is intrinsic and each primary is 17 (1) A constant or subobject of a constant, 18 (2) An object designator with a base object that is a dummy argument that has neither the 19 OPTIONAL nor the INTENT (OUT) attribute, 20 (3) An object designator with a base object that is in a common block, 21 (4) An object designator with a base object that is made accessible by use association or host 22 association, 23 (5) An array constructor where each element and the bounds and strides of each implied-DO 24 are restricted expressions, 25 (6) A structure constructor where each component is a restricted expression, 26 (7) A specification inquiry where each designator or function argument is 27 (a) a restricted expression or 28 (b) a variable whose properties inquired about are not 29 (i) dependent on the upper bound of the last dimension of an assumed-size array, 30 (ii) deferred, or 31 (iii) defined by an expression that is not a restricted expression, 32 (8) A reference to any other standard intrinsic function where each argument is a restricted 33 expression, 34 (9) A reference to a specification function where each argument is a restricted expression, 35 (10) A type parameter of the derived type being defined, 36 (11) An implied-DO variable within an array constructor where the bounds and strides of the 37 corresponding implied-DO are restricted expressions, or 38 (12) A restricted expression enclosed in parentheses, 39 where each subscript, section subscript, substring starting point, substring ending point, and type pa- 40 rameter value is a restricted expression, and where any final subroutine that is invoked is pure. 41 A specification inquiry is a reference to SEP 2002 COMMITTEE DRAFT 125 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 (1) an array inquiry function (13.5.7), 2 (2) the bit inquiry function BIT SIZE, 3 (3) the character inquiry function LEN, 4 (4) the kind inquiry function KIND, 5 (5) a numeric inquiry function (13.5.6), 6 (6) a type parameter inquiry (6.1.3), or 7 (7) an IEEE inquiry function (14.8.1), 8 A function is a specification function if it is a pure function, is not a standard intrinsic function, is 9 not an internal function, is not a statement function, and does not have a dummy procedure argument. 10 Evaluation of a specification expression shall not directly or indirectly cause a procedure defined by the 11 subprogram in which it appears to be invoked. NOTE 7.9 Specification functions are nonintrinsic functions that may be used in specification expressions to determine the attributes of data objects. The requirement that they be pure ensures that they cannot have side effects that could affect other objects being declared in the same specification-part . The requirement that they not be internal ensures that they cannot inquire, via host association, about other objects being declared in the same specification-part . The prohibition against recursion avoids the creation of a new activation record while construction of one is in progress. 12 A variable in a specification expression shall have its type and type parameters, if any, specified by a 13 previous declaration in the same scoping unit, by the implicit typing rules in effect for the scoping unit, 14 or by host or use association. If a variable in a specification expression is typed by the implicit typing 15 rules, its appearance in any subsequent type declaration statement shall confirm the implied type and 16 type parameters. 17 If a specification expression includes a specification inquiry that depends on a type parameter or an 18 array bound of an entity specified in the same specification-part , the type parameter or array bound 19 shall be specified in a prior specification of the specification-part . The prior specification may be to the 20 left of the specification inquiry in the same statement, but shall not be within the same entity-decl . If a 21 specification expression includes a reference to the value of an element of an array specified in the same 22 specification-part , the array shall be completely specified in prior declarations. NOTE 7.10 The following are examples of specification expressions: LBOUND (B, 1) + 5 ! B is an assumed-shape dummy array M + LEN (C) ! M and C are dummy arguments 2 * PRECISION (A) ! A is a real variable made accessible ! by a USE statement 23 7.1.7 Initialization expression 24 An initialization expression is an expression with limitations that make it suitable for use as a kind 25 type parameter, initializer, or named constant. It is an expression in which each operation is intrinsic, 26 and each primary is 27 (1) A constant or subobject of a constant, 28 (2) An array constructor where each element and the bounds and strides of each implied-DO 29 are initialization expressions, 126 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 (3) A structure constructor where each component-spec corresponding to an allocatable com- 2 ponent is a reference to the transformational intrinsic function NULL, and each other 3 component-spec is an initialization expression, 4 (4) A reference to an elemental standard intrinsic function, where each argument is an initial- 5 ization expression, 6 (5) A reference to a transformational standard intrinsic function other than NULL, where each 7 argument is an initialization expression, 8 (6) A reference to the transformational intrinsic function NULL that does not have an argu- 9 ment with a type parameter that is assumed or is defined by an expression that is not an 10 initialization expression, 11 (7) A reference to the transformational function IEEE SELECTED REAL KIND from the in- 12 trinsic module IEEE ARITHMETIC (14), where each argument is an initialization expres- 13 sion. 14 (8) A specification inquiry where each designator or function argument is 15 (a) an initialization expression or 16 (b) a variable whose properties inquired about are not 17 (i) assumed, 18 (ii) deferred, or 19 (iii) defined by an expression that is not an initialization expression, 20 (9) A kind type parameter of the derived type being defined, 21 (10) An implied-DO variable within an array constructor where the bounds and strides of the 22 corresponding implied-DO are initialization expressions, or 23 (11) An initialization expression enclosed in parentheses, 24 and where each subscript, section subscript, substring starting point, substring ending point, and type 25 parameter value is an initialization expression. 26 R730 initialization-expr is expr 27 C711 (R730) initialization-expr shall be an initialization expression. 28 R731 char-initialization-expr is char-expr 29 C712 (R731) char-initialization-expr shall be an initialization expression. 30 R732 int-initialization-expr is int-expr 31 C713 (R732) int-initialization-expr shall be an initialization expression. 32 R733 logical-initialization-expr is logical-expr 33 C714 (R733) logical-initialization-expr shall be an initialization expression. 34 If an initialization expression includes a specification inquiry that depends on a type parameter or an 35 array bound of an entity specified in the same specification-part , the type parameter or array bound 36 shall be specified in a prior specification of the specification-part . The prior specification may be to the 37 left of the specification inquiry in the same statement, but shall not be within the same entity-decl . NOTE 7.11 The following are examples of initialization expressions: 3 SEP 2002 COMMITTEE DRAFT 127 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 7.11 (cont.) -3 + 4 'AB' 'AB' // 'CD' ('AB' // 'CD') // 'EF' SIZE (A) DIGITS (X) + 4 4.0 * atan(1.0) ceiling(number_of_decimal_digits / log10(radix(0.0))) where A is an explicit-shaped array with constant bounds and X is of type default real. 1 7.1.8 Evaluation of operations 2 An intrinsic operation requires the values of its operands. 3 The execution of any numeric operation whose result is not defined by the arithmetic used by the 4 processor is prohibited. Raising a negative-valued primary of type real to a real power is prohibited. 5 The evaluation of a function reference shall neither affect nor be affected by the evaluation of any other 6 entity within the statement. If a function reference causes definition or undefinition of an actual argument 7 of the function, that argument or any associated entities shall not appear elsewhere in the same statement. 8 However, execution of a function reference in the logical expression in an IF statement (8.1.2.4), the mask 9 expression in a WHERE statement (7.4.3.1), or the subscripts and strides in a FORALL statement (7.4.4) 10 is permitted to define variables in the statement that is conditionally executed. NOTE 7.12 For example, the statements A (I) = F (I) Y = G (X) + X are prohibited if the reference to F defines or undefines I or the reference to G defines or undefines X. However, in the statements IF (F (X)) A = X WHERE (G (X)) B = X F or G may define X. 11 The declared type of an expression in which a function reference appears does not affect, and is not 12 affected by, the evaluation of the actual arguments of the function. 13 Execution of an array element reference requires the evaluation of its subscripts. The type of an expres- 14 sion in which the array element reference appears does not affect, and is not affected by, the evaluation 15 of its subscripts. Execution of an array section reference requires the evaluation of its section subscripts. 16 The type of an expression in which an array section appears does not affect, and is not affected by, the 17 evaluation of the array section subscripts. Execution of a substring reference requires the evaluation of 18 its substring expressions. The type of an expression in which a substring appears does not affect, and 19 is not affected by, the evaluation of the substring expressions. It is not necessary for a processor to 20 evaluate any subscript expressions or substring expressions for an array of zero size or a character entity 128 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 of zero length. 2 The appearance of an array constructor requires the evaluation of the bounds and stride of any array 3 constructor implied-DO it may contain. The type of an expression in which an array constructor appears 4 does not affect, and is not affected by, the evaluation of such bounds and stride expressions. 5 When an elemental binary operation is applied to a scalar and an array or to two arrays of the same 6 shape, the operation is performed element-by-element on corresponding array elements of the array 7 operands. The processor may perform the element-by-element operations in any order. NOTE 7.13 For example, the array expression A + B produces an array of the same shape as A and B. The individual array elements of the result have the values of the first element of A added to the first element of B, the second element of A added to the second element of B, etc. 8 When an elemental unary operator operates on an array operand, the operation is performed element- 9 by-element, in any order, and the result is the same shape as the operand. 10 7.1.8.1 Evaluation of operands 11 It is not necessary for a processor to evaluate all of the operands of an expression, or to evaluate entirely 12 each operand, if the value of the expression can be determined otherwise. NOTE 7.14 This principle is most often applicable to logical expressions, zero-sized arrays, and zero-length strings, but it applies to all expressions. For example, in evaluating the expression X > Y .OR. L (Z) where X, Y, and Z are real and L is a function of type logical, the function reference L (Z) need not be evaluated if X is greater than Y. Similarly, in the array expression W (Z) + A where A is of size zero and W is a function, the function reference W (Z) need not be evaluated. 13 If a statement contains a function reference in a part of an expression that need not be evaluated, all 14 entities that would have become defined in the execution of that reference become undefined at the 15 completion of evaluation of the expression containing the function reference. NOTE 7.15 In the examples in Note 7.14, if L or W defines its argument, evaluation of the expressions under the specified conditions causes Z to become undefined, no matter whether or not L(Z) or W(Z) is evaluated. SEP 2002 COMMITTEE DRAFT 129 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 7.1.8.2 Integrity of parentheses 2 The sections that follow state certain conditions under which a processor may evaluate an expression that 3 is different from the one specified by applying the rules given in 7.1.1 and 7.2. However, any expression 4 in parentheses shall be treated as a data entity. NOTE 7.16 For example, in evaluating the expression A + (B ­ C) where A, B, and C are of numeric types, the difference of B and C shall be evaluated before the addition operation is performed; the processor shall not evaluate the mathematically equivalent expression (A + B) ­ C. 5 7.1.8.3 Evaluation of numeric intrinsic operations 6 The rules given in 7.2.1 specify the interpretation of a numeric intrinsic operation. Once the interpreta- 7 tion has been established in accordance with those rules, the processor may evaluate any mathematically 8 equivalent expression, provided that the integrity of parentheses is not violated. 9 Two expressions of a numeric type are mathematically equivalent if, for all possible values of their 10 primaries, their mathematical values are equal. However, mathematically equivalent expressions of 11 numeric type may produce different computational results. NOTE 7.17 Any difference between the values of the expressions (1./3.)*3. and 1. is a computational difference, not a mathematical difference. The difference between the values of the expressions 5/2 and 5./2. is a mathematical difference, not a computational difference. The mathematical definition of integer division is given in 7.2.1.1. NOTE 7.18 The following are examples of expressions with allowable alternative forms that may be used by the processor in the evaluation of those expressions. A, B, and C represent arbitrary real or complex operands; I and J represent arbitrary integer operands; and X, Y, and Z represent arbitrary operands of numeric type. Expression Allowable alternative form X + Y Y + X X * Y Y * X -X + Y Y - X X + Y + Z X + (Y + Z) X - Y + Z X - (Y - Z) X * A / Z X * (A / Z) X * Y - X * Z X * (Y - Z) A / B / C A / (B * C) A / 5.0 0.2 * A The following are examples of expressions with forbidden alternative forms that shall not be used by a processor in the evaluation of those expressions. 130 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 7.18 (cont.) Expression Forbidden alternative form I / 2 0.5 * I X * I / J X * (I / J) I / J / A I / (J * A) (X + Y) + Z X + (Y + Z) (X * Y) - (X * Z) X * (Y - Z) X * (Y - Z) X * Y - X * Z 1 In addition to the parentheses required to establish the desired interpretation, parentheses may be 2 included to restrict the alternative forms that may be used by the processor in the actual evaluation 3 of the expression. This is useful for controlling the magnitude and accuracy of intermediate values 4 developed during the evaluation of an expression. NOTE 7.19 For example, in the expression A + (B - C) the parenthesized expression (B ­ C) shall be evaluated and then added to A. The inclusion of parentheses may change the mathematical value of an expression. For example, the two expressions A * I / J A * (I / J) may have different mathematical values if I and J are of type integer. 5 Each operand in a numeric intrinsic operation has a type that may depend on the order of evaluation 6 used by the processor. NOTE 7.20 For example, in the evaluation of the expression Z + R + I where Z, R, and I represent data objects of complex, real, and integer type, respectively, the type of the operand that is added to I may be either complex or real, depending on which pair of operands (Z and R, R and I, or Z and I) is added first. 7 7.1.8.4 Evaluation of the character intrinsic operation 8 The rules given in 7.2.2 specify the interpretation of the character intrinsic operation. A processor is 9 required to evaluate only as much of the character intrinsic operation as is required by the context in 10 which the expression appears. NOTE 7.21 For example, the statements SEP 2002 COMMITTEE DRAFT 131 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 7.21 (cont.) CHARACTER (LEN = 2) C1, C2, C3, CF C1 = C2 // CF (C3) do not require the function CF to be evaluated, because only the value of C2 is needed to determine the value of C1 because C1 and C2 both have a length of 2. 1 7.1.8.5 Evaluation of relational intrinsic operations 2 The rules given in 7.2.3 specify the interpretation of relational intrinsic operations. Once the interpre- 3 tation of an expression has been established in accordance with those rules, the processor may evaluate 4 any other expression that is relationally equivalent, provided that the integrity of parentheses in any 5 expression is not violated. NOTE 7.22 For example, the processor may choose to evaluate the expression I > J where I and J are integer variables, as J - I < 0 6 Two relational intrinsic operations are relationally equivalent if their logical values are equal for all 7 possible values of their primaries. 8 7.1.8.6 Evaluation of logical intrinsic operations 9 The rules given in 7.2.4 specify the interpretation of logical intrinsic operations. Once the interpretation 10 of an expression has been established in accordance with those rules, the processor may evaluate any 11 other expression that is logically equivalent, provided that the integrity of parentheses in any expression 12 is not violated. NOTE 7.23 For example, for the variables L1, L2, and L3 of type logical, the processor may choose to evaluate the expression L1 .AND. L2 .AND. L3 as L1 .AND. (L2 .AND. L3) 13 Two expressions of type logical are logically equivalent if their values are equal for all possible values of 14 their primaries. 15 7.1.8.7 Evaluation of a defined operation 16 The rules given in 7.2 specify the interpretation of a defined operation. Once the interpretation of an 17 expression has been established in accordance with those rules, the processor may evaluate any other 18 expression that is equivalent, provided that the integrity of parentheses is not violated. 19 Two expressions of derived type are equivalent if their values are equal for all possible values of their 132 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 primaries. 2 7.2 Interpretation of operations 3 The intrinsic operations are those defined in 7.1.2. These operations are divided into the following 4 categories: numeric, character, relational, and logical. The interpretations defined in the following 5 sections apply to both scalars and arrays; the interpretation for arrays is obtained by applying the 6 interpretation for scalars element by element. 7 The interpretation of a defined operation is provided by the function that defines the operation. The type, 8 type parameters and interpretation of an expression that consists of an intrinsic or defined operation are 9 independent of the type and type parameters of the context or any larger expression in which it appears. NOTE 7.24 For example, if X is of type real, J is of type integer, and INT is the real-to-integer intrinsic conversion function, the expression INT (X + J) is an integer expression and X + J is a real expression. 10 The operators <, <=, >, >=, ==, and /= always have the same interpretations as the operators .LT., 11 .LE., .GT., .GE., .EQ., and .NE., respectively. 12 7.2.1 Numeric intrinsic operations 13 A numeric operation is used to express a numeric computation. Evaluation of a numeric operation 14 produces a numeric value. The permitted data types for operands of the numeric intrinsic operations 15 are specified in 7.1.2. 16 The numeric operators and their interpretation in an expression are given in Table 7.2, where x1 denotes 17 the operand to the left of the operator and x2 denotes the operand to the right of the operator. Table 7.2: Interpretation of the numeric intrinsic operators Operator Representing Use of operator Interpretation ** Exponentiation x1 ** x2 Raise x1 to the power x2 / Division x1 / x2 Divide x1 by x2 * Multiplication x1 * x2 Multiply x1 by x2 - Subtraction x1 - x2 Subtract x2 from x1 - Negation - x2 Negate x2 + Addition x1 + x2 Add x1 and x2 + Identity + x2 Same as x2 18 The interpretation of a division operation depends on the types of the operands (7.2.1.1). 19 If x1 and x2 are of type integer and x2 has a negative value, the interpretation of x1 ** x2 is the same 20 as the interpretation of 1/(x1 ** ABS (x2)), which is subject to the rules of integer division (7.2.1.1). NOTE 7.25 For example, 2 ** (­3) has the value of 1/(2 ** 3), which is zero. 21 7.2.1.1 Integer division 22 One operand of type integer may be divided by another operand of type integer. Although the math- 23 ematical quotient of two integers is not necessarily an integer, Table 7.1 specifies that an expression SEP 2002 COMMITTEE DRAFT 133 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 involving the division operator with two operands of type integer is interpreted as an expression of type 2 integer. The result of such an operation is the integer closest to the mathematical quotient and between 3 zero and the mathematical quotient inclusively. NOTE 7.26 For example, the expression (­8) / 3 has the value (­2). 4 7.2.1.2 Complex exponentiation 5 In the case of a complex value raised to a complex power, the value of the operation x1 ** x2 is the 6 principal value of xx2 . 1 7 7.2.2 Character intrinsic operation 8 The character intrinsic operator // is used to concatenate two operands of type character with the same 9 kind type parameter. Evaluation of the character intrinsic operation produces a result of type character. 10 The interpretation of the character intrinsic operator // when used to form an expression is given in 11 Table 7.3, where x1 denotes the operand to the left of the operator and x2 denotes the operand to the 12 right of the operator. Table 7.3: Interpretation of the character intrinsic operator // Operator Representing Use of operator Interpretation // Concatenation x1 // x2 Concatenate x1 with x2 13 The result of the character intrinsic operation // is a character string whose value is the value of x1 14 concatenated on the right with the value of x2 and whose length is the sum of the lengths of x1 and x2. 15 Parentheses used to specify the order of evaluation have no effect on the value of a character expression. NOTE 7.27 For example, the value of ('AB' // 'CDE') // 'F' is the string 'ABCDEF'. Also, the value of 'AB' // ('CDE' // 'F') is the string 'ABCDEF'. 16 7.2.3 Relational intrinsic operations 17 A relational intrinsic operation is used to compare values of two operands using the relational intrinsic 18 operators .LT., .LE., .GT., .GE., .EQ., .NE., <, <=, >, >=, ==, and /=. The permitted types for 19 operands of the relational intrinsic operators are specified in 7.1.2. NOTE 7.28 As shown in Table 7.1, a relational intrinsic operator cannot be used to compare the value of an expression of a numeric type with one of type character or logical. Also, two operands of type logical cannot be compared, a complex operand may be compared with another numeric operand only when the operator is .EQ., .NE., ==, or /=, and two character operands cannot be compared unless they have the same kind type parameter value. 20 Evaluation of a relational intrinsic operation produces a result of type default logical. 21 The interpretation of the relational intrinsic operators is given in Table 7.4, where x1 denotes the operand 22 to the left of the operator and x2 denotes the operand to the right of the operator. 134 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 Table 7.4: Interpretation of the relational intrinsic operators Operator Representing Use of operator Interpretation .LT. Less than x1 .LT. x2 x1 less than x2 < Less than x1 < x2 x1 less than x2 .LE. Less than or equal to x1 .LE. x2 x1 less than or equal to x2 <= Less than or equal to x1 <= x2 x1 less than or equal to x2 .GT. Greater than x1 .GT. x2 x1 greater than x2 > Greater than x1 > x2 x1 greater than x2 .GE. Greater than or equal to x1 .GE. x2 x1 greater than or equal to x2 >= Greater than or equal to x1 >= x2 x1 greater than or equal to x2 .EQ. Equal to x1 .EQ. x2 x1 equal to x2 == Equal to x1 == x2 x1 equal to x2 .NE. Not equal to x1 .NE. x2 x1 not equal to x2 /= Not equal to x1 /= x2 x1 not equal to x2 1 A numeric relational intrinsic operation is interpreted as having the logical value true if the values of 2 the operands satisfy the relation specified by the operator. A numeric relational intrinsic operation is 3 interpreted as having the logical value false if the values of the operands do not satisfy the relation 4 specified by the operator. 5 In the numeric relational operation 6 x1 rel-op x2 7 if the types or kind type parameters of x1 and x2 differ, their values are converted to the type and kind 8 type parameter of the expression x1 + x2 before evaluation. 9 A character relational intrinsic operation is interpreted as having the logical value true if the values of 10 the operands satisfy the relation specified by the operator. A character relational intrinsic operation 11 is interpreted as having the logical value false if the values of the operands do not satisfy the relation 12 specified by the operator. 13 For a character relational intrinsic operation, the operands are compared one character at a time in 14 order, beginning with the first character of each character operand. If the operands are of unequal 15 length, the shorter operand is treated as if it were extended on the right with blanks to the length of 16 the longer operand. If both x1 and x2 are of zero length, x1 is equal to x2; if every character of x1 is 17 the same as the character in the corresponding position in x2, x1 is equal to x2. Otherwise, at the first 18 position where the character operands differ, the character operand x1 is considered to be less than x2 19 if the character value of x1 at this position precedes the value of x2 in the collating sequence (4.4.4.1); 20 x1 is greater than x2 if the character value of x1 at this position follows the value of x2 in the collating 21 sequence. NOTE 7.29 The collating sequence depends partially on the processor; however, the result of the use of the operators .EQ., .NE., ==, and /= does not depend on the collating sequence. For nondefault character types, the blank padding character is processor dependent. 22 7.2.4 Logical intrinsic operations 23 A logical operation is used to express a logical computation. Evaluation of a logical operation produces 24 a result of type logical. The permitted types for operands of the logical intrinsic operations are specified 25 in 7.1.2. SEP 2002 COMMITTEE DRAFT 135 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 The logical operators and their interpretation when used to form an expression are given in Table 7.5, 2 where x1 denotes the operand to the left of the operator and x2 denotes the operand to the right of the 3 operator. Table 7.5: Interpretation of the logical intrinsic operators Operator Representing Use of operator Interpretation .NOT. Logical negation .NOT. x2 True if x2 is false .AND. Logical conjunction x1 .AND. x2 True if x1 and x2 are both true .OR. Logical inclusive disjunction x1 .OR. x2 True if x1 and/or x2 is true True if either x .NEQV. Logical nonequivalence x 1 or x2 is true, but 1 .NEQV. x2 not both True if both x .EQV. Logical equivalence x 1 and x2 are true or 1 .EQV. x2 both are false 4 The values of the logical intrinsic operations are shown in Table 7.6. Table 7.6: The values of operations involving logical intrinsic operators x1 x2 .NOT. x2 x1 .AND. x2 x1 .OR. x2 x1 .EQV. x2 x1 .NEQV. x2 true true false true true true false true false true false true false true false true false false true false true false false true false false true false 5 7.3 Precedence of operators 6 There is a precedence among the intrinsic and extension operations corresponding to the form of expres- 7 sions specified in 7.1.1, which determines the order in which the operands are combined unless the order 8 is changed by the use of parentheses. This precedence order is summarized in Table 7.7. Table 7.7: Categories of operations and relative precedence Category of operation Operators Precedence Extension defined-unary-op Highest Numeric ** . Numeric * or / . Numeric unary + or ­ . Numeric binary + or ­ . Character // . Relational .EQ., .NE., .LT., .LE., .GT., .GE., ==, /=, <, <=, >, >= . Logical .NOT. . Logical .AND. . Logical .OR. . Logical .EQV. or .NEQV. . Extension defined-binary-op Lowest 9 The precedence of a defined operation is that of its operator. 136 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 7.30 For example, in the expression -A ** 2 the exponentiation operator (**) has precedence over the negation operator (­); therefore, the operands of the exponentiation operator are combined to form an expression that is used as the operand of the negation operator. The interpretation of the above expression is the same as the interpretation of the expression - (A ** 2) 1 The general form of an expression (7.1.1) also establishes a precedence among operators in the same 2 syntactic class. This precedence determines the order in which the operands are to be combined in 3 determining the interpretation of the expression unless the order is changed by the use of parentheses. NOTE 7.31 In interpreting a level-2-expr containing two or more binary operators + or ­, each operand (add- operand ) is combined from left to right. Similarly, the same left-to-right interpretation for a mult- operand in add-operand , as well as for other kinds of expressions, is a consequence of the general form. However, for interpreting a mult-operand expression when two or more exponentiation operators ** combine level-1-expr operands, each level-1-expr is combined from right to left. For example, the expressions 2.1 + 3.4 + 4.9 2.1 * 3.4 * 4.9 2.1 / 3.4 / 4.9 2 ** 3 ** 4 'AB' // 'CD' // 'EF' have the same interpretations as the expressions (2.1 + 3.4) + 4.9 (2.1 * 3.4) * 4.9 (2.1 / 3.4) / 4.9 2 ** (3 ** 4) ('AB' // 'CD') // 'EF' As a consequence of the general form (7.1.1), only the first add-operand of a level-2-expr may be preceded by the identity (+) or negation (­) operator. These formation rules do not permit expressions containing two consecutive numeric operators, such as A ** ­B or A + ­B. However, expressions such as A ** (­B) and A + (­B) are permitted. The rules do allow a binary operator or an intrinsic unary operator to be followed by a defined unary operator, such as: A * .INVERSE. B - .INVERSE. (B) As another example, in the expression A .OR. B .AND. C SEP 2002 COMMITTEE DRAFT 137 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 7.31 (cont.) the general form implies a higher precedence for the .AND. operator than for the .OR. opera- tor; therefore, the interpretation of the above expression is the same as the interpretation of the expression A .OR. (B .AND. C) NOTE 7.32 An expression may contain more than one category of operator. The logical expression L .OR. A + B >= C where A, B, and C are of type real, and L is of type logical, contains a numeric operator, a relational operator, and a logical operator. This expression would be interpreted the same as the expression L .OR. ((A + B) >= C) NOTE 7.33 If (1) The operator ** is extended to type logical, (2) The operator .STARSTAR. is defined to duplicate the function of ** on type real, (3) .MINUS. is defined to duplicate the unary operator ­, and (4) L1 and L2 are type logical and X and Y are type real, then in precedence: L1 ** L2 is higher than X * Y; X * Y is higher than X .STARSTAR. Y; and .MINUS. X is higher than ­X. 1 7.4 Assignment 2 Execution of an assignment statement causes a variable to become defined or redefined. Execution of a 3 pointer assignment statement causes a pointer to become associated with a target or causes its pointer 4 association status to become disassociated or undefined. Execution of a WHERE statement or WHERE 5 construct masks the evaluation of expressions and assignment of values in array assignment statements 6 according to the value of a logical array expression. Execution of a FORALL statement or FORALL 7 construct controls the assignment to elements of arrays by using a set of index variables and a mask 8 expression. 9 7.4.1 Assignment statement 10 A variable may be defined or redefined by execution of an assignment statement. 11 7.4.1.1 General form 12 R734 assignment-stmt is variable = expr 13 C715 (R734) The variable in an assignment-stmt shall not be a whole assumed-size array. 138 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 7.34 Examples of an assignment statement are: A = 3.5 + X * Y I = INT (A) 1 An assignment-stmt shall meet the requirements of either a defined assignment statement or an intrinsic 2 assignment statement. 3 7.4.1.2 Intrinsic assignment statement 4 An intrinsic assignment statement is an assignment statement that is not a defined assignment 5 statement (7.4.1.4). In an intrinsic assignment statement, variable shall not be polymorphic, and 6 (1) If expr is an array then variable shall also be an array, 7 (2) The shape of variable and expr shall conform, and 8 (3) The declared types of variable and expr shall conform as specified in Table 7.8. 9 Table 7.8: Type conformance for the intrinsic assignment statement Type of variable Type of expr integer integer, real, complex real integer, real, complex complex integer, real, complex character character of the same kind type parameter as variable logical logical derived type same derived type and type parameters as variable 10 A numeric intrinsic assignment statement is an intrinsic assignment statement for which variable 11 and expr are of numeric type. A character intrinsic assignment statement is an intrinsic assign- 12 ment statement for which variable and expr are of type character. A logical intrinsic assignment 13 statement is an intrinsic assignment statement for which variable and expr are of type logical. A 14 derived-type intrinsic assignment statement is an intrinsic assignment statement for which vari- 15 able and expr are of derived type. 16 An array intrinsic assignment statement is an intrinsic assignment statement for which variable is 17 an array. The variable shall not be a many-one array section (6.2.2.3.2). 18 If variable is a pointer, it shall be associated with a definable target such that the type, type parameters, 19 and shape of the target and expr conform. 20 7.4.1.3 Interpretation of intrinsic assignments 21 Execution of an intrinsic assignment causes, in effect, the evaluation of the expression expr and all 22 expressions within variable (7.1.8), the possible conversion of expr to the type and type parameters 23 of variable (Table 7.9), and the definition of variable with the resulting value. The execution of the 24 assignment shall have the same effect as if the evaluation of all operations in expr and variable occurred 25 before any portion of variable is defined by the assignment. The evaluation of expressions within variable 26 shall neither affect nor be affected by the evaluation of expr . No value is assigned to variable if variable 27 is of type character and zero length, or is an array of size zero. 28 If variable is a pointer, the value of expr is assigned to the target of variable. 29 Both variable and expr may contain references to any portion of variable. SEP 2002 COMMITTEE DRAFT 139 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 7.35 For example, in the character intrinsic assignment statement: STRING (2:5) = STRING (1:4) the assignment of the first character of STRING to the second character does not affect the evaluation of STRING (1:4). If the value of STRING prior to the assignment was 'ABCDEF', the value following the assignment is 'AABCDF'. 1 If expr in an intrinsic assignment is a scalar and variable is an array, the expr is treated as if it were an 2 array of the same shape as variable with every element of the array equal to the scalar value of expr . 3 If variable in an intrinsic assignment is an array, the assignment is performed element-by-element on 4 corresponding array elements of variable and expr . NOTE 7.36 For example, if A and B are arrays of the same shape, the array intrinsic assignment A = B assigns the corresponding elements of B to those of A; that is, the first element of B is assigned to the first element of A, the second element of B is assigned to the second element of A, etc. 5 The processor may perform the element-by-element assignment in any order. NOTE 7.37 For example, the following program segment results in the values of the elements of array X being reversed: REAL X (10) ... X (1:10) = X (10:1:-1) 6 For a numeric intrinsic assignment statement, variable and expr may have different numeric types or 7 different kind type parameters, in which case the value of expr is converted to the type and kind type 8 parameter of variable according to the rules of Table 7.9. Table 7.9: Numeric conversion and the assignment statement Type of variable Value Assigned integer INT (expr , KIND = KIND (variable)) real REAL (expr , KIND = KIND (variable)) complex CMPLX (expr , KIND = KIND (variable)) Note: The functions INT, REAL, CMPLX, and KIND are the generic functions defined in 13.7. 9 For a logical intrinsic assignment statement, variable and expr may have different kind type parameters, 10 in which case the value of expr is converted to the kind type parameter of variable. 11 For a character intrinsic assignment statement, variable and expr shall have the same kind type parameter 12 value, but may have different character length parameters in which case the conversion of expr to the 13 length of variable is as follows: 140 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 (1) If the length of variable is less than that of expr , the value of expr is truncated from the 2 right until it is the same length as variable. 3 (2) If the length of variable is greater than that of expr , the value of expr is extended on the 4 right with blanks until it is the same length as variable. NOTE 7.38 For nondefault character types, the blank padding character is processor dependent. 5 A derived-type intrinsic assignment is performed as if each component of variable were assigned from 6 the corresponding component of expr using pointer assignment (7.4.2) for each pointer component, 7 defined assignment for each nonpointer nonallocatable component of a type that has a type-bound 8 defined assignment consistent with the component, and intrinsic assignment for each other nonpointer 9 nonallocatable component. For an allocatable component the following sequence of operations is applied: 10 (1) If the component of variable is allocated, it is deallocated. 11 (2) If the component of expr is allocated, the corresponding component of variable is allocated 12 with the same dynamic type and type parameters as the component of expr . If it is an array, 13 it is allocated with the same bounds. The value of the component of expr is then assigned 14 to the corresponding component of variable using defined assignment if the declared type 15 of the component has a type-bound defined assignment consistent with the component, and 16 intrinsic assignment for the dynamic type of that component otherwise. 17 The processor may perform the component-by-component assignment in any order or by any means that 18 has the same effect. NOTE 7.39 For an example of a derived-type intrinsic assignment statement, if C and D are of the same derived type with a pointer component P and nonpointer components S, T, U, and V of type integer, logical, character, and another derived type, respectively, the intrinsic C = D pointer assigns D % P to C % P. It assigns D % S to C % S, D % T to C % T, and D % U to C % U using intrinsic assignment. It assigns D % V to C % V using defined assignment if objects of that type have a compatible type-bound defined assignment, and intrinsic assignment otherwise. NOTE 7.40 If an allocatable component of expr is unallocated, the corresponding component of variable has an allocation status of unallocated after execution of the assignment. 19 When variable is a subobject, the assignment does not affect the definition status or value of other parts 20 of the object. For example, if variable is an array section, the assignment does not affect the definition 21 status or value of the elements of the array not specified by the array section. 22 7.4.1.4 Defined assignment statement 23 A defined assignment statement is an assignment statement that is defined by a subroutine and a 24 generic interface (4.5.1, 12.3.2.1.2) that specifies ASSIGNMENT (=). A defined elemental assign- 25 ment statement is a defined assignment statement for which the subroutine is elemental (12.7). 26 A subroutine defines the defined assignment x1 = x2 if 27 (1) The subroutine is specified with a SUBROUTINE (12.5.2.2) or ENTRY (12.5.2.4) statement 28 that specifies two dummy arguments, d1 and d2, SEP 2002 COMMITTEE DRAFT 141 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 (2) Either 2 (a) A generic interface (12.3.2.1) provides the subroutine with a generic-spec of ASSIGN- 3 MENT (=), or 4 (b) There is a type-bound generic binding (4.5.1) in the declared type of x1 or x2 with 5 a generic-spec of ASSIGNMENT (=) and there is a corresponding binding to the 6 subroutine in the dynamic type of x1 or x2, respectively, 7 (3) The types of d1 and d2 are compatible with the dynamic types of x1 and x2, respectively, 8 (4) The type parameters, if any, of d1 and d2 match the corresponding type parameters of x1 9 and x2, respectively, and 10 (5) Either 11 (a) The ranks of x1 and x2 match those of d1 and d2 or 12 (b) The subroutine is elemental, x1 and x2 are conformable, and there is no other sub- 13 routine that defines the operation. 14 If d1 or d2 is an array, the shapes of x1 and x2 shall match the shapes of d1 and d2, respectively. 15 The types of x1 and x2 shall not both be numeric, both be logical, or both be character with the same 16 kind type parameter value. 17 7.4.1.5 Interpretation of defined assignment statements 18 The interpretation of a defined assignment is provided by the subroutine that defines it. 19 If the defined assignment is an elemental assignment and the variable in the assignment is an array, the 20 defined assignment is performed element-by-element, in any order, on corresponding elements of variable 21 and expr . If expr is a scalar, it is treated as if it were an array of the same shape as variable with every 22 element of the array equal to the scalar value of expr . NOTE 7.41 The rules of defined assignment (12.3.2.1.2), procedure references (12.4), subroutine references (12.4.3), and elemental subroutine arguments (12.7.3) ensure that the defined assignment has the same effect as if the evaluation of all operations in x2 and x1 occurs before any portion of x1 is defined. 23 7.4.2 Pointer assignment 24 Pointer assignment causes a pointer to become associated with a target or causes its pointer association 25 status to become disassociated or undefined. Any previous association between the pointer and a target 26 is broken. 27 Pointer assignment for a pointer component of a structure may also take place by execution of a derived- 28 type intrinsic assignment statement (7.4.1.3). 29 A pointer may also become associated with a target by allocation of the pointer. 30 R735 pointer-assignment-stmt is data-pointer-object [ (bounds-spec-list ) ] => data-target 31 or data-pointer-object (bounds-remapping-list ) => data-target 32 or proc-pointer-object => proc-target 33 R736 data-pointer-object is variable-name 34 or variable % data-pointer-component-name 35 C716 (R735) If data-target is polymorphic (5.1.1.8), data-pointer-object shall be polymorphic. 142 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 C717 (R735) A data-pointer-object shall be type compatible (5.1.1.8) with data-target , and the corre- 2 sponding kind type parameters shall be equal. 3 C718 (R735) If bounds-spec-list is specified, the number of bounds-specs shall equal the rank of data- 4 pointer-object . 5 C719 (R735) If bounds-remapping-list is specified, the number of bounds-remappings shall equal the 6 rank of data-pointer-object . 7 C720 (R735) If bounds-remapping-list is specified, data-target shall have rank one; otherwise, the 8 ranks of data-pointer-object and data-target shall be the same. 9 C721 (R736) A variable-name shall have the POINTER attribute. 10 C722 (R736) A data-pointer-component-name shall be the name of a component of variable that is a 11 data pointer. 12 R737 bounds-spec is lower-bound : 13 R738 bounds-remapping is lower-bound : upper-bound 14 R739 data-target is variable 15 or expr 16 C723 (R739) A variable shall have either the TARGET or POINTER attribute, and shall not be an 17 array section with a vector subscript. 18 C724 (R739) An expr shall be a reference to a function whose result is a data pointer. 19 R740 proc-pointer-object is proc-pointer-name 20 or variable % procedure-component-name 21 C725 (R740) A procedure-component-name shall be the name of a procedure pointer component of 22 variable. 23 R741 proc-target is expr 24 or procedure-name 25 C726 (R741) An expr shall be a reference to a function whose result is a procedure pointer. 26 C727 (R741) A procedure-name shall be the name of an external, module, or dummy procedure, a 27 specific intrinsic function listed in 13.6 and not marked with a bullet (·), or a procedure pointer. 28 C728 (R741) The proc-target shall not be a nonintrinsic elemental procedure. 29 7.4.2.1 Data pointer assignment 30 If data-target is not a pointer, data-pointer-object becomes pointer associated with data-target . Other- 31 wise, the pointer association status of data-pointer-object becomes that of data-target ; if data-target is 32 associated with an object, data-pointer-object becomes associated with the same object. If data-target 33 is allocatable, it shall be allocated. 34 If data-pointer-object is polymorphic (5.1.1.8), it assumes the dynamic type of data-target . 35 If data-target is a disassociated pointer, all nondeferred type parameters of the declared type of data- 36 pointer-object that correspond to nondeferred type parameters of data-target shall have the same values 37 as the corresponding type parameters of data-target . Otherwise, all nondeferred type parameters of the 38 declared type of data-pointer-object shall have the same values as the corresponding type parameters of 39 data-target . SEP 2002 COMMITTEE DRAFT 143 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 If pointer-object has nondeferred type parameters that correspond to deferred type parameters of data- 2 target , data-target shall not be a pointer with undefined association status. 3 If bounds-remapping-list is specified, data-target shall not be a disassociated or undefined pointer, and 4 the size of data-target shall not be less than the size of data-pointer-object . The elements of the target 5 of data-pointer-object , in array element order (6.2.2.2), are the first SIZE(pointer-object ) elements of 6 data-target . 7 If no bounds-remapping-list is specified, the extent of a dimension of data-pointer-object is the extent of 8 the corresponding dimension of data-target . If bounds-spec-list is present, it specifies the lower bounds; 9 otherwise, the lower bound of each dimension is the result of the intrinsic function LBOUND (13.7.58) 10 applied to the corresponding dimension of data-target . The upper bound of each dimension is one less 11 than the sum of the lower bound and the extent. 12 7.4.2.2 Procedure pointer assignment 13 If the proc-target is not a pointer, proc-pointer-object becomes pointer associated with proc-target . Other- 14 wise, the pointer association status of proc-pointer-object becomes that of proc-target ; if proc-target is 15 associated with a procedure, proc-pointer-object becomes associated with the same procedure. 16 If proc-pointer-object has an explicit interface, its characteristics shall be the same as proc-target except 17 that proc-target may be pure even if proc-pointer-object is not pure and proc-target may be an elemental 18 intrinsic procedure even if proc-pointer-object is not elemental. 19 If the characteristics of proc-pointer-object or proc-target are such that an explicit interface is required, 20 both proc-pointer-object and proc-target shall have an explicit interface. 21 If proc-pointer-object has an implicit interface and is explicitly typed or referenced as a function, proc- 22 target shall be a function. If proc-pointer-object has an implicit interface and is referenced as a subroutine, 23 proc-target shall be a subroutine. 24 If proc-target and proc-pointer-object are functions, they shall have the same type; corresponding type 25 parameters shall either both be deferred or both have the same value. 26 If procedure-name is a specific procedure name that is also a generic name, only the specific procedure 27 is associated with pointer-object. 28 7.4.2.3 Examples NOTE 7.42 The following are examples of pointer assignment statements. (See Note 12.14 for declarations of P and BESSEL.) NEW_NODE % LEFT => CURRENT_NODE SIMPLE_NAME => TARGET_STRUCTURE % SUBSTRUCT % COMPONENT PTR => NULL ( ) ROW => MAT2D (N, :) WINDOW => MAT2D (I-1:I+1, J-1:J+1) POINTER_OBJECT => POINTER_FUNCTION (ARG_1, ARG_2) EVERY_OTHER => VECTOR (1:N:2) WINDOW2 (0:, 0:) => MAT2D (ML:MU, NL:NU) ! P is a procedure pointer and BESSEL is a procedure with a ! compatible interface. P => BESSEL 144 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 7.42 (cont.) ! Likewise for a structure component. STRUCT % COMPONENT => BESSEL NOTE 7.43 It is possible to obtain high-rank views of (parts of) rank-one objects by specifying upper bounds in pointer assignment statements. Consider the following example, in which a matrix is under consideration. The matrix is stored as a rank-one object in MYDATA because its diagonal is needed for some reason ­ the diagonal cannot be gotten as a single object from a rank-two representation. The matrix is represented as a rank-two view of MYDATA. real, target :: MYDATA ( NR*NC ) ! An automatic array real, pointer :: MATRIX ( :, : ) ! A rank-two view of MYDATA real, pointer :: VIEW_DIAG ( : ) MATRIX( 1:NR, 1:NC ) => MYDATA ! The MATRIX view of the data VIEW_DIAG => MYDATA( 1::NR+1 ) ! The diagonal of MATRIX Rows, columns, or blocks of the matrix can be accessed as sections of MATRIX. 1 7.4.3 Masked array assignment ­ WHERE 2 The masked array assignment is used to mask the evaluation of expressions and assignment of values in 3 array assignment statements, according to the value of a logical array expression. 4 7.4.3.1 General form of the masked array assignment 5 A masked array assignment is either a WHERE statement or a WHERE construct. 6 R742 where-stmt is WHERE ( mask-expr ) where-assignment-stmt 7 R743 where-construct is where-construct-stmt 8 [ where-body-construct ] ... 9 [ masked-elsewhere-stmt 10 [ where-body-construct ] ... ] ... 11 [ elsewhere-stmt 12 [ where-body-construct ] ... ] 13 end-where-stmt 14 R744 where-construct-stmt is [where-construct-name:] WHERE ( mask-expr ) 15 R745 where-body-construct is where-assignment-stmt 16 or where-stmt 17 or where-construct 18 R746 where-assignment-stmt is assignment-stmt 19 R747 mask-expr is logical-expr 20 R748 masked-elsewhere-stmt is ELSEWHERE (mask-expr ) [where-construct-name] 21 R749 elsewhere-stmt is ELSEWHERE [where-construct-name] 22 R750 end-where-stmt is END WHERE [where-construct-name] 23 C729 (R746) A where-assignment-stmt that is a defined assignment shall be elemental. 24 C730 (R743) If the where-construct-stmt is identified by a where-construct-name, the corresponding 25 end-where-stmt shall specify the same where-construct-name. If the where-construct-stmt is 26 not identified by a where-construct-name, the corresponding end-where-stmt shall not specify 27 a where-construct-name. If an elsewhere-stmt or a masked-elsewhere-stmt is identified by a 28 where-construct-name, the corresponding where-construct-stmt shall specify the same where- SEP 2002 COMMITTEE DRAFT 145 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 construct-name. 2 C731 (R745) A statement that is part of a where-body-construct shall not be a branch target statement. 3 If a where-construct contains a where-stmt , a masked-elsewhere-stmt , or another where-construct then 4 each mask-expr within the where-construct shall have the same shape. In each where-assignment-stmt , 5 the mask-expr and the variable being defined shall be arrays of the same shape. NOTE 7.44 Examples of a masked array assignment are: WHERE (TEMP > 100.0) TEMP = TEMP - REDUCE_TEMP WHERE (PRESSURE <= 1.0) PRESSURE = PRESSURE + INC_PRESSURE TEMP = TEMP - 5.0 ELSEWHERE RAINING = .TRUE. END WHERE 6 7.4.3.2 Interpretation of masked array assignments 7 When a WHERE statement or a where-construct-stmt is executed, a control mask is established. In 8 addition, when a WHERE construct statement is executed, a pending control mask is established. If 9 the statement does not appear as part of a where-body-construct , the mask-expr of the statement is 10 evaluated, and the control mask is established to be the value of mask-expr . The pending control mask 11 is established to have the value .NOT. mask-expr upon execution of a WHERE construct statement that 12 does not appear as part of a where-body-construct . The mask-expr is evaluated only once. 13 Each statement in a WHERE construct is executed in sequence. 14 Upon execution of a masked-elsewhere-stmt , the following actions take place in sequence: 15 (1) The control mask mc is established to have the value of the pending control mask. 16 (2) The pending control mask is established to have the value mc .AND. (.NOT. mask-expr ). 17 (3) The control mask mc is established to have the value mc .AND. mask-expr . 18 The mask-expr is evaluated only once. 19 Upon execution of an ELSEWHERE statement, the control mask is established to have the value of the 20 pending control mask. No new pending control mask value is established. 21 Upon execution of an ENDWHERE statement, the control mask and pending control mask are es- 22 tablished to have the values they had prior to the execution of the corresponding WHERE construct 23 statement. Following the execution of a WHERE statement that appears as a where-body-construct , the 24 control mask is established to have the value it had prior to the execution of the WHERE statement. NOTE 7.45 The establishment of control masks and the pending control mask is illustrated with the following example: WHERE(cond1) ! Statement 1 . . . ELSEWHERE(cond2) ! Statement 2 . . . 146 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 7.45 (cont.) ELSEWHERE ! Statement 3 . . . END WHERE Following execution of statement 1, the control mask has the value cond1 and the pending control mask has the value .NOT. cond1. Following execution of statement 2, the control mask has the value (.NOT. cond1) .AND. cond2 and the pending control mask has the value (.NOT. cond1) .AND. (.NOT. cond2). Following execution of statement 3, the control mask has the value (.NOT. cond1) .AND. (.NOT. cond2). The false condition values are propagated through the execution of the masked ELSEWHERE statement. 1 Upon execution of a WHERE construct statement that is part of a where-body-construct , the pending 2 control mask is established to have the value mc .AND. (.NOT. mask-expr ). The control mask is then 3 established to have the value mc .AND. mask-expr . The mask-expr is evaluated only once. 4 Upon execution of a WHERE statement that is part of a where-body-construct , the control mask is 5 established to have the value mc .AND. mask-expr . The pending mask is not altered. 6 If a nonelemental function reference occurs in the expr or variable of a where-assignment-stmt or in a 7 mask-expr , the function is evaluated without any masked control; that is, all of its argument expressions 8 are fully evaluated and the function is fully evaluated. If the result is an array and the reference is not 9 within the argument list of a nonelemental function, elements corresponding to true values in the control 10 mask are selected for use in evaluating the expr , variable or mask-expr . 11 If an elemental operation or function reference occurs in the expr or variable of a where-assignment-stmt 12 or in a mask-expr , and is not within the argument list of a nonelemental function reference, the operation 13 is performed or the function is evaluated only for the elements corresponding to true values of the control 14 mask. 15 If an array constructor appears in a where-assignment-stmt or in a mask-expr , the array constructor is 16 evaluated without any masked control and then the where-assignment-stmt is executed or the mask-expr 17 is evaluated. 18 When a where-assignment-stmt is executed, the values of expr that correspond to true values of the 19 control mask are assigned to the corresponding elements of variable. 20 The value of the control mask is established by the execution of a WHERE statement, a WHERE con- 21 struct statement, an ELSEWHERE statement, a masked ELSEWHERE statement, or an ENDWHERE 22 statement. Subsequent changes to the value of entities in a mask-expr have no effect on the value of the 23 control mask. The execution of a function reference in the mask expression of a WHERE statement is 24 permitted to affect entities in the assignment statement. NOTE 7.46 Examples of function references in masked array assignments are: WHERE (A > 0.0) A = LOG (A) ! LOG is invoked only for positive elements. A = A / SUM (LOG (A)) ! LOG is invoked for all elements ! because SUM is transformational. END WHERE SEP 2002 COMMITTEE DRAFT 147 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 7.4.4 FORALL 2 FORALL constructs and statements are used to control the execution of assignment and pointer assign- 3 ment statements with selection by sets of index values and an optional mask expression. 4 7.4.4.1 The FORALL Construct 5 The FORALL construct allows multiple assignments, masked array (WHERE) assignments, and nested 6 FORALL constructs and statements to be controlled by a single forall-triplet-spec-list and scalar-mask- 7 expr . 8 R751 forall-construct is forall-construct-stmt 9 [forall-body-construct ] ... 10 end-forall-stmt 11 R752 forall-construct-stmt is [forall-construct-name :] FORALL forall-header 12 R753 forall-header is (forall-triplet-spec-list [, scalar-mask-expr ] ) 13 R754 forall-triplet-spec is index-name = subscript : subscript [ : stride] 14 R618 subscript is scalar-int-expr 15 R621 stride is scalar-int-expr 16 R755 forall-body-construct is forall-assignment-stmt 17 or where-stmt 18 or where-construct 19 or forall-construct 20 or forall-stmt 21 R756 forall-assignment-stmt is assignment-stmt 22 or pointer-assignment-stmt 23 R757 end-forall-stmt is END FORALL [forall-construct-name ] 24 C732 (R757) If the forall-construct-stmt has a forall-construct-name, the end-forall-stmt shall have 25 the same forall-construct-name. If the end-forall-stmt has a forall-construct-name, the forall- 26 construct-stmt shall have the same forall-construct-name. 27 C733 (R753) The scalar-mask-expr shall be scalar and of type logical. 28 C734 (R753) Any procedure referenced in the scalar-mask-expr , including one referenced by a defined 29 operation, shall be a pure procedure (12.6). 30 C735 (R754) The index-name shall be a named scalar variable of type integer. 31 C736 (R754) A subscript or stride in a forall-triplet-spec shall not contain a reference to any index- 32 name in the forall-triplet-spec-list in which it appears. 33 C737 (R755) A statement in a forall-body-construct shall not define an index-name of the forall- 34 construct . 35 C738 (R755) Any procedure referenced in a forall-body-construct , including one referenced by a defined 36 operation, assignment, or finalization, shall be a pure procedure. 37 C739 (R755) A forall-body-construct shall not be a branch target. NOTE 7.47 An example of a FORALL construct is: REAL :: A(10, 10), B(10, 10) = 1.0 . . . 148 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 7.47 (cont.) FORALL (I = 1:10, J = 1:10, B(I, J) /= 0.0) A(I, J) = REAL (I + J - 2) B(I, J) = A(I, J) + B(I, J) * REAL (I * J) END FORALL NOTE 7.48 An assignment statement that is a FORALL body construct may be a scalar or array assignment statement, or a defined assignment statement. The variable being defined will normally use each index name in the forall-triplet-spec-list. For example FORALL (I = 1:N, J = 1:N) A(:, I, :, J) = 1.0 / REAL(I + J - 1) END FORALL broadcasts scalar values to rank-two subarrays of A. NOTE 7.49 An example of a FORALL construct containing a pointer assignment statement is: TYPE ELEMENT REAL ELEMENT_WT CHARACTER (32), POINTER :: NAME END TYPE ELEMENT TYPE(ELEMENT) CHART(200) REAL WEIGHTS (1000) CHARACTER (32), TARGET :: NAMES (1000) . . . FORALL (I = 1:200, WEIGHTS (I + N - 1) > .5) CHART(I) % ELEMENT_WT = WEIGHTS (I + N - 1) CHART(I) % NAME => NAMES (I + N - 1) END FORALL The results of this FORALL construct cannot be achieved with a WHERE construct because a pointer assignment statement is not permitted in a WHERE construct. 1 An index-name in a forall-construct has a scope of the construct (16.3). It is a scalar variable that has 2 the type and type parameters that it would have if it were the name of a variable in the scoping unit 3 that includes the FORALL, and this type shall be integer type; it has no other attributes. NOTE 7.50 The use of index-name variables in a FORALL construct does not affect variables of the same name, for example: INTEGER :: X = -1 REAL A(5, 4) J = 100 . . . FORALL (X = 1:5, J = 1:4) A (X, J) = J SEP 2002 COMMITTEE DRAFT 149 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 7.50 (cont.) END FORALL After execution of the FORALL, the variables X and J have the values -1 and 100 and A has the value 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 7.4.4.2 Execution of the FORALL construct 2 There are three stages in the execution of a FORALL construct: 3 (1) Determination of the values for index-name variables, 4 (2) Evaluation of the scalar-mask-expr , and 5 (3) Execution of the FORALL body constructs. 6 7.4.4.2.1 Determination of the values for index variables 7 The subscript and stride expressions in the forall-triplet-spec-list are evaluated. These expressions may 8 be evaluated in any order. The set of values that a particular index-name variable assumes is determined 9 as follows: 10 (1) The lower bound m1, the upper bound m2, and the stride m3 are of type integer with the 11 same kind type parameter as the index-name. Their values are established by evaluating 12 the first subscript, the second subscript, and the stride expressions, respectively, including, 13 if necessary, conversion to the kind type parameter of the index-name according to the rules 14 for numeric conversion (Table 7.9). If a stride does not appear, m3 has the value 1. The 15 value m3 shall not be zero. 16 (2) Let the value of max be (m2 - m1 + m3)/m3. If max 0 for some index-name, the execution 17 of the construct is complete. Otherwise, the set of values for the index-name is 18 m1 + (k - 1) × m3 where k = 1, 2, ..., max. 19 The set of combinations of index-name values is the Cartesian product of the sets defined by each triplet 20 specification. An index-name becomes defined when this set is evaluated. NOTE 7.51 The stride may be positive or negative; the FORALL body constructs are executed as long as max > 0. For the forall-triplet-spec I = 10:1:-1 max has the value 10 21 7.4.4.2.2 Evaluation of the mask expression 22 The scalar-mask-expr , if any, is evaluated for each combination of index-name values. If the scalar- 23 mask-expr is not present, it is as if it were present with the value true. The index-name variables may 24 be primaries in the scalar-mask-expr . 25 The active combination of index-name values is defined to be the subset of all possible combinations 150 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 (7.4.4.2.1) for which the scalar-mask-expr has the value true. NOTE 7.52 The index-name variables may appear in the mask, for example FORALL (I=1:10, J=1:10, A(I) > 0.0 .AND. B(J) < 1.0) . . . 2 7.4.4.2.3 Execution of the FORALL body constructs 3 The forall-body-construct s are executed in the order in which they appear. Each construct is executed 4 for all active combinations of the index-name values with the following interpretation: 5 Execution of a forall-assignment-stmt that is an assignment-stmt causes the evaluation of expr and all 6 expressions within variable for all active combinations of index-name values. These evaluations may be 7 done in any order. After all these evaluations have been performed, each expr value is assigned to the 8 corresponding variable. The assignments may occur in any order. 9 Execution of a forall-assignment-stmt that is a pointer-assignment-stmt causes the evaluation of all 10 expressions within data-target and pointer-object , the determination of any pointers within pointer- 11 object , and the determination of the target for all active combinations of index-name values. These 12 evaluations may be done in any order. After all these evaluations have been performed, each pointer- 13 object is associated with the corresponding data-target . These associations may occur in any order. 14 In a forall-assignment-stmt , a defined assignment subroutine shall not reference any variable that be- 15 comes defined or pointer-object that becomes associated by the statement. NOTE 7.53 The following FORALL construct contains two assignment statements. The assignment to array B uses the values of array A computed in the previous statement, not the values A had prior to execution of the FORALL. FORALL (I = 2:N-1, J = 2:N-1 ) A (I, J) = A(I, J-1) + A(I, J+1) + A(I-1, J) + A(I+1, J) B (I, J) = 1.0 / A(I, J) END FORALL Computations that would otherwise cause error conditions can be avoided by using an appropriate scalar-mask-expr that limits the active combinations of the index-name values. For example: FORALL (I = 1:N, Y(I) /= 0.0) X(I) = 1.0 / Y(I) END FORALL 16 Each statement in a where-construct (7.4.3) within a forall-construct is executed in sequence. When 17 a where-stmt , where-construct-stmt or masked-elsewhere-stmt is executed, the statement's mask-expr is 18 evaluated for all active combinations of index-name values as determined by the outer forall-construct s, 19 masked by any control mask corresponding to outer where-construct s. Any where-assignment-stmt is 20 executed for all active combinations of index-name values, masked by the control mask in effect for the 21 where-assignment-stmt . SEP 2002 COMMITTEE DRAFT 151 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 7.54 This FORALL construct contains a WHERE statement and an assignment statement. INTEGER A(5,4), B(5,4) FORALL ( I = 1:5 ) WHERE ( A(I,:) == 0 ) A(I,:) = I B (I,:) = I / A(I,:) END FORALL When executed with the input array 0 0 0 0 1 1 1 0 A = 2 2 0 2 1 0 2 3 0 0 0 0 the results will be 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 1 A = 2 2 3 2 B = 1 1 1 1 1 4 2 3 4 1 2 1 5 5 5 5 1 1 1 1 For an example of a FORALL construct containing a WHERE construct with an ELSEWHERE statement, see C.4.5. 1 Execution of a forall-stmt or forall-construct causes the evaluation of the subscript and stride expressions 2 in the forall-triplet-spec-list for all active combinations of the index-name values of the outer FORALL 3 construct. The set of combinations of index-name values for the inner FORALL is the union of the sets 4 defined by these bounds and strides for each active combination of the outer index-name values; it also 5 includes the outer index-name values. The scalar-mask-expr is then evaluated for all combinations of the 6 index-name values of the inner construct to produce a set of active combinations for the inner construct. 7 If there is no scalar-mask-expr , it is as if it were present with the value .TRUE.. Each statement in the 8 inner FORALL is then executed for each active combination of the index-name values. NOTE 7.55 This FORALL construct contains a nested FORALL construct. It assigns the transpose of the strict lower triangle of array A (the section below the main diagonal) to the strict upper triangle of A. INTEGER A (3, 3) FORALL (I = 1:N-1 ) FORALL ( J=I+1:N ) A(I,J) = A(J,I) END FORALL END FORALL If prior to execution N = 3 and 152 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 7.55 (cont.) 0 3 6 A = 1 4 7 2 5 8 then after execution 0 1 2 A = 1 4 5 2 5 8 1 7.4.4.3 The FORALL statement 2 The FORALL statement allows a single assignment statement or pointer assignment to be controlled by 3 a set of index values and an optional mask expression. 4 R758 forall-stmt is FORALL forall-header forall-assignment-stmt 5 A FORALL statement is equivalent to a FORALL construct containing a single forall-body-construct 6 that is a forall-assignment-stmt . 7 The scope of an index-name in a forall-stmt is the statement itself (16.3). NOTE 7.56 Examples of FORALL statements are: FORALL (I=1:N) A(I,I) = X(I) This statement assigns the elements of vector X to the elements of the main diagonal of matrix A. FORALL (I = 1:N, J = 1:N) X(I,J) = 1.0 / REAL (I+J-1) Array element X(I,J) is assigned the value (1.0 / REAL (I+J-1)) for values of I and J between 1 and N, inclusive. FORALL (I=1:N, J=1:N, Y(I,J) /= 0 .AND. I /= J) X(I,J) = 1.0 / Y(I,J) This statement takes the reciprocal of each nonzero off-diagonal element of array Y(1:N, 1:N) and assigns it to the corresponding element of array X. Elements of Y that are zero or on the diagonal do not participate, and no assignments are made to the corresponding elements of X. The results from the execution of the example in Note 7.55 could be obtained with a single FORALL statement: FORALL ( I = 1:N-1, J=1:N, J > I ) A(I,J) = A(J,I) For more examples of FORALL statements, see C.4.6. 8 7.4.4.4 Restrictions on FORALL constructs and statements 9 A many-to-one assignment is more than one assignment to the same object, or association of more 10 than one target with the same pointer, whether the object is referenced directly or indirectly through a 11 pointer. A many-to-one assignment shall not occur within a single statement in a FORALL construct or 12 statement. It is possible to assign or pointer assign to the same object in different assignment statements SEP 2002 COMMITTEE DRAFT 153 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 in a FORALL construct. NOTE 7.57 The appearance of each index-name in the identification of the left-hand side of an assignment statement is helpful in eliminating many-to-one assignments, but it is not sufficient to guarantee there will be none. For example, the following is allowed FORALL (I = 1:10) A (INDEX (I)) = B(I) END FORALL if and only if INDEX(1:10) contains no repeated values. 2 Within the scope of a FORALL construct, a nested FORALL statement or FORALL construct shall 3 not have the same index-name. The forall-header expressions within a nested FORALL may depend on 4 the values of outer index-name variables. 154 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 Section 8: Execution control 2 The execution sequence may be controlled by constructs containing blocks and by certain executable 3 statements that are used to alter the execution sequence. 4 8.1 Executable constructs containing blocks 5 The following are executable constructs that contain blocks: 6 (1) ASSOCIATE construct 7 (2) CASE construct 8 (3) DO construct 9 (4) IF construct 10 (5) SELECT TYPE construct 11 There is also a nonblock form of the DO construct. 12 A block is a sequence of executable constructs that is treated as a unit. 13 R801 block is [ execution-part-construct ] ... 14 Executable constructs may be used to control which blocks of a program are executed or how many times 15 a block is executed. Blocks are always bounded by statements that are particular to the construct in 16 which they are embedded; however, in some forms of the DO construct, a sequence of executable constructs without 17 a terminating boundary statement shall obey all other rules governing blocks (8.1.1). NOTE 8.1 A block need not contain any executable constructs. Execution of such a block has no effect. 18 Any of these constructs may be named. If a construct is named, the name shall be the first lexical token 19 of the first statement of the construct and the last lexical token of the construct. In fixed source form, the 20 name preceding the construct shall be placed after character position 6. 21 A statement belongs to the innermost construct in which it appears unless it contains a construct name, 22 in which case it belongs to the named construct. NOTE 8.2 An example of a construct containing a block is: IF (A > 0.0) THEN B = SQRT (A) ! These two statements C = LOG (A) ! form a block. END IF 23 8.1.1 Rules governing blocks 24 8.1.1.1 Executable constructs in blocks 25 If a block contains an executable construct, the executable construct shall be entirely within the block. SEP 2002 COMMITTEE DRAFT 155 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 8.1.1.2 Control flow in blocks 2 Transfer of control to the interior of a block from outside the block is prohibited. Transfers within a 3 block and transfers from the interior of a block to outside the block may occur. 4 Subroutine and function references (12.4.2, 12.4.3) may appear in a block. 5 8.1.1.3 Execution of a block 6 Execution of a block begins with the execution of the first executable construct in the block. Execution 7 of the block is completed when the last executable construct in the sequence is executed or when a 8 branch out of the block takes place. NOTE 8.3 The action that takes place at the terminal boundary depends on the particular construct and on the block within that construct. It is usually a transfer of control. 9 8.1.2 IF construct 10 The IF construct selects for execution at most one of its constituent blocks. The selection is based 11 on a sequence of logical expressions. The IF statement controls the execution of a single statement 12 (8.1.2.4) based on a single logical expression. 13 8.1.2.1 Form of the IF construct 14 R802 if-construct is if-then-stmt 15 block 16 [ else-if-stmt 17 block ] ... 18 [ else-stmt 19 block ] 20 end-if-stmt 21 R803 if-then-stmt is [ if-construct-name : ] IF ( scalar-logical-expr ) THEN 22 R804 else-if-stmt is ELSE IF ( scalar-logical-expr ) THEN [ if-construct-name ] 23 R805 else-stmt is ELSE [ if-construct-name ] 24 R806 end-if-stmt is END IF [ if-construct-name ] 25 C801 (R802) If the if-then-stmt of an if-construct specifies an if-construct-name, the corresponding 26 end-if-stmt shall specify the same if-construct-name. If the if-then-stmt of an if-construct does 27 not specify an if-construct-name, the corresponding end-if-stmt shall not specify an if-construct- 28 name. If an else-if-stmt or else-stmt specifies an if-construct-name, the corresponding if-then- 29 stmt shall specify the same if-construct-name. 30 8.1.2.2 Execution of an IF construct 31 At most one of the blocks in the IF construct is executed. If there is an ELSE statement in the construct, 32 exactly one of the blocks in the construct is executed. The scalar logical expressions are evaluated in 33 the order of their appearance in the construct until a true value is found or an ELSE statement or END 34 IF statement is encountered. If a true value or an ELSE statement is found, the block immediately 35 following is executed and this completes the execution of the construct. The scalar logical expressions 36 in any remaining ELSE IF statements of the IF construct are not evaluated. If none of the evaluated 37 expressions is true and there is no ELSE statement, the execution of the construct is completed without 38 the execution of any block within the construct. 39 An ELSE IF statement or an ELSE statement shall not be a branch target statement. It is permissible 156 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 to branch to an END IF statement only from within its IF construct. Execution of an END IF statement 2 has no effect. 3 8.1.2.3 Examples of IF constructs NOTE 8.4 IF (CVAR == 'RESET') THEN I = 0; J = 0; K = 0 END IF PROOF_DONE: IF (PROP) THEN WRITE (3, '(''QED'')') STOP ELSE PROP = NEXTPROP END IF PROOF_DONE IF (A > 0) THEN B = C/A IF (B > 0) THEN D = 1.0 END IF ELSE IF (C > 0) THEN B = A/C D = -1.0 ELSE B = ABS (MAX (A, C)) D = 0 END IF 4 8.1.2.4 IF statement 5 The IF statement controls a single action statement (R214). 6 R807 if-stmt is IF ( scalar-logical-expr ) action-stmt 7 C802 (R807) The action-stmt in the if-stmt shall not be an if-stmt , end-program-stmt , end-function- 8 stmt , or end-subroutine-stmt . 9 Execution of an IF statement causes evaluation of the scalar logical expression. If the value of the 10 expression is true, the action statement is executed. If the value is false, the action statement is not 11 executed and execution continues. 12 The execution of a function reference in the scalar logical expression may affect entities in the action 13 statement. NOTE 8.5 An example of an IF statement is: IF (A > 0.0) A = LOG (A) SEP 2002 COMMITTEE DRAFT 157 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 8.1.3 CASE construct 2 The CASE construct selects for execution at most one of its constituent blocks. The selection is 3 based on the value of an expression. 4 8.1.3.1 Form of the CASE construct 5 R808 case-construct is select-case-stmt 6 [ case-stmt 7 block ] ... 8 end-select-stmt 9 R809 select-case-stmt is [ case-construct-name : ] SELECT CASE ( case-expr ) 10 R810 case-stmt is CASE case-selector [case-construct-name] 11 R811 end-select-stmt is END SELECT [ case-construct-name ] 12 C803 (R808) If the select-case-stmt of a case-construct specifies a case-construct-name, the corre- 13 sponding end-select-stmt shall specify the same case-construct-name. If the select-case-stmt 14 of a case-construct does not specify a case-construct-name, the corresponding end-select-stmt 15 shall not specify a case-construct-name. If a case-stmt specifies a case-construct-name, the 16 corresponding select-case-stmt shall specify the same case-construct-name. 17 R812 case-expr is scalar-int-expr 18 or scalar-char-expr 19 or scalar-logical-expr 20 R813 case-selector is ( case-value-range-list ) 21 or DEFAULT 22 C804 (R808) No more than one of the selectors of one of the CASE statements shall be DEFAULT. 23 R814 case-value-range is case-value 24 or case-value : 25 or : case-value 26 or case-value : case-value 27 R815 case-value is scalar-int-initialization-expr 28 or scalar-char-initialization-expr 29 or scalar-logical-initialization-expr 30 C805 (R808) For a given case-construct , each case-value shall be of the same type as case-expr . For 31 character type, the kind type parameters shall be the same; character length differences are 32 allowed. 33 C806 (R808) A case-value-range using a colon shall not be used if case-expr is of type logical. 34 C807 (R808) For a given case-construct , the case-value-ranges shall not overlap; that is, there shall 35 be no possible value of the case-expr that matches more than one case-value-range. 36 8.1.3.2 Execution of a CASE construct 37 The execution of the SELECT CASE statement causes the case expression to be evaluated. The resulting 38 value is called the case index. For a case value range list, a match occurs if the case index matches any 39 of the case value ranges in the list. For a case index with a value of c, a match is determined as follows: 40 (1) If the case value range contains a single value v without a colon, a match occurs for type 41 logical if the expression c .EQV. v is true, and a match occurs for type integer or character 42 if the expression c == v is true. 43 (2) If the case value range is of the form low : high, a match occurs if the expression low <= c 44 .AND. c <= high is true. 158 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 (3) If the case value range is of the form low :, a match occurs if the expression low <= c is true. 2 (4) If the case value range is of the form : high, a match occurs if the expression c <= high is 3 true. 4 (5) If no other selector matches and a DEFAULT selector appears, it matches the case index. 5 (6) If no other selector matches and the DEFAULT selector does not appear, there is no match. 6 The block following the CASE statement containing the matching selector, if any, is executed. This 7 completes execution of the construct. 8 At most one of the blocks of a CASE construct is executed. 9 A CASE statement shall not be a branch target statement. It is permissible to branch to an end-select- 10 stmt only from within its CASE construct. 11 8.1.3.3 Examples of CASE constructs NOTE 8.6 An integer signum function: INTEGER FUNCTION SIGNUM (N) SELECT CASE (N) CASE (:-1) SIGNUM = -1 CASE (0) SIGNUM = 0 CASE (1:) SIGNUM = 1 END SELECT END NOTE 8.7 A code fragment to check for balanced parentheses: CHARACTER (80) :: LINE ... LEVEL = 0 SCAN_LINE: DO I = 1, 80 CHECK_PARENS: SELECT CASE (LINE (I:I)) CASE ('(') LEVEL = LEVEL + 1 CASE (')') LEVEL = LEVEL - 1 IF (LEVEL < 0) THEN PRINT *, 'UNEXPECTED RIGHT PARENTHESIS' EXIT SCAN_LINE END IF CASE DEFAULT ! Ignore all other characters END SELECT CHECK_PARENS END DO SCAN_LINE IF (LEVEL > 0) THEN SEP 2002 COMMITTEE DRAFT 159 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 8.7 (cont.) PRINT *, 'MISSING RIGHT PARENTHESIS' END IF NOTE 8.8 The following three fragments are equivalent: IF (SILLY == 1) THEN CALL THIS ELSE CALL THAT END IF SELECT CASE (SILLY == 1) CASE (.TRUE.) CALL THIS CASE (.FALSE.) CALL THAT END SELECT SELECT CASE (SILLY) CASE DEFAULT CALL THAT CASE (1) CALL THIS END SELECT NOTE 8.9 A code fragment showing several selections of one block: SELECT CASE (N) CASE (1, 3:5, 8) ! Selects 1, 3, 4, 5, 8 CALL SUB CASE DEFAULT CALL OTHER END SELECT 1 8.1.4 ASSOCIATE construct 2 The ASSOCIATE construct associates named entities with expressions or variables during the execution 3 of its block. These named construct entities (16.3) are associating entities (16.4.1.5). The names are 4 associate names. 5 8.1.4.1 Form of the ASSOCIATE construct 6 R816 associate-construct is associate-stmt 7 block 8 end-associate-stmt 9 R817 associate-stmt is [ associate-construct-name : ] ASSOCIATE 10 (association-list ) 11 R818 association is associate-name => selector 12 R819 selector is expr 13 or variable 160 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 C808 (R818) If selector is not a variable or is a variable that has a vector subscript, associate-name 2 shall not appear in a variable definition context (16.5.7). 3 R820 end-associate-stmt is END ASSOCIATE [ associate-construct-name ] 4 C809 (R820) If the associate-stmt of an associate-construct specifies an associate-construct-name, 5 the corresponding end-associate-stmt shall specify the same associate-construct-name. If the 6 associate-stmt of an associate-construct does not specify an associate-construct-name, the cor- 7 responding end-associate-stmt shall not specify an associate-construct-name. 8 8.1.4.2 Execution of the ASSOCIATE construct 9 Execution of an ASSOCIATE construct causes execution of its associate-stmt followed by execution of 10 its block. During execution of that block each associate name identifies an entity, which is associated 11 (16.4.1.5) with the corresponding selector. The associating entity assumes the declared type and type 12 parameters of the selector. If and only if the selector is polymorphic, the associating entity is polymorphic 13 and assumes the dynamic type and type parameters of the selector. 14 The other attributes of the associating entity are described in 8.1.4.3. 15 It is permissible to branch to an end-associate-stmt only from within its ASSOCIATE construct. 16 8.1.4.3 Attributes of associate names 17 Within a SELECT TYPE or ASSOCIATE construct, each associating entity has the same rank as its 18 associated selector. The lower bound of each dimension is the result of the intrinsic function LBOUND 19 (13.7.58) applied to the corresponding dimension of selector . The upper bound of each dimension is one 20 less than the sum of the lower bound and the extent. The associating entity has the ASYNCHRONOUS, 21 INTENT, TARGET, or VOLATILE attribute if and only if the selector is a variable and has the attribute. 22 If the selector has the OPTIONAL attribute, it shall be present. 23 If the selector (8.1.4.1) is not permitted to appear in a variable definition context (16.5.7) or is an array 24 with a vector subscript, the associate name shall not appear in a variable definition context. 25 8.1.4.4 Examples of the ASSOCIATE construct NOTE 8.10 The following example illustrates an association with an expression. ASSOCIATE ( Z => EXP(-(X**2+Y**2)) * COS(THETA) ) PRINT *, A+Z, A-Z END ASSOCIATE The following example illustrates an association with a derived-type variable. ASSOCIATE ( XC => AX%B(I,J)%C ) XC%DV = XC%DV + PRODUCT(XC%EV(1:N)) END ASSOCIATE The following example illustrates association with an array section. ASSOCIATE ( ARRAY => AX%B(I,:)%C ) ARRAY(N)%EV = ARRAY(N-1)%EV SEP 2002 COMMITTEE DRAFT 161 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 8.10 (cont.) END ASSOCIATE The following example illustrates multiple associations. ASSOCIATE ( W => RESULT(I,J)%W, ZX => AX%B(I,J)%D, ZY => AY%B(I,J)%D ) W = ZX*X + ZY*Y END ASSOCIATE 1 8.1.5 SELECT TYPE construct 2 The SELECT TYPE construct selects for execution at most one of its constituent blocks. The selection 3 is based on the dynamic type of an expression. A name is associated with the expression (16.3, 16.4.1.5), 4 in the same way as for the ASSOCIATE construct. 5 8.1.5.1 Form of the SELECT TYPE construct 6 R821 select-type-construct is select-type-stmt 7 [ type-guard-stmt 8 block ] ... 9 end-select-type-stmt 10 R822 select-type-stmt is [ select-construct-name : ] SELECT TYPE 11 ( [ associate-name => ] selector ) 12 C810 (R822) If selector is not a named variable, associate-name => shall appear. 13 C811 (R822) If selector is not a variable or is a variable that has a vector subscript, associate-name 14 shall not appear in a variable definition context (16.5.7). 15 C812 (R822) The selector in a select-type-stmt shall be polymorphic. 16 R823 type-guard-stmt is TYPE IS ( extensible-type-name ) [ select-construct-name ] 17 or CLASS IS ( extensible-type-name ) [ select-construct-name ] 18 or CLASS DEFAULT [ select-construct-name ] 19 C813 (R823) If selector is not unlimited polymorphic, the extensible-type-name shall be the name of 20 an extension of the declared type of selector . 21 C814 (R823) For a given select-type-construct , the same extensible-type-name shall not be specified in 22 more than one TYPE IS type-guard-stmt and shall not be specified in more than one CLASS IS 23 type-guard-stmt . 24 C815 (R823) For a given select-type-construct , there shall be at most one CLASS DEFAULT type- 25 guard-stmt . 26 R824 end-select-type-stmt is END SELECT [ select-construct-name ] 27 C816 (R821) If the select-type-stmt of a select-type-construct specifies a select-construct-name, the 28 corresponding end-select-type-stmt shall specify the same select-construct-name. If the select- 29 type-stmt of a select-type-construct does not specify a select-construct-name, the corresponding 30 end-select-type-stmt shall not specify a select-construct-name. If a type-guard-stmt specifies a 31 select-construct-name, the corresponding select-type-stmt shall specify the same select-construct- 32 name. 33 The associate name of a SELECT TYPE construct is the associate-name if specified; otherwise it is the 34 name that constitutes the selector . 162 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 8.1.5.2 Execution of the SELECT TYPE construct 2 Execution of a SELECT TYPE construct whose selector is not a variable causes the selector expression 3 to be evaluated. 4 A SELECT TYPE construct selects at most one block to be executed. During execution of that block, 5 the associate name identifies an entity, which is associated (16.4.1.5) with the selector. 6 The block to be executed is selected as follows: 7 (1) If the dynamic type of the selector is the same as the type named in a TYPE IS type guard 8 statement, the block following that statement is executed. 9 (2) Otherwise, if the dynamic type of the selector is an extension of exactly one type named in 10 a CLASS IS type guard statement, the block following that statement is executed. 11 (3) Otherwise, if the dynamic type of the selector is an extension of several types named in 12 CLASS IS type guard statements, one of these statements must specify a type that is an 13 extension of all the types specified in the others; the block following that statement is 14 executed. 15 (4) Otherwise, if there is a CLASS DEFAULT type guard statement, the block following that 16 statement is executed. NOTE 8.11 This algorithm does not examine the type guard statements in source text order when it looks for a match; it selects the most particular type guard when there are several potential matches. 17 Within the block following a TYPE IS type guard statement, the associating entity (16.4.5) is not 18 polymorphic (5.1.1.8), has the type named in the type guard statement, and has the type parameters of 19 the selector. 20 Within the block following a CLASS IS type guard statement, the associating entity is polymorphic and 21 has the declared type named in the type guard statement. The type parameters of the associating entity 22 are those of the type specified in the CLASS IS type guard statement. 23 Within the block following a CLASS DEFAULT type guard statement, the associating entity is poly- 24 morphic and has the same declared type as the selector. The type parameters of the associating entity 25 are those of the declared type of the selector. NOTE 8.12 If the declared type of the selector is T, specifying CLASS DEFAULT has the same effect as specifying CLASS IS (T). 26 The other attributes of the associating entity are described in 8.1.4.3. 27 A type guard statement shall not be a branch target statement. It is permissible to branch to an 28 end-select-type-stmt only from within its SELECT TYPE construct. 29 8.1.5.3 Examples of the SELECT TYPE construct NOTE 8.13 TYPE, EXTENSIBLE :: POINT REAL :: X, Y END TYPE POINT SEP 2002 COMMITTEE DRAFT 163 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 8.13 (cont.) TYPE, EXTENDS(POINT) :: POINT_3D REAL :: Z END TYPE POINT_3D TYPE, EXTENDS(POINT) :: COLOR_POINT INTEGER :: COLOR END TYPE COLOR_POINT TYPE(POINT), TARGET :: P TYPE(POINT_3D), TARGET :: P3 TYPE(COLOR_POINT), TARGET :: C CLASS(POINT), POINTER :: P_OR_C P_OR_C => C SELECT TYPE ( A => P_OR_C ) CLASS IS ( POINT ) ! "CLASS ( POINT ) :: A" implied here PRINT *, A%X, A%Y ! This block gets executed TYPE IS ( POINT_3D ) ! "TYPE ( POINT_3D ) :: A" implied here PRINT *, A%X, A%Y, A%Z END SELECT NOTE 8.14 The following example illustrates the omission of associate-name. It uses the declarations from Note 8.13. P_OR_C => P3 SELECT TYPE ( P_OR_C ) CLASS IS ( POINT ) ! "CLASS ( POINT ) :: P_OR_C" implied here PRINT *, P_OR_C%X, P_OR_C%Y TYPE IS ( POINT_3D ) ! "TYPE ( POINT_3D ) :: P_OR_C" implied here PRINT *, P_OR_C%X, P_OR_C%Y, P_OR_C%Z ! This block gets executed END SELECT 1 8.1.6 DO construct 2 The DO construct specifies the repeated execution of a sequence of executable constructs. Such a 3 repeated sequence is called a loop. The EXIT and CYCLE statements may be used to modify the 4 execution of a loop. 5 The number of iterations of a loop may be determined at the beginning of execution of the DO construct, 6 or may be left indefinite ("DO forever" or DO WHILE). In either case, an EXIT statement (8.1.6.4.4) 7 anywhere in the DO construct may be executed to terminate the loop immediately. The current iteration 8 of the loop may be curtailed by executing a CYCLE statement (8.1.6.4.3). 9 8.1.6.1 Forms of the DO construct 10 The DO construct may be written in either a block form or a nonblock form. 11 R825 do-construct is block-do-construct 12 or nonblock-do-construct 164 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 8.1.6.1.1 Form of the block DO construct 2 R826 block-do-construct is do-stmt 3 do-block 4 end-do 5 R827 do-stmt is label-do-stmt 6 or nonlabel-do-stmt 7 R828 label-do-stmt is [ do-construct-name : ] DO label [ loop-control ] 8 R829 nonlabel-do-stmt is [ do-construct-name : ] DO [ loop-control ] 9 R830 loop-control is [ , ] do-variable = scalar-int-expr , scalar-int-expr 10 [ , scalar-int-expr ] 11 or [ , ] WHILE ( scalar-logical-expr ) 12 R831 do-variable is scalar-int-variable 13 C817 (R831) The do-variable shall be a named scalar variable of type integer. 14 R832 do-block is block 15 R833 end-do is end-do-stmt 16 or continue-stmt 17 R834 end-do-stmt is END DO [ do-construct-name ] 18 C818 (R826) If the do-stmt of a block-do-construct specifies a do-construct-name, the corresponding 19 end-do shall be an end-do-stmt specifying the same do-construct-name. If the do-stmt of a 20 block-do-construct does not specify a do-construct-name, the corresponding end-do shall not 21 specify a do-construct-name. 22 C819 (R826) If the do-stmt is a nonlabel-do-stmt , the corresponding end-do shall be an end-do-stmt . 23 C820 (R826) If the do-stmt is a label-do-stmt , the corresponding end-do shall be identified with the 24 same label . 25 8.1.6.1.2 Form of the nonblock DO construct 26 R835 nonblock-do-construct is action-term-do-construct 27 or outer-shared-do-construct 28 R836 action-term-do-construct is label-do-stmt 29 do-body 30 do-term-action-stmt 31 R837 do-body is [ execution-part-construct ] ... 32 R838 do-term-action-stmt is action-stmt 33 C821 (R838) A do-term-action-stmt shall not be a continue-stmt , a goto-stmt , a return-stmt , a stop-stmt , an exit-stmt , 34 a cycle-stmt , an end-function-stmt , an end-subroutine-stmt , an end-program-stmt , or an arithmetic-if-stmt . 35 C822 (R835) The do-term-action-stmt shall be identified with a label and the corresponding label-do-stmt shall refer 36 to the same label. 37 R839 outer-shared-do-construct is label-do-stmt 38 do-body 39 shared-term-do-construct 40 R840 shared-term-do-construct is outer-shared-do-construct 41 or inner-shared-do-construct 42 R841 inner-shared-do-construct is label-do-stmt 43 do-body 44 do-term-shared-stmt 45 R842 do-term-shared-stmt is action-stmt 46 C823 (R842) A do-term-shared-stmt shall not be a goto-stmt , a return-stmt , a stop-stmt , an exit-stmt , a cycle-stmt , 47 an end-function-stmt , an end-subroutine-stmt , an end-program-stmt , or an arithmetic-if-stmt . 48 C824 (R840) The do-term-shared-stmt shall be identified with a label and all of the label-do-stmt s of the shared-term- 49 do-construct shall refer to the same label. SEP 2002 COMMITTEE DRAFT 165 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 The do-term-action-stmt , do-term-shared-stmt , or shared-term-do-construct following the do-body of a nonblock DO con- 2 struct is called the DO termination of that construct. 3 Within a scoping unit, all DO constructs whose DO statements refer to the same label are nonblock DO constructs, and 4 are said to share the statement identified by that label. 5 8.1.6.2 Range of the DO construct 6 The range of a block DO construct is the do-block , which shall satisfy the rules for blocks (8.1.1). In 7 particular, transfer of control to the interior of such a block from outside the block is prohibited. It 8 is permitted to branch to the end-do of a block DO construct only from within the range of that DO 9 construct. 10 The range of a nonblock DO construct consists of the do-body and the following DO termination. The end of such a 11 range is not bounded by a particular statement as for the other executable constructs (e.g., END IF); nevertheless, the 12 range satisfies the rules for blocks (8.1.1). Transfer of control into the do-body or to the DO termination from outside the 13 range is prohibited; in particular, it is permitted to branch to a do-term-shared-stmt only from within the range of the 14 corresponding inner-shared-do-construct . 15 8.1.6.3 Active and inactive DO constructs 16 A DO construct is either active or inactive. Initially inactive, a DO construct becomes active only 17 when its DO statement is executed. 18 Once active, the DO construct becomes inactive only when the construct is terminated (8.1.6.4.4). 19 8.1.6.4 Execution of a DO construct 20 A DO construct specifies a loop, that is, a sequence of executable constructs that is executed repeatedly. 21 There are three phases in the execution of a DO construct: initiation of the loop, execution of the loop 22 range, and termination of the loop. 23 8.1.6.4.1 Loop initiation 24 When the DO statement is executed, the DO construct becomes active. If loop-control is 25 [ , ] do-variable = scalar-int-expr 1 , scalar-int-expr 2 [ , scalar-int-expr 3 ] 26 the following steps are performed in sequence: 27 (1) The initial parameter m1, the terminal parameter m2, and the incrementation parameter m3 28 are of type integer with the same kind type parameter as the do-variable. Their values are es- 29 tablished by evaluating scalar-int-expr 1, scalar-int-expr 2, and scalar-int-expr 3, respectively, 30 including, if necessary, conversion to the kind type parameter of the do-variable according 31 to the rules for numeric conversion (Table 7.9). If scalar-int-expr 3 does not appear, m3 has 32 the value 1. The value of m3 shall not be zero. 33 (2) The DO variable becomes defined with the value of the initial parameter m1. 34 (3) The iteration count is established and is the value of the expression (m2 - m1 + m3)/m3, 35 unless that value is negative, in which case the iteration count is 0. NOTE 8.15 The iteration count is zero whenever: m1 > m2 and m3 > 0, or m1 < m2 and m3 < 0. 166 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 If loop-control is omitted, no iteration count is calculated. The effect is as if a large positive iteration 2 count, impossible to decrement to zero, were established. If loop-control is [ , ] WHILE (scalar-logical- 3 expr ), the effect is as if loop-control were omitted and the following statement inserted as the first 4 statement of the do-block : 5 IF (.NOT. (scalar- logical-expr )) EXIT 6 At the completion of the execution of the DO statement, the execution cycle begins. 7 8.1.6.4.2 The execution cycle 8 The execution cycle of a DO construct consists of the following steps performed in sequence repeatedly 9 until termination: 10 (1) The iteration count, if any, is tested. If it is zero, the loop terminates and the DO construct 11 becomes inactive. If loop-control is [ , ] WHILE (scalar-logical-expr ), the scalar-logical-expr 12 is evaluated; if the value of this expression is false, the loop terminates and the DO construct 13 becomes inactive. If, as a result, all of the DO constructs sharing the do-term-shared-stmt are inactive, 14 the execution of all of these constructs is complete. However, if some of the DO constructs sharing the 15 do-term-shared-stmt are active, execution continues with step (3) of the execution cycle of the active DO 16 construct whose DO statement was most recently executed. 17 (2) If the iteration count is nonzero, the range of the loop is executed. 18 (3) The iteration count, if any, is decremented by one. The DO variable, if any, is incremented 19 by the value of the incrementation parameter m3. 20 Except for the incrementation of the DO variable that occurs in step (3), the DO variable shall neither 21 be redefined nor become undefined while the DO construct is active. 22 8.1.6.4.3 CYCLE statement 23 Step (2) in the above execution cycle may be curtailed by executing a CYCLE statement from within 24 the range of the loop. 25 R843 cycle-stmt is CYCLE [ do-construct-name ] 26 C825 (R843) If a cycle-stmt refers to a do-construct-name, it shall be within the range of that do- 27 construct ; otherwise, it shall be within the range of at least one do-construct . 28 A CYCLE statement belongs to a particular DO construct. If the CYCLE statement refers to a DO 29 construct name, it belongs to that DO construct; otherwise, it belongs to the innermost DO construct 30 in which it appears. 31 Execution of a CYCLE statement causes immediate progression to step (3) of the current execution cycle 32 of the DO construct to which it belongs. If this construct is a nonblock DO construct, the do-term-action-stmt or 33 do-term-shared-stmt is not executed. 34 In a block DO construct, a transfer of control to the end-do has the same effect as execution of a CYCLE 35 statement belonging to that construct. In a nonblock DO construct, transfer of control to the do-term-action-stmt 36 or do-term-shared-stmt causes that statement or construct itself to be executed. Unless a further transfer of control results, 37 step (3) of the current execution cycle of the DO construct is then executed. 38 8.1.6.4.4 Loop termination 39 The EXIT statement provides one way of terminating a loop. 40 R844 exit-stmt is EXIT [ do-construct-name ] SEP 2002 COMMITTEE DRAFT 167 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 C826 (R844) If an exit-stmt refers to a do-construct-name, it shall be within the range of that do- 2 construct ; otherwise, it shall be within the range of at least one do-construct . 3 An EXIT statement belongs to a particular DO construct. If the EXIT statement refers to a DO 4 construct name, it belongs to that DO construct; otherwise, it belongs to the innermost DO construct 5 in which it appears. 6 The loop terminates, and the DO construct becomes inactive, when any of the following occurs: 7 (1) Determination that the iteration count is zero or the scalar-logical-expr is false, when tested 8 during step (1) of the above execution cycle 9 (2) Execution of an EXIT statement belonging to the DO construct 10 (3) Execution of an EXIT statement or a CYCLE statement that is within the range of the DO 11 construct, but that belongs to an outer DO construct 12 (4) Transfer of control from a statement within the range of a DO construct to a statement that 13 is neither the end-do nor within the range of the same DO construct 14 (5) Execution of a RETURN statement within the range of the DO construct 15 (6) Execution of a STOP statement anywhere in the program; or termination of the program 16 for any other reason. 17 When a DO construct becomes inactive, the DO variable, if any, of the DO construct retains its last 18 defined value. 19 8.1.6.5 Examples of DO constructs NOTE 8.16 The following program fragment computes a tensor product of two arrays: DO I = 1, M DO J = 1, N C (I, J) = SUM (A (I, J, :) * B (:, I, J)) END DO END DO NOTE 8.17 The following program fragment contains a DO construct that uses the WHILE form of loop- control . The loop will continue to execute until an end-of-file or input/output error is encountered, at which point the DO statement terminates the loop. When a negative value of X is read, the program skips immediately to the next READ statement, bypassing most of the range of the loop. READ (IUN, '(1X, G14.7)', IOSTAT = IOS) X DO WHILE (IOS == 0) IF (X >= 0.) THEN CALL SUBA (X) CALL SUBB (X) ... CALL SUBZ (X) ENDIF READ (IUN, '(1X, G14.7)', IOSTAT = IOS) X END DO 168 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 8.18 The following example behaves exactly the same as the one in Note 8.17. However, the READ statement has been moved to the interior of the range, so that only one READ statement is needed. Also, a CYCLE statement has been used to avoid an extra level of IF nesting. DO ! A "DO WHILE + 1/2" loop READ (IUN, '(1X, G14.7)', IOSTAT = IOS) X IF (IOS /= 0) EXIT IF (X < 0.) CYCLE CALL SUBA (X) CALL SUBB (X) . . . CALL SUBZ (X) END DO NOTE 8.19 Additional examples of DO constructs are in C.5.3. 1 8.2 Branching 2 Branching is used to alter the normal execution sequence. A branch causes a transfer of control from 3 one statement in a scoping unit to a labeled branch target statement in the same scoping unit. Branching 4 may be caused by a GOTO statement, a computed GOTO statement, an arithmetic IF statement, a 5 CALL statement that has an alt-return-spec, or an input/output statement that has an END= or ERR= 6 specifier. Although procedure references and control constructs can cause transfer of control, they are 7 not branches. A branch target statement is an action-stmt , an associate-stmt , an end-associate-stmt , 8 an if-then-stmt , an end-if-stmt , a select-case-stmt , an end-select-stmt , a select-type-stmt , an end-select- 9 type-stmt , a do-stmt , an end-do-stmt , a forall-construct-stmt , a do-term-action-stmt, a do-term-shared-stmt, or 10 a where-construct-stmt . 11 8.2.1 GO TO statement 12 R845 goto-stmt is GO TO label 13 C827 (R845) The label shall be the statement label of a branch target statement that appears in the 14 same scoping unit as the goto-stmt . 15 Execution of a GO TO statement causes a transfer of control so that the branch target statement 16 identified by the label is executed next. 17 8.2.2 Computed GO TO statement 18 R846 computed-goto-stmt is GO TO ( label -list ) [ , ] scalar-int-expr 19 C828 (R846 Each label in label -list shall be the statement label of a branch target statement that appears in the same 20 scoping unit as the computed-goto-stmt . NOTE 8.20 The same statement label may appear more than once in a label list. 21 Execution of a computed GO TO statement causes evaluation of the scalar integer expression. If this value is i such that 22 1 i n where n is the number of labels in label -list, a transfer of control occurs so that the next statement executed is SEP 2002 COMMITTEE DRAFT 169 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 the one identified by the ith label in the list of labels. If i is less than 1 or greater than n, the execution sequence continues 2 as though a CONTINUE statement were executed. 3 8.2.3 Arithmetic IF statement 4 R847 arithmetic-if-stmt is IF ( scalar-numeric-expr ) label , label , label 5 C829 (R847) Each label shall be the label of a branch target statement that appears in the same scoping unit as the 6 arithmetic-if-stmt . 7 C830 (R847) The scalar-numeric-expr shall not be of type complex. NOTE 8.21 The same label may appear more than once in one arithmetic IF statement. 8 Execution of an arithmetic IF statement causes evaluation of the numeric expression followed by a transfer of control. The 9 branch target statement identified by the first label, the second label, or the third label is executed next depending on 10 whether the value of the numeric expression is less than zero, equal to zero, or greater than zero, respectively. 11 8.3 CONTINUE statement 12 Execution of a CONTINUE statement has no effect. 13 R848 continue-stmt is CONTINUE 14 8.4 STOP statement 15 R849 stop-stmt is STOP [ stop-code ] 16 R850 stop-code is scalar-char-constant 17 or digit [ digit [ digit [ digit [ digit ] ] ] ] 18 C831 (R850) scalar-char-constant shall be of type default character. 19 Execution of a STOP statement causes normal termination (2.3.4) of execution of the program. At the 20 time of termination, the stop code, if any, is available in a processor-dependent manner. Leading zero 21 digits in the stop code are not significant. If any exception (14) is signaling, the processor shall issue 22 a warning indicating which exceptions are signaling; this warning shall be on the unit identified by the 23 named constant ERROR UNIT from the ISO FORTRAN ENV intrinsic module (13.8.3.1.3). 170 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 Section 9: Input/output statements 2 Input statements provide the means of transferring data from external media to internal storage or 3 from an internal file to internal storage. This process is called reading. Output statements provide 4 the means of transferring data from internal storage to external media or from internal storage to an 5 internal file. This process is called writing. Some input/output statements specify that editing of the 6 data is to be performed. 7 In addition to the statements that transfer data, there are auxiliary input/output statements to ma- 8 nipulate the external medium, or to describe or inquire about the properties of the connection to the 9 external medium. 10 The input/output statements are the OPEN, CLOSE, READ, WRITE, PRINT, BACKSPACE, END- 11 FILE, REWIND, FLUSH, WAIT, and INQUIRE statements. 12 The READ statement is a data transfer input statement. The WRITE statement and the PRINT 13 statement are data transfer output statements. The OPEN statement and the CLOSE state- 14 ment are file connection statements. The INQUIRE statement is a file inquiry statement. The 15 BACKSPACE, ENDFILE, and REWIND statements are file positioning statements. 16 A file is composed of either a sequence of file storage units or a sequence of records, which provide an 17 extra level of organization to the file. A file composed of records is called a record file. A file composed 18 of file storage units is called a stream file. A processor may allow a file to be viewed both as a record 19 file and as a stream file; in this case the relationship between the file storage units when viewed as a 20 stream file and the records when viewed as a record file is processor dependent. 21 A file is either an external file or an internal file. 22 9.1 Records 23 A record is a sequence of values or a sequence of characters. For example, a line on a terminal is usually 24 considered to be a record. However, a record does not necessarily correspond to a physical entity. There 25 are three kinds of records: 26 (1) Formatted 27 (2) Unformatted 28 (3) Endfile NOTE 9.1 What is called a "record" in Fortran is commonly called a "logical record". There is no concept in Fortran of a "physical record." 29 9.1.1 Formatted record 30 A formatted record consists of a sequence of characters that are capable of representation in the 31 processor; however, a processor may prohibit some control characters (3.1) from appearing in a formatted 32 record. The length of a formatted record is measured in characters and depends primarily on the number 33 of characters put into the record when it is written. However, it may depend on the processor and the 34 external medium. The length may be zero. Formatted records may be read or written only by formatted 35 input/output statements. SEP 2002 COMMITTEE DRAFT 171 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 Formatted records may be prepared by means other than Fortran. 2 9.1.2 Unformatted record 3 An unformatted record consists of a sequence of values in a processor-dependent form and may contain 4 data of any type or may contain no data. The length of an unformatted record is measured in file storage 5 units (9.2.4) and depends on the output list (9.5.2) used when it is written, as well as on the processor 6 and the external medium. The length may be zero. Unformatted records may be read or written only 7 by unformatted input/output statements. 8 9.1.3 Endfile record 9 An endfile record is written explicitly by the ENDFILE statement; the file shall be connected for 10 sequential access. An endfile record is written implicitly to a file connected for sequential access when 11 the most recent data transfer statement referring to the file is a data transfer output statement, no 12 intervening file positioning statement referring to the file has been executed, and 13 (1) A REWIND or BACKSPACE statement references the unit to which the file is connected 14 or 15 (2) The unit is closed, either explicitly by a CLOSE statement, implicitly by a program termi- 16 nation not caused by an error condition, or implicitly by another OPEN statement for the 17 same unit. 18 An endfile record may occur only as the last record of a file. An endfile record does not have a length 19 property. NOTE 9.2 An endfile record does not necessarily have any physical embodiment. The processor may use a record count or other means to register the position of the file at the time an ENDFILE statement is executed, so that it can take appropriate action when that position is reached again during a read operation. The endfile record, however it is implemented, is considered to exist for the BACKSPACE statement (9.7.1). 20 9.2 External files 21 An external file is any file that exists in a medium external to the program. 22 At any given time, there is a processor-dependent set of allowed access methods, a processor-dependent 23 set of allowed forms, a processor-dependent set of allowed actions, and a processor-dependent set of 24 allowed record lengths for a file. NOTE 9.3 For example, the processor-dependent set of allowed actions for a printer would likely include the write action, but not the read action. 25 A file may have a name; a file that has a name is called a named file. The name of a named file is 26 represented by a character string value. The set of allowable names for a file is processor dependent. 27 An external file that is connected to a unit has a position property (9.2.3). NOTE 9.4 For more explanatory information on external files, see C.6.1. 172 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 9.2.1 File existence 2 At any given time, there is a processor-dependent set of external files that are said to exist for a program. 3 A file may be known to the processor, yet not exist for a program at a particular time. NOTE 9.5 Security reasons may prevent a file from existing for a program. A newly created file may exist but contain no records. 4 To create a file means to cause a file to exist that did not exist previously. To delete a file means to 5 terminate the existence of the file. 6 All input/output statements may refer to files that exist. An INQUIRE, OPEN, CLOSE, WRITE, 7 PRINT, REWIND, FLUSH, or ENDFILE statement also may refer to a file that does not exist. Execu- 8 tion of a WRITE, PRINT, or ENDFILE statement referring to a preconnected file that does not exist 9 creates the file. 10 9.2.2 File access 11 There are three methods of accessing the data of an external file: sequential, direct, and stream. Some 12 files may have more than one allowed access method; other files may be restricted to one access method. NOTE 9.6 For example, a processor may allow only sequential access to a file on magnetic tape. Thus, the set of allowed access methods depends on the file and the processor. 13 The method of accessing a file is determined when the file is connected to a unit (9.4.3) or when the file 14 is created if the file is preconnected (9.4.4). 15 9.2.2.1 Sequential access 16 Sequential access is a method of accessing the records of an external record file in order. 17 When connected for sequential access, an external file has the following properties: 18 (1) The order of the records is the order in which they were written if the direct access method 19 is not a member of the set of allowed access methods for the file. If the direct access method 20 is also a member of the set of allowed access methods for the file, the order of the records 21 is the same as that specified for direct access. In this case, the first record accessible by 22 sequential access is the record whose record number is 1 for direct access. The second record 23 accessible by sequential access is the record whose record number is 2 for direct access, etc. 24 A record that has not been written since the file was created shall not be read. 25 (2) The records of the file are either all formatted or all unformatted, except that the last record 26 of the file may be an endfile record. Unless the previous reference to the file was a data 27 transfer output statement or a file positioning statement, the last record, if any, of the file 28 shall be an endfile record. 29 (3) The records of the file shall be read or written only by sequential access input/output 30 statements. 31 9.2.2.2 Direct access 32 Direct access is a method of accessing the records of an external record file in arbitrary order. 33 When connected for direct access, an external file has the following properties: SEP 2002 COMMITTEE DRAFT 173 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 (1) Each record of the file is uniquely identified by a positive integer called the record number. 2 The record number of a record is specified when the record is written. Once established, 3 the record number of a record can never be changed. The order of the records is the order 4 of their record numbers. NOTE 9.7 A record may not be deleted; however, a record may be rewritten. 5 (2) The records of the file are either all formatted or all unformatted. If the sequential access 6 method is also a member of the set of allowed access methods for the file, its endfile record, 7 if any, is not considered to be part of the file while it is connected for direct access. If the 8 sequential access method is not a member of the set of allowed access methods for the file, 9 the file shall not contain an endfile record. 10 (3) The records of the file shall be read or written only by direct access input/output statements. 11 (4) All records of the file have the same length. 12 (5) Records need not be read or written in the order of their record numbers. Any record may 13 be written into the file while it is connected to a unit. For example, it is permissible to write 14 record 3, even though records 1 and 2 have not been written. Any record may be read from 15 the file while it is connected to a unit, provided that the record has been written since the 16 file was created, and if a READ statement for this connection is permitted. 17 (6) The records of the file shall not be read or written using list-directed formatting (10.9), 18 namelist formatting (10.10), or a nonadvancing input/output statement (9.2.3.1). 19 9.2.2.3 Stream access 20 Stream access is a method of accessing the file storage units (9.2.4) of an external stream file. 21 The properties of an external file connected for stream access depend on whether the connection is for 22 unformatted or formatted access. 23 When connected for unformatted stream access, an external file has the following properties: 24 (1) The file storage units of the file shall be read or written only by stream access input/output 25 statements. 26 (2) Each file storage unit in the file is uniquely identified by a positive integer called the position. 27 The first file storage unit in the file is at position 1. The position of each subsequent file 28 storage unit is one greater than that of its preceding file storage unit. 29 (3) If it is possible to position the file, the file storage units need not be read or written in 30 order of their position. For example, it might be permissible to write the file storage unit 31 at position 3, even though the file storage units at positions 1 and 2 have not been written. 32 Any file storage unit may be read from the file while it is connected to a unit, provided that 33 the file storage unit has been written since the file was created, and if a READ statement 34 for this connection is permitted. 35 When connected for formatted stream access, an external file has the following properties: 36 (1) Some file storage units of the file may contain record markers; this imposes a record structure 37 on the file in addition to its stream structure. There may or may not be a record marker 38 at the end of the file. If there is no record marker at the end of the file, the final record is 39 incomplete. 40 (2) No maximum length (9.4.5.11) is applicable to these records. 41 (3) Writing an empty record with no record marker has no effect. 174 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 9.8 Because the record structure is determined from the record markers that are stored in the file itself, an incomplete record at the end of the file is necessarily not empty. 1 (4) The file storage units of the file shall be read or written only by formatted stream access 2 input/output statements. 3 (5) Each file storage unit in the file is uniquely identified by a positive integer called the position. 4 The first file storage unit in the file is at position 1. The relationship between positions of 5 successive file storage units is processor dependent; not all positive integers need correspond 6 to valid positions. 7 (6) If it is possible to position the file, the file position can be set to a position that was 8 previously identified by the POS= specifier in an INQUIRE statement. NOTE 9.9 There may be some character positions in the file that do not correspond to characters written; this is because on some processors a record marker may be written to the file as a carriage-return/line- feed or other sequence. The means of determining the position in a file connected for stream access is via the POS= specifier in an INQUIRE statement (9.9.1.20). 9 9.2.3 File position 10 Execution of certain input/output statements affects the position of an external file. Certain circum- 11 stances can cause the position of a file to become indeterminate. 12 The initial point of a file is the position just before the first record or file storage unit. The terminal 13 point is the position just after the last record or file storage unit. If there are no records or file storage 14 units in the file, the initial point and the terminal point are the same position. 15 If a record file is positioned within a record, that record is the current record; otherwise, there is no 16 current record. 17 Let n be the number of records in the file. If 1 < i n and a file is positioned within the ith record or 18 between the (i - 1)th record and the ith record, the (i - 1)th record is the preceding record. If n 1 19 and the file is positioned at its terminal point, the preceding record is the nth and last record. If n = 0 20 or if a file is positioned at its initial point or within the first record, there is no preceding record. 21 If 1 i < n and a file is positioned within the ith record or between the ith and (i + 1)th record, the 22 (i + 1)th record is the next record. If n 1 and the file is positioned at its initial point, the first record 23 is the next record. If n = 0 or if a file is positioned at its terminal point or within the nth (last) record, 24 there is no next record. 25 For a file connected for stream access, the file position is either between two file storage units, at the 26 initial point of the file, at the terminal point of the file, or undefined. 27 9.2.3.1 Advancing and nonadvancing input/output 28 An advancing input/output statement always positions a record file after the last record read or 29 written, unless there is an error condition. 30 A nonadvancing input/output statement may position a record file at a character position within 31 the current record, or a subsequent record (10.7.2). Using nonadvancing input/output, it is possible to 32 read or write a record of the file by a sequence of input/output statements, each accessing a portion 33 of the record. It is also possible to read variable-length records and be notified of their lengths. If a 34 nonadvancing output statement leaves a file positioned within a current record and no further output 35 statement is executed for the file before it is closed or a BACKSPACE, ENDFILE, or REWIND statement SEP 2002 COMMITTEE DRAFT 175 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 is executed for it, the effect is as if the output statement were the corresponding advancing output 2 statement. 3 9.2.3.2 File position prior to data transfer 4 The positioning of the file prior to data transfer depends on the method of access: sequential, direct, or 5 stream. 6 For sequential access on input, if there is a current record, the file position is not changed. Otherwise, 7 the file is positioned at the beginning of the next record and this record becomes the current record. 8 Input shall not occur if there is no next record or if there is a current record and the last data transfer 9 statement accessing the file performed output. 10 If the file contains an endfile record, the file shall not be positioned after the endfile record prior to data 11 transfer. However, a REWIND or BACKSPACE statement may be used to reposition the file. 12 For sequential access on output, if there is a current record, the file position is not changed and the 13 current record becomes the last record of the file. Otherwise, a new record is created as the next record 14 of the file; this new record becomes the last and current record of the file and the file is positioned at 15 the beginning of this record. 16 For direct access, the file is positioned at the beginning of the record specified by the REC= specifier. 17 This record becomes the current record. 18 For stream access, the file is positioned immediately before the file storage unit specified by the POS= 19 specifier; if there is no POS= specifier, the file position is not changed. 20 File positioning for child data transfer statements is described in 9.5.3.7. 21 9.2.3.3 File position after data transfer 22 If an error condition (9.10) occurred, the position of the file is indeterminate. If no error condition 23 occurred, but an end-of-file condition (9.10) occurred as a result of reading an endfile record, the file is 24 positioned after the endfile record. 25 For unformatted stream access, if no error condition occurred, the file position is not changed. For 26 unformatted stream output, if the file position exceeds the previous terminal point of the file, the 27 terminal point is set to the file position. NOTE 9.10 An unformatted stream output statement with a POS= specifier and an empty output list can have the effect of extending the terminal point of a file without actually writing any data. 28 For a formatted stream output statement, if no error condition occurred, the terminal point of the file 29 is set to the highest-numbered position to which data was transferred by the statement. NOTE 9.11 The highest-numbered position might not be the current one if the output involved T or TL edit descriptors (10.7.1.1). 30 For formatted stream input, if an end-of-file condition occurred, the file position is not changed. 31 For nonadvancing input, if no error condition or end-of-file condition occurred, but an end-of-record 32 condition (9.10) occurred, the file is positioned after the record just read. If no error condition, end-of- 33 file condition, or end-of-record condition occurred in a nonadvancing input statement, the file position 176 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 is not changed. If no error condition occurred in a nonadvancing output statement, the file position is 2 not changed. 3 In all other cases, the file is positioned after the record just read or written and that record becomes the 4 preceding record. 5 9.2.4 File storage units 6 A file storage unit is the basic unit of storage in a stream file or an unformatted record file. It is the 7 unit of file position for stream access, the unit of record length for unformatted files, and the unit of file 8 size for all external files. 9 Every value in a stream file or an unformatted record file shall occupy an integer number of file storage 10 units; if the stream or record file is unformatted, this number shall be the same for all scalar values of 11 the same type and type parameters. The number of file storage units required for an item of a given type 12 and type parameters may be determined using the IOLENGTH= specifier of the INQUIRE statement 13 (9.9.3). 14 For a file connected for unformatted stream access, the processor shall not have alignment restrictions 15 that prevent a value of any type from being stored at any positive integer file position. 16 It is recommended that the file storage unit be an 8-bit octet where this choice is practical. NOTE 9.12 The requirement that every data value occupy an integer number of file storage units implies that data items inherently smaller than a file storage unit will require padding. This suggests that the file storage unit be small to avoid wasted space. Ideally, the file storage unit would be chosen such that padding is never required. A file storage unit of one bit would always meet this goal, but would likely be impractical because of the alignment requirements. The prohibition on alignment restrictions prohibits the processor from requiring data alignments larger than the file storage unit. The 8-bit octet is recommended as a good compromise that is small enough to accommodate the requirements of many applications, yet not so small that the data alignment requirements are likely to cause significant performance problems. 17 9.3 Internal files 18 Internal files provide a means of transferring and converting data from internal storage to internal 19 storage. 20 An internal file is a record file with the following properties: 21 (1) The file is a variable of default character type that is not an array section with a vector 22 subscript. 23 (2) A record of an internal file is a scalar character variable. 24 (3) If the file is a scalar character variable, it consists of a single record whose length is the same 25 as the length of the scalar character variable. If the file is a character array, it is treated 26 as a sequence of character array elements. Each array element, if any, is a record of the 27 file. The ordering of the records of the file is the same as the ordering of the array elements 28 in the array (6.2.2.2) or the array section (6.2.2.3). Every record of the file has the same 29 length, which is the length of an array element in the array. 30 (4) A record of the internal file becomes defined by writing the record. If the number of 31 characters written in a record is less than the length of the record, the remaining portion SEP 2002 COMMITTEE DRAFT 177 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 of the record is filled with blanks. The number of characters to be written shall not exceed 2 the length of the record. 3 (5) A record may be read only if the record is defined. 4 (6) A record of an internal file may become defined (or undefined) by means other than an 5 output statement. For example, the character variable may become defined by a character 6 assignment statement. 7 (7) An internal file is always positioned at the beginning of the first record prior to data transfer, 8 except for child data transfer statements (9.5.3.7). This record becomes the current record. 9 (8) The initial value of a connection mode (9.4.1) is the value that would be implied by an 10 initial OPEN statement without the corresponding keyword. 11 (9) Reading and writing records shall be accomplished only by sequential access formatted 12 input/output statements. 13 (10) An internal file shall not be specified as the unit in a file connection statement, a file 14 positioning statement, or a file inquiry statement. 15 9.4 File connection 16 A unit, specified by an io-unit , provides a means for referring to a file. 17 R901 io-unit is file-unit-number 18 or * 19 or internal-file-variable 20 R902 file-unit-number is scalar-int-expr 21 R903 internal-file-variable is default-char-variable 22 C901 (R903) The default-char-variable shall not be an array section with a vector subscript. 23 A unit is either an external unit or an internal unit. An external unit is used to refer to an external 24 file and is specified by an asterisk or a file-unit-number whose value is nonnegative or equal to one of 25 the named constants INPUT UNIT, OUTPUT UNIT, or ERROR UNIT of the ISO FORTRAN ENV 26 module (13.8.3). An internal unit is used to refer to an internal file and is specified by an internal- 27 file-variable or a file-unit-number whose value is equal to the unit argument of an active derived-type 28 input/output procedure (9.5.3.7). The value of a file-unit-number shall identify a valid unit. 29 The external unit identified by a particular value of a scalar-int-expr is the same external unit in all 30 program units of the program. NOTE 9.13 In the example: SUBROUTINE A READ (6) X ... SUBROUTINE B N = 6 REWIND N the value 6 used in both program units identifies the same external unit. 31 An asterisk identifies particular processor-dependent external units that are preconnected for format- 32 ted sequential access (9.5.3.2). These units are also identified by unit numbers defined by the named 33 constants INPUT UNIT and OUTPUT UNIT of the ISO FORTRAN ENV module (13.8.3). 178 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 This standard identifies a processor-dependent external unit for the purpose of error reporting. This 2 unit shall be preconnected for sequential formatted output. The processor may define this to be the 3 same as the output unit identified by an asterisk. This unit is also identified by a unit number defined 4 by the named constant ERROR UNIT of the ISO FORTRAN ENV intrinsic module. 5 9.4.1 Connection modes 6 A connection for formatted input/output has several changeable modes: the blank interpretation mode 7 (10.7.6), delimiter mode (10.9.2, 10.10.2.1), sign mode (10.7.4), decimal edit mode (10.7.8), I/O round- 8 ing mode (10.6.1.2.6), pad mode (9.5.3.4.2), and scale factor (10.7.5). A connection for unformatted 9 input/output has no changeable modes. 10 Values for the modes of a connection are established when the connection is initiated. If the connection 11 is initiated by an OPEN statement, the values are as specified, either explicitly or implicitly, by the 12 OPEN statement. If the connection is initiated other than by an OPEN statement (that is, if the file is 13 an internal file or preconnected file) the values established are those that would be implied by an initial 14 OPEN statement without the corresponding keywords. 15 The scale factor cannot be explicitly specified in an OPEN statement; it is implicitly 0. 16 The modes of a connection to an external file may be changed by a subsequent OPEN statement that 17 modifies the connection. 18 The modes of a connection may be temporarily changed by a corresponding keyword specifier in a 19 data transfer statement or by an edit descriptor. Keyword specifiers take effect at the beginning of 20 execution of the data transfer statement. Edit descriptors take effect when they are encountered in 21 format processing. When a data transfer statement terminates, the values for the modes are reset to the 22 values in effect immediately before the data transfer statement was executed. 23 9.4.2 Unit existence 24 At any given time, there is a processor-dependent set of external units that are said to exist for a 25 program. 26 All input/output statements may refer to units that exist. The CLOSE, INQUIRE, and WAIT state- 27 ments also may refer to units that do not exist. 28 9.4.3 Connection of a file to a unit 29 An external unit has a property of being connected or not connected. If connected, it refers to an 30 external file. An external unit may become connected by preconnection or by the execution of an OPEN 31 statement. The property of connection is symmetric; the unit is connected to a file if and only if the file 32 is connected to the unit. 33 Every input/output statement except an OPEN, CLOSE, INQUIRE, or WAIT statement shall refer to 34 a unit that is connected to a file and thereby make use of or affect that file. 35 A file may be connected and not exist (9.2.1). NOTE 9.14 An example is a preconnected external file that has not yet been written. 36 A unit shall not be connected to more than one file at the same time, and a file shall not be connected to 37 more than one unit at the same time. However, means are provided to change the status of an external 38 unit and to connect a unit to a different file. SEP 2002 COMMITTEE DRAFT 179 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 This standard defines means of portable interoperation with C. C streams are described in 7.19.2 of the C 2 standard. Whether a unit may be connected to a file which is also connected to a C stream is processor 3 dependent. It is processor dependent whether the files connected to the units INPUT UNIT, OUT- 4 PUT UNIT, and ERROR UNIT correspond to the predefined C text streams standard input, standard 5 output, and standard error. 6 After an external unit has been disconnected by the execution of a CLOSE statement, it may be con- 7 nected again within the same program to the same file or to a different file. After an external file has 8 been disconnected by the execution of a CLOSE statement, it may be connected again within the same 9 program to the same unit or to a different unit. NOTE 9.15 The only means of referencing a file that has been disconnected is by the appearance of its name in an OPEN or INQUIRE statement. There may be no means of reconnecting an unnamed file once it is disconnected. 10 An internal unit is always connected to the internal file designated by the variable that identifies the 11 unit. NOTE 9.16 For more explanatory information on file connection properties, see C.6.5. 12 9.4.4 Preconnection 13 Preconnection means that the unit is connected to a file at the beginning of execution of the program 14 and therefore it may be specified in input/output statements without the prior execution of an OPEN 15 statement. 16 9.4.5 The OPEN statement 17 An OPEN statement initiates or modifies the connection between an external file and a specified unit. 18 The OPEN statement may be used to connect an existing file to a unit, create a file that is preconnected, 19 create a file and connect it to a unit, or change certain modes of a connection between a file and a unit. 20 An external unit may be connected by an OPEN statement in any program unit of a program and, once 21 connected, a reference to it may appear in any program unit of the program. 22 If a unit is connected to a file that exists, execution of an OPEN statement for that unit is permitted. 23 If the FILE= specifier is not included in such an OPEN statement, the file to be connected to the unit 24 is the same as the file to which the unit is already connected. 25 If the file to be connected to the unit does not exist but is the same as the file to which the unit is 26 preconnected, the modes specified by an OPEN statement become a part of the connection. 27 If the file to be connected to the unit is not the same as the file to which the unit is connected, the effect 28 is as if a CLOSE statement without a STATUS= specifier had been executed for the unit immediately 29 prior to the execution of an OPEN statement. 30 If the file to be connected to the unit is the same as the file to which the unit is connected, only the 31 specifiers for changeable modes (9.4.1) may have values different from those currently in effect. If the 32 POSITION= specifier appears in such an OPEN statement, the value specified shall not disagree with 33 the current position of the file. If the STATUS= specifier is included in such an OPEN statement, it shall 34 be specified with the value OLD. Execution of such an OPEN statement causes any new values of the 35 specifiers for changeable modes to be in effect, but does not cause any change in any of the unspecified 36 specifiers and the position of the file is unaffected. The ERR=, IOSTAT=, and IOMSG= specifiers from 180 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 any previously executed OPEN statement have no effect on any currently executed OPEN statement. 2 A STATUS= specifier with a value of OLD is always allowed when the file to be connected to the unit is 3 the same as the file to which the unit is connected. In this case, if the status of the file was SCRATCH 4 before execution of the OPEN statement, the file will still be deleted when the unit is closed, and the 5 file is still considered to have a status of SCRATCH. 6 If a file is already connected to a unit, execution of an OPEN statement on that file and a different unit 7 is not permitted. 8 R904 open-stmt is OPEN ( connect-spec-list ) 9 R905 connect-spec is [ UNIT = ] file-unit-number 10 or ACCESS = scalar-default-char-expr 11 or ACTION = scalar-default-char-expr 12 or ASYNCHRONOUS = scalar-default-char-expr 13 or BLANK = scalar-default-char-expr 14 or DECIMAL = scalar-default-char-expr 15 or DELIM = scalar-default-char-expr 16 or ERR = label 17 or FILE = file-name-expr 18 or FORM = scalar-default-char-expr 19 or IOMSG = iomsg-variable 20 or IOSTAT = scalar-int-variable 21 or PAD = scalar-default-char-expr 22 or POSITION = scalar-default-char-expr 23 or RECL = scalar-int-expr 24 or ROUND = scalar-default-char-expr 25 or SIGN = scalar-default-char-expr 26 or STATUS = scalar-default-char-expr 27 R906 file-name-expr is scalar-default-char-expr 28 R907 iomsg-variable is scalar-default-char-variable 29 C902 (R905) No specifier shall appear more than once in a given connect-spec-list. 30 C903 (R905) A file-unit-number shall be specified; if the optional characters UNIT= are omitted, the 31 file-unit-number shall be the first item in the connect-spec-list. 32 C904 (R905) The label used in the ERR= specifier shall be the statement label of a branch target 33 statement that appears in the same scoping unit as the OPEN statement. 34 If the STATUS= specifier has the value NEW or REPLACE, the FILE= specifier shall appear. If the 35 STATUS= specifier has the value SCRATCH, the FILE= specifier shall not appear. If the STATUS= 36 specifier has the value OLD, the FILE= specifier shall appear unless the unit is connected and the file 37 connected to the unit exists. 38 A specifier that requires a scalar-default-char-expr may have a limited list of character values. These 39 values are listed for each such specifier. Any trailing blanks are ignored. The value specified is without 40 regard to case. Some specifiers have a default value if the specifier is omitted. 41 The IOSTAT=, ERR=, and IOMSG= specifiers are described in 9.10. NOTE 9.17 An example of an OPEN statement is: OPEN (10, FILE = 'employee.names', ACTION = 'READ', PAD = 'YES') SEP 2002 COMMITTEE DRAFT 181 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 9.18 For more explanatory information on the OPEN statement, see C.6.4. 1 9.4.5.1 ACCESS= specifier in the OPEN statement 2 The scalar-default-char-expr shall evaluate to SEQUENTIAL, DIRECT, or STREAM. The ACCESS= 3 specifier specifies the access method for the connection of the file as being sequential, direct, or stream. 4 If this specifier is omitted, the default value is SEQUENTIAL. For an existing file, the specified access 5 method shall be included in the set of allowed access methods for the file. For a new file, the processor 6 creates the file with a set of allowed access methods that includes the specified method. 7 9.4.5.2 ACTION= specifier in the OPEN statement 8 The scalar-default-char-expr shall evaluate to READ, WRITE, or READWRITE. READ specifies that 9 the WRITE, PRINT, and ENDFILE statements shall not refer to this connection. WRITE specifies 10 that READ statements shall not refer to this connection. READWRITE permits any input/output 11 statements to refer to this connection. If this specifier is omitted, the default value is processor dependent. 12 If READWRITE is included in the set of allowable actions for a file, both READ and WRITE also shall 13 be included in the set of allowed actions for that file. For an existing file, the specified action shall be 14 included in the set of allowed actions for the file. For a new file, the processor creates the file with a set 15 of allowed actions that includes the specified action. 16 9.4.5.3 ASYNCHRONOUS= specifier in the OPEN statement 17 The scalar-default-char-expr shall evaluate to YES or NO. If YES is specified, asynchronous input/output 18 on the unit is allowed. If NO is specified, asynchronous input/output on the unit is not allowed. If this 19 specifier is omitted, the default value is NO. 20 9.4.5.4 BLANK= specifier in the OPEN statement 21 The scalar-default-char-expr shall evaluate to NULL or ZERO. The BLANK= specifier is permitted only 22 for a connection for formatted input/output. It specifies the current value of the blank interpretation 23 mode (10.7.6, 9.5.1.5) for input for this connection. This mode has no effect on output. It is a changeable 24 mode (9.4.1). If this specifier is omitted in an OPEN statement that initiates a connection, the default 25 value is NULL. 26 9.4.5.5 DECIMAL= specifier in the OPEN statement 27 The scalar-default-char-expr shall evaluate to COMMA or POINT. The DECIMAL= specifier is per- 28 mitted only for a connection for formatted input/output. It specifies the current value of the decimal 29 edit mode (10.7.8, 9.5.1.6) for this connection. This is a changeable mode (9.4.1). If this specifier is 30 omitted in an OPEN statement that initiates a connection, the default value is POINT. 31 9.4.5.6 DELIM= specifier in the OPEN statement 32 The scalar-default-char-expr shall evaluate to APOSTROPHE, QUOTE, or NONE. The DELIM= spec- 33 ifier is permitted only for a connection for formatted input/output. It specifies the current value of the 34 delimiter mode (9.5.1.7) for list-directed (10.9.2) and namelist (10.10.2.1) output for the connection. 35 This mode has no effect on input. It is a changeable mode (9.4.1). If this specifier is omitted in an 36 OPEN statement that initiates a connection, the default value is NONE. 37 9.4.5.7 FILE= specifier in the OPEN statement 38 The value of the FILE= specifier is the name of the file to be connected to the specified unit. Any trailing 39 blanks are ignored. The file-name-expr shall be a name that is allowed by the processor. If this specifier 182 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 is omitted and the unit is not connected to a file, the STATUS= specifier shall be specified with a value 2 of SCRATCH; in this case, the connection is made to a processor-dependent file. The interpretation of 3 case is processor dependent. 4 9.4.5.8 FORM= specifier in the OPEN statement 5 The scalar-default-char-expr shall evaluate to FORMATTED or UNFORMATTED. The FORM= spec- 6 ifier determines whether the file is being connected for formatted or unformatted input/output. If this 7 specifier is omitted, the default value is UNFORMATTED if the file is being connected for direct access 8 or stream access, and the default value is FORMATTED if the file is being connected for sequential 9 access. For an existing file, the specified form shall be included in the set of allowed forms for the file. 10 For a new file, the processor creates the file with a set of allowed forms that includes the specified form. 11 9.4.5.9 PAD= specifier in the OPEN statement 12 The scalar-default-char-expr shall evaluate to YES or NO. The PAD= specifier is permitted only for a 13 connection for formatted input/output. It specifies the current value of the pad mode (9.5.3.4.2, 9.5.1.9) 14 for input for this connection. This mode has no effect on output. It is a changeable mode (9.4.1). If this 15 specifier is omitted in an OPEN statement that initiates a connection, the default value is YES. NOTE 9.19 For nondefault character types, the blank padding character is processor dependent. 16 9.4.5.10 POSITION= specifier in the OPEN statement 17 The scalar-default-char-expr shall evaluate to ASIS, REWIND, or APPEND. The connection shall be 18 for sequential or stream access. A new file is positioned at its initial point. REWIND positions an 19 existing file at its initial point. APPEND positions an existing file such that the endfile record is the 20 next record, if it has one. If an existing file does not have an endfile record, APPEND positions the 21 file at its terminal point. ASIS leaves the position unchanged if the file exists and already is connected. 22 ASIS leaves the position unspecified if the file exists but is not connected. If this specifier is omitted, 23 the default value is ASIS. 24 9.4.5.11 RECL= specifier in the OPEN statement 25 The value of the RECL= specifier shall be positive. It specifies the length of each record in a file being 26 connected for direct access, or specifies the maximum length of a record in a file being connected for 27 sequential access. This specifier shall not appear when a file is being connected for stream access. This 28 specifier shall appear when a file is being connected for direct access. If this specifier is omitted when 29 a file is being connected for sequential access, the default value is processor dependent. If the file is 30 being connected for formatted input/output, the length is the number of characters for all records that 31 contain only characters of type default character. When a record contains any nondefault characters, 32 the appropriate value for the RECL= specifier is processor dependent. If the file is being connected for 33 unformatted input/output, the length is measured in file storage units. For an existing file, the value of 34 the RECL= specifier shall be included in the set of allowed record lengths for the file. For a new file, 35 the processor creates the file with a set of allowed record lengths that includes the specified value. 36 9.4.5.12 ROUND= specifier in the OPEN statement 37 The scalar-default-char-expr shall evaluate to one of UP, DOWN, ZERO, NEAREST, COMPATIBLE, 38 or PROCESSOR DEFINED. The ROUND= specifier is permitted only for a connection for formatted 39 input/output. It specifies the current value of the I/O rounding mode (10.6.1.2.6, 9.5.1.12) for this 40 connection. This is a changeable mode (9.4.1). If this specifier is omitted in an OPEN statement that 41 initiates a connection, the I/O rounding mode is processor dependent; it shall be one of the above modes. SEP 2002 COMMITTEE DRAFT 183 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 9.20 A processor is free to select any I/O rounding mode for the default mode. The mode might correspond to UP, DOWN, ZERO, NEAREST, or COMPATIBLE; or it might be a completely different I/O rounding mode. 1 9.4.5.13 SIGN= specifier in the OPEN statement 2 The scalar-default-char-expr shall evaluate to one of PLUS, SUPPRESS, or PROCESSOR DEFINED. 3 The SIGN= specifier is permitted only for a connection for formatted input/output. It specifies the 4 current value of the sign mode (10.7.4, 9.5.1.13) for this connection. This is a changeable mode (9.4.1). 5 If this specifier is omitted in an OPEN statement that initiates a connection, the default value is PRO- 6 CESSOR DEFINED. 7 9.4.5.14 STATUS= specifier in the OPEN statement 8 The scalar-default-char-expr shall evaluate to OLD, NEW, SCRATCH, REPLACE, or UNKNOWN. If 9 OLD is specified, the file shall exist. If NEW is specified, the file shall not exist. 10 Successful execution of an OPEN statement with NEW specified creates the file and changes the status 11 to OLD. If REPLACE is specified and the file does not already exist, the file is created and the status is 12 changed to OLD. If REPLACE is specified and the file does exist, the file is deleted, a new file is created 13 with the same name, and the status is changed to OLD. If SCRATCH is specified, the file is created 14 and connected to the specified unit for use by the program but is deleted at the execution of a CLOSE 15 statement referring to the same unit or at the normal termination of the program. NOTE 9.21 SCRATCH shall not be specified with a named file. 16 If UNKNOWN is specified, the status is processor dependent. If this specifier is omitted, the default 17 value is UNKNOWN. 18 9.4.6 The CLOSE statement 19 The CLOSE statement is used to terminate the connection of a specified unit to an external file. 20 Execution of a CLOSE statement for a unit may occur in any program unit of a program and need not 21 occur in the same program unit as the execution of an OPEN statement referring to that unit. 22 Execution of a CLOSE statement performs a wait operation for any pending asynchronous data transfer 23 operations for the specified unit. 24 Execution of a CLOSE statement specifying a unit that does not exist or has no file connected to it is 25 permitted and affects no file. 26 After a unit has been disconnected by execution of a CLOSE statement, it may be connected again 27 within the same program, either to the same file or to a different file. After a named file has been 28 disconnected by execution of a CLOSE statement, it may be connected again within the same program, 29 either to the same unit or to a different unit, provided that the file still exists. 30 At normal termination of execution of a program, all units that are connected are closed. Each unit 31 is closed with status KEEP unless the file status prior to termination of execution was SCRATCH, in 32 which case the unit is closed with status DELETE. 184 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 9.22 The effect is as though a CLOSE statement without a STATUS= specifier were executed on each connected unit. 1 R908 close-stmt is CLOSE ( close-spec-list ) 2 R909 close-spec is [ UNIT = ] file-unit-number 3 or IOSTAT = scalar-int-variable 4 or IOMSG = iomsg-variable 5 or ERR = label 6 or STATUS = scalar-default-char-expr 7 C905 (R909) No specifier shall appear more than once in a given close-spec-list. 8 C906 (R909) A file-unit-number shall be specified; if the optional characters UNIT= are omitted, the 9 file-unit-number shall be the first item in the close-spec-list. 10 C907 (R909) The label used in the ERR= specifier shall be the statement label of a branch target 11 statement that appears in the same scoping unit as the CLOSE statement. 12 The scalar-default-char-expr has a limited list of character values. Any trailing blanks are ignored. The 13 value specified is without regard to case. 14 The IOSTAT=, ERR=, and IOMSG= specifiers are described in 9.10. NOTE 9.23 An example of a CLOSE statement is: CLOSE (10, STATUS = 'KEEP') NOTE 9.24 For more explanatory information on the CLOSE statement, see C.6.6. 15 9.4.6.1 STATUS= specifier in the CLOSE statement 16 The scalar-default-char-expr shall evaluate to KEEP or DELETE. The STATUS= specifier determines 17 the disposition of the file that is connected to the specified unit. KEEP shall not be specified for a file 18 whose status prior to execution of a CLOSE statement is SCRATCH. If KEEP is specified for a file that 19 exists, the file continues to exist after the execution of a CLOSE statement. If KEEP is specified for a 20 file that does not exist, the file will not exist after the execution of a CLOSE statement. If DELETE is 21 specified, the file will not exist after the execution of a CLOSE statement. If this specifier is omitted, the 22 default value is KEEP, unless the file status prior to execution of the CLOSE statement is SCRATCH, 23 in which case the default value is DELETE. 24 9.5 Data transfer statements 25 The READ statement is the data transfer input statement. The WRITE statement and the 26 PRINT statement are the data transfer output statements. 27 R910 read-stmt is READ ( io-control-spec-list ) [ input-item-list ] 28 or READ format [ , input-item-list ] 29 R911 write-stmt is WRITE ( io-control-spec-list ) [ output-item-list ] 30 R912 print-stmt is PRINT format [ , output-item-list ] SEP 2002 COMMITTEE DRAFT 185 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 9.25 Examples of data transfer statements are: READ (6, *) SIZE READ 10, A, B WRITE (6, 10) A, S, J PRINT 10, A, S, J 10 FORMAT (2E16.3, I5) 1 9.5.1 Control information list 2 A control information list is an io-control-spec-list. It governs data transfer. 3 R913 io-control-spec is [ UNIT = ] io-unit 4 or [ FMT = ] format 5 or [ NML = ] namelist-group-name 6 or ADVANCE = scalar-default-char-expr 7 or ASYNCHRONOUS = scalar-char-initialization-expr 8 or BLANK = scalar-default-char-expr 9 or DECIMAL = scalar-default-char-expr 10 or DELIM = scalar-default-char-expr 11 or END = label 12 or EOR = label 13 or ERR = label 14 or ID = scalar-int-variable 15 or IOMSG = iomsg-variable 16 or IOSTAT = scalar-int-variable 17 or PAD = scalar-default-char-expr 18 or POS = scalar-int-expr 19 or REC = scalar-int-expr 20 or ROUND = scalar-default-char-expr 21 or SIGN = scalar-default-char-expr 22 or SIZE = scalar-int-variable 23 C908 (R913) No specifier shall appear more than once in a given io-control-spec-list. 24 C909 (R913) An io-unit shall be specified; if the optional characters UNIT= are omitted, the io-unit 25 shall be the first item in the io-control-spec-list. 26 C910 (R913) A DELIM= or SIGN= specifier shall not appear in a read-stmt . 27 C911 (R913) A BLANK=, PAD=, END=, EOR=, or SIZE= specifier shall not appear in a write-stmt . 28 C912 (R913) The label in the ERR=, EOR=, or END= specifier shall be the statement label of a 29 branch target statement that appears in the same scoping unit as the data transfer statement. 30 C913 (R913) A namelist-group-name shall be the name of a namelist group. 31 C914 (R913) A namelist-group-name shall not appear if an input-item-list or an output-item-list 32 appears in the data transfer statement. 33 C915 (R913) An io-control-spec-list shall not contain both a format and a namelist-group-name. 34 C916 (R913) If format appears without a preceding FMT=, it shall be the second item in the io- 35 control-spec-list and the first item shall be io-unit . 186 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 C917 (R913) If namelist-group-name appears without a preceding NML=, it shall be the second item 2 in the io-control-spec-list and the first item shall be io-unit . 3 C918 (R913) If io-unit is not a file-unit-number , the io-control-spec-list shall not contain a REC= 4 specifier or a POS= specifier. 5 C919 (R913) If the REC= specifier appears, an END= specifier shall not appear, a namelist-group- 6 name shall not appear, and the format , if any, shall not be an asterisk. 7 C920 (R913) An ADVANCE= specifier may appear only in a formatted sequential or stream in- 8 put/output statement with explicit format specification (10.1) whose control information list 9 does not contain an internal-file-variable as the io-unit . 10 C921 (R913) If an EOR= specifier appears, an ADVANCE= specifier also shall appear. 11 C922 (R913) If a SIZE= specifier appears, an ADVANCE= specifier also shall appear. 12 C923 (R913) The scalar-char-initialization-expr in an ASYNCHRONOUS= specifier shall be of type 13 default character and shall have the value YES or NO. 14 C924 (R913) An ASYNCHRONOUS= specifier with a value YES shall not appear unless io-unit is a 15 file-unit-number . 16 C925 (R913) If an ID= specifier appears, an ASYNCHRONOUS= specifier with the value YES shall 17 also appear. 18 C926 (R913) If a POS= specifier appears, the io-control-spec-list shall not contain a REC= specifier. 19 C927 (R913) If a DECIMAL=, BLANK=, PAD=, SIGN=, or ROUND= specifier appears, a format 20 or namelist-group-name shall also appear. 21 C928 (R913) If a DELIM= specifier appears, either format shall be an asterisk or namelist-group-name 22 shall appear. 23 A SIZE= specifier may appear only in an input statement that contains an ADVANCE= specifier with 24 the value NO. 25 An EOR= specifier may appear only in an input statement that contains an ADVANCE= specifier with 26 the value NO. 27 If the data transfer statement contains a format or namelist-group-name, the statement is a formatted 28 input/output statement; otherwise, it is an unformatted input/output statement. 29 The ADVANCE=, ASYNCHRONOUS=, DECIMAL=, BLANK=, DELIM=, PAD=, SIGN=, and 30 ROUND= specifiers have a limited list of character values. Any trailing blanks are ignored. The 31 values specified are without regard to case. 32 The IOSTAT=, ERR=, EOR=, END=, and IOMSG= specifiers are described in 9.10. NOTE 9.26 An example of a READ statement is: READ (IOSTAT = IOS, UNIT = 6, FMT = '(10F8.2)') A, B SEP 2002 COMMITTEE DRAFT 187 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 9.5.1.1 FMT= specifier in a data transfer statement 2 The FMT= specifier supplies a format specification or specifies list-directed formatting for a formatted 3 input/output statement. 4 R914 format is default-char-expr 5 or label 6 or * 7 C929 (R914) The label shall be the label of a FORMAT statement that appears in the same scoping 8 unit as the statement containing the FMT= specifier. 9 The default-char-expr shall evaluate to a valid format specification (10.1.1 and 10.1.2). NOTE 9.27 A default-char-expr includes a character constant. 10 If default-char-expr is an array, it is treated as if all of the elements of the array were specified in array 11 element order and were concatenated. 12 If format is *, the statement is a list-directed input/output statement. NOTE 9.28 An example in which the format is a character expression is: READ (6, FMT = "(" // CHAR_FMT // ")" ) X, Y, Z where CHAR FMT is a default character variable. 13 9.5.1.2 NML= specifier in a data transfer statement 14 The NML= specifier supplies the namelist-group-name (5.4). This name identifies a particular collection 15 of data objects on which transfer is to be performed. 16 If a namelist-group-name appears, the statement is a namelist input/output statement. 17 9.5.1.3 ADVANCE= specifier in a data transfer statement 18 The scalar-default-char-expr shall evaluate to YES or NO. The ADVANCE= specifier determines wheth- 19 er advancing input/output occurs for this input/output statement. If YES is specified, advancing in- 20 put/output occurs. If NO is specified, nonadvancing input/output occurs (9.2.3.1). If this specifier is 21 omitted from an input/output statement that allows the specifier, the default value is YES. 22 9.5.1.4 ASYNCHRONOUS= specifier in a data transfer statement 23 The ASYNCHRONOUS= specifier determines whether this input/output statement is synchronous or 24 asynchronous. If YES is specified, the statement and the input/output operation are said to be asyn- 25 chronous. If NO is specified or if the specifier is omitted, the statement and the input/output operation 26 are said to be synchronous. 27 Asynchronous input/output is permitted only for external files opened with an ASYNCHRONOUS= 28 specifier with the value YES in the OPEN statement. 188 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 9.29 Both synchronous and asynchronous input/output are allowed for files opened with an ASYN- CHRONOUS= specifier of YES. For other files, only synchronous input/output is allowed; this includes files opened with an ASYNCHRONOUS= specifier of NO, files opened without an ASYN- CHRONOUS= specifier, preconnected files accessed without an OPEN statement, and internal files. The ASYNCHRONOUS= specifier value in a data transfer statement is an initialization expression because it effects compiler optimizations and, therefore, needs to be known at compile time. 1 The processor may perform an asynchronous data transfer operation asynchronously, but it is not re- 2 quired to do so. Records and file storage units read or written by asynchronous data transfer statements 3 are read, written, and processed in the same order as they would have been if the data transfer statements 4 were synchronous. 5 If a variable is used in an asynchronous data transfer statement as 6 (1) an item in an input/output list, 7 (2) a group object in a namelist, or 8 (3) a SIZE= specifier 9 the base object of the data-ref is implicitly given the ASYNCHRONOUS attribute in the scoping unit 10 of the data transfer statement. This attribute may be confirmed by explicit declaration. 11 When an asynchronous input/output statement is executed, the set of storage units specified by the 12 item list or NML= specifier, plus the storage units specified by the SIZE= specifier, is defined to be the 13 pending input/output storage sequence for the data transfer operation. NOTE 9.30 A pending input/output storage sequence is not necessarily a contiguous set of storage units. 14 A pending input/output storage sequence affector is a variable of which any part is associated with a 15 storage unit in a pending input/output storage sequence. 16 9.5.1.5 BLANK= specifier in a data transfer statement 17 The scalar-default-char-expr shall evaluate to NULL or ZERO. The BLANK= specifier temporarily 18 changes (9.4.1) the blank interpretation mode (10.7.6, 9.4.5.4) for the connection. If the specifier is 19 omitted, the mode is not changed. 20 9.5.1.6 DECIMAL= specifier in a data transfer statement 21 The scalar-default-char-expr shall evaluate to COMMA or POINT. The DECIMAL= specifier temporar- 22 ily changes (9.4.1) the decimal edit mode (10.7.8, 9.4.5.5) for the connection. If the specifier is omitted, 23 the mode is not changed. 24 9.5.1.7 DELIM= specifier in a data transfer statement 25 The scalar-default-char-expr shall evaluate to APOSTROPHE, QUOTE, or NONE. The DELIM= spec- 26 ifier temporarily changes (9.4.1) the delimiter mode (10.9.2, 10.10.2.1, 9.4.5.6) for the connection. If the 27 specifier is omitted, the mode is not changed. SEP 2002 COMMITTEE DRAFT 189 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 9.5.1.8 ID= specifier in a data transfer statement 2 Successful execution of an asynchronous data transfer statement containing an ID= specifier causes the 3 variable specified in the ID= specifier to become defined with a processor-dependent value. This value 4 is referred to as the identifier of the data transfer operation. It can be used in a subsequent WAIT or 5 INQUIRE statement to identify the particular data transfer operation. 6 If an error occurs during the execution of a data transfer statement containing an ID= specifier, the 7 variable specified in the ID= specifier becomes undefined. 8 A child data transfer statement shall not specify the ID= specifier. 9 9.5.1.9 PAD= specifier in a data transfer statement 10 The scalar-default-char-expr shall evaluate to YES or NO. The PAD= specifier temporarily changes 11 (9.4.1) the pad mode (9.5.3.4.2, 9.4.5.9) for the connection. If the specifier is omitted, the mode is not 12 changed. 13 9.5.1.10 POS= specifier in a data transfer statement 14 The POS= specifier specifies the file position in file storage units. This specifier may appear only in 15 an input/output statement that specifies a unit connected for stream access. A child data transfer 16 statement shall not specify this specifier. 17 A processor may prohibit the use of POS= with particular files that do not have the properties necessary 18 to support random positioning. A processor may also prohibit positioning a particular file to any 19 position prior to its current file position if the file does not have the properties necessary to support such 20 positioning. NOTE 9.31 A file that represents connection to a device or data stream might not be positionable. 21 If the file is connected for formatted stream access, the file position specified by POS= shall be equal to 22 either 1 (the beginning of the file) or a value previously returned by a POS= specifier in an INQUIRE 23 statement for the file. 24 9.5.1.11 REC= specifier in a data transfer statement 25 The REC= specifier specifies the number of the record that is to be read or written. This specifier 26 may appear only in an input/output statement that specifies a unit connected for direct access; it 27 shall not appear in a child data transfer statement. If the control information list contains a REC= 28 specifier, the statement is a direct access input/output statement. A child data transfer statement 29 is a direct access data transfer statement if the parent is a direct access data transfer statement. Any 30 other data transfer statement is a sequential access input/output statement or a stream access 31 input/output statement, depending on whether the file connection is for sequential access or stream 32 access. 33 9.5.1.12 ROUND= specifier in a data transfer statement 34 The scalar-default-char-expr shall evaluate to one of the values specified in 9.4.5.12. The ROUND= 35 specifier temporarily changes (9.4.1) the I/O rounding mode (10.6.1.2.6, 9.4.5.12) for the connection. If 36 the specifier is omitted, the mode is not changed. 190 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 9.5.1.13 SIGN= specifier in a data transfer statement 2 The scalar-default-char-expr shall evaluate to PLUS, SUPPRESS, or PROCESSOR DEFINED. The 3 SIGN= specifier temporarily changes (9.4.1) the sign mode (10.7.4, 9.4.5.13) for the connection. If the 4 specifier is omitted, the mode is not changed. 5 9.5.1.14 SIZE= specifier in a data transfer statement 6 When a synchronous nonadvancing input statement terminates, the variable specified in the SIZE= 7 specifier becomes defined with the count of the characters transferred by data edit descriptors during 8 execution of the current input statement. Blanks inserted as padding (9.5.3.4.2) are not counted. 9 For asynchronous nonadvancing input, the storage units specified in the SIZE= specifier become defined 10 with the count of the characters transferred when the corresponding wait operation is executed. 11 9.5.2 Data transfer input/output list 12 An input/output list specifies the entities whose values are transferred by a data transfer input/output 13 statement. 14 R915 input-item is variable 15 or io-implied-do 16 R916 output-item is expr 17 or io-implied-do 18 R917 io-implied-do is ( io-implied-do-object -list , io-implied-do-control ) 19 R918 io-implied-do-object is input-item 20 or output-item 21 R919 io-implied-do-control is do-variable = scalar-int-expr , 22 scalar-int-expr [ , scalar-int-expr ] 23 C930 (R915) A variable that is an input-item shall not be a whole assumed-size array. 24 C931 (R915) A variable that is an input-item shall not be a procedure pointer. 25 C932 (R919) The do-variable shall be a named scalar variable of type integer. 26 C933 (R918) In an input-item-list, an io-implied-do-object shall be an input-item. In an output-item- 27 list, an io-implied-do-object shall be an output-item. 28 C934 (R916) An expression that is an output-item shall not have a value that is a procedure pointer. 29 An input-item shall not appear as, nor be associated with, the do-variable of any io-implied-do that 30 contains the input-item. NOTE 9.32 A constant, an expression involving operators or function references, or an expression enclosed in parentheses may appear as an output list item but shall not appear as an input list item. 31 If an input item is a pointer, it shall be associated with a definable target and data are transferred from 32 the file to the associated target. If an output item is a pointer, it shall be associated with a target and 33 data are transferred from the target to the file. SEP 2002 COMMITTEE DRAFT 191 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 9.33 Data transfers always involve the movement of values between a file and internal storage. A pointer as such cannot be read or written. Therefore, a pointer may not appear as an item in an input/output list unless it is associated with a target that can receive a value (input) or can deliver a value (output). 1 If an input item or an output item is allocatable, it shall be allocated. 2 A list item shall not be polymorphic unless it is processed by a user-defined derived-type input/output 3 procedure (9.5.3.7). 4 The do-variable of an io-implied-do that is in another io-implied-do shall not appear as, nor be associated 5 with, the do-variable of the containing io-implied-do. 6 The following rules describing whether to expand an input/output list item are re-applied to each 7 expanded list item until none of the rules apply. 8 If an array appears as an input/output list item, it is treated as if the elements, if any, were specified in 9 array element order (6.2.2.2). However, no element of that array may affect the value of any expression 10 in the input-item, nor may any element appear more than once in an input-item. NOTE 9.34 For example: INTEGER A (100), J (100) ... READ *, A (A) ! Not allowed READ *, A (LBOUND (A, 1) : UBOUND (A, 1)) ! Allowed READ *, A (J) ! Allowed if no two elements ! of J have the same value A(1) = 1; A(10) = 10 READ *, A (A (1) : A (10)) ! Not allowed 11 If a list item of derived type in an unformatted input/output statement is not processed by a user-defined 12 derived-type input/output procedure (9.5.3.7), and if any subobject of that list item would be processed 13 by a user-defined derived-type input/output procedure, the list item is treated as if all of the components 14 of the object were specified in the list in component order (4.5.4); those components shall be accessible 15 in the scoping unit containing the input/output statement and shall not be pointers or allocatable. 16 An effective input/output list item of derived type in an unformatted input/output statement is treated 17 as a single value in a processor-dependent form unless the list item or a subobject thereof is processed 18 by a user-defined derived-type input/output procedure (9.5.3.7). NOTE 9.35 The appearance of a derived-type object as an input/output list item in an unformatted in- put/output statement is not equivalent to the list of its components. Unformatted input/output involving derived-type list items forms the single exception to the rule that the appearance of an aggregate list item (such as an array) is equivalent to the appearance of its expanded list of component parts. This exception permits the processor greater latitude in improving efficiency or in matching the processor-dependent sequence of values for a derived-type object to similar sequences for aggregate objects used by means other than Fortran. However, 192 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 9.35 (cont.) formatted input/output of all list items and unformatted input/output of list items other than those of derived types adhere to the above rule. 1 If a list item of derived type in a formatted input/output statement is not processed by a user-defined 2 derived-type input/output procedure, that list item is treated as if all of the components of the list item 3 were specified in the list in component order; those components shall be accessible in the scoping unit 4 containing the input/output statement and shall not be pointers or allocatable. 5 If a derived-type list item is not treated as a list of its individual components, that list item's ultimate 6 components shall not have the POINTER or ALLOCATABLE attribute unless that list item is processed 7 by a user-defined derived-type input/output procedure. 8 The scalar objects resulting when a data transfer statement's list items are expanded according to the 9 rules in this section for handling array and derived-type list items are called effective items. Zero-sized 10 arrays and implied-DO lists with an iteration count of zero do not contribute to the effective list items. 11 A scalar character item of zero length is an effective list item. NOTE 9.36 In a formatted input/output statement, edit descriptors are associated with effective list items, which are always scalar. The rules in 9.5.2 determine the set of effective list items corresponding to each actual list item in the statement. These rules may have to be applied repetitively until all of the effective list items are scalar items. 12 For an implied-DO, the loop initialization and execution is the same as for a DO construct (8.1.6.4). 13 An input/output list shall not contain an item of nondefault character type if the input/output statement 14 specifies an internal file. NOTE 9.37 An example of an output list with an implied-DO is: WRITE (LP, FMT = '(10F8.2)') (LOG (A (I)), I = 1, N + 9, K), G 15 9.5.3 Execution of a data transfer input/output statement 16 Execution of a WRITE or PRINT statement for a file that does not exist creates the file unless an error 17 condition occurs. 18 The effect of executing a synchronous data transfer input/output statement shall be as if the following 19 operations were performed in the order specified: 20 (1) Determine the direction of data transfer. 21 (2) Identify the unit. 22 (3) Perform a wait operation for all pending input/output operations for the unit. If an error, 23 end-of-file, or end-of-record condition occurs during any of the wait operations, steps 4 24 through 8 are skipped for the current data transfer statement. 25 (4) Establish the format if one is specified. 26 (5) Position the file prior to data transfer (9.2.3.2) unless the statement is a child data transfer 27 statement (9.5.3.7). 28 (6) Transfer data between the file and the entities specified by the input/output list (if any) or 29 namelist. SEP 2002 COMMITTEE DRAFT 193 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 (7) Determine whether an error, end-of-file, or end-of-record condition has occurred. 2 (8) Position the file after data transfer (9.2.3.3) unless the statement is a child data transfer 3 statement (9.5.3.7). 4 (9) Cause any variable specified in a SIZE= specifier to become defined. 5 (10) If an error, end-of-file, or end-of-record condition occurred, processing continues as specified 6 in 9.10; otherwise any variable specified in an IOSTAT= specifier is assigned the value zero. 7 The effect of executing an asynchronous data transfer input/output statement shall be as if the following 8 operations were performed in the order specified: 9 (1) Determine the direction of data transfer. 10 (2) Identify the unit. 11 (3) Establish the format if one is specified. 12 (4) Position the file prior to data transfer (9.2.3.2). 13 (5) Establish the set of storage units identified by the input/output list. For a READ statement, 14 this might require some or all of the data in the file to be read if an input variable is used 15 in an implied-DO in the input/output list, as a subscript , substring-range, stride, or is 16 otherwise referenced. 17 (6) Initiate an asynchronous data transfer between the file and the entities specified by the 18 input/output list (if any) or namelist. The asynchronous data transfer may complete (and 19 an error, end-of-file, or end-of-record condition may occur) during the execution of this data 20 transfer statement or during a later wait operation. 21 (7) Determine whether an error, end-of-file, or end-of-record condition has occurred. The con- 22 ditions may occur during the execution of this data transfer statement or during the corre- 23 sponding wait operation, but not both. 24 Also, any of these conditions that would have occurred during the corresponding wait oper- 25 ation for a previously pending data transfer operation that does not have an ID= specifier 26 may occur during the execution of this data transfer statement. 27 (8) Position the file as if the data transfer had finished (9.2.3.3). 28 (9) Cause any variable specified in a SIZE= specifier to become undefined. 29 (10) If an error, end-of-file, or end-of-record condition occurred, processing continues as specified 30 in 9.10; otherwise any variable specified in an IOSTAT= specifier is assigned the value zero. 31 For an asynchronous data transfer statement, the data transfers may occur during execution of the 32 statement, during execution of the corresponding wait operation, or anywhere between. The data transfer 33 operation is considered to be pending until a corresponding wait operation is performed. 34 For asynchronous output, a pending input/output storage sequence affector (9.5.1.4) shall not be rede- 35 fined, become undefined, or have its pointer association status changed. 36 For asynchronous input, a pending input/output storage sequence affector shall not be referenced, be- 37 come defined, become undefined, become associated with a dummy argument that has the VALUE 38 attribute, or have its pointer association status changed. 39 Error, end-of-file, and end-of-record conditions in an asynchronous data transfer operation may occur 40 during execution of either the data transfer statement or the corresponding wait operation. If an ID= 41 specifier does not appear in the initiating data transfer statement, the conditions may occur during the 42 execution of any subsequent data transfer or wait operation for the same unit. When a condition occurs 43 for a previously executed asynchronous data transfer statement, a wait operation is performed for all 44 pending data transfer operations on that unit. When a condition occurs during a subsequent statement, 45 any actions specified by IOSTAT=, IOMSG=, ERR=, END=, and EOR= specifiers for that statement 46 are taken. 194 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 9.38 Because end-of-file and error conditions for asynchronous data transfer statements without an ID= specifier may be reported by the processor during the execution of a subsequent data transfer statement, it may be impossible for the user to determine which input/output statement caused the condition. Reliably detecting which READ statement caused an end-of-file condition requires that all asynchronous READ statements for the unit include an ID= specifier. 1 9.5.3.1 Direction of data transfer 2 Execution of a READ statement causes values to be transferred from a file to the entities specified by 3 the input list, if any, or specified within the file itself for namelist input. Execution of a WRITE or 4 PRINT statement causes values to be transferred to a file from the entities specified by the output list 5 and format specification, if any, or by the namelist-group-name for namelist output. 6 9.5.3.2 Identifying a unit 7 A data transfer input/output statement that contains an input/output control list includes a UNIT= 8 specifier that identifies an external or internal unit. A READ statement that does not contain an 9 input/output control list specifies a particular processor-dependent unit, which is the same as the unit 10 identified by * in a READ statement that contains an input/output control list. The PRINT statement 11 specifies some other processor-dependent unit, which is the same as the unit identified by * in a WRITE 12 statement. Thus, each data transfer input/output statement identifies an external or internal unit. 13 The unit identified by a data transfer input/output statement shall be connected to a file when execution 14 of the statement begins. NOTE 9.39 The file may be preconnected. 15 9.5.3.3 Establishing a format 16 If the input/output control list contains * as a format, list-directed formatting is established. If namelist- 17 group-name appears, namelist formatting is established. If no format or namelist-group-name is spec- 18 ified, unformatted data transfer is established. Otherwise, the format specification identified by the 19 FMT= specifier is established. 20 On output, if an internal file has been specified, a format specification that is in the file or is associated 21 with the file shall not be specified. 22 9.5.3.4 Data transfer 23 Data are transferred between the file and the entities specified by the input/output list or namelist. 24 The list items are processed in the order of the input/output list for all data transfer input/output 25 statements except namelist formatted data transfer statements. The list items for a namelist input 26 statement are processed in the order of the entities specified within the input records. The list items 27 for a namelist output statement are processed in the order in which the variables are specified in the 28 namelist-group-object -list. Effective items are derived from the input/output list items as described in 29 9.5.2. 30 All values needed to determine which entities are specified by an input/output list item are determined 31 at the beginning of the processing of that item. 32 All values are transmitted to or from the entities specified by a list item prior to the processing of any 33 succeeding list item for all data transfer input/output statements. SEP 2002 COMMITTEE DRAFT 195 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 9.40 In the example, READ (N) N, X (N) the old value of N identifies the unit, but the new value of N is the subscript of X. 1 All values following the name= part of the namelist entity (10.10) within the input records are transmit- 2 ted to the matching entity specified in the namelist-group-object -list prior to processing any succeeding 3 entity within the input record for namelist input statements. If an entity is specified more than once 4 within the input record during a namelist formatted data transfer input statement, the last occurrence 5 of the entity specifies the value or values to be used for that entity. 6 An input list item, or an entity associated with it, shall not contain any portion of an established format 7 specification. 8 If the input/output item is a pointer, data are transferred between the file and the associated target. 9 If an internal file has been specified, an input/output list item shall not be in the file or associated with 10 the file. NOTE 9.41 The file is a data object. 11 A DO variable becomes defined and its iteration count established at the beginning of processing of the 12 items that constitute the range of an io-implied-do. 13 On output, every entity whose value is to be transferred shall be defined. 14 9.5.3.4.1 Unformatted data transfer 15 During unformatted data transfer, data are transferred without editing between the file and the entities 16 specified by the input/output list. If the file is connected for sequential or direct access, exactly one 17 record is read or written. 18 Objects of intrinsic or derived types may be transferred by means of an unformatted data transfer 19 statement. 20 A value in the file is stored in a contiguous sequence of file storage units, beginning with the file storage 21 unit immediately following the current file position. 22 After each value is transferred, the current file position is moved to a point immediately after the last 23 file storage unit of the value. 24 On input from a file connected for sequential or direct access, the number of file storage units required 25 by the input list shall be less than or equal to the number of file storage units in the record. 26 On input, if the file storage units transferred do not contain a value with the same type and type 27 parameters as the input list entity, then the resulting value of the entity is processor-dependent except 28 in the following cases: 29 (1) A complex list entity may correspond to two real values of the same kind stored in the file, 30 or vice-versa. 31 (2) A default character list entity of length n may correspond to n default characters stored in 32 the file, regardless of the length parameters of the entities that were written to these storage 33 units of the file. If the file is connected for stream input, the characters may have been 196 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 written by formatted stream output. 2 On output to a file connected for unformatted direct access, the output list shall not specify more values 3 than can fit into the record. If the file is connected for direct access and the values specified by the 4 output list do not fill the record, the remainder of the record is undefined. 5 If the file is connected for unformatted sequential access, the record is created with a length sufficient 6 to hold the values from the output list. This length shall be one of the set of allowed record lengths for 7 the file and shall not exceed the value specified in the RECL= specifier, if any, of the OPEN statement 8 that established the connection. 9 If the file is not connected for unformatted input/output, unformatted data transfer is prohibited. 10 The unit specified shall be an external unit. 11 9.5.3.4.2 Formatted data transfer 12 During formatted data transfer, data are transferred with editing between the file and the entities 13 specified by the input/output list or by the namelist-group-name. Format control is initiated and editing 14 is performed as described in Section 10. 15 The current record and possibly additional records are read or written. 16 Values may be transferred by means of a formatted data transfer statement to or from objects of intrinsic 17 or derived types. In the latter case, the transfer is in the form of values of intrinsic types to or from the 18 components of intrinsic types that ultimately comprise these structured objects unless the derived-type 19 list item is processed by a user-defined derived-type input/output procedure (9.5.3.7). 20 If the file is not connected for formatted input/output, formatted data transfer is prohibited. 21 During advancing input when the pad mode has the value NO, the input list and format specification 22 shall not require more characters from the record than the record contains. 23 During advancing input when the pad mode has the value YES, blank characters are supplied by the 24 processor if the input list and format specification require more characters from the record than the 25 record contains. 26 During nonadvancing input when the pad mode has the value NO, an end-of-record condition (9.10) 27 occurs if the input list and format specification require more characters from the record than the record 28 contains, and the record is complete (9.2.2.3). If the record is incomplete, an end-of-file condition occurs 29 instead of an end-of-record condition. 30 During nonadvancing input when the pad mode has the value YES, blank characters are supplied by the 31 processor if an input item and its corresponding data edit descriptor require more characters from the 32 record than the record contains. If the record is incomplete, an end-of-file condition occurs; otherwise 33 an end-of-record condition occurs. 34 If the file is connected for direct access, the record number is increased by one as each succeeding record 35 is read or written. 36 On output, if the file is connected for direct access or is an internal file and the characters specified by 37 the output list and format do not fill a record, blank characters are added to fill the record. 38 On output, the output list and format specification shall not specify more characters for a record than 39 have been specified by a RECL= specifier in the OPEN statement or the record length of an internal 40 file. SEP 2002 COMMITTEE DRAFT 197 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 9.5.3.5 List-directed formatting 2 If list-directed formatting has been established, editing is performed as described in 10.9. 3 9.5.3.6 Namelist formatting 4 If namelist formatting has been established, editing is performed as described in 10.10. 5 Every allocatable namelist-group-object in the namelist group shall be allocated and every namelist- 6 group-object that is a pointer shall be associated with a target. If a namelist-group-object is polymorphic 7 or has an ultimate component that is allocatable or a pointer, that object shall be processed by a user- 8 defined derived-type input/output procedure (9.5.3.7). 9 9.5.3.7 User-defined derived-type input/output 10 User-defined derived-type input/output procedures allow a program to override the default handling of 11 derived-type objects and values in data transfer input/output statements described in 9.5.2. 12 A user-defined derived-type input/output procedure is a procedure accessible by a dtio-generic-spec 13 (12.3.2.1). A particular user-defined derived-type input/output procedure is selected as described in 14 9.5.3.7.3. 15 9.5.3.7.1 Executing user-defined derived-type input/output data transfers 16 If a derived-type input/output procedure is selected as specified in 9.5.3.7.3, the processor shall call the se- 17 lected user-defined derived-type input/output procedure for any appropriate data transfer input/output 18 statements executed in that scoping unit. The user-defined derived-type input/output procedure controls 19 the actual data transfer operations for the derived-type list item. 20 A data transfer statement that includes a derived-type list item and that causes a user-defined derived- 21 type input/output procedure to be invoked is called a parent data transfer statement. A data 22 transfer statement that is executed while a parent data transfer statement is being processed and that 23 specifies the unit passed into a user-defined derived-type input/output procedure is called a child data 24 transfer statement. NOTE 9.42 A user-defined derived-type input/output procedure will usually contain child data transfer state- ments that read values from or write values to the current record or at the current file position. The effect of executing the user-defined derived-type input/output procedure is similar to that of substituting the list items from any child data transfer statements into the parent data transfer statement's list items, along with similar substitutions in the format specification. NOTE 9.43 A particular execution of a READ, WRITE or PRINT statement can be both a parent and a child data transfer statement. A user-defined derived-type input/output procedure can indirectly call itself or another user-defined derived-type input/output procedure by executing a child data transfer statement containing a list item of derived type, where a matching interface is accessible for that derived type. If a user-defined derived-type input/output procedure calls itself indirectly in this manner, it shall be declared RECURSIVE. 25 A child data transfer statement is processed differently from a nonchild data transfer statement in the 26 following ways: 27 · Executing a child data transfer statement does not position the file prior to data transfer. 198 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 · An unformatted child data transfer statement does not position the file after data transfer is 2 complete. 3 9.5.3.7.2 User-defined derived-type input/output procedures 4 For a particular derived type and a particular set of kind type parameter values, there are four possible 5 sets of characteristics for user-defined derived-type input/output procedures; one each for formatted 6 input, formatted output, unformatted input, and unformatted output. The user need not supply all four 7 procedures. The procedures are specified to be used for derived-type input/output by interface blocks 8 (12.3.2.1) or by derived-type procedure bindings (4.5.1.5), with a dtio-generic-spec. 9 In the four interfaces, which specify the characteristics of user-defined procedures for derived-type in- 10 put/output, the following syntax term is used: 11 R920 dtv-type-spec is TYPE( derived-type-spec ) 12 or CLASS( derived-type-spec ) 13 C935 (R920) If derived-type-spec specifies an extensible type, the CLASS keyword shall be used; 14 otherwise, the TYPE keyword shall be used. 15 C936 (R920) All nonkind type parameters of derived-type-spec shall be assumed. 16 If the generic-spec is READ (FORMATTED), the characteristics shall be the same as those specified by 17 the following interface: 18 SUBROUTINE my_read_routine_formatted & 19 (dtv, & 20 unit, & 21 iotype, v_list, & 22 iostat, iomsg) 23 ! the derived-type value/variable 24 dtv-type-spec , INTENT(INOUT) :: dtv 25 INTEGER, INTENT(IN) :: unit ! unit number 26 ! the edit descriptor string 27 CHARACTER (LEN=*), INTENT(IN) :: iotype 28 INTEGER, INTENT(IN) :: v_list(:) 29 INTEGER, INTENT(OUT) :: iostat 30 CHARACTER (LEN=*), INTENT(INOUT) :: iomsg 31 END 32 If the generic-spec is READ (UNFORMATTED), the characteristics shall be the same as those specified 33 by the following interface: 34 SUBROUTINE my_read_routine_unformatted & 35 (dtv, & 36 unit, & 37 iostat, iomsg) 38 ! the derived-type value/variable 39 dtv-type-spec , INTENT(INOUT) :: dtv 40 INTEGER, INTENT(IN) :: unit 41 INTEGER, INTENT(OUT) :: iostat 42 CHARACTER (LEN=*), INTENT(INOUT) :: iomsg 43 END SEP 2002 COMMITTEE DRAFT 199 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 If the generic-spec is WRITE (FORMATTED), the characteristics shall be the same as those specified 2 by the following interface: 3 SUBROUTINE my_write_routine_formatted & 4 (dtv, & 5 unit, & 6 iotype, v_list, & 7 iostat, iomsg) 8 ! the derived-type value/variable 9 dtv-type-spec , INTENT(IN) :: dtv 10 INTEGER, INTENT(IN) :: unit 11 ! the edit descriptor string 12 CHARACTER (LEN=*), INTENT(IN) :: iotype 13 INTEGER, INTENT(IN) :: v_list(:) 14 INTEGER, INTENT(OUT) :: iostat 15 CHARACTER (LEN=*), INTENT(INOUT) :: iomsg 16 END 17 If the generic-spec is WRITE (UNFORMATTED), the characteristics shall be the same as those specified 18 by the following interface: 19 SUBROUTINE my_write_routine_unformatted & 20 (dtv, & 21 unit, & 22 iostat, iomsg) 23 ! the derived-type value/variable 24 dtv-type-spec , INTENT(IN) :: dtv 25 INTEGER, INTENT(IN) :: unit 26 INTEGER, INTENT(OUT) :: iostat 27 CHARACTER (LEN=*), INTENT(INOUT) :: iomsg 28 END 29 The actual specific procedure names (the my ... routine ... procedure names above) are not signifi- 30 cant. In the discussion here and elsewhere, the dummy arguments in these interfaces are referred by the 31 names given above; the names are, however, arbitrary. 32 In addition to the characteristics specified by the above interfaces, the dtv dummy argument may 33 optionally have the VOLATILE attribute. 34 When a user-defined derived-type input/output procedure is invoked, the processor shall pass a unit 35 argument that has a value as follows: 36 · If the parent data transfer statement uses a file-unit-number , the value of the unit argument shall 37 be that of the file-unit-number . 38 · If the parent data transfer statement is a WRITE statement with an asterisk unit or a PRINT 39 statement, the unit argument shall have the same value as the OUTPUT UNIT named constant 40 of the ISO FORTRAN ENV intrinsic module (13.8.3). 41 · If the parent data transfer statement is a READ statement with an asterisk unit or a READ 42 statement without an io-control-spec-list, the unit argument shall have the same value as the 43 INPUT UNIT named constant of the ISO FORTRAN ENV intrinsic module (13.8.3). 200 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 · Otherwise the parent data transfer statement must access an internal file, in which case the unit 2 argument shall have a processor-dependent negative value. NOTE 9.44 Because the unit argument value will be negative when the parent data transfer statement speci- fies an internal file, a user-defined derived-type input/output procedure should not execute an IN- QUIRE statement without checking that the unit argument is nonnegative or is equal to one of the named constants INPUT UNIT, OUTPUT UNIT, or ERROR UNIT of the ISO FORTRAN ENV intrinsic module(13.8.3.1). 3 For formatted data transfer, the processor shall pass an iotype argument that has a value as follows: 4 · "LISTDIRECTED" if the parent data transfer statement specified list directed formatting, 5 · "NAMELIST" if the parent data transfer statement specified namelist formatting, or 6 · "DT" concatenated with the char-literal-constant , if any, of the edit descriptor, if the parent data 7 transfer statement contained a format specification and the list item's corresponding edit descriptor 8 was a DT edit descriptor. 9 If the parent data transfer statement is a READ statement, the dtv dummy argument is argument 10 associated with the effective list item that caused the user-defined derived-type input procedure to be 11 invoked, as if the effective list item were an actual argument in this procedure reference (2.5.6). 12 If the parent data transfer statement is a WRITE or PRINT statement, the processor shall provide the 13 value of the effective list item in the dtv dummy argument. 14 If the v -list of the edit descriptor appears in the parent data transfer statement, the processor shall 15 provide the values from it in the v list dummy argument, with the same number of elements in the 16 same order as v -list. If there is no v -list in the edit descriptor or if the data transfer statement specifies 17 list-directed or namelist formatting, the processor shall provide v list as a zero-sized array. NOTE 9.45 The user's procedure may chose to interpret an element of the v list argument as a field width, but this is not required. If it does, it would be appropriate to fill an output field with "*"s if the width is too small. 18 The iostat argument is used to report whether an error, end-of-record, or end-of-file condition (9.10) 19 occurs. If an error condition occurs, the user-defined derived-type input/output procedure shall assign 20 a positive value to the iostat argument. Otherwise, if an end-of-file condition occurs, the user-defined 21 derived-type input procedure shall assign the value of the named constant IOSTAT END (13.8.3.2.1) 22 to the iostat argument. Otherwise, if an end-of-record condition occurs, the user-defined derived-type 23 input procedure shall assign the value of the named constant IOSTAT EOR (13.8.3.2.2) to iostat. 24 Otherwise, the user-defined derived-type input/output procedure shall assign the value zero to the 25 iostat argument. 26 If the user-defined derived-type input/output procedure returns a nonzero value for the iostat argument, 27 the procedure shall also return an explanatory message in the iomsg argument. Otherwise, the procedure 28 shall not change the value of the iomsg argument. NOTE 9.46 The values of the iostat and iomsg arguments set in a user-defined derived-type input/output procedure need not be passed to all of the parent data transfer statements. SEP 2002 COMMITTEE DRAFT 201 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 If the iostat argument of the user-defined derived-type input/output procedure has a nonzero value 2 when that procedure returns, and the processor therefore terminates execution of the program as de- 3 scribed in 9.10, the processor shall make the value of the iomsg argument available in a processor- 4 dependent manner. 5 When a parent READ statement is active, an input/output statement shall not read from any external 6 unit other than the one specified by the dummy argument unit and shall not perform output to any 7 external unit. 8 When a parent WRITE or PRINT statement is active, an input/output statement shall not perform 9 output to any external unit other than the one specified by the dummy argument unit and shall not 10 read from any external unit. 11 When a parent data transfer statement is active, a data transfer statement that specifies an internal file 12 is permitted. 13 OPEN, CLOSE, BACKSPACE, ENDFILE, and REWIND statements shall not be executed while a 14 parent data transfer statement is active. 15 A user-defined derived-type input/output procedure may use a FORMAT with a DT edit descriptor for 16 handling a component of the derived type that is itself of a derived type. A child data transfer statement 17 that is a list directed or namelist input/output statement may contain a list item of derived type. 18 Because a child data transfer statement does not position the file prior to data transfer, the child data 19 transfer statement starts transferring data from where the file was positioned by the parent data transfer 20 statement's most recently processed effective list item or record positioning edit descriptor. This is not 21 necessarily at the beginning of a record. 22 A record positioning edit descriptor, such as TL and TR, used on unit by a child data transfer statement 23 shall not cause the record position to be positioned before the record position at the time the user-defined 24 derived-type input/output procedure was invoked. NOTE 9.47 A robust user-defined derived-type input/output procedure may wish to use INQUIRE to deter- mine the settings of BLANK=, PAD=, ROUND=, DECIMAL=, and DELIM= for an external unit. The INQUIRE provides values as specified in 9.9. 25 Neither a parent nor child data transfer statement shall be asynchronous. 26 A user-defined derived-type input/output procedure, and any procedures invoked therefrom, shall not 27 define, nor cause to become undefined, any storage location referenced by any input/output list item, 28 the corresponding format, or any specifer in any active parent data transfer statement, except through 29 the dtv argument. NOTE 9.48 A child data transfer statement shall not specify the ID=, POS=, or REC= specifiers in an input/output control list. 30 9.5.3.7.3 Resolving derived-type input/output procedure references 31 A suitable generic interface for user-defined derived-type input/output of an effective item is one that 32 has a dtio-generic-spec that is appropriate to the direction (read or write) and form (formatted or 33 unformatted) of the data transfer as specified in 9.5.3.7, and has a specific interface whose dtv argument 34 is compatible with the effective item according to the rules for argument association in 12.4.1.2. 202 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 When an effective item (9.5.2) that is of derived-type is encountered during a data transfer, user-defined 2 derived-type input/output occurs if both of the following conditions are true: 3 (1) The circumstances of the input/output are such that user-defined derived-type input/output 4 is permitted; that is, either 5 (a) the transfer was initiated by a list-directed, namelist, or unformatted input/output 6 statement, or 7 (b) a format specification is supplied for the input/output statement, and the edit de- 8 scriptor corresponding to the effective item is a DT edit descriptor. 9 (2) A suitable user-defined derived-type input/output procedure is available; that is, either 10 (a) the declared type of the effective item has a suitable type-bound generic binding, or 11 (b) a suitable generic interface is accessible. 12 If (2a) is true, the procedure referenced is determined as for explicit type-bound procedure references 13 (12.4); that is, the binding with the appropriate specific interface is located in the declared type of the 14 effective item, and the corresponding binding in the dynamic type of the effective item is selected. 15 If (2a) is false and (2b) is true, the reference is to the procedure identified by the appropriate specific 16 interface in the interface block. This reference shall not be to a dummy procedure or dummy procedure 17 pointer that is not present, or a disassociated procedure pointer. 18 9.5.4 Termination of data transfer statements 19 Termination of an input/output data transfer statement occurs when any of the following conditions are 20 met: 21 (1) Format processing encounters a data edit descriptor and there are no remaining elements 22 in the input-item-list or output-item-list. 23 (2) Unformatted or list-directed data transfer exhausts the input-item-list or output-item-list. 24 (3) Namelist output exhausts the namelist-group-object -list. 25 (4) An error condition occurs. 26 (5) An end-of-file condition occurs. 27 (6) A slash (/) is encountered as a value separator (10.9, 10.10) in the record being read during 28 list-directed or namelist input. 29 (7) An end-of-record condition occurs during execution of a nonadvancing input statement 30 (9.10). 31 9.6 Waiting on pending data transfer 32 Execution of an asynchronous data transfer statement in which neither an error, end-of-record, nor end- 33 of-file condition occurs initiates a pending data transfer operation. There may be multiple pending data 34 transfer operations for the same or multiple units simultaneously. A pending data transfer operation 35 remains pending until a corresponding wait operation is performed. A wait operation may be performed 36 by a WAIT, INQUIRE, CLOSE, or file positioning statement. 37 9.6.1 WAIT statement 38 A WAIT statement performs a wait operation for specified pending asynchronous data transfer opera- 39 tions. NOTE 9.49 The CLOSE, INQUIRE, and file positioning statements may also perform wait operations. SEP 2002 COMMITTEE DRAFT 203 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 R921 wait-stmt is WAIT (wait-spec-list ) 2 R922 wait-spec is [ UNIT = ] file-unit-number 3 or END = label 4 or EOR = label 5 or ERR = label 6 or ID = scalar-int-variable 7 or IOMSG = iomsg-variable 8 or IOSTAT = scalar-int-variable 9 C937 (R922) No specifier shall appear more than once in a given wait-spec-list. 10 C938 (R922) A file-unit-number shall be specified; if the optional characters UNIT= are omitted, the 11 file-unit-number shall be the first item in the wait-spec-list. 12 C939 (R922) The label in the ERR=, EOR=, or END= specifier shall be the statement label of a 13 branch target statement that appears in the same scoping unit as the WAIT statement. 14 The IOSTAT=, ERR=, EOR=, END=, and IOMSG= specifiers are described in 9.10. 15 The value of the variable specified in the ID= specifier shall be the identifier of a pending data transfer 16 operation for the specified unit. If the ID= specifier appears, a wait operation for the specified data 17 transfer operation is performed. If the ID= specifier is omitted, wait operations for all pending data 18 transfers for the specified unit are performed. 19 Execution of a WAIT statement specifying a unit that does not exist, has no file connected to it, or was 20 not opened for asynchronous input/output is permitted, provided that the WAIT statement has no ID= 21 specifier; such a WAIT statement does not cause an error or end-of-file condition to occur. NOTE 9.50 An EOR= specifier has no effect if the pending data transfer operation is not a nonadvancing read. And END= specifier has no effect if the pending data transfer operation is not a READ. 22 9.6.2 Wait operation 23 A wait operation terminates a pending data transfer operation. Each wait operation terminates only a 24 single data transfer operation, although a single statement may perform multiple wait operations. 25 If the actual data transfer is not yet complete, the wait operation first waits for its completion. If the 26 data transfer operation is an input operation that completed without error, the storage units of the 27 input/output storage sequence then become defined with the values as described in 9.5.1.14 and 9.5.3.4. 28 If any error, end-of-file, or end-of-record conditions occur, the applicable actions specified by the IO- 29 STAT=, IOMSG=, ERR=, END=, and EOR= specifiers of the statement that performs the wait oper- 30 ation are taken. 31 If an error or end-of-file condition occurs during a wait operation for a unit, the processor performs a 32 wait operation for all pending data transfer operations for that unit. NOTE 9.51 Error, end-of-file, and end-of-record conditions may be raised either during the data transfer state- ment that initiates asynchronous input/output, a subsequent asynchronous data transfer statement for the same unit, or during the wait operation. If such conditions are raised during a data transfer statement, they trigger actions according to the IOSTAT=, ERR=, END=, and EOR= specifiers of that statement; if they are raised during the wait operation, the actions are in accordance with the specifiers of the statement that performs the wait operation. 204 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 After completion of the wait operation, the data transfer operation and its input/output storage sequence 2 are no longer considered to be pending. 3 9.7 File positioning statements 4 R923 backspace-stmt is BACKSPACE file-unit-number 5 or BACKSPACE ( position-spec-list ) 6 R924 endfile-stmt is ENDFILE file-unit-number 7 or ENDFILE ( position-spec-list ) 8 R925 rewind-stmt is REWIND file-unit-number 9 or REWIND ( position-spec-list ) 10 A file that is connected for direct access shall not be referred to by a BACKSPACE, ENDFILE, or 11 REWIND statement. A file that is connected for unformatted stream access shall not be referred to by a 12 BACKSPACE statement. A file that is connected with an ACTION= specifier having the value READ 13 shall not be referred to by an ENDFILE statement. 14 R926 position-spec is [ UNIT = ] file-unit-number 15 or IOMSG = iomsg-variable 16 or IOSTAT = scalar-int-variable 17 or ERR = label 18 C940 (R926) No specifier shall appear more than once in a given position-spec-list. 19 C941 (R926) A file-unit-number shall be specified; if the optional characters UNIT= are omitted, the 20 file-unit-number shall be the first item in the position-spec-list. 21 C942 (R926) The label in the ERR= specifier shall be the statement label of a branch target statement 22 that appears in the same scoping unit as the file positioning statement. 23 The IOSTAT=, ERR=, and IOMSG= specifiers are described in 9.10. 24 Execution of a file positioning statement performs a wait operation for all pending asynchronous data 25 transfer operations for the specified unit. 26 9.7.1 BACKSPACE statement 27 Execution of a BACKSPACE statement causes the file connected to the specified unit to be positioned 28 before the current record if there is a current record, or before the preceding record if there is no current 29 record. If the file is at its initial point, the position of the file is not changed. NOTE 9.52 If the preceding record is an endfile record, the file is positioned before the endfile record. 30 If a BACKSPACE statement causes the implicit writing of an endfile record, the file is positioned before 31 the record that precedes the endfile record. 32 Backspacing a file that is connected but does not exist is prohibited. 33 Backspacing over records written using list-directed or namelist formatting is prohibited. NOTE 9.53 An example of a BACKSPACE statement is: SEP 2002 COMMITTEE DRAFT 205 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 9.53 (cont.) BACKSPACE (10, ERR = 20) 1 9.7.2 ENDFILE statement 2 Execution of an ENDFILE statement for a file connected for sequential access writes an endfile record 3 as the next record of the file. The file is then positioned after the endfile record, which becomes the last 4 record of the file. If the file also may be connected for direct access, only those records before the endfile 5 record are considered to have been written. Thus, only those records may be read during subsequent 6 direct access connections to the file. 7 After execution of an ENDFILE statement for a file connected for sequential access, a BACKSPACE 8 or REWIND statement shall be used to reposition the file prior to execution of any data transfer 9 input/output statement or ENDFILE statement. 10 Execution of an ENDFILE statement for a file connected for stream access causes the terminal point of 11 the file to become equal to the current file position. Only file storage units before the current position are 12 considered to have been written; thus only those file storage units may be subsequently read. Subsequent 13 stream output statements may be used to write further data to the file. 14 Execution of an ENDFILE statement for a file that is connected but does not exist creates the file; if 15 the file is connected for sequential access, it is created prior to writing the endfile record. NOTE 9.54 An example of an ENDFILE statement is: ENDFILE K 16 9.7.3 REWIND statement 17 Execution of a REWIND statement causes the specified file to be positioned at its initial point. NOTE 9.55 If the file is already positioned at its initial point, execution of this statement has no effect on the position of the file. 18 Execution of a REWIND statement for a file that is connected but does not exist is permitted and has 19 no effect. NOTE 9.56 An example of a REWIND statement is: REWIND 10 20 9.8 FLUSH statement 21 The form of the FLUSH statement is: 22 R927 flush-stmt is FLUSH file-unit-number 23 or FLUSH ( flush-spec-list ) 24 R928 flush-spec is [UNIT =] file-unit-number 206 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 or IOSTAT = scalar-int-variable 2 or IOMSG = iomsg-variable 3 or ERR = label 4 C943 (R928) No specifier shall appear more than once in a given flush-spec-list. 5 C944 (R928) A file-unit-number shall be specified; if the optional characters UNIT= are omitted from 6 the unit specifier, the file-unit-number shall be the first item in the flush-spec-list. 7 C945 (R928) The label in the ERR= specifier shall be the statement label of a branch target statement 8 that appears in the same scoping unit as the flush statement. 9 The IOSTAT=, IOMSG= and ERR= specifiers are described in 9.10. The IOSTAT= variable shall be 10 set to a processor-dependent positive value if an error occurs, to zero if the processor-dependent flush 11 operation was successful, or to a processor-dependent negative value to indicate a processor-dependent 12 condition such as the flush operation is not appropriate for the unit specified. NOTE 9.57 The negative values for the IOSTAT= variable allow a flush operation on a unit where it is ineffective or inappropriate to be treated as a "harmless condition" that does not require an error to occur. 13 Execution of a FLUSH statement causes data written to an external file to be available to other processes, 14 or causes data placed in an external file by means other than Fortran to be available to a READ 15 statement. The action is processor dependent. 16 Execution of a FLUSH statement for a file that is connected but does not exist is permitted and has no 17 effect. A FLUSH statement has no effect on file position. NOTE 9.58 Since this standard does not specify the mechanism of file storage, the exact meaning of the flush operation is left vague. The intention is that the flush operation should make all data written to a file available to other processes or devices, or make data recently added to a file by other processes or devices available to the program via a subsequent read operation. This is commonly called "flushing I/O buffers". NOTE 9.59 An example of a FLUSH statement is: FLUSH( 10, ERR=20) 18 9.9 File inquiry 19 The INQUIRE statement may be used to inquire about properties of a particular named file or of the 20 connection to a particular unit. There are three forms of the INQUIRE statement: inquire by file, 21 which uses the FILE= specifier, inquire by unit, which uses the UNIT= specifier, and inquire by 22 output list, which uses only the IOLENGTH= specifier. All specifier value assignments are performed 23 according to the rules for assignment statements. 24 An INQUIRE statement may be executed before, while, or after a file is connected to a unit. All values 25 assigned by an INQUIRE statement are those that are current at the time the statement is executed. 26 R929 inquire-stmt is INQUIRE ( inquire-spec-list ) SEP 2002 COMMITTEE DRAFT 207 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 or INQUIRE ( IOLENGTH = scalar-int-variable ) 2 output-item-list NOTE 9.60 Examples of INQUIRE statements are: INQUIRE (IOLENGTH = IOL) A (1:N) INQUIRE (UNIT = JOAN, OPENED = LOG_01, NAMED = LOG_02, & FORM = CHAR_VAR, IOSTAT = IOS) 3 9.9.1 Inquiry specifiers 4 Unless constrained, the following inquiry specifiers may be used in either of the inquire by file or inquire 5 by unit forms of the INQUIRE statement: 6 R930 inquire-spec is [ UNIT = ] file-unit-number 7 or FILE = file-name-expr 8 or ACCESS = scalar-default-char-variable 9 or ACTION = scalar-default-char-variable 10 or ASYNCHRONOUS = scalar-default-char-variable 11 or BLANK = scalar-default-char-variable 12 or DECIMAL = scalar-default-char-variable 13 or DELIM = scalar-default-char-variable 14 or DIRECT = scalar-default-char-variable 15 or ERR = label 16 or EXIST = scalar-default-logical-variable 17 or FORM = scalar-default-char-variable 18 or FORMATTED = scalar-default-char-variable 19 or ID = scalar-int-variable 20 or IOMSG = iomsg-variable 21 or IOSTAT = scalar-int-variable 22 or NAME = scalar-default-char-variable 23 or NAMED = scalar-default-logical-variable 24 or NEXTREC = scalar-int-variable 25 or NUMBER = scalar-int-variable 26 or OPENED = scalar-default-logical-variable 27 or PAD = scalar-default-char-variable 28 or PENDING = scalar-default-logical-variable 29 or POS = scalar-int-variable 30 or POSITION = scalar-default-char-variable 31 or READ = scalar-default-char-variable 32 or READWRITE = scalar-default-char-variable 33 or RECL = scalar-int-variable 34 or ROUND = scalar-default-char-variable 35 or SEQUENTIAL = scalar-default-char-variable 36 or SIGN = scalar-default-char-variable 37 or SIZE = scalar-int-variable 38 or STREAM = scalar-default-char-variable 39 or UNFORMATTED = scalar-default-char-variable 40 or WRITE = scalar-default-char-variable 41 C946 (R930) No specifier shall appear more than once in a given inquire-spec-list. 42 C947 (R930) An inquire-spec-list shall contain one FILE= specifier or one UNIT= specifier, but not 208 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 both. 2 C948 (R930) In the inquire by unit form of the INQUIRE statement, if the optional characters UNIT= 3 are omitted, the file-unit-number shall be the first item in the inquire-spec-list. 4 C949 (R930) If an ID= specifier appears, a PENDING= specifier shall also appear. 5 The value of file-unit-number shall be nonnegative or equal to one of the named constants INPUT UNIT, 6 OUTPUT UNIT, or ERROR UNIT of the ISO FORTRAN ENV intrinsic module (13.8.3.1). 7 When a returned value of a specifier other than the NAME= specifier is of type character, the value 8 returned is in upper case. 9 If an error condition occurs during execution of an INQUIRE statement, all of the inquiry specifier 10 variables become undefined, except for variables in the IOSTAT= and IOMSG= specifiers (if any). 11 The IOSTAT=, ERR=, and IOMSG= specifiers are described in 9.10. 12 9.9.1.1 FILE= specifier in the INQUIRE statement 13 The value of the file-name-expr in the FILE= specifier specifies the name of the file being inquired about. 14 The named file need not exist or be connected to a unit. The value of the file-name-expr shall be of a 15 form acceptable to the processor as a file name. Any trailing blanks are ignored. The interpretation of 16 case is processor dependent. 17 9.9.1.2 ACCESS= specifier in the INQUIRE statement 18 The scalar-default-char-variable in the ACCESS= specifier is assigned the value SEQUENTIAL if the 19 file is connected for sequential access, DIRECT if the file is connected for direct access, or STREAM if 20 the file is connected for stream access. If there is no connection, it is assigned the value UNDEFINED. 21 9.9.1.3 ACTION= specifier in the INQUIRE statement 22 The scalar-default-char-variable in the ACTION= specifier is assigned the value READ if the file is 23 connected for input only, WRITE if the file is connected for output only, and READWRITE if it 24 is connected for both input and output. If there is no connection, the scalar-default-char-variable is 25 assigned the value UNDEFINED. 26 9.9.1.4 ASYNCHRONOUS= specifier in the INQUIRE statement 27 The scalar-default-char-variable in the ASYNCHRONOUS= specifier is assigned the value YES if the 28 file is connected and asynchronous input/output on the unit is allowed; it is assigned the value NO if the 29 file is connected and asynchronous input/output on the unit is not allowed. If there is no connection, 30 the scalar-default-char-variable is assigned the value UNDEFINED. 31 9.9.1.5 BLANK= specifier in the INQUIRE statement 32 The scalar-default-char-variable in the BLANK= specifier is assigned the value ZERO or NULL, corre- 33 sponding to the blank interpretation mode in effect for a connection for formatted input/output. If there 34 is no connection, or if the connection is not for formatted input/output, the scalar-default-char-variable 35 is assigned the value UNDEFINED. 36 9.9.1.6 DECIMAL= specifier in the INQUIRE statement 37 The scalar-default-char-variable in the DECIMAL= specifier is assigned the value COMMA or POINT, 38 corresponding to the decimal edit mode in effect for a connection for formatted input/output. If there SEP 2002 COMMITTEE DRAFT 209 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 is no connection, or if the connection is not for formatted input/output, the scalar-default-char-variable 2 is assigned the value UNDEFINED. 3 9.9.1.7 DELIM= specifier in the INQUIRE statement 4 The scalar-default-char-variable in the DELIM= specifier is assigned the value APOSTROPHE, QUOTE, 5 or NONE, corresponding to the delimiter mode in effect for a connection for formatted input/output. 6 If there is no connection or if the connection is not for formatted input/output, the scalar-default-char- 7 variable is assigned the value UNDEFINED. 8 9.9.1.8 DIRECT= specifier in the INQUIRE statement 9 The scalar-default-char-variable in the DIRECT= specifier is assigned the value YES if DIRECT is 10 included in the set of allowed access methods for the file, NO if DIRECT is not included in the set of 11 allowed access methods for the file, and UNKNOWN if the processor is unable to determine whether or 12 not DIRECT is included in the set of allowed access methods for the file. 13 9.9.1.9 EXIST= specifier in the INQUIRE statement 14 Execution of an INQUIRE by file statement causes the scalar-default-logical-variable in the EXIST= 15 specifier to be assigned the value true if there exists a file with the specified name; otherwise, false is 16 assigned. Execution of an INQUIRE by unit statement causes true to be assigned if the specified unit 17 exists; otherwise, false is assigned. 18 9.9.1.10 FORM= specifier in the INQUIRE statement 19 The scalar-default-char-variable in the FORM= specifier is assigned the value FORMATTED if the 20 file is connected for formatted input/output, and is assigned the value UNFORMATTED if the file is 21 connected for unformatted input/output. If there is no connection, it is assigned the value UNDEFINED. 22 9.9.1.11 FORMATTED= specifier in the INQUIRE statement 23 The scalar-default-char-variable in the FORMATTED= specifier is assigned the value YES if FORMAT- 24 TED is included in the set of allowed forms for the file, NO if FORMATTED is not included in the set 25 of allowed forms for the file, and UNKNOWN if the processor is unable to determine whether or not 26 FORMATTED is included in the set of allowed forms for the file. 27 9.9.1.12 ID= specifier in the INQUIRE statement 28 The value of the variable specified in the ID= specifier shall be the identifier of a pending data transfer 29 operation for the specified unit. This specifier interacts with the PENDING= specifier (9.9.1.19). 30 9.9.1.13 NAME= specifier in the INQUIRE statement 31 The scalar-default-char-variable in the NAME= specifier is assigned the value of the name of the file if 32 the file has a name; otherwise, it becomes undefined. NOTE 9.61 If this specifier appears in an INQUIRE by file statement, its value is not necessarily the same as the name given in the FILE= specifier. However, the value returned shall be suitable for use as the value of the file-name-expr in the FILE= specifier in an OPEN statement. The processor may return a file name qualified by a user identification, device, directory, or other relevant information. 210 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 The case of the characters assigned to scalar-default-char-variable is processor dependent. 2 9.9.1.14 NAMED= specifier in the INQUIRE statement 3 The scalar-default-logical-variable in the NAMED= specifier is assigned the value true if the file has a 4 name; otherwise, it is assigned the value false. 5 9.9.1.15 NEXTREC= specifier in the INQUIRE statement 6 The scalar-int-variable in the NEXTREC= specifier is assigned the value n + 1, where n is the record 7 number of the last record read from or written to the file connected for direct access. If the file is con- 8 nected but no records have been read or written since the connection, the scalar-int-variable is assigned 9 the value 1. If the file is not connected for direct access or if the position of the file is indeterminate 10 because of a previous error condition, the scalar-int-variable becomes undefined. If there are pending 11 data transfer operations for the specified unit, the value assigned is computed as if all the pending data 12 transfers had already completed. 13 9.9.1.16 NUMBER= specifier in the INQUIRE statement 14 The scalar-int-variable in the NUMBER= specifier is assigned the value of the external unit number of 15 the unit that is connected to the file. If there is no unit connected to the file, the value ­1 is assigned. 16 9.9.1.17 OPENED= specifier in the INQUIRE statement 17 Execution of an INQUIRE by file statement causes the scalar-default-logical-variable in the OPENED= 18 specifier to be assigned the value true if the file specified is connected to a unit; otherwise, false is 19 assigned. Execution of an INQUIRE by unit statement causes the scalar-default-logical-variable to be 20 assigned the value true if the specified unit is connected to a file; otherwise, false is assigned. 21 9.9.1.18 PAD= specifier in the INQUIRE statement 22 The scalar-default-char-variable in the PAD= specifier is assigned the value YES or NO, corresponding 23 to the pad mode in effect for a connection for formatted input/output. If there is no connection or if 24 the connection is not for formatted input/output, the scalar-default-char-variable is assigned the value 25 UNDEFINED. 26 9.9.1.19 PENDING= specifier in the INQUIRE statement 27 The PENDING= specifier is used to determine whether or not previously pending asynchronous data 28 transfers are complete. A data transfer operation is previously pending if it is pending at the beginning 29 of execution of the INQUIRE statement. 30 The value of the variable specified in the ID= specifier (9.9.1.12) shall be the identifier of a pending 31 data transfer operation for the specified unit. If an ID= specifier appears and the specified data transfer 32 operation is complete, then the variable specified in the PENDING= specifier is assigned the value false 33 and the INQUIRE statement performs the wait operation for the specified data transfer. 34 If the ID= specifier is omitted and all previously pending data transfer operations for the specified unit 35 are complete, then the variable specified in the PENDING= specifier is assigned the value false and the 36 INQUIRE statement performs wait operations for all previously pending data transfers for the specified 37 unit. 38 In all other cases, the variable specified in the PENDING= specifier is assigned the value true and no 39 wait operations are performed; in this case the previously pending data transfers remain pending after 40 the execution of the INQUIRE statement. SEP 2002 COMMITTEE DRAFT 211 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 9.62 The processor has considerable flexibility in defining when it considers a transfer to be complete. Any of the following approaches could be used: (1) The INQUIRE statement could consider an asynchronous data transfer to be incom- plete until after the corresponding wait operation. In this case PENDING= would always return true unless there were no previously pending data transfers for the unit. (2) The INQUIRE statement could wait for all specified data transfers to complete and then always return false for PENDING=. (3) The INQUIRE statement could actually test the state of the specified data transfer operations. 1 9.9.1.20 POS= specifier in the INQUIRE statement 2 The scalar-int-variable in the POS= specifier is assigned the number of the file storage unit immediately 3 following the current position of a file connected for stream access. If the file is positioned at its terminal 4 position, the variable is assigned a value one greater than the number of the highest-numbered file storage 5 unit in the file. If the file is not connected for stream access or if the position of the file is indeterminate 6 because of previous error conditions, the variable becomes undefined. 7 9.9.1.21 POSITION= specifier in the INQUIRE statement 8 The scalar-default-char-variable in the POSITION= specifier is assigned the value REWIND if the file 9 is connected by an OPEN statement for positioning at its initial point, APPEND if the file is connected 10 for positioning before its endfile record or at its terminal point, and ASIS if the file is connected without 11 changing its position. If there is no connection or if the file is connected for direct access, the scalar- 12 default-char-variable is assigned the value UNDEFINED. If the file has been repositioned since the 13 connection, the scalar-default-char-variable is assigned a processor-dependent value, which shall not be 14 REWIND unless the file is positioned at its initial point and shall not be APPEND unless the file is 15 positioned so that its endfile record is the next record or at its terminal point if it has no endfile record. 16 9.9.1.22 READ= specifier in the INQUIRE statement 17 The scalar-default-char-variable in the READ= specifier is assigned the value YES if READ is included 18 in the set of allowed actions for the file, NO if READ is not included in the set of allowed actions for 19 the file, and UNKNOWN if the processor is unable to determine whether or not READ is included in 20 the set of allowed actions for the file. 21 9.9.1.23 READWRITE= specifier in the INQUIRE statement 22 The scalar-default-char-variable in the READWRITE= specifier is assigned the value YES if READ- 23 WRITE is included in the set of allowed actions for the file, NO if READWRITE is not included in the 24 set of allowed actions for the file, and UNKNOWN if the processor is unable to determine whether or 25 not READWRITE is included in the set of allowed actions for the file. 26 9.9.1.24 RECL= specifier in the INQUIRE statement 27 The scalar-int-variable in the RECL= specifier is assigned the value of the record length of a file con- 28 nected for direct access, or the value of the maximum record length for a file connected for sequential 29 access. If the file is connected for formatted input/output, the length is the number of characters for all 30 records that contain only characters of type default character. If the file is connected for unformatted 31 input/output, the length is measured in file storage units. If there is no connection, or if the connection 32 is for stream access, the scalar-int-variable becomes undefined. 212 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 9.9.1.25 ROUND= specifier in the INQUIRE statement 2 The scalar-default-char-variable in the ROUND= specifier is assigned the value UP, DOWN, ZERO, 3 NEAREST, COMPATIBLE, or PROCESSOR DEFINED, corresponding to the I/O rounding mode in 4 effect for a connection for formatted input/output. If there is no connection or if the connection is not 5 for formatted input/output, the scalar-default-char-variable is assigned the value UNDEFINED. The 6 processor shall return the value PROCESSOR DEFINED only if the I/O rounding mode currently in 7 effect behaves differently than the UP, DOWN, ZERO, NEAREST, and COMPATIBLE modes. 8 9.9.1.26 SEQUENTIAL= specifier in the INQUIRE statement 9 The scalar-default-char-variable in the SEQUENTIAL= specifier is assigned the value YES if SEQUEN- 10 TIAL is included in the set of allowed access methods for the file, NO if SEQUENTIAL is not included 11 in the set of allowed access methods for the file, and UNKNOWN if the processor is unable to determine 12 whether or not SEQUENTIAL is included in the set of allowed access methods for the file. 13 9.9.1.27 SIGN= specifier in the INQUIRE statement 14 The scalar-default-char-variable in the SIGN= specifier is assigned the value PLUS, SUPPRESS, or 15 PROCESSOR DEFINED, corresponding to the sign mode in effect for a connection for formatted in- 16 put/output. If there is no connection, or if the connection is not for formatted input/output, the 17 scalar-default-char-variable is assigned the value UNDEFINED. 18 9.9.1.28 SIZE= specifier in the INQUIRE statement 19 The scalar-int-variable in the SIZE= specifier is assigned the size of the file in file storage units. If the 20 file size cannot be determined, the variable is assigned the value -1. 21 For a file that may be connected for stream access, the file size is the number of the highest-numbered 22 file storage unit in the file. 23 For a file that may be connected for sequential or direct access, the file size may be different from the 24 number of storage units implied by the data in the records; the exact relationship is processor-dependent. 25 9.9.1.29 STREAM= specifier in the INQUIRE statement 26 The scalar-default-char-variable in the STREAM= specifier is assigned the value YES if STREAM is 27 included in the set of allowed access methods for the file, NO if STREAM is not included in the set of 28 allowed access methods for the file, and UNKNOWN if the processor is unable to determine whether or 29 not STREAM is included in the set of allowed access methods for the file. 30 9.9.1.30 UNFORMATTED= specifier in the INQUIRE statement 31 The scalar-default-char-variable in the UNFORMATTED= specifier is assigned the value YES if UN- 32 FORMATTED is included in the set of allowed forms for the file, NO if UNFORMATTED is not included 33 in the set of allowed forms for the file, and UNKNOWN if the processor is unable to determine whether 34 or not UNFORMATTED is included in the set of allowed forms for the file. 35 9.9.1.31 WRITE= specifier in the INQUIRE statement 36 The scalar-default-char-variable in the WRITE= specifier is assigned the value YES if WRITE is included 37 in the set of allowed actions for the file, NO if WRITE is not included in the set of allowed actions for 38 the file, and UNKNOWN if the processor is unable to determine whether or not WRITE is included in 39 the set of allowed actions for the file. SEP 2002 COMMITTEE DRAFT 213 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 9.9.2 Restrictions on inquiry specifiers 2 The inquire-spec-list in an INQUIRE by file statement shall contain exactly one FILE= specifier and 3 shall not contain a UNIT= specifier. The inquire-spec-list in an INQUIRE by unit statement shall 4 contain exactly one UNIT= specifier and shall not contain a FILE= specifier. The unit specified need 5 not exist or be connected to a file. If it is connected to a file, the inquiry is being made about the 6 connection and about the file connected. 7 9.9.3 Inquire by output list 8 The inquire by output list form of the INQUIRE statement has only an IOLENGTH= specifier and an 9 output list. 10 The scalar-int-variable in the IOLENGTH= specifier is assigned the processor-dependent number of file 11 storage units that would be required to store the data of the output list in an unformatted file. The 12 value shall be suitable as a RECL= specifier in an OPEN statement that connects a file for unformatted 13 direct access when there are input/output statements with the same input/output list. 14 The output list in an INQUIRE statement shall not contain any derived-type list items that require a 15 user-defined derived-type input/output procedure as described in section 9.5.2. If a derived-type list item 16 appears in the output list, the value returned for the IOLENGTH specifier assumes that no user-defined 17 derived-type input/output procedure will be invoked. 18 9.10 Error, end-of-record, and end-of-file conditions 19 The set of input/output error conditions is processor dependent. 20 An end-of-record condition occurs when a nonadvancing input statement attempts to transfer data 21 from a position beyond the end of the current record, unless the file is a stream file and the current 22 record is at the end of the file (an end-of-file condition occurs instead). 23 An end-of-file condition occurs in the following cases: 24 (1) When an endfile record is encountered during the reading of a file connected for sequential 25 access. 26 (2) When an attempt is made to read a record beyond the end of an internal file. 27 (3) When an attempt is made to read beyond the end of a stream file. 28 An end-of-file condition may occur at the beginning of execution of an input statement. An end-of-file 29 condition also may occur during execution of a formatted input statement when more than one record 30 is required by the interaction of the input list and the format. An end-of-file condition also may occur 31 during execution of a stream input statement. 32 9.10.1 Error conditions and the ERR= specifier 33 If an error condition occurs during execution of an input/output statement, the position of the file 34 becomes indeterminate. 35 If an error condition occurs during execution of an input/output statement that contains neither an 36 ERR= nor IOSTAT= specifier, execution of the program is terminated. If an error condition occurs 37 during execution of an input/output statement that contains either an ERR= specifier or an IOSTAT= 38 specifier then 39 (1) Processing of the input/output list, if any, terminates, 214 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 (2) If the statement is a data transfer statement or the error occurs during a wait operation, 2 all implied DO variables in the statement that initiated the transfer become undefined, 3 (3) If an IOSTAT= specifier appears, the scalar-int-variable in the IOSTAT= specifier becomes 4 defined as specified in 9.10.4, 5 (4) If an IOMSG= specifier appears, the iomsg-variable becomes defined as specified in 9.10.5, 6 (5) If the statement is a READ statement and it contains a SIZE= specifier, the scalar-int- 7 variable in the SIZE= specifier becomes defined as specified in 9.5.1.14, 8 (6) If the statement is a READ statement or the error condition occurs in a wait operation for 9 a transfer initiated by a READ statement, all input items or namelist group objects in the 10 statement that initiated the transfer become undefined, and 11 (7) If an ERR= specifier appears, execution continues with the statement labeled by the label 12 in the ERR= specifier. 13 9.10.2 End-of-file conditions and the END= specifier 14 If an end-of-file condition occurs during execution of an input/output statement that contains neither 15 an END= specifier nor an IOSTAT= specifier, execution of the program is terminated. If an end-of-file 16 condition occurs during execution of an input/output statement that contains either an END= specifier 17 or an IOSTAT= specifier, and an error condition does not occur then 18 (1) Processing of the input list, if any, terminates, 19 (2) If the statement is a data transfer statement or the error occurs during a wait operation, 20 all implied DO variables in the statement that initiated the transfer become undefined, 21 (3) If the statement is a READ statement or the end-of-file condition occurs in a wait operation 22 for a transfer initiated by a READ statement, all input list items or namelist group objects 23 in the statement that initiated the transfer become undefined, 24 (4) If the file specified in the input statement is an external record file, it is positioned after the 25 endfile record, 26 (5) If an IOSTAT= specifier appears, the scalar-int-variable in the IOSTAT= specifier becomes 27 defined as specified in 9.10.4, 28 (6) If an IOMSG= specifier appears, the iomsg-variable becomes defined as specified in 9.10.5, 29 and 30 (7) If an END= specifier appears, execution continues with the statement labeled by the label 31 in the END= specifier. 32 9.10.3 End-of-record conditions and the EOR= specifier 33 If an end-of-record condition occurs during execution of an input/output statement that contains neither 34 an EOR= specifier nor an IOSTAT= specifier, execution of the program is terminated. If an end-of- 35 record condition occurs during execution of an input/output statement that contains either an EOR= 36 specifier or an IOSTAT= specifier, and an error condition does not occur then 37 (1) If the pad mode has the value YES, the record is padded with blanks to satisfy the input 38 list item (9.5.3.4.2) and corresponding data edit descriptor that requires more characters 39 than the record contains. If the pad mode has the value NO, the input list item becomes 40 undefined. 41 (2) Processing of the input list, if any, terminates, 42 (3) If the statement is a data transfer statement or the error occurs during a wait operation, 43 all implied DO variables in the statement that initiated the transfer become undefined, 44 (4) The file specified in the input statement is positioned after the current record, 45 (5) If an IOSTAT= specifier appears, the scalar-int-variable in the IOSTAT= specifier becomes 46 defined as specified in 9.10.4, SEP 2002 COMMITTEE DRAFT 215 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 (6) If an IOMSG= specifier appears, the iomsg-variable becomes defined as specified in 9.10.5, 2 (7) If a SIZE= specifier appears, the scalar-int-variable in the SIZE= specifier becomes defined 3 as specified in (9.5.1.14), and 4 (8) If an EOR= specifier appears, execution continues with the statement labeled by the label 5 in the EOR= specifier. 6 9.10.4 IOSTAT= specifier 7 Execution of an input/output statement containing the IOSTAT= specifier causes the scalar-int-variable 8 in the IOSTAT= specifier to become defined 9 (1) With a zero value if neither an error condition, an end-of-file condition, nor an end-of-record 10 condition occurs, 11 (2) With a processor-dependent positive integer value if an error condition occurs, 12 (3) With the processor-dependent negative integer value of the constant IOSTAT END (13.8.3.2.1) 13 if an end-of-file condition occurs and no error condition occurs, or 14 (4) With a processor-dependent negative integer value of the constant IOSTAT EOR (13.8.3.2.2) 15 if an end-of-record condition occurs and no error condition or end-of-file condition occurs. NOTE 9.63 An end-of-file condition may occur only for sequential or stream input and an end-of-record con- dition may occur only for nonadvancing input. Consider the example: READ (FMT = "(E8.3)", UNIT = 3, IOSTAT = IOSS) X IF (IOSS < 0) THEN ! Perform end-of-file processing on the file connected to unit 3. CALL END_PROCESSING ELSE IF (IOSS > 0) THEN ! Perform error processing CALL ERROR_PROCESSING END IF 16 9.10.5 IOMSG= specifier 17 If an error, end-of-file, or end-of-record condition occurs during execution of an input/output statement, 18 the processor shall assign an explanatory message to iomsg-variable. If no such condition occurs, the 19 processor shall not change the value of iomsg-variable. 20 9.11 Restrictions on input/output statements 21 If a unit, or a file connected to a unit, does not have all of the properties required for the execution of 22 certain input/output statements, those statements shall not refer to the unit. 23 An input/output statement that is executed while another input/output statement is being executed is 24 called a recursive input/output statement. 25 A recursive input/output statement shall not identify an external unit except that a child data transfer 26 statement may identify its parent data transfer statement external unit. 27 An input/output statement shall not cause the value of any established format specification to be 28 modified. 216 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 A recursive input/output statement shall not modify the value of any internal unit except that a recursive 2 WRITE statement may modify the internal unit identified by that recursive WRITE statement. 3 The value of a specifier in an input/output statement shall not depend on any input-item, io-implied- 4 do do-variable, or on the definition or evaluation of any other specifier in the io-control-spec-list or 5 inquire-spec-list in that statement. 6 The value of any subscript or substring bound of a variable that appears in a specifier in an input/output 7 statement shall not depend on any input-item, io-implied-do do-variable, or on the definition or evalua- 8 tion of any other specifier in the io-control-spec-list or inquire-spec-list in that statement. 9 In a data transfer statement, the variable specified in an IOSTAT=, IOMSG=, or SIZE= specifier, if 10 any, shall not be associated with any entity in the data transfer input/output list (9.5.2) or namelist- 11 group-object -list, nor with a do-variable of an io-implied-do in the data transfer input/output list. 12 In a data transfer statement, if a variable specified in an IOSTAT=, IOMSG=, or SIZE= specifier is an 13 array element reference, its subscript values shall not be affected by the data transfer, the io-implied-do 14 processing, or the definition or evaluation of any other specifier in the io-control-spec-list. 15 A variable that may become defined or undefined as a result of its use in a specifier in an INQUIRE 16 statement, or any associated entity, shall not appear in another specifier in the same INQUIRE statement. 17 A STOP statement shall not be executed during execution of an input/output statement. NOTE 9.64 Restrictions on the evaluation of expressions (7.1.8) prohibit certain side effects. SEP 2002 COMMITTEE DRAFT 217 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 218 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 Section 10: Input/output editing 2 A format used in conjunction with an input/output statement provides information that directs the 3 editing between the internal representation of data and the characters of a sequence of formatted records. 4 A FMT= specifier (9.5.1.1) in an input/output statement may refer to a FORMAT statement or to a 5 character expression that contains a format specification. A format specification provides explicit editing 6 information. The FMT= specifier alternatively may be an asterisk (*), which indicates list-directed 7 formatting (10.9). Namelist formatting (10.10) may be indicated by specifying a namelist-group-name 8 instead of a format . 9 10.1 Explicit format specification methods 10 Explicit format specification may be given 11 (1) In a FORMAT statement or 12 (2) In a character expression. 13 10.1.1 FORMAT statement 14 R1001 format-stmt is FORMAT format-specification 15 R1002 format-specification is ( [ format-item-list ] ) 16 C1001 (R1001) The format-stmt shall be labeled. 17 C1002 (R1002) The comma used to separate format-items in a format-item-list may be omitted 18 (1) Between a P edit descriptor and an immediately following F, E, EN, ES, D, or G edit 19 descriptor (10.7.5), 20 (2) Before a slash edit descriptor when the optional repeat specification is not present (10.7.2), 21 (3) After a slash edit descriptor, or 22 (4) Before or after a colon edit descriptor (10.7.3) 23 Blank characters may precede the initial left parenthesis of the format specification. Additional blank 24 characters may appear at any point within the format specification, with no effect on the interpretation 25 of the format specification, except within a character string edit descriptor (10.8). NOTE 10.1 Examples of FORMAT statements are: 5 FORMAT (1PE12.4, I10) 9 FORMAT (I12, /, ' Dates: ', 2 (2I3, I5)) 26 10.1.2 Character format specification 27 A character expression used as a format in a formatted input/output statement shall evaluate to a 28 character string whose leading part is a valid format specification. NOTE 10.2 The format specification begins with a left parenthesis and ends with a right parenthesis. SEP 2002 COMMITTEE DRAFT 219 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 All character positions up to and including the final right parenthesis of the format specification shall be 2 defined at the time the input/output statement is executed, and shall not become redefined or undefined 3 during the execution of the statement. Character positions, if any, following the right parenthesis that 4 ends the format specification need not be defined and may contain any character data with no effect on 5 the interpretation of the format specification. 6 If the format is a character array, it is treated as if all of the elements of the array were specified in array 7 element order and were concatenated. However, if a format is a character array element, the format 8 specification shall be entirely within that array element. NOTE 10.3 If a character constant is used as a format in an input/output statement, care shall be taken that the value of the character constant is a valid format specification. In particular, if a format specification delimited by apostrophes contains a character constant edit descriptor delimited with apostrophes, two apostrophes shall be written to delimit the edit descriptor and four apostrophes shall be written for each apostrophe that occurs within the edit descriptor. For example, the text: 2 ISN'T 3 may be written by various combinations of output statements and format specifications: WRITE (6, 100) 2, 3 100 FORMAT (1X, I1, 1X, 'ISN''T', 1X, I1) WRITE (6, '(1X, I1, 1X, ''ISN''''T'', 1X, I1)') 2, 3 WRITE (6, '(A)') ' 2 ISN''T 3' Doubling of internal apostrophes usually can be avoided by using quotation marks to delimit the format specification and doubling of internal quotation marks usually can be avoided by using apostrophes as delimiters. 9 10.2 Form of a format item list 10 R1003 format-item is [ r ] data-edit-desc 11 or control-edit-desc 12 or char-string-edit-desc 13 or [ r ] ( format-item-list ) 14 R1004 r is int-literal-constant 15 C1003 (R1004) r shall be positive. 16 C1004 (R1004) r shall not have a kind parameter specified for it. 17 The integer literal constant r is called a repeat specification. 18 10.2.1 Edit descriptors 19 An edit descriptor is a data edit descriptor, a control edit descriptor, or a character string 20 edit descriptor. 21 R1005 data-edit-desc is I w [ . m ] 22 or B w [ . m ] 23 or O w [ . m ] 24 or Z w [ . m ] 25 or F w . d 220 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 or E w . d [ E e ] 2 or EN w . d [ E e ] 3 or ES w . d [ E e ] 4 or G w . d [ E e ] 5 or L w 6 or A [ w ] 7 or D w . d 8 or DT [ char-literal-constant ] [ ( v -list ) ] 9 R1006 w is int-literal-constant 10 R1007 m is int-literal-constant 11 R1008 d is int-literal-constant 12 R1009 e is int-literal-constant 13 R1010 v is signed-int-literal-constant 14 C1005 (R1009) e shall be positive. 15 C1006 (R1006) w shall be zero or positive for the I, B, O, Z, and F edit descriptors. w shall be positive 16 for all other edit descriptors. 17 C1007 (R1005) w , m, d , e, and v shall not have kind parameters specified for them. 18 C1008 (R1005) The char-literal-constant in the DT edit descriptor shall not have a kind parameter 19 specified for it. 20 I, B, O, Z, F, E, EN, ES, G, L, A, D, and DT indicate the manner of editing. 21 R1011 control-edit-desc is position-edit-desc 22 or [ r ] / 23 or : 24 or sign-edit-desc 25 or k P 26 or blank-interp-edit-desc 27 or round-edit-desc 28 or decimal-edit-desc 29 R1012 k is signed-int-literal-constant 30 C1009 (R1012) k shall not have a kind parameter specified for it. 31 In k P, k is called the scale factor. 32 R1013 position-edit-desc is T n 33 or TL n 34 or TR n 35 or n X 36 R1014 n is int-literal-constant 37 C1010 (R1014) n shall be positive. 38 C1011 (R1014) n shall not have a kind parameter specified for it. 39 R1015 sign-edit-desc is SS 40 or SP 41 or S 42 R1016 blank-interp-edit-desc is BN 43 or BZ 44 R1017 round-edit-desc is RU 45 or RD SEP 2002 COMMITTEE DRAFT 221 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 or RZ 2 or RN 3 or RC 4 or RP 5 R1018 decimal-edit-desc is DC 6 or DP 7 T, TL, TR, X, slash, colon, SS, SP, S, P, BN, BZ, RU, RD, RZ, RN, RC, RP, DC, and DP indicate the 8 manner of editing. 9 R1019 char-string-edit-desc is char-literal-constant 10 C1012 (R1019) The char-literal-constant shall not have a kind parameter specified for it. 11 Each rep-char in a character string edit descriptor shall be one of the characters capable of representation 12 by the processor. 13 The character string edit descriptors provide constant data to be output, and are not valid for input. 14 The edit descriptors are without regard to case except for the characters in the character constants. 15 10.2.2 Fields 16 A field is a part of a record that is read on input or written on output when format control encounters 17 a data edit descriptor or a character string edit descriptor. The field width is the size in characters of 18 the field. 19 10.3 Interaction between input/output list and format 20 The start of formatted data transfer using a format specification initiates format control (9.5.3.4.2). 21 Each action of format control depends on information jointly provided by 22 (1) The next edit descriptor in the format specification and 23 (2) The next effective item in the input/output list, if one exists. 24 If an input/output list specifies at least one effective list item, at least one data edit descriptor shall 25 exist in the format specification. NOTE 10.4 An empty format specification of the form ( ) may be used only if the input/output list has no effective list items (9.5.3.4). Zero length character items are effective list items, but zero sized arrays and implied-DO lists with an iteration count of zero are not. 26 A format specification is interpreted from left to right. The exceptions are format items preceded by a 27 repeat specification r , and format reversion (described below). 28 A format item preceded by a repeat specification is processed as a list of r items, each identical to the 29 format item but without the repeat specification and separated by commas. NOTE 10.5 An omitted repeat specification is treated in the same way as a repeat specification whose value is one. 30 To each data edit descriptor interpreted in a format specification, there corresponds one effective item 31 specified by the input/output list (9.5.2), except that an input/output list item of type complex requires 222 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 the interpretation of two F, E, EN, ES, D, or G edit descriptors. For each control edit descriptor or 2 character edit descriptor, there is no corresponding item specified by the input/output list, and format 3 control communicates information directly with the record. 4 Whenever format control encounters a data edit descriptor in a format specification, it determines 5 whether there is a corresponding effective item specified by the input/output list. If there is such an 6 item, it transmits appropriately edited information between the item and the record, and then format 7 control proceeds. If there is no such item, format control terminates. 8 If format control encounters a colon edit descriptor in a format specification and another effective in- 9 put/output list item is not specified, format control terminates. 10 If format control encounters the rightmost parenthesis of a complete format specification and another 11 effective input/output list item is not specified, format control terminates. However, if another effective 12 input/output list item is specified, the file is positioned in a manner identical to the way it is positioned 13 when a slash edit descriptor is processed (10.7.2). Format control then reverts to the beginning of the 14 format item terminated by the last preceding right parenthesis that is not part of a DT edit descriptor. 15 If there is no such preceding right parenthesis, format control reverts to the first left parenthesis of the 16 format specification. If any reversion occurs, the reused portion of the format specification shall contain 17 at least one data edit descriptor. If format control reverts to a parenthesis that is preceded by a repeat 18 specification, the repeat specification is reused. Reversion of format control, of itself, has no effect on 19 the changeable modes (9.4.1). NOTE 10.6 Example: The format specification: 10 FORMAT (1X, 2(F10.3, I5)) with an output list of WRITE (10,10) 10.1, 3, 4.7, 1, 12.4, 5, 5.2, 6 produces the same output as the format specification: 10 FORMAT (1X, F10.3, I5, F10.3, I5/F10.3, I5, F10.3, I5) 20 10.4 Positioning by format control 21 After each data edit descriptor or character string edit descriptor is processed, the file is positioned after 22 the last character read or written in the current record. 23 After each T, TL, TR, or X edit descriptor is processed, the file is positioned as described in 10.7.1. 24 After each slash edit descriptor is processed, the file is positioned as described in 10.7.2. 25 During formatted stream output, processing of an A edit descriptor may cause file positioning to occur 26 (10.6.3). 27 If format control reverts as described in 10.3, the file is positioned in a manner identical to the way it is 28 positioned when a slash edit descriptor is processed (10.7.2). 29 During a read operation, any unprocessed characters of the current record are skipped whenever the 30 next record is read. SEP 2002 COMMITTEE DRAFT 223 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 10.5 Decimal symbol 2 The decimal symbol is the character that separates the whole and fractional parts in the decimal 3 representation of a real number in an internal or external file. When the decimal edit mode is POINT, 4 the decimal symbol is a decimal point. When the decimal edit mode is COMMA, the decimal symbol is 5 a comma. 6 10.6 Data edit descriptors 7 Data edit descriptors cause the conversion of data to or from its internal representation; during formatted 8 stream output, the A data edit descriptor may also cause file positioning. Characters in the record shall 9 be of default kind if they correspond to the value of a numeric, logical, or default character data entity, 10 and shall be of nondefault kind if they correspond to the value of a data entity of nondefault character 11 type. Characters transmitted to a record as a result of processing a character string edit descriptor 12 shall be of default kind. On input, the specified variable becomes defined unless an error condition, 13 an end-of-file condition, or an end-of-record condition occurs. On output, the specified expression is 14 evaluated. 15 10.6.1 Numeric editing 16 The I, B, O, Z, F, E, EN, ES, D, and G edit descriptors may be used to specify the input/output of 17 integer, real, and complex data. The following general rules apply: 18 (1) On input, leading blanks are not significant. The interpretation of blanks, other than leading 19 blanks, is determined by the blank interpretation mode (10.7.6). Plus signs may be omitted. 20 A field containing only blanks is considered to be zero. 21 (2) On input, with F, E, EN, ES, D, and G editing, a decimal symbol appearing in the input 22 field overrides the portion of an edit descriptor that specifies the decimal symbol location. 23 The input field may have more digits than the processor uses to approximate the value of 24 the datum. 25 (3) On output with I, F, E, EN, ES, D, and G editing, the representation of a positive or zero 26 internal value in the field may be prefixed with a plus sign, as controlled by the S, SP, and 27 SS edit descriptors or the processor. The representation of a negative internal value in the 28 field shall be prefixed with a minus sign. 29 (4) On output, the representation is right-justified in the field. If the number of characters 30 produced by the editing is smaller than the field width, leading blanks are inserted in the 31 field. 32 (5) On output, if the number of characters produced exceeds the field width or if an exponent 33 exceeds its specified length using the Ew.d Ee, ENw.d Ee, ESw.d Ee, or Gw.d Ee edit 34 descriptor, the processor shall fill the entire field of width w with asterisks. However, 35 the processor shall not produce asterisks if the field width is not exceeded when optional 36 characters are omitted. NOTE 10.7 When an SP edit descriptor is in effect, a plus sign is not optional. 37 (6) On output, with I, B, O, Z, and F editing, the specified value of the field width w may be 38 zero. In such cases, the processor selects the smallest positive actual field width that does 39 not result in a field filled with asterisks. The specified value of w shall not be zero on input. 40 10.6.1.1 Integer editing 41 The Iw, Iw.m, Bw, Bw.m, Ow, Ow.m, Zw, and Zw.m edit descriptors indicate that the field to be edited 42 occupies w positions, except when w is zero. When w is zero, the processor selects the field width. On 224 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 input, w shall not be zero. The specified input/output list item shall be of type integer. The G edit 2 descriptor also may be used to edit integer data (10.6.4.1.1). 3 On input, m has no effect. 4 In the input field for the I edit descriptor, the character string shall be a signed-digit-string (R405), 5 except for the interpretation of blanks. For the B, O, and Z edit descriptors, the character string shall 6 consist of binary, octal, or hexadecimal digits (as in R409, R410, R411) in the respective input field. The 7 lower-case hexadecimal digits a through f in a hexadecimal input field are equivalent to the corresponding 8 upper-case hexadecimal digits. 9 The output field for the Iw edit descriptor consists of zero or more leading blanks followed by a minus 10 sign if the value of the internal datum is negative, or an optional plus sign otherwise, followed by the 11 magnitude of the internal value as a digit-string without leading zeros. NOTE 10.8 A digit-string always consists of at least one digit. 12 The output field for the Bw, Ow, and Zw descriptors consists of zero or more leading blanks followed by 13 the internal value in a form identical to the digits of a binary, octal, or hexadecimal constant, respectively, 14 with the same value and without leading zeros. NOTE 10.9 A binary, octal, or hexadecimal constant always consists of at least one digit. 15 The output field for the Iw.m, Bw.m, Ow.m, and Zw.m edit descriptor is the same as for the Iw, Bw, 16 Ow, and Zw edit descriptor, respectively, except that the digit-string consists of at least m digits. If 17 necessary, sufficient leading zeros are included to achieve the minimum of m digits. The value of m shall 18 not exceed the value of w , except when w is zero. If m is zero and the value of the internal datum is 19 zero, the output field consists of only blank characters, regardless of the sign control in effect. When m 20 and w are both zero, and the value of the internal datum is zero, one blank character is produced. 21 10.6.1.2 Real and complex editing 22 The F, E, EN, ES, and D edit descriptors specify the editing of real and complex data. An input/output 23 list item corresponding to an F, E, EN, ES, or D edit descriptor shall be real or complex. The G edit 24 descriptor also may be used to edit real and complex data (10.6.4.1.2). 25 A lower-case letter is equivalent to the corresponding upper-case letter in the exponent in a numeric 26 input field. 27 10.6.1.2.1 F editing 28 The Fw.d edit descriptor indicates that the field occupies w positions, the fractional part of which 29 consists of d digits. When w is zero, the processor selects the field width. On input, w shall not be zero. 30 The input field consists of an optional sign, followed by a string of one or more digits optionally containing 31 a decimal symbol, including any blanks interpreted as zeros. The d has no effect on input if the input 32 field contains a decimal symbol. If the decimal symbol is omitted, the rightmost d digits of the string, 33 with leading zeros assumed if necessary, are interpreted as the fractional part of the value represented. 34 The string of digits may contain more digits than a processor uses to approximate the value. The basic 35 form may be followed by an exponent of one of the following forms: 36 (1) A sign followed by a digit-string 37 (2) E followed by zero or more blanks, followed by a signed-digit-string SEP 2002 COMMITTEE DRAFT 225 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 (3) D followed by zero or more blanks, followed by a signed-digit-string 2 An exponent containing a D is processed identically to an exponent containing an E. NOTE 10.10 If the input field does not contain an exponent, the effect is as if the basic form were followed by an exponent with a value of -k, where k is the established scale factor (10.7.5). 3 The output field consists of blanks, if necessary, followed by a minus sign if the internal value is negative, 4 or an optional plus sign otherwise, followed by a string of digits that contains a decimal symbol and 5 represents the magnitude of the internal value, as modified by the established scale factor and rounded 6 to d fractional digits. Leading zeros are not permitted except for an optional zero immediately to the 7 left of the decimal symbol if the magnitude of the value in the output field is less than one. The optional 8 zero shall appear if there would otherwise be no digits in the output field. 9 10.6.1.2.2 E and D editing 10 The Ew.d, Dw.d, and Ew.d Ee edit descriptors indicate that the external field occupies w positions, the 11 fractional part of which consists of d digits, unless a scale factor greater than one is in effect, and the 12 exponent part consists of e digits. The e has no effect on input. 13 The form and interpretation of the input field is the same as for Fw.d editing (10.6.1.2.1). 14 The form of the output field for a scale factor of zero is: 15 [ ± ] [0].x1x2 . . . xdexp 16 where: 17 ± signifies a plus sign or a minus sign. 18 . signifies a decimal symbol (10.5). 19 x1x2 . . . xd are the d most significant digits of the datum value after rounding. 20 exp is a decimal exponent having one of the following forms: Edit Absolute Value Form of Descriptor of Exponent Exponent Ew.d |exp| 99 E±z1z2 or ±0z1z2 99 < |exp| 999 ±z1z2z3 Ew.d Ee |exp| 10e - 1 E±z1z2 . . . ze Dw.d |exp| 99 D±z1z2 or E±z1z2 or ±0z1z2 99 < |exp| 999 ±z1z2z3 21 where each z is a digit. 22 The sign in the exponent is produced. A plus sign is produced if the exponent value is zero. The edit 23 descriptor forms Ew.d and Dw.d shall not be used if |exp| > 999. 24 The scale factor k controls the decimal normalization (10.2.1, 10.7.5). If -d < k 0, the output field 25 contains exactly |k| leading zeros and d - |k| significant digits after the decimal symbol. If 0 < k < d + 2, 26 the output field contains exactly k significant digits to the left of the decimal symbol and d - k + 1 27 significant digits to the right of the decimal symbol. Other values of k are not permitted. 226 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 10.6.1.2.3 EN editing 2 The EN edit descriptor produces an output field in the form of a real number in engineering notation 3 such that the decimal exponent is divisible by three and the absolute value of the significand (R415) is 4 greater than or equal to 1 and less than 1000, except when the output value is zero. The scale factor 5 has no effect on output. 6 The forms of the edit descriptor are ENw.d and ENw.d Ee indicating that the external field occupies w 7 positions, the fractional part of which consists of d digits and the exponent part consists of e digits. 8 The form and interpretation of the input field is the same as for Fw.d editing (10.6.1.2.1). 9 The form of the output field is: 10 [ ± ] yyy . x1x2 . . . xdexp 11 where: 12 ± signifies a plus sign or a minus sign. 13 yyy are the 1 to 3 decimal digits representative of the most significant digits of the value 14 of the datum after rounding (yyy is an integer such that 1 yyy < 1000 or, if the output 15 value is zero, yyy = 0). 16 . signifies a decimal symbol (10.5). 17 x1x2 . . . xd are the d next most significant digits of the value of the datum after rounding. 18 exp is a decimal exponent, divisible by three, of one of the following forms: Edit Absolute Value Form of Descriptor of Exponent Exponent ENw.d |exp| 99 E±z1z2 or ±0z1z2 99 < |exp| 999 ±z1z2z3 ENw.d Ee |exp| 10e - 1 E±z1z2 . . . ze 19 where each z is a digit. 20 The sign in the exponent is produced. A plus sign is produced if the exponent value is zero. The edit 21 descriptor form ENw.d shall not be used if |exp| > 999. NOTE 10.11 Examples: Internal Value Output field Using SS, EN12.3 6.421 6.421E+00 ­.5 ­500.000E­03 .00217 2.170E-03 4721.3 4.721E+03 22 10.6.1.2.4 ES editing 23 The ES edit descriptor produces an output field in the form of a real number in scientific notation such 24 that the absolute value of the significand (R415) is greater than or equal to 1 and less than 10, except 25 when the output value is zero. The scale factor has no effect on output. 26 The forms of the edit descriptor are ESw.d and ESw.d Ee indicating that the external field occupies w 27 positions, the fractional part of which consists of d digits and the exponent part consists of e digits. 28 The form and interpretation of the input field is the same as for Fw.d editing (10.6.1.2.1). SEP 2002 COMMITTEE DRAFT 227 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 The form of the output field is: 2 [ ± ] y . x1x2 . . . xdexp 3 where: 4 ± signifies a plus sign or a minus sign. 5 y is a decimal digit representative of the most significant digit of the value of the datum 6 after rounding. 7 . signifies a decimal symbol (10.5). 8 x1x2 . . . xd are the d next most significant digits of the value of the datum after rounding. 9 exp is a decimal exponent having one of the following forms: Edit Absolute Value Form of Descriptor of Exponent Exponent ESw.d |exp| 99 E±z1z2 or ±0z1z2 99 < |exp| 999 ±z1z2z3 ESw.d Ee |exp| 10e - 1 E±z1z2 . . . ze 10 where each z is a digit. 11 The sign in the exponent is produced. A plus sign is produced if the exponent value is zero. The edit 12 descriptor form ESw.d shall not be used if |exp| > 999. NOTE 10.12 Examples: Internal Value Output field Using SS, ES12.3 6.421 6.421E+00 ­.5 ­5.000E­01 .00217 2.170E-03 4721.3 4.721E+03 13 10.6.1.2.5 Complex editing 14 A complex datum consists of a pair of separate real data. The editing of a scalar datum of complex type 15 is specified by two edit descriptors each of which specifies the editing of real data. The first of the edit 16 descriptors specifies the real part; the second specifies the imaginary part. The two edit descriptors may 17 be different. Control and character string edit descriptors may be processed between the edit descriptor 18 for the real part and the edit descriptor for the imaginary part. 19 10.6.1.2.6 Rounding mode 20 The rounding mode can be specified by an OPEN statement (9.4.1), a data transfer input/output 21 statement (9.5.1.12), or an edit descriptor (10.7.7). 22 In what follows, the term "decimal value" means the exact decimal number as given by the character 23 string, while the term "internal value" means the number actually stored (typically in binary form) in 24 the processor. For example, in dealing with the decimal constant 0.1, the decimal value is the exact 25 mathematical quantity 1/10, which has no exact representation on most processors. Formatted output 26 of real data involves conversion from an internal value to a decimal value; formatted input involves 27 conversion from a decimal value to an internal value. 28 When the I/O rounding mode is UP, the value resulting from conversion shall be the smallest repre- 29 sentable value that is greater than or equal to the original value. When the I/O rounding mode is 228 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 DOWN, the value resulting from conversion shall be the largest representable value that is less than or 2 equal to the original value. When the I/O rounding mode is ZERO, the value resulting from conversion 3 shall be the value closest to the original value and no greater in magnitude than the original value. When 4 the I/O rounding mode is NEAREST, the value resulting from conversion shall be the closer of the two 5 nearest representable values if one is closer than the other. If the two nearest representable values are 6 equidistant from the original value, it is processor dependent which one of them is chosen. When the 7 I/O rounding mode is COMPATIBLE, the value resulting from conversion shall be the closer of the 8 two nearest representable values or the value away from zero if halfway between them. When the I/O 9 rounding mode is PROCESSOR DEFINED, rounding during conversion shall be a processor dependent 10 default mode, which may correspond to one of the other modes. 11 On processors that support IEEE rounding on conversions, NEAREST shall correspond to round to 12 nearest, as specified in the IEEE standard. NOTE 10.13 On processors that support IEEE rounding on conversions, the I/O rounding modes COMPATI- BLE and NEAREST will produce the same results except when the datum is halfway between the two representable values. In that case, NEAREST will pick the even value, but COMPATIBLE will pick the value away from zero. The I/O rounding modes UP, DOWN, and ZERO have the same effect as those specified in the IEEE standard for round toward +, round toward -, and round toward 0, respectively. 13 10.6.2 Logical editing 14 The Lw edit descriptor indicates that the field occupies w positions. The specified input/output list 15 item shall be of type logical. The G edit descriptor also may be used to edit logical data (10.6.4.2). 16 The input field consists of optional blanks, optionally followed by a period, followed by a T for true or 17 F for false. The T or F may be followed by additional characters in the field, which are ignored. 18 A lower-case letter is equivalent to the corresponding upper-case letter in a logical input field. NOTE 10.14 The logical constants .TRUE. and .FALSE. are acceptable input forms. 19 The output field consists of w - 1 blanks followed by a T or F, depending on whether the value of the 20 internal datum is true or false, respectively. 21 10.6.3 Character editing 22 The A[w ] edit descriptor is used with an input/output list item of type character. The G edit descriptor 23 also may be used to edit character data (10.6.4.3). The kind type parameter of all characters transferred 24 and converted under control of one A or G edit descriptor is implied by the kind of the corresponding 25 list item. 26 If a field width w is specified with the A edit descriptor, the field consists of w characters. If a field 27 width w is not specified with the A edit descriptor, the number of characters in the field is the length of 28 the corresponding list item, regardless of the value of the kind type parameter. 29 Let len be the length of the input/output list item. If the specified field width w for an A edit descriptor 30 corresponding to an input item is greater than or equal to len, the rightmost len characters will be 31 taken from the input field. If the specified field width w is less than len, the w characters will appear 32 left-justified with len-w trailing blanks in the internal representation. SEP 2002 COMMITTEE DRAFT 229 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 If the specified field width w for an A edit descriptor corresponding to an output item is greater than 2 len, the output field will consist of w - len blanks followed by the len characters from the internal 3 representation. If the specified field width w is less than or equal to len, the output field will consist of 4 the leftmost w characters from the internal representation. NOTE 10.15 For nondefault character types, the blank padding character is processor dependent. 5 If the file is connected for stream access, the output may be split across more than one record if it 6 contains newline characters. A newline character is the character returned by the intrinsic function 7 reference ACHAR(10). Beginning with the first character of the output field, each character that is 8 not a newline is written to the current record in successive positions; each newline character causes file 9 positioning at that point as if by slash editing (the current record is terminated at that point, a new 10 empty record is created following the current record, this new record becomes the last and current record 11 of the file, and the file is positioned at the beginning of this new record). NOTE 10.16 Output field splitting by newline characters can occur only on those processors that can represent the character in position 10 of the ASCII collating sequence. 12 10.6.4 Generalized editing 13 The Gw.d and Gw.d Ee edit descriptors are used with an input/output list item of any intrinsic type. 14 These edit descriptors indicate that the external field occupies w positions, the fractional part of which 15 consists of a maximum of d digits and the exponent part consists of e digits. When these edit descriptors 16 are used to specify the input/output of integer, logical, or character data, d and e have no effect. 17 10.6.4.1 Generalized numeric editing 18 When used to specify the input/output of integer, real, and complex data, the Gw.d and Gw.d Ee edit 19 descriptors follow the general rules for numeric editing (10.6.1). NOTE 10.17 The Gw.d Ee edit descriptor follows any additional rules for the Ew.d Ee edit descriptor. 20 10.6.4.1.1 Generalized integer editing 21 When used to specify the input/output of integer data, the Gw.d and Gw.d Ee edit descriptors follow 22 the rules for the Iw edit descriptor (10.6.1.1), except that w shall not be zero. 23 10.6.4.1.2 Generalized real and complex editing 24 The form and interpretation of the input field is the same as for Fw.d editing (10.6.1.2.1). 25 The method of representation in the output field depends on the magnitude of the datum being edited. 26 Let N be the magnitude of the internal datum and r be the rounded value defined in the table below. 27 If 0 < N < 0.1 - r × 10-d-1 or N 10d - r, or N is identically 0 and d is 0, Gw.d output editing is 28 the same as k PEw.d output editing and Gw.d Ee output editing is the same as k PEw.d Ee output 29 editing, where k is the scale factor (10.7.5) currently in effect. If 0.1 - r × 10-d-1 N < 10d - r or N is 30 identically 0 and d is not zero, the scale factor has no effect, and the value of N determines the editing 31 as follows: Magnitude of Datum Equivalent Conversion N = 0 F(w - n).(d - 1), n('b') 230 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 Magnitude of Datum Equivalent Conversion 0.1 - r × 10-d-1 N < 1 - r × 10-d F(w - n).d, n('b') 1 - r × 10-d N < 10 - r × 10-d+1 F(w - n).(d - 1), n('b') 10 - r × 10-d+1 N < 100 - r × 10-d+2 F(w - n).(d - 2), n('b') · · · · · · 10d-2 - r × 10-2 N < 10d-1 - r × 10-1 F(w - n).1, n('b') 10d-1 - r × 10-1 N < 10d - r F(w - n).0, n('b') 1 where b is a blank, n is 4 for Gw.d and e + 2 for Gw.d Ee, w - n shall be positive, and r is defined for 2 each rounding mode as follows: I/O Rounding Mode r COMPATIBLE 0.5 0.5 if the higher value is even NEAREST -0.5 if the lower value is even UP 1 DOWN 0 1 if datum is negative ZERO 0 if datum is positive NOTE 10.18 The scale factor has no effect on output unless the magnitude of the datum to be edited is outside the range that permits effective use of F editing. 3 10.6.4.2 Generalized logical editing 4 When used to specify the input/output of logical data, the Gw.d and Gw.d Ee edit descriptors follow 5 the rules for the Lw edit descriptor (10.6.2). 6 10.6.4.3 Generalized character editing 7 When used to specify the input/output of character data, the Gw.d and Gw.d Ee edit descriptors follow 8 the rules for the Aw edit descriptor (10.6.3). 9 10.6.5 User-defined derived-type editing 10 The DT edit descriptor allows a user-provided procedure to be used instead of the processor's default 11 input/output formatting for processing a list item of derived type. 12 The DT edit descriptor may include a character literal constant. The character value "DT" concatenated 13 with the character literal constant is passed to the user-defined derived-type input/output procedure as 14 the iotype argument (9.5.3.7). The v values of the edit descriptor are passed to the user-defined 15 derived-type input/output procedure as the v list array argument. NOTE 10.19 For the edit descriptor DT'Link List'(10, 4, 2), iotype is "DTLink List" and v list is (/10, 4, 2/). 16 If a derived-type variable or value corresponds to a DT edit descriptor, there shall be an accessible SEP 2002 COMMITTEE DRAFT 231 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 interface to a corresponding derived-type input/output procedure for that derived type (9.5.3.7). A DT 2 edit descriptor shall not correspond with a list item that is not of a derived type. 3 10.7 Control edit descriptors 4 A control edit descriptor does not cause the transfer of data or the conversion of data to or from internal 5 representation, but may affect the conversions performed by subsequent data edit descriptors. 6 10.7.1 Position editing 7 The T, TL, TR, and X edit descriptors specify the position at which the next character will be transmitted 8 to or from the record. If any character skipped by a T, TL, TR, or X edit descriptor is of type nondefault 9 character, the result of that position editing is processor dependent. 10 The position specified by a T edit descriptor may be in either direction from the current position. On 11 input, this allows portions of a record to be processed more than once, possibly with different editing. 12 The position specified by an X edit descriptor is forward from the current position. On input, a position 13 beyond the last character of the record may be specified if no characters are transmitted from such 14 positions. NOTE 10.20 An nX edit descriptor has the same effect as a TRn edit descriptor. 15 On output, a T, TL, TR, or X edit descriptor does not by itself cause characters to be transmitted and 16 therefore does not by itself affect the length of the record. If characters are transmitted to positions at 17 or after the position specified by a T, TL, TR, or X edit descriptor, positions skipped and not previously 18 filled are filled with blanks. The result is as if the entire record were initially filled with blanks. 19 On output, a character in the record may be replaced. However, a T, TL, TR, or X edit descriptor never 20 directly causes a character already placed in the record to be replaced. Such edit descriptors may result 21 in positioning such that subsequent editing causes a replacement. 22 10.7.1.1 T, TL, and TR editing 23 The left tab limit affects file positioning by the T and TL edit descriptors. Immediately prior to data 24 transfer, the left tab limit becomes defined as the character position of the current record or the current 25 position of the stream file. If, during data transfer, the file is positioned to another record, the left tab 26 limit becomes defined as character position one of that record. 27 The Tn edit descriptor indicates that the transmission of the next character to or from a record is to 28 occur at the nth character position of the record, relative to the left tab limit. 29 The TLn edit descriptor indicates that the transmission of the next character to or from the record is 30 to occur at the character position n characters backward from the current position. However, if n is 31 greater than the difference between the current position and the left tab limit, the TLn edit descriptor 32 indicates that the transmission of the next character to or from the record is to occur at the left tab 33 limit. 34 The TRn edit descriptor indicates that the transmission of the next character to or from the record is 35 to occur at the character position n characters forward from the current position. NOTE 10.21 The n in a Tn, TLn, or TRn edit descriptor shall be specified and shall be greater than zero. 232 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 10.7.1.2 X editing 2 The nX edit descriptor indicates that the transmission of the next character to or from a record is to 3 occur at the position n characters forward from the current position. NOTE 10.22 The n in an nX edit descriptor shall be specified and shall be greater than zero. 4 10.7.2 Slash editing 5 The slash edit descriptor indicates the end of data transfer to or from the current record. 6 On input from a file connected for sequential or stream access, the remaining portion of the current 7 record is skipped and the file is positioned at the beginning of the next record. This record becomes 8 the current record. On output to a file connected for sequential or stream access, a new empty record 9 is created following the current record; this new record then becomes the last and current record of the 10 file and the file is positioned at the beginning of this new record. 11 For a file connected for direct access, the record number is increased by one and the file is positioned 12 at the beginning of the record that has that record number, if there is such a record, and this record 13 becomes the current record. NOTE 10.23 A record that contains no characters may be written on output. If the file is an internal file or a file connected for direct access, the record is filled with blank characters. An entire record may be skipped on input. 14 The repeat specification is optional in the slash edit descriptor. If it is not specified, the default value is 15 one. 16 10.7.3 Colon editing 17 The colon edit descriptor terminates format control if there are no more effective items in the in- 18 put/output list (9.5.2). The colon edit descriptor has no effect if there are more effective items in the 19 input/output list. 20 10.7.4 SS, SP, and S editing 21 The SS, SP, and S edit descriptors temporarily change (9.4.1) the sign mode (9.4.5.13, 9.5.1.13) for the 22 connection. The edit descriptors SS, SP, and S set the sign mode corresponding to the SIGN= specifier 23 values SUPPRESS, PLUS, and PROCESSOR DEFINED, respectively. 24 The sign mode controls optional plus characters in numeric output fields. When the sign mode is PLUS, 25 the processor shall produce a plus sign in any position that normally contains an optional plus sign. 26 When the sign mode is SUPPRESS, the processor shall not produce a plus sign in such positions. When 27 the sign mode is PROCESSOR DEFINED, the processor has the option of producing a plus sign or not 28 in such positions, subject to 10.6.1(5). 29 The SS, SP, and S edit descriptors affect only I, F, E, EN, ES, D, and G editing during the execution of 30 an output statement. The SS, SP, and S edit descriptors have no effect during the execution of an input 31 statement. SEP 2002 COMMITTEE DRAFT 233 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 10.7.5 P editing 2 The k P edit descriptor temporarily changes (9.4.1) the scale factor for the connection to k . The scale 3 factor affects the editing of F, E, EN, ES, D, and G edit descriptors for numeric quantities. 4 The scale factor k affects the appropriate editing in the following manner: 5 (1) On input, with F, E, EN, ES, D, and G editing (provided that no exponent exists in the 6 field) and F output editing, the scale factor effect is that the externally represented number 7 equals the internally represented number multiplied by 10k. 8 (2) On input, with F, E, EN, ES, D, and G editing, the scale factor has no effect if there is an 9 exponent in the field. 10 (3) On output, with E and D editing, the significand (R415) part of the quantity to be produced 11 is multiplied by 10k and the exponent is reduced by k. 12 (4) On output, with G editing, the effect of the scale factor is suspended unless the magnitude 13 of the datum to be edited is outside the range that permits the use of F editing. If the use 14 of E editing is required, the scale factor has the same effect as with E output editing. 15 (5) On output, with EN and ES editing, the scale factor has no effect. 16 If UP, DOWN, ZERO, or NEAREST I/O rounding mode is in effect then 17 (1) On input, the scale factor is applied to the external decimal value and then this is converted 18 using the current I/O rounding mode, and 19 (2) On output, the internal value is converted using the current I/O rounding mode and then 20 the scale factor is applied to the converted decimal value. 21 10.7.6 BN and BZ editing 22 The BN and BZ edit descriptors temporarily change (9.4.1) the blank interpretation mode (9.4.5.4, 23 9.5.1.5) for the connection. The edit descriptors BN and BZ set the blank interpretation mode corre- 24 sponding to the BLANK= specifier values NULL and ZERO, respectively. 25 The blank interpretation mode controls the interpretation of nonleading blanks in numeric input fields. 26 Such blank characters are interpreted as zeros when the blank interpretation mode has the value ZERO; 27 they are ignored when the blank interpretation mode has the value NULL. The effect of ignoring blanks 28 is to treat the input field as if blanks had been removed, the remaining portion of the field right-justified, 29 and the blanks replaced as leading blanks. However, a field containing only blanks has the value zero. 30 The blank interpretation mode affects only numeric editing (10.6.1) and generalized numeric editing 31 (10.6.4.1) on input. It has no effect on output. 32 10.7.7 RU, RD, RZ, RN, RC, and RP editing 33 The round edit descriptors temporarily change (9.4.1) the connection's I/O rounding mode (9.4.5.12, 34 9.5.1.12, 10.6.1.2.6). The round edit descriptors RU, RD, RZ, RN, RC, and RP set the I/O rounding 35 mode corresponding to the ROUND= specifier values UP, DOWN, ZERO, NEAREST, COMPATIBLE, 36 and PROCESSOR DEFINED, respectively. The I/O rounding mode affects the conversion of real and 37 complex values in formatted input/output. It affects only D, E, EN, ES, F, and G editing. 38 10.7.8 DC and DP editing 39 The decimal edit descriptors temporarily change (9.4.1) the decimal edit mode (9.4.5.5, 9.5.1.6) for the 40 connection. The edit descriptors DC and DP set the decimal edit mode corresponding to the DECIMAL= 41 specifier values COMMA and POINT, respectively. 234 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 The decimal edit mode controls the representation of the decimal symbol (10.5) during conversion of 2 real and complex values in formatted input/output. The decimal edit mode affects only D, E, EN, ES, 3 F, and G editing. 4 10.8 Character string edit descriptors 5 A character string edit descriptor shall not be used on input. 6 The character string edit descriptor causes characters to be written from the enclosed characters of the 7 edit descriptor itself, including blanks. For a character string edit descriptor, the width of the field is 8 the number of characters between the delimiting characters. Within the field, two consecutive delimiting 9 characters are counted as a single character. NOTE 10.24 A delimiter for a character string edit descriptor is either an apostrophe or quote. 10 10.9 List-directed formatting 11 List-directed input/output allows data editing according to the type of the list item instead of by a 12 format specification. It also allows data to be free-field, that is, separated by commas (or semicolons) 13 or blanks. 14 The characters in one or more list-directed records constitute a sequence of values and value separators. 15 The end of a record has the same effect as a blank character, unless it is within a character constant. Any 16 sequence of two or more consecutive blanks is treated as a single blank, unless it is within a character 17 constant. 18 Each value is either a null value or one of the forms: c r *c 19 r * 20 where c is a literal constant, optionally signed if integer or real, or a nondelimited character constant 21 and r is an unsigned, nonzero, integer literal constant. Neither c nor r shall have kind type parameters 22 specified. The constant c is interpreted as though it had the same kind type parameter as the corre- 23 sponding list item. The r *c form is equivalent to r successive appearances of the constant c, and the 24 r * form is equivalent to r successive appearances of the null value. Neither of these forms may contain 25 embedded blanks, except where permitted within the constant c. 26 A value separator is 27 (1) A comma optionally preceded by one or more contiguous blanks and optionally followed by 28 one or more contiguous blanks, unless the decimal edit mode is COMMA, in which case a 29 semicolon is used in place of the comma, 30 (2) A slash optionally preceded by one or more contiguous blanks and optionally followed by 31 one or more contiguous blanks, or 32 (3) One or more contiguous blanks between two nonblank values or following the last nonblank 33 value, where a nonblank value is a constant, an r *c form, or an r * form. NOTE 10.25 Although a slash encountered in an input record is referred to as a separator, it actually causes termination of list-directed and namelist input statements; it does not actually separate two values. SEP 2002 COMMITTEE DRAFT 235 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 10.26 If no list items are specified in a list-directed input/output statement, one input record is skipped or one empty output record is written. 1 10.9.1 List-directed input 2 Input forms acceptable to edit descriptors for a given type are acceptable for list-directed formatting, 3 except as noted below. The form of the input value shall be acceptable for the type of the next effective 4 item in the list. Blanks are never used as zeros, and embedded blanks are not permitted in constants, 5 except within character constants and complex constants as specified below. 6 For the r *c form of an input value, the constant c is interpreted as a nondelimited character constant if 7 the first list item corresponding to this value is of type default character, there is a nonblank character 8 immediately after r *, and that character is not an apostrophe or a quotation mark; otherwise, c is 9 interpreted as a literal constant. NOTE 10.27 The end of a record has the effect of a blank, except when it appears within a character constant. 10 When the next effective item is of type integer, the value in the input record is interpreted as if an Iw 11 edit descriptor with a suitable value of w were used. 12 When the next effective item is of type real, the input form is that of a numeric input field. A numeric 13 input field is a field suitable for F editing (10.6.1.2.1) that is assumed to have no fractional digits unless 14 a decimal symbol appears within the field. 15 When the next effective item is of type complex, the input form consists of a left parenthesis followed 16 by an ordered pair of numeric input fields separated by a separator, and followed by a right parenthesis. 17 The first numeric input field is the real part of the complex constant and the second is the imaginary 18 part. Each of the numeric input fields may be preceded or followed by any number of blanks and ends of 19 records. The separator is a comma if the decimal edit mode is POINT; it is a semicolon if the decimal 20 edit mode is COMMA. The end of a record may occur between the real part and the separator or between 21 the separator and the imaginary part. 22 When the next effective item is of type logical, the input form shall not include value separators among 23 the optional characters permitted for L editing. 24 When the next effective item is of type character, the input form consists of a possibly delimited sequence 25 of zero or more rep-char s whose kind type parameter is implied by the kind of the effective list item. 26 Character sequences may be continued from the end of one record to the beginning of the next record, 27 but the end of record shall not occur between a doubled apostrophe in an apostrophe-delimited character 28 sequence, nor between a doubled quote in a quote-delimited character sequence. The end of the record 29 does not cause a blank or any other character to become part of the character sequence. The character 30 sequence may be continued on as many records as needed. The characters blank, comma, and slash may 31 appear in default character sequences. 32 If the next effective item is of type default character and 33 (1) The character sequence does not contain value separators, 34 (2) The character sequence does not cross a record boundary, 35 (3) The first nonblank character is not a quotation mark or an apostrophe, 36 (4) The leading characters are not digit s followed by an asterisk, and 37 (5) The character sequence contains at least one character, 236 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 the delimiting apostrophes or quotation marks are not required. If the delimiters are omitted, the 2 character sequence is terminated by the first blank, comma, slash, or end of record; apostrophes and 3 quotation marks within the datum are not to be doubled. 4 Let len be the length of the next effective item, and let w be the length of the character sequence. If 5 len is less than or equal to w, the leftmost len characters of the sequence are transmitted to the next 6 effective item. If len is greater than w, the sequence is transmitted to the leftmost w characters of the 7 next effective item and the remaining len-w characters of the next effective item are filled with blanks. 8 The effect is as though the sequence were assigned to the next effective item in a character assignment 9 statement (7.4.1.3). 10 10.9.1.1 Null values 11 A null value is specified by 12 (1) The r * form, 13 (2) No characters between consecutive value separators, or 14 (3) No characters before the first value separator in the first record read by each execution of a 15 list-directed input statement. NOTE 10.28 The end of a record following any other value separator, with or without separating blanks, does not specify a null value in list-directed input. 16 A null value has no effect on the definition status of the next effective item. A null value shall not be 17 used for either the real or imaginary part of a complex constant, but a single null value may represent 18 an entire complex constant. 19 A slash encountered as a value separator during execution of a list-directed input statement causes 20 termination of execution of that input statement after the assignment of the previous value. Any 21 characters remaining in the current record are ignored. If there are additional items in the input list, 22 the effect is as if null values had been supplied for them. Any implied-DO variable in the input list is 23 defined as though enough null values had been supplied for any remaining input list items. NOTE 10.29 All blanks in a list-directed input record are considered to be part of some value separator except for the following: (1) Blanks embedded in a character sequence (2) Embedded blanks surrounding the real or imaginary part of a complex constant (3) Leading blanks in the first record read by each execution of a list-directed input statement, unless immediately followed by a slash or comma NOTE 10.30 List-directed input example: INTEGER I; REAL X (8); CHARACTER (11) P; COMPLEX Z; LOGICAL G ... READ *, I, X, P, Z, G SEP 2002 COMMITTEE DRAFT 237 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 10.30 (cont.) ... The input data records are: 12345,12345,,2*1.5,4* ISN'T_BOB'S,(123,0),.TEXAS$ The results are: Variable Value I 12345 X (1) 12345.0 X (2) unchanged X (3) 1.5 X (4) 1.5 X (5) ­ X (8) unchanged P ISN'T BOB'S Z (123.0,0.0) G true 1 10.9.2 List-directed output 2 The form of the values produced is the same as that required for input, except as noted otherwise. With 3 the exception of adjacent nondelimited character sequences, the values are separated by one or more 4 blanks or by a comma, or a semicolon if the decimal edit mode is comma, optionally preceded by one or 5 more blanks and optionally followed by one or more blanks. 6 The processor may begin new records as necessary, but the end of record shall not occur within a 7 constant except for complex constants and character sequences. The processor shall not insert blanks 8 within character sequences or within constants, except for complex constants. 9 Logical output values are T for the value true and F for the value false. 10 Integer output constants are produced with the effect of an Iw edit descriptor. 11 Real constants are produced with the effect of either an F edit descriptor or an E edit descriptor, 12 depending on the magnitude x of the value and a range 10d1 x < 10d2 , where d1 and d2 are processor- 13 dependent integers. If the magnitude x is within this range or is zero, the constant is produced using 14 0PFw.d ; otherwise, 1PEw.d Ee is used. 15 For numeric output, reasonable processor-dependent values of w , d , and e are used for each of the 16 numeric constants output. 17 Complex constants are enclosed in parentheses with a separator between the real and imaginary parts, 18 each produced as defined above for real constants. The separator is a comma if the decimal edit mode is 19 POINT; it is a semicolon if the decimal edit mode is COMMA. The end of a record may occur between 20 the separator and the imaginary part only if the entire constant is as long as, or longer than, an entire 21 record. The only embedded blanks permitted within a complex constant are between the separator and 22 the end of a record and one blank at the beginning of the next record. 23 Character sequences produced when the delimiter mode has a value of NONE 24 (1) Are not delimited by apostrophes or quotation marks, 25 (2) Are not separated from each other by value separators, 26 (3) Have each internal apostrophe or quotation mark represented externally by one apostrophe 238 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 or quotation mark, and 2 (4) Have a blank character inserted by the processor at the beginning of any record that begins 3 with the continuation of a character sequence from the preceding record. 4 Character sequences produced when the delimiter mode has a value of QUOTE are delimited by quotes, 5 are preceded and followed by a value separator, and have each internal quote represented on the external 6 medium by two contiguous quotes. 7 Character sequences produced when the delimiter mode has a value of APOSTROPHE are delimited 8 by apostrophes, are preceded and followed by a value separator, and have each internal apostrophe 9 represented on the external medium by two contiguous apostrophes. 10 If two or more successive values in an output record have identical values, the processor has the option 11 of producing a repeated constant of the form r *c instead of the sequence of identical values. 12 Slashes, as value separators, and null values are not produced as output by list-directed formatting. 13 Except for continuation of delimited character sequences, each output record begins with a blank char- 14 acter. NOTE 10.31 The length of the output records is not specified exactly and may be processor dependent. 15 10.10 Namelist formatting 16 Namelist input/output allows data editing with NAME=value subsequences. This facilitates documen- 17 tation of input and output files and more flexibility on input. 18 The characters in one or more namelist records constitute a sequence of name-value subsequences, 19 each of which consists of an object designator followed by an equals and followed by one or more values 20 and value separators. The equals may optionally be preceded or followed by one or more contiguous 21 blanks. The end of a record has the same effect as a blank character, unless it is within a character 22 constant. Any sequence of two or more consecutive blanks is treated as a single blank, unless it is within 23 a character constant. 24 The name may be any name in the namelist-group-object -list (5.4). 25 Each value is either a null value (10.10.1.4) or one of the forms c r *c 26 r * 27 where c is a literal constant, optionally signed if integer or real, and r is an unsigned, nonzero, integer 28 literal constant. Neither c nor r may have kind type parameters specified. The constant c is interpreted 29 as though it had the same kind type parameter as the corresponding list item. The r *c form is equivalent 30 to r successive appearances of the constant c, and the r * form is equivalent to r successive null values. 31 Neither of these forms may contain embedded blanks, except where permitted within the constant c. 32 A value separator for namelist formatting is the same as for list-directed formatting (10.9). 33 10.10.1 Namelist input 34 Input for a namelist input statement consists of 35 (1) Optional blanks and namelist comments, SEP 2002 COMMITTEE DRAFT 239 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 (2) The character & followed immediately by the namelist-group-name as specified in the 2 NAMELIST statement, 3 (3) One or more blanks, 4 (4) A sequence of zero or more name-value subsequences separated by value separators, and 5 (5) A slash to terminate the namelist input. NOTE 10.32 A slash encountered in a namelist input record causes the input statement to terminate. A slash may not be used to separate two values in a namelist input statement. 6 In each name-value subsequence, the name shall be the name of a namelist group object list item with 7 an optional qualification and the name with the optional qualification shall not be a zero-sized array, a 8 zero-sized array section, or a zero-length character string. The optional qualification, if any, shall not 9 contain a vector subscript. 10 A group name or object name is without regard to case. 11 10.10.1.1 Namelist group object names 12 Within the input data, each name shall correspond to a particular namelist group object name. Sub- 13 scripts, strides, and substring range expressions used to qualify group object names shall be optionally 14 signed integer literal constants with no kind type parameters specified. If a namelist group object is 15 an array, the input record corresponding to it may contain either the array name or the designator of 16 a subobject of that array, using the syntax of object designators (R603). If the namelist group object 17 name is the name of a variable of derived type, the name in the input record may be either the name of 18 the variable or the designator of one of its components, indicated by qualifying the variable name with 19 the appropriate component name. Successive qualifications may be applied as appropriate to the shape 20 and type of the variable represented. 21 The order of names in the input records need not match the order of the namelist group object items. 22 The input records need not contain all the names of the namelist group object items. The definition 23 status of any names from the namelist-group-object -list that do not occur in the input record remains 24 unchanged. In the input record, each object name or subobject designator may be preceded and followed 25 by one or more optional blanks but shall not contain embedded blanks. 26 10.10.1.2 Namelist input values 27 The datum c (10.10) is any input value acceptable to format specifications for a given type, except for a 28 restriction on the form of input values corresponding to list items of types logical, integer, and character 29 as specified in 10.10.1.3. The form of a real or complex value is dependent on the decimal edit mode 30 in effect (10.7.8). The form of an input value shall be acceptable for the type of the namelist group 31 object list item. The number and forms of the input values that may follow the equals in a name-value 32 subsequence depend on the shape and type of the object represented by the name in the input record. 33 When the name in the input record is that of a scalar variable of an intrinsic type, the equals shall 34 not be followed by more than one value. Blanks are never used as zeros, and embedded blanks are not 35 permitted in constants except within character constants and complex constants as specified in 10.10.1.3. 36 The name-value subsequences are evaluated serially, in left-to-right order. A namelist group object 37 designator may appear in more than one name-value sequence. 38 When the name in the input record represents an array variable or a variable of derived type, the effect 39 is as if the variable represented were expanded into a sequence of scalar list items of intrinsic data types, 40 in the same way that formatted input/output list items are expanded (9.5.2). Each input value following 41 the equals shall then be acceptable to format specifications for the intrinsic type of the list item in the 240 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 corresponding position in the expanded sequence, except as noted in 10.10.1.3. The number of values 2 following the equals shall not exceed the number of list items in the expanded sequence, but may be less; 3 in the latter case, the effect is as if sufficient null values had been appended to match any remaining list 4 items in the expanded sequence. NOTE 10.33 For example, if the name in the input record is the name of an integer array of size 100, at most 100 values, each of which is either a digit string or a null value, may follow the equals; these values would then be assigned to the elements of the array in array element order. 5 A slash encountered as a value separator during the execution of a namelist input statement causes 6 termination of execution of that input statement after assignment of the previous value. If there are 7 additional items in the namelist group object being transferred, the effect is as if null values had been 8 supplied for them. 9 A namelist comment may appear after any value separator except a slash. A namelist comment is also 10 permitted to start in the first nonblank position of an input record except within a character literal 11 constant. 12 Successive namelist records are read by namelist input until a slash is encountered; the remainder of the 13 record is ignored and need not follow the rules for namelist input values. 14 10.10.1.3 Namelist group object list items 15 When the next effective namelist group object list item is of type real, the input form of the input value 16 is that of a numeric input field. A numeric input field is a field suitable for F editing (10.6.1.2.1) that is 17 assumed to have no fractional digits unless a decimal symbol appears within the field. 18 When the next effective item is of type complex, the input form of the input value consists of a left 19 parenthesis followed by an ordered pair of numeric input fields separated by a comma and followed by a 20 right parenthesis. The first numeric input field is the real part of the complex constant and the second 21 part is the imaginary part. Each of the numeric input fields may be preceded or followed by any number 22 of blanks and ends of records. The end of a record may occur between the real part and the comma or 23 between the comma and the imaginary part. 24 When the next effective item is of type logical, the input form of the input value shall not include equals 25 or value separators among the optional characters permitted for L editing (10.6.2). 26 When the next effective item is of type integer, the value in the input record is interpreted as if an Iw 27 edit descriptor with a suitable value of w were used. 28 When the next effective item is of type character, the input form consists of a delimited sequence of zero 29 or more rep-char s whose kind type parameter is implied by the kind of the corresponding list item. Such 30 a sequence may be continued from the end of one record to the beginning of the next record, but the 31 end of record shall not occur between a doubled apostrophe in an apostrophe-delimited sequence, nor 32 between a doubled quote in a quote-delimited sequence. The end of the record does not cause a blank 33 or any other character to become part of the sequence. The sequence may be continued on as many 34 records as needed. The characters blank, comma, and slash may appear in such character sequences. NOTE 10.34 A character sequence corresponding to a namelist input item of character type shall be delimited either with apostrophes or with quotes. The delimiter is required to avoid ambiguity between undelimited character sequences and object names. The value of the DELIM= specifier, if any, in the OPEN statement for an external file is ignored during namelist input (9.4.5.6). SEP 2002 COMMITTEE DRAFT 241 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 Let len be the length of the next effective item, and let w be the length of the character sequence. If 2 len is less than or equal to w, the leftmost len characters of the sequence are transmitted to the next 3 effective item. If len is greater than w, the constant is transmitted to the leftmost w characters of the 4 next effective item and the remaining len-w characters of the next effective item are filled with blanks. 5 The effect is as though the sequence were assigned to the next effective item in a character assignment 6 statement (7.4.1.3). 7 10.10.1.4 Null values 8 A null value is specified by 9 (1) The r * form, 10 (2) Blanks between two consecutive value separators following an equals, 11 (3) Zero or more blanks preceding the first value separator and following an equals, or 12 (4) Two consecutive nonblank value separators. 13 A null value has no effect on the definition status of the corresponding input list item. If the namelist 14 group object list item is defined, it retains its previous value; if it is undefined, it remains undefined. A 15 null value shall not be used as either the real or imaginary part of a complex constant, but a single null 16 value may represent an entire complex constant. NOTE 10.35 The end of a record following a value separator, with or without intervening blanks, does not specify a null value in namelist input. 17 10.10.1.5 Blanks 18 All blanks in a namelist input record are considered to be part of some value separator except for 19 (1) Blanks embedded in a character constant, 20 (2) Embedded blanks surrounding the real or imaginary part of a complex constant, 21 (3) Leading blanks following the equals unless followed immediately by a slash or comma, or a 22 semicolon if the decimal edit mode is comma, and 23 (4) Blanks between a name and the following equals. 24 10.10.1.6 Namelist Comments 25 Except within a character literal constant, a "!" character after a value separator or in the first nonblank 26 position of a namelist input record initiates a comment. The comment extends to the end of the current 27 input record and may contain any graphic character in the processor-dependent character set. The 28 comment is ignored. A slash within the namelist comment does not terminate execution of the namelist 29 input statement. Namelist comments are not allowed in stream input because comments depend on 30 record structure. NOTE 10.36 Namelist input example: INTEGER I; REAL X (8); CHARACTER (11) P; COMPLEX Z; LOGICAL G NAMELIST / TODAY / G, I, P, Z, X READ (*, NML = TODAY) The input data records are: 242 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 10.36 (cont.) &TODAY I = 12345, X(1) = 12345, X(3:4) = 2*1.5, I=6, ! This is a comment. P = ''ISN'T_BOB'S'', Z = (123,0)/ The results stored are: Variable Value I 6 X (1) 12345.0 X (2) unchanged X (3) 1.5 X (4) 1.5 X (5) ­ X (8) unchanged P ISN'T BOB'S Z (123.0,0.0) G unchanged 1 10.10.2 Namelist output 2 The form of the output produced is the same as that required for input, except for the forms of real, 3 character, and logical values. The name in the output is in upper case. With the exception of adjacent 4 nondelimited character values, the values are separated by one or more blanks or by a comma, or a 5 semicolon if the decimal edit mode is COMMA, optionally preceded by one or more blanks and optionally 6 followed by one or more blanks. 7 Namelist output shall not include namelist comments. 8 The processor may begin new records as necessary. However, except for complex constants and character 9 values, the end of a record shall not occur within a constant, character value, or name, and blanks shall 10 not appear within a constant, character value, or name. NOTE 10.37 The length of the output records is not specified exactly and may be processor dependent. 11 10.10.2.1 Namelist output editing 12 Logical output values are T for the value true and F for the value false. 13 Integer output constants are produced with the effect of an Iw edit descriptor. 14 Real constants are produced with the effect of either an F edit descriptor or an E edit descriptor, 15 depending on the magnitude x of the value and a range 10d1 x < 10d2 , where d1 and d2 are processor- 16 dependent integers. If the magnitude x is within this range or is zero, the constant is produced using 17 0PFw.d ; otherwise, 1PEw.d Ee is used. 18 For numeric output, reasonable processor-dependent integer values of w, d, and e are used for each of 19 the numeric constants output. 20 Complex constants are enclosed in parentheses with a separator between the real and imaginary parts, 21 each produced as defined above for real constants. The separator is a comma if the decimal edit mode is 22 POINT; it is a semicolon if the decimal edit mode is COMMA. The end of a record may occur between 23 the separator and the imaginary part only if the entire constant is as long as, or longer than, an entire 24 record. The only embedded blanks permitted within a complex constant are between the separator and 25 the end of a record and one blank at the beginning of the next record. SEP 2002 COMMITTEE DRAFT 243 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 Character sequences produced when the delimiter mode has a value of NONE 2 (1) Are not delimited by apostrophes or quotation marks, 3 (2) Are not separated from each other by value separators, 4 (3) Have each internal apostrophe or quotation mark represented externally by one apostrophe 5 or quotation mark, and 6 (4) Have a blank character inserted by the processor at the beginning of any record that begins 7 with the continuation of a character sequence from the preceding record. NOTE 10.38 Namelist output records produced with a DELIM= specifier with a value of NONE and which contain a character sequence may not be acceptable as namelist input records. 8 Character sequences produced when the delimiter mode has a value of QUOTE are delimited by quotes, 9 are preceded and followed by a value separator, and have each internal quote represented on the external 10 medium by two contiguous quotes. 11 Character sequences produced when the delimiter mode has a value of APOSTROPHE are delimited 12 by apostrophes, are preceded and followed by a value separator, and have each internal apostrophe 13 represented on the external medium by two contiguous apostrophes. 14 10.10.2.2 Namelist output records 15 If two or more successive values in an array in an output record produced have identical values, the 16 processor has the option of producing a repeated constant of the form r *c instead of the sequence of 17 identical values. 18 The name of each namelist group object list item is placed in the output record followed by an equals 19 and a list of values of the namelist group object list item. 20 An ampersand character followed immediately by a namelist-group-name will be produced by namelist 21 formatting at the start of the first output record to indicate which particular group of data objects is 22 being output. A slash is produced by namelist formatting to indicate the end of the namelist formatting. 23 A null value is not produced by namelist formatting. 24 Except for continuation of delimited character sequences, each output record begins with a blank char- 25 acter. 244 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 Section 11: Program units 2 The terms and basic concepts of program units were introduced in 2.2. A program unit is a main 3 program, an external subprogram, a module, or a block data program unit. 4 This section describes main programs, modules, and block data program units. Section 12 describes 5 external subprograms. 6 11.1 Main program 7 A Fortran main program is a program unit that does not contain a SUBROUTINE, FUNCTION, 8 MODULE, or BLOCK DATA statement as its first statement. 9 R1101 main-program is [ program-stmt ] 10 [ specification-part ] 11 [ execution-part ] 12 [ internal-subprogram-part ] 13 end-program-stmt 14 R1102 program-stmt is PROGRAM program-name 15 R1103 end-program-stmt is END [ PROGRAM [ program-name ] ] 16 C1101 (R1101) In a main-program, the execution-part shall not contain a RETURN statement or an 17 ENTRY statement. 18 C1102 (R1101) The program-name may be included in the end-program-stmt only if the optional 19 program-stmt is used and, if included, shall be identical to the program-name specified in the 20 program-stmt . 21 C1103 (R1101) An automatic object shall not appear in the specification-part (R204) of a main program. NOTE 11.1 The program name is global to the program (16.1). For explanatory information about uses for the program name, see section C.8.1. NOTE 11.2 An example of a main program is: PROGRAM ANALYZE REAL A, B, C (10,10) ! Specification part CALL FIND ! Execution part CONTAINS SUBROUTINE FIND ! Internal subprogram ... END SUBROUTINE FIND END PROGRAM ANALYZE 22 The main program may be defined by means other than Fortran; in that case, the program shall not 23 contain a main-program program unit. 24 A reference to a Fortran main-program shall not appear in any program unit in the program, including SEP 2002 COMMITTEE DRAFT 245 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 itself. 2 11.2 Modules 3 A module contains specifications and definitions that are to be accessible to other program units. A 4 module that is provided as an inherent part of the processor is an intrinsic module. A nonintrinsic 5 module is defined by a module program unit or a means other than Fortran. 6 Procedures and types defined in an intrinsic module are not themselves intrinsic. 7 R1104 module is module-stmt 8 [ specification-part ] 9 [ module-subprogram-part ] 10 end-module-stmt 11 R1105 module-stmt is MODULE module-name 12 R1106 end-module-stmt is END [ MODULE [ module-name ] ] 13 R1107 module-subprogram-part is contains-stmt 14 module-subprogram 15 [ module-subprogram ] ... 16 R1108 module-subprogram is function-subprogram 17 or subroutine-subprogram 18 C1104 (R1104) If the module-name is specified in the end-module-stmt , it shall be identical to the 19 module-name specified in the module-stmt . 20 C1105 (R1104) A module specification-part shall not contain a stmt-function-stmt , an entry-stmt , or a 21 format-stmt . 22 C1106 (R1104) An automatic object shall not appear in the specification-part of a module. 23 C1107 (R1104) If an object of a type for which component-initialization is specified (R435) appears 24 in the specification-part of a module and does not have the ALLOCATABLE or POINTER 25 attribute, the object shall have the SAVE attribute. NOTE 11.3 The module name is global to the program (16.1). NOTE 11.4 Although statement function definitions, ENTRY statements, and FORMAT statements shall not appear in the specification part of a module, they may appear in the specification part of a module subprogram in the module. A module is host to any module subprograms (12.1.2.2) it contains, and the entities in the module are therefore accessible in the module subprograms through host association. NOTE 11.5 For a discussion of the impact of modules on dependent compilation, see section C.8.2. NOTE 11.6 For examples of the use of modules, see section C.8.3. 246 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 11.2.1 Module reference 2 A USE statement specifying a module name is a module reference. At the time a module reference is 3 processed, the public portions of the specified module shall be available. A module shall not reference 4 itself, either directly or indirectly. 5 The accessibility, public or private, of specifications and definitions in a module to a scoping unit mak- 6 ing reference to the module may be controlled in both the module and the scoping unit making the 7 reference. In the module, the PRIVATE statement, the PUBLIC statement (5.2.1), their equivalent 8 attributes (5.1.2.1), and the PRIVATE statement in a derived-type definition (4.5.1) are used to control 9 the accessibility of module entities outside the module. The PROTECTED statement (5.2.11) and the 10 PROTECTED attribute (5.1.2.12) are used to control the definability of module entities outside the 11 module. NOTE 11.7 For a discussion of the impact of accessibility on dependent compilation, see section C.8.2.2. 12 In a scoping unit making reference to a module, the ONLY option in the USE statement may be used 13 to further limit the accessibility, in that referencing scoping unit, of the public entities in the module. 14 11.2.2 The USE statement and use association 15 The USE statement provides the means by which a scoping unit accesses named data objects, derived 16 types, type aliases, interface blocks, procedures, abstract interfaces, generic identifiers (12.3.2.1), and 17 namelist groups in a module. The entities in the scoping unit are said to be use associated with the 18 entities in the module. The accessed entities have the attributes specified in the module. The entities 19 made accessible are identified by the names or generic identifiers used to identify them in the module. 20 By default, they are identified by the same identifiers in the scoping unit containing the USE statement, 21 but it is possible to specify that different local identifiers be used. 22 R1109 use-stmt is USE [ [ , module-nature ] :: ] module-name [ , rename-list ] 23 or USE [ [ , module-nature ] :: ] module-name , 24 ONLY : [ only-list ] 25 R1110 module-nature is INTRINSIC 26 or NON INTRINSIC 27 R1111 rename is local-name => use-name 28 or OPERATOR (local-defined-operator ) => 29 OPERATOR (use-defined-operator ) 30 R1112 only is generic-spec 31 or only-use-name 32 or rename 33 R1113 only-use-name is use-name 34 C1108 (R1109) If module-nature is INTRINSIC, module-name shall be the name of an intrinsic module. 35 C1109 (R1109) If module-nature is NON INTRINSIC, module-name shall be the name of a nonintrinsic 36 module. 37 C1110 (R1111) OPERATOR(use-defined-operator ) shall not identify a generic-binding. 38 C1111 (R1112) The generic-spec shall not identify a generic-binding. NOTE 11.8 The above two constraints do not prevent accessing a generic-spec that is declared by an interface block, even if a generic-binding has the same generic-spec. SEP 2002 COMMITTEE DRAFT 247 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 C1112 (R1112) Each generic-spec shall be a public entity in the module. 2 C1113 (R1113) Each use-name shall be the name of a public entity in the module. 3 R1114 local-defined-operator is defined-unary-op 4 or defined-binary-op 5 R1115 use-defined-operator is defined-unary-op 6 or defined-binary-op 7 C1114 (R1115) Each use-defined-operator shall be a public entity in the module. 8 A use-stmt without a module-nature provides access either to an intrinsic or to a nonintrinsic module. 9 If the module-name is the name of both an intrinsic and a nonintrinsic module, the nonintrinsic module 10 is accessed. 11 The USE statement without the ONLY option provides access to all public entities in the specified 12 module. 13 A USE statement with the ONLY option provides access only to those entities that appear as generic- 14 specs, use-names, or use-defined-operator s in the only-list. 15 More than one USE statement for a given module may appear in a scoping unit. If one of the USE 16 statements is without an ONLY qualifier, all public entities in the module are accessible. If all the USE 17 statements have ONLY qualifiers, only those entities in one or more of the only-list s are accessible. 18 An accessible entity in the referenced module has one or more local identifiers. These identifiers are 19 (1) The identifier of the entity in the referenced module if that identifier appears as an only- 20 use-name or as the defined-operator of a generic-spec in any only for that module, 21 (2) Each of the local-names or local-defined-operator s that the entity is given in any rename for 22 that module, and 23 (3) The identifier of the entity in the referenced module if that identifier does not appear as a 24 use-name or use-defined-operator in any rename for that module. 25 Two or more accessible entities, other than generic interfaces or defined operators, may have the same 26 identifier only if the identifier is not used to refer to an entity in the scoping unit. Generic interfaces and 27 defined operators are handled as described in section 16.2.3. Except for these cases, the local identifier 28 of any entity given accessibility by a USE statement shall differ from the local identifiers of all other 29 entities accessible to the scoping unit through USE statements and otherwise. NOTE 11.9 There is no prohibition against a use-name or use-defined-operator appearing multiple times in one USE statement or in multiple USE statements involving the same module. As a result, it is possible for one use-associated entity to be accessible by more than one local identifier. 30 The local identifier of an entity made accessible by a USE statement shall not appear in any other 31 nonexecutable statement that would cause any attribute (5.1.2) of the entity to be specified in the 32 scoping unit that contains the USE statement, except that it may appear in a PUBLIC or PRIVATE 33 statement in the scoping unit of a module and it may be given the ASYNCHRONOUS or VOLATILE 34 attribute. 35 The appearance of such a local identifier in a PUBLIC statement in a module causes the entity accessible 36 by the USE statement to be a public entity of that module. If the identifier appears in a PRIVATE 37 statement in a module, the entity is not a public entity of that module. If the local identifier does not 38 appear in either a PUBLIC or PRIVATE statement, it assumes the default accessibility attribute (5.2.1) 39 of that scoping unit. 248 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 11.10 The constraints in sections 5.5.1, 5.5.2, and 5.4 prohibit the local-name from appearing as a common-block-object in a COMMON statement, an equivalence-object in an EQUIVALENCE state- ment, or a namelist-group-name in a NAMELIST statement, respectively. There is no prohibition against the local-name appearing as a common-block-name or a namelist-group-object . 1 If a procedure declared in the scoping unit of a module has an implicit interface, it shall explicitly be 2 given the EXTERNAL attribute in that scoping unit; if it is a function, its type and type parameters 3 shall be explicitly declared in a type declaration statement in that scoping unit. 4 If an intrinsic procedure is declared in the scoping unit of a module, it shall explicitly be given the 5 INTRINSIC attribute in that scoping unit or be used as an intrinsic procedure in that scoping unit. NOTE 11.11 For a discussion of the impact of the ONLY clause and renaming on dependent compilation, see section C.8.2.1. NOTE 11.12 Examples: USE STATS LIB provides access to all public entities in the module STATS LIB. USE MATH LIB; USE STATS LIB, SPROD => PROD makes all public entities in both MATH LIB and STATS LIB accessible. If MATH LIB contains an entity called PROD, it is accessible by its own name while the entity PROD of STATS LIB is accessible by the name SPROD. USE STATS LIB, ONLY: YPROD; USE STATS LIB, ONLY : PROD makes public entities YPROD and PROD in STATS LIB accessible. USE STATS LIB, ONLY : YPROD; USE STATS LIB makes all public entities in STATS LIB accessible. 6 11.3 Block data program units 7 A block data program unit is used to provide initial values for data objects in named common blocks. 8 R1116 block-data is block-data-stmt 9 [ specification-part ] 10 end-block-data-stmt 11 R1117 block-data-stmt is BLOCK DATA [ block-data-name ] 12 R1118 end-block-data-stmt is END [ BLOCK DATA [ block-data-name ] ] 13 C1115 (R1116) The block-data-name may be included in the end-block-data-stmt only if it was provided 14 in the block-data-stmt and, if included, shall be identical to the block-data-name in the block- 15 data-stmt . SEP 2002 COMMITTEE DRAFT 249 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 C1116 (R1116) A block-data specification-part may contain only USE statements, type declaration 2 statements, IMPLICIT statements, PARAMETER statements, derived-type definitions, and 3 the following specification statements: COMMON, DATA, DIMENSION, EQUIVALENCE, IN- 4 TRINSIC, POINTER, SAVE, and TARGET. 5 C1117 (R1116) A type declaration statement in a block-data specification-part shall not contain AL- 6 LOCATABLE, EXTERNAL, or BIND attribute specifiers. NOTE 11.13 For explanatory information about the uses for the block-data-name, see section C.8.1. 7 If an object in a named common block is initially defined, all storage units in the common block storage 8 sequence shall be specified even if they are not all initially defined. More than one named common block 9 may have objects initially defined in a single block data program unit. NOTE 11.14 In the example BLOCK DATA INIT REAL A, B, C, D, E, F COMMON /BLOCK1/ A, B, C, D DATA A /1.2/, C /2.3/ COMMON /BLOCK2/ E, F DATA F /6.5/ END BLOCK DATA INIT common blocks BLOCK1 and BLOCK2 both have objects that are being initialized in a single block data program unit. B, D, and E are not initialized but they need to be specified as part of the common blocks. 10 Only an object in a named common block may be initially defined in a block data program unit. NOTE 11.15 Objects associated with an object in a common block are considered to be in that common block. 11 The same named common block shall not be specified in more than one block data program unit in a 12 program. 13 There shall not be more than one unnamed block data program unit in a program. NOTE 11.16 An example of a block data program unit is: BLOCK DATA WORK COMMON /WRKCOM/ A, B, C (10, 10) REAL :: A, B, C DATA A /1.0/, B /2.0/, C /100 * 0.0/ END BLOCK DATA WORK 250 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 Section 12: Procedures 2 The concept of a procedure was introduced in 2.2.3. This section contains a complete description of 3 procedures. The actions specified by a procedure are performed when the procedure is invoked by 4 execution of a reference to it. 5 The sequence of actions encapsulated by a procedure has access to entities in the invoking scoping 6 unit by way of argument association (12.4.1). A dummy argument is a name that appears in the 7 SUBROUTINE, FUNCTION, or ENTRY statement in the declaration of a procedure (R1232). Dummy 8 arguments are also specified for intrinsic procedures and procedures in intrinsic modules in Sections 13, 9 14, and 15. 10 The entities in the invoking scoping unit are specified by actual arguments. An actual argument is an 11 entity that appears in a procedure reference (R1221). 12 A procedure may also have access to entities in other scoping units, not necessarily the invoking scoping 13 unit, by use association (16.4.1.2), host association (16.4.1.3), linkage association (16.4.1.4), storage 14 association (16.4.3), or by reference to external procedures (5.1.2.6). 15 12.1 Procedure classifications 16 A procedure is classified according to the form of its reference and the way it is defined. 17 12.1.1 Procedure classification by reference 18 The definition of a procedure specifies it to be a function or a subroutine. A reference to a function either 19 appears explicitly as a primary within an expression, or is implied by a defined operation (7.1.3) within 20 an expression. A reference to a subroutine is a CALL statement or a defined assignment statement 21 (7.4.1.4). 22 A procedure is classified as elemental if it is a procedure that may be referenced elementally (12.7). 23 12.1.2 Procedure classification by means of definition 24 A procedure is either an intrinsic procedure, an external procedure, a module procedure, an internal 25 procedure, a dummy procedure (which may be a dummy procedure pointer), a nondummy procedure 26 pointer, or a statement function. 27 12.1.2.1 Intrinsic procedures 28 A procedure that is provided as an inherent part of the processor is an intrinsic procedure. 29 12.1.2.2 External, internal, and module procedures 30 An external procedure is a procedure that is defined by an external subprogram or by a means other 31 than Fortran. 32 An internal procedure is a procedure that is defined by an internal subprogram. Internal subprograms 33 may appear in the main program, in an external subprogram, or in a module subprogram. Internal 34 subprograms shall not appear in other internal subprograms. Internal subprograms are the same as 35 external subprograms except that the name of the internal procedure is not a global entity, an internal SEP 2002 COMMITTEE DRAFT 251 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 subprogram shall not contain an ENTRY statement, the internal procedure name shall not be argument 2 associated with a dummy procedure (12.4.1.3), and the internal subprogram has access to host entities 3 by host association. 4 A module procedure is a procedure that is defined by a module subprogram. 5 A subprogram defines a procedure for the SUBROUTINE or FUNCTION statement. If the subprogram 6 has one or more ENTRY statements, it also defines a procedure for each of them. 7 12.1.2.3 Dummy procedures 8 A dummy argument that is specified to be a procedure or appears in a procedure reference is a dummy 9 procedure. A dummy procedure with the POINTER attribute is a dummy procedure pointer. 10 12.1.2.4 Procedure pointers 11 A procedure pointer is a procedure that has the EXTERNAL and POINTER attributes; it may be 12 pointer associated with an external procedure, a module procedure, an intrinsic procedure, or a dummy 13 procedure that is not a procedure pointer. A procedure pointer may be a dummy argument, a structure 14 component, or a local entity. 15 12.1.2.5 Statement functions 16 A function that is defined by a single statement is a statement function (12.5.4). 17 12.2 Characteristics of procedures 18 The characteristics of a procedure are the classification of the procedure as a function or subroutine, 19 whether it is pure, whether it is elemental, whether it has the BIND attribute, the characteristics of its 20 dummy arguments, and the characteristics of its result value if it is a function. 21 12.2.1 Characteristics of dummy arguments 22 Each dummy argument has the characteristic that it is a dummy data object, a dummy procedure, a 23 dummy procedure pointer, or an asterisk (alternate return indicator). A dummy argument other than an asterisk 24 may be specified to have the OPTIONAL attribute. This attribute means that the dummy argument 25 need not be associated with an actual argument for any particular reference to the procedure. 26 12.2.1.1 Characteristics of dummy data objects 27 The characteristics of a dummy data object are its type, its type parameters (if any), its shape, its 28 intent (5.1.2.7, 5.2.7), whether it is optional (5.1.2.9, 5.2.8), whether it is allocatable (5.1.2.5.3), whether 29 it has the VALUE (5.1.2.15), ASYNCHRONOUS (5.1.2.3), or VOLATILE (5.1.2.16) attributes, whether 30 it is polymorphic, and whether it is a pointer (5.1.2.11, 5.2.10) or a target (5.1.2.14, 5.2.13). If a type 31 parameter of an object or a bound of an array is not an initialization expression, the exact dependence 32 on the entities in the expression is a characteristic. If a shape, size, or type parameter is assumed or 33 deferred, it is a characteristic. 34 12.2.1.2 Characteristics of dummy procedures and dummy procedure pointers 35 The characteristics of a dummy procedure are the explicitness of its interface (12.3.1), its characteristics 36 as a procedure if the interface is explicit, whether it is a pointer, and whether it is optional (5.1.2.9, 5.2.8). 252 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 12.2.1.3 Characteristics of asterisk dummy arguments 2 An asterisk as a dummy argument has no characteristics. 3 12.2.2 Characteristics of function results 4 The characteristics of a function result are its type, type parameters (if any), rank, whether it is poly- 5 morphic, whether it is allocatable, whether it is a pointer, and whether it is a procedure pointer. If a 6 function result is an array that is not allocatable or a pointer, its shape is a characteristic. If a type 7 parameter of a function result or a bound of a function result array is not an initialization expression, the 8 exact dependence on the entities in the expression is a characteristic. If type parameters of a function 9 result are deferred, which parameters are deferred is a characteristic. If the length of a character function 10 result is assumed, this is a characteristic. 11 12.3 Procedure interface 12 An abstract interface consists of procedure characteristics and the names of dummy arguments. 13 The interface of a procedure determines the forms of reference through which it may be invoked. 14 The procedure's interface consists of its abstract interface, its name, its binding label if any, and the 15 procedure's generic identifiers, if any. The characteristics of a procedure are fixed, but the remainder of 16 the interface may differ in different scoping units. NOTE 12.1 For more explanatory information on procedure interfaces, see C.9.3. 17 12.3.1 Implicit and explicit interfaces 18 If a procedure is accessible in a scoping unit, its interface is either explicit or implicit in that scoping 19 unit. The interface of an internal procedure, module procedure, or intrinsic procedure is always explicit 20 in such a scoping unit. The interface of a subroutine or a function with a separate result name is explicit 21 within the subprogram that defines it. The interface of a statement function is always implicit. The interface of 22 an external procedure or dummy procedure is explicit in a scoping unit other than its own if an interface 23 body (12.3.2.1) for the procedure is supplied or accessible, and implicit otherwise. NOTE 12.2 For example, the subroutine LLS of C.8.3.5 has an explicit interface. 24 12.3.1.1 Explicit interface 25 A procedure other than a statement function shall have an explicit interface if it is referenced and 26 (1) A reference to the procedure appears 27 (a) With an argument keyword (12.4.1), 28 (b) As a reference by its generic name (12.3.2.1), 29 (c) As a defined assignment (subroutines only), 30 (d) In an expression as a defined operator (functions only), or 31 (e) In a context that requires it to be pure, 32 (2) The procedure has a dummy argument that 33 (a) has the ALLOCATABLE, ASYNCHRONOUS, OPTIONAL, POINTER, TARGET, 34 VALUE, or VOLATILE attribute, SEP 2002 COMMITTEE DRAFT 253 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 (b) is an assumed-shape array, 2 (c) is of a parameterized derived type, or 3 (d) is polymorphic, 4 (3) The procedure has a result that 5 (a) is an array, 6 (b) is a pointer or is allocatable, or 7 (c) has a nonassumed type parameter value that is not an initialization expression, 8 (4) The procedure is elemental, or 9 (5) The procedure has the BIND attribute. 10 12.3.2 Specification of the procedure interface 11 The interface for an internal, external, module, or dummy procedure is specified by a FUNCTION, 12 SUBROUTINE, or ENTRY statement and by specification statements for the dummy arguments and 13 the result of a function. These statements may appear in the procedure definition, in an interface body, 14 or both, except that the ENTRY statement shall not appear in an interface body. NOTE 12.3 An interface body cannot be used to describe the interface of an internal procedure, a module procedure, or an intrinsic procedure because the interfaces of such procedures are already explicit. However, the name of a procedure may appear in a PROCEDURE statement in an interface block (12.3.2.1). 15 12.3.2.1 Interface block 16 R1201 interface-block is interface-stmt 17 [ interface-specification ] ... 18 end-interface-stmt 19 R1202 interface-specification is interface-body 20 or procedure-stmt 21 R1203 interface-stmt is INTERFACE [ generic-spec ] 22 or ABSTRACT INTERFACE 23 R1204 end-interface-stmt is END INTERFACE [ generic-spec ] 24 R1205 interface-body is function-stmt 25 [ specification-part ] 26 end-function-stmt 27 or subroutine-stmt 28 [ specification-part ] 29 end-subroutine-stmt 30 C1201 (R1201) An interface-block in a subprogram shall not contain an interface-body for a procedure 31 defined by that subprogram. 32 C1202 (R1201) The generic-spec may be included in the end-interface-stmt only if it was provided in the 33 interface-stmt . If the end-interface-stmt includes generic-name, the interface-stmt shall specify 34 the same generic-name. If the end-interface-stmt includes ASSIGNMENT(=), the interface- 35 stmt shall specify ASSIGNMENT(=). If the end-interface-stmt includes dtio-generic-spec, 36 the interface-stmt shall specify the same dtio-generic-spec. If the end-interface-stmt includes 37 OPERATOR(defined-operator ), the interface-stmt shall specify the same defined-operator . If 38 one defined-operator is .LT., .LE., .GT., .GE., .EQ., or .NE., the other is permitted to be the 39 corresponding operator <, <=, >, >=, ==, or /=. 254 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 C1203 (R1203) If the interface-stmt is ABSTRACT INTERFACE, then the function-name in the 2 function-stmt or the subroutine-name in the subroutine-stmt shall not be the same as a keyword 3 that specifies an intrinsic type. 4 C1204 (R1202) A procedure-stmt is allowed only in an interface block that has a generic-spec. 5 C1205 (R1205) An interface-body of a pure procedure shall specify the intents of all dummy arguments 6 except pointer, alternate return, and procedure arguments. 7 C1206 (R1205) An interface-body shall not contain an entry-stmt , data-stmt , format-stmt , or stmt- 8 function-stmt . 9 R1206 procedure-stmt is [ MODULE ] PROCEDURE procedure-name-list 10 R1207 generic-spec is generic-name 11 or OPERATOR ( defined-operator ) 12 or ASSIGNMENT ( = ) 13 or dtio-generic-spec 14 R1208 dtio-generic-spec is READ (FORMATTED) 15 or READ (UNFORMATTED) 16 or WRITE (FORMATTED) 17 or WRITE (UNFORMATTED) 18 C1207 (R1206) A procedure-name shall have an explicit interface and shall refer to an accessible pro- 19 cedure pointer, external procedure, dummy procedure, or module procedure. 20 C1208 (R1206) If MODULE appears in a procedure-stmt , each procedure-name in that statement shall 21 be accessible in the current scope as a module procedure. 22 C1209 (R1206) A procedure-name shall not specify a procedure that is specified previously in any 23 procedure-stmt in any accessible interface with the same generic identifier. 24 R1209 import-stmt is IMPORT [[ :: ] import-name-list ] 25 C1210 (R1209) The IMPORT statement is allowed only in an interface-body. 26 C1211 (R1209) Each import-name shall be the name of an entity in the host scoping unit. 27 An external or module subprogram specifies a specific interface for the procedures defined in that 28 subprogram. Such a specific interface is explicit for module procedures and implicit for external proce- 29 dures. 30 An interface block introduced by ABSTRACT INTERFACE is an abstract interface block. An 31 interface body in an abstract interface block specifies an abstract interface. An interface block with 32 a generic specification is a generic interface block. An interface block without a generic specification 33 is a specific interface block. 34 The name of the entity declared by an interface body is the function-name in the function-stmt or the 35 subroutine-name in the subroutine-stmt that begins the interface body. 36 An interface body in a generic or specific interface block specifies the EXTERNAL attribute and an 37 explicit specific interface for an external procedure or a dummy procedure. If the name of the declared 38 procedure is that of a dummy argument in the subprogram containing the interface body, the procedure 39 is a dummy procedure; otherwise, it is an external procedure. An interface body in an abstract interface 40 block specifies an abstract interface. 41 An interface body specifies all of the characteristics of the explicit interface or abstract interface. The 42 specification part of an interface body may specify attributes or define values for data entities that do 43 not determine characteristics of the procedure. Such specifications have no effect. SEP 2002 COMMITTEE DRAFT 255 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 If an explicit specific interface is specified by an interface body or a procedure declaration statement 2 (12.3.2.3) for an external procedure, the characteristics shall be consistent with those specified in the 3 procedure definition, except that the interface may specify a procedure that is not pure if the procedure 4 is defined to be pure. An interface for a procedure named by an ENTRY statement may be specified by 5 using the entry name as the procedure name in the interface body. An explicit specific interface may 6 be specified by an interface body for an external procedure that does not exist in the program if the 7 procedure is never used in any way. A procedure shall not have more than one explicit specific interface 8 in a given scoping unit. NOTE 12.4 The dummy argument names may be different because the name of a dummy argument is not a characteristic. 9 The IMPORT statement specifies that the named entities from the host scoping unit are accessible in 10 the interface body by host association. An entity that is imported in this manner and is defined in the 11 host scoping unit shall be explicitly declared prior to the interface body. The name of an entity made 12 accessible by an IMPORT statement shall not appear in any of the contexts described in 16.4.1.3 that 13 cause the host entity of that name to be inaccessible. 14 Within an interface body, if an IMPORT statement with no import-name-list appears, each host entity 15 not named in an IMPORT statement also is made accessible by host association if its name does not 16 appear in any of the contexts described in 16.4.1.3 that cause the host entity of that name to be 17 inaccessible. NOTE 12.5 An example of an interface block without a generic specification is: INTERFACE SUBROUTINE EXT1 (X, Y, Z) REAL, DIMENSION (100, 100) :: X, Y, Z END SUBROUTINE EXT1 SUBROUTINE EXT2 (X, Z) REAL X COMPLEX (KIND = 4) Z (2000) END SUBROUTINE EXT2 FUNCTION EXT3 (P, Q) LOGICAL EXT3 INTEGER P (1000) LOGICAL Q (1000) END FUNCTION EXT3 END INTERFACE This interface block specifies explicit interfaces for the three external procedures EXT1, EXT2, and EXT3. Invocations of these procedures may use argument keywords (12.4.1); for example: EXT3 (Q = P_MASK (N+1 : N+1000), P = ACTUAL_P) NOTE 12.6 The IMPORT statement can be used to allow module procedures to have dummy arguments that are procedures with assumed-shape arguments of an opaque type. For example: 256 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 12.6 (cont.) MODULE M TYPE T PRIVATE ! T is an opaque type ... END TYPE CONTAINS SUBROUTINE PROCESS(X,Y,RESULT,MONITOR) TYPE(T),INTENT(IN) :: X(:,:),Y(:,:) TYPE(T),INTENT(OUT) :: RESULT(:,:) INTERFACE SUBROUTINE MONITOR(ITERATION_NUMBER,CURRENT_ESTIMATE) IMPORT T INTEGER,INTENT(IN) :: ITERATION_NUMBER TYPE(T),INTENT(IN) :: CURRENT_ESTIMATE(:,:) END SUBROUTINE END INTERFACE ... END SUBROUTINE END MODULE The MONITOR dummy procedure requires an explicit interface because it has an assumed-shape array argument, but TYPE(T) would not be available inside the interface body without the IM- PORT statement. 1 A generic interface block specifies a generic interface for each of the procedures in the interface 2 block. The PROCEDURE statement lists procedure pointers, external procedures, dummy procedures, 3 or module procedures that have this generic interface. The characteristics of module procedures are 4 not given in interface blocks, but are assumed from the module subprograms. The characteristics of a 5 procedure pointer are defined by a procedure declaration statement (12.3.2.3). A generic interface is 6 always explicit. 7 Any procedure may be referenced via its specific interface if the specific interface is accessible. It also 8 may be referenced via a generic interface. The generic-spec in an interface-stmt is a generic identifier 9 for all the procedures in the interface block. The rules specifying how any two procedures with the same 10 generic identifier shall differ are given in 16.2.3. They ensure that any generic invocation applies to at 11 most one specific procedure. 12 A generic name specifies a single name to reference all of the procedure names in the interface block. 13 A generic name may be the same as any one of the procedure names in the interface block, or the same 14 as any accessible generic name. 15 A generic name may be the same as a derived-type name, in which case all of the procedures in the 16 interface block shall be functions. NOTE 12.7 An example of a generic procedure interface is: INTERFACE SWITCH SUBROUTINE INT_SWITCH (X, Y) INTEGER, INTENT (INOUT) :: X, Y END SUBROUTINE INT_SWITCH SEP 2002 COMMITTEE DRAFT 257 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 12.7 (cont.) SUBROUTINE REAL_SWITCH (X, Y) REAL, INTENT (INOUT) :: X, Y END SUBROUTINE REAL_SWITCH SUBROUTINE COMPLEX_SWITCH (X, Y) COMPLEX, INTENT (INOUT) :: X, Y END SUBROUTINE COMPLEX_SWITCH END INTERFACE SWITCH Any of these three subroutines (INT SWITCH, REAL SWITCH, COMPLEX SWITCH) may be referenced with the generic name SWITCH, as well as by its specific name. For example, a reference to INT SWITCH could take the form: CALL SWITCH (MAX_VAL, LOC_VAL) ! MAX_VAL and LOC_VAL are of type INTEGER 1 An interface-stmt having a dtio-generic-spec is an interface for a user-defined derived-type input/output 2 procedure (9.5.3.7) 3 12.3.2.1.1 Defined operations 4 If OPERATOR is specified in a generic specification, all of the procedures specified in the generic interface 5 shall be functions that may be referenced as defined operations (7.1.3,7.1.8.7, 7.2, 12.4). In the case of 6 functions of two arguments, infix binary operator notation is implied. In the case of functions of one 7 argument, prefix operator notation is implied. OPERATOR shall not be specified for functions with no 8 arguments or for functions with more than two arguments. The dummy arguments shall be nonoptional 9 dummy data objects and shall be specified with INTENT (IN). The function result shall not have assumed 10 character length. If the operator is an intrinsic-operator (R310), the number of function arguments shall 11 be consistent with the intrinsic uses of that operator. 12 A defined operation is treated as a reference to the function. For a unary defined operation, the operand 13 corresponds to the function's dummy argument; for a binary operation, the left-hand operand corre- 14 sponds to the first dummy argument of the function and the right-hand operand corresponds to the 15 second dummy argument. NOTE 12.8 An example of the use of the OPERATOR generic specification is: INTERFACE OPERATOR ( * ) FUNCTION BOOLEAN_AND (B1, B2) LOGICAL, INTENT (IN) :: B1 (:), B2 (SIZE (B1)) LOGICAL :: BOOLEAN_AND (SIZE (B1)) END FUNCTION BOOLEAN_AND END INTERFACE OPERATOR ( * ) This allows, for example SENSOR (1:N) * ACTION (1:N) as an alternative to the function call BOOLEAN_AND (SENSOR (1:N), ACTION (1:N)) ! SENSOR and ACTION are ! of type LOGICAL 258 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 A given defined operator may, as with generic names, apply to more than one function, in which case 2 it is generic in exact analogy to generic procedure names. For intrinsic operator symbols, the generic 3 properties include the intrinsic operations they represent. Because both forms of each relational operator 4 have the same interpretation (7.2), extending one form (such as <=) has the effect of defining both forms 5 (<= and .LE.). NOTE 12.9 In Fortran 90 and Fortran 95, it was not possible to define operators on pointers because pointer dummy arguments were disallowed from having an INTENT attribute. The restriction against INTENT for pointer dummy arguments is now lifted, so defined operators on pointers are now possible. However, the POINTER attribute cannot be used to resolve generic procedures (16.2.3), so it is not possible to define a generic operator that has one procedure for pointers and another procedure for nonpointers. 6 12.3.2.1.2 Defined assignments 7 If ASSIGNMENT ( = ) is specified in a generic specification, all the procedures in the generic interface 8 shall be subroutines that may be referenced as defined assignments (7.4.1.4). Defined assignment may, 9 as with generic names, apply to more than one subroutine, in which case it is generic in exact analogy 10 to generic procedure names. Each of these subroutines shall have exactly two dummy arguments. Each 11 argument shall be nonoptional. The first argument shall have INTENT (OUT) or INTENT (INOUT) 12 and the second argument shall have INTENT (IN). A defined assignment is treated as a reference to the 13 subroutine, with the left-hand side as the first argument and the right-hand side enclosed in parentheses 14 as the second argument. The ASSIGNMENT generic specification specifies that the assignment operation 15 is extended or redefined. NOTE 12.10 An example of the use of the ASSIGNMENT generic specification is: INTERFACE ASSIGNMENT ( = ) SUBROUTINE LOGICAL_TO_NUMERIC (N, B) INTEGER, INTENT (OUT) :: N LOGICAL, INTENT (IN) :: B END SUBROUTINE LOGICAL_TO_NUMERIC SUBROUTINE CHAR_TO_STRING (S, C) USE STRING_MODULE ! Contains definition of type STRING TYPE (STRING), INTENT (OUT) :: S ! A variable-length string CHARACTER (*), INTENT (IN) :: C END SUBROUTINE CHAR_TO_STRING END INTERFACE ASSIGNMENT ( = ) Example assignments are: KOUNT = SENSOR (J) ! CALL LOGICAL_TO_NUMERIC (KOUNT, (SENSOR (J))) NOTE = '89AB' ! CALL CHAR_TO_STRING (NOTE, ('89AB')) 16 12.3.2.1.3 User-defined derived-type input/output procedure interfaces 17 All of the procedures specified in an interface block for a user-defined derived-type input/output proce- 18 dure shall be subroutines that have interfaces as described in 9.5.3.7.2. SEP 2002 COMMITTEE DRAFT 259 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 12.3.2.2 EXTERNAL statement 2 An EXTERNAL statement specifies the EXTERNAL attribute (5.1.2.6) for a list of names. 3 R1210 external-stmt is EXTERNAL [ :: ] external-name-list 4 Each external-name shall be the name of an external procedure, a dummy argument, a procedure 5 pointer, an abstract interface, or a block data program unit. In an external subprogram, an EXTERNAL 6 statement shall not specify the name of a procedure defined by the subprogram. 7 The appearance of the name of a block data program unit in an EXTERNAL statement confirms that 8 the block data program unit is a part of the program. NOTE 12.11 For explanatory information on potential portability problems with external procedures, see section C.9.1. NOTE 12.12 An example of an EXTERNAL statement is: EXTERNAL FOCUS 9 12.3.2.3 Procedure declaration statement 10 A procedure declaration statement declares procedure pointers, dummy procedures, and external pro- 11 cedures. It specifies the EXTERNAL attribute (5.1.2.6) for all procedure entities in the proc-decl -list. 12 R1211 procedure-declaration-stmt is PROCEDURE ( [ proc-interface ] ) 13 [ [ , proc-attr-spec ] ... :: ] proc-decl -list 14 R1212 proc-interface is interface-name 15 or declaration-type-spec 16 R1213 proc-attr-spec is access-spec 17 or proc-language-binding-spec 18 or INTENT ( intent-spec ) 19 or OPTIONAL 20 or POINTER 21 or SAVE 22 R1214 proc-decl is procedure-entity-name[ => null-init ] 23 R1215 interface-name is name 24 C1212 (R1215) The name shall be the name of an abstract interface or of a procedure that has an 25 explicit interface. If name is declared by a procedure-declaration-stmt it shall be previously 26 declared. If name denotes an intrinsic procedure it shall be one that is listed in 13.6 and not 27 marked with a bullet (·). 28 C1213 (R1215) The name shall not be the same as a keyword that specifies an intrinsic type. 29 C1214 If a procedure entity has the INTENT attribute or SAVE attribute, it shall also have the 30 POINTER attribute. 31 C1215 (R1211) If a proc-interface describes an elemental procedure, each procedure-entity-name shall 32 specify an external procedure. 33 C1216 (R1214) If => appears in proc-decl , the procedure entity shall have the POINTER attribute. 34 C1217 (R1211) If proc-language-binding-spec with a NAME= is specified, then proc-decl -list shall con- 260 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 tain exactly one proc-decl , which shall neither have the POINTER attribute nor be a dummy 2 procedure. 3 C1218 (R1211) If proc-language-binding-spec is specified, the proc-interface shall appear, it shall be an 4 interface-name, and interface-name shall be declared with a proc-language-binding-spec. 5 If proc-interface appears and consists of interface-name, it specifies an explicit specific interface (12.3.2.1) 6 for the declared procedures or procedure pointers. The abstract interface (12.3) is that specified by the 7 interface named by interface-name. 8 If proc-interface appears and consists of declaration-type-spec, it specifies that the declared procedures 9 or procedure pointers are functions having implicit interfaces and the specified result type. If a type is 10 specified for an external function, its function definition (12.5.2.1) shall specify the same result type and 11 type parameters. 12 If proc-interface does not appear, the procedure declaration statement does not specify whether the 13 declared procedures or procedure pointers are subroutines or functions. NOTE 12.13 In contrast to the EXTERNAL statement, it is not possible to use the PROCEDURE statement to identify a BLOCK DATA subprogram. NOTE 12.14 ABSTRACT INTERFACE FUNCTION REAL_FUNC (X) REAL, INTENT (IN) :: X REAL :: REAL_FUNC END FUNCTION REAL_FUNC END INTERFACE INTERFACE SUBROUTINE SUB (X) REAL, INTENT (IN) :: X END SUBROUTINE SUB END INTERFACE !-- Some external or dummy procedures with explicit interface. PROCEDURE (REAL_FUNC) :: BESSEL, GAMMA PROCEDURE (SUB) :: PRINT_REAL !-- Some procedure pointers with explicit interface, !-- one initialized to NULL(). PROCEDURE (REAL_FUNC), POINTER :: P, R => NULL() PROCEDURE (REAL_FUNC), POINTER :: PTR_TO_GAMMA !-- A derived type with a procedure pointer component ... TYPE STRUCT_TYPE PROCEDURE (REAL_FUNC), POINTER :: COMPONENT END TYPE STRUCT_TYPE !-- ... and a variable of that type. TYPE(STRUCT_TYPE) :: STRUCT !-- An external or dummy function with implicit interface PROCEDURE (REAL) :: PSI SEP 2002 COMMITTEE DRAFT 261 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 12.15 A procedure pointer is not interoperable with a C pointer. However, it is possible to pass a C pointer to a procedure from Fortran to C through the use of the C LOC function from the ISO C BINDING module (15.1.2). For such application, the argument of the C LOC function would have to be a procedure with a BIND attribute. 1 12.3.2.4 INTRINSIC statement 2 An INTRINSIC statement specifies a list of names that have the INTRINSIC attribute (5.1.2.8). 3 R1216 intrinsic-stmt is INTRINSIC [ :: ] intrinsic-procedure-name-list 4 C1219 (R1216) Each intrinsic-procedure-name shall be the name of an intrinsic procedure. NOTE 12.16 A name shall not be explicitly specified to have both the EXTERNAL and INTRINSIC attributes in the same scoping unit. 5 12.3.2.5 Implicit interface specification 6 In a scoping unit where the interface of a function is implicit, the type and type parameters of the 7 function result are specified by an implicit or explicit type specification of the function name. The type, 8 type parameters, and shape of dummy arguments of a procedure referenced from a scoping unit where 9 the interface of the procedure is implicit shall be such that the actual arguments are consistent with the 10 characteristics of the dummy arguments. 11 12.4 Procedure reference 12 The form of a procedure reference is dependent on the interface of the procedure or procedure pointer, 13 but is independent of the means by which the procedure is defined. The forms of procedure references 14 are: 15 R1217 function-reference is procedure-designator ( [ actual-arg-spec-list ] ) 16 C1220 (R1217) The procedure-designator shall designate a function. 17 C1221 (R1217) The actual-arg-spec-list shall not contain an alt-return-spec. 18 R1218 call-stmt is CALL procedure-designator [ ( [ actual-arg-spec-list ] ) ] 19 C1222 (R1218) The procedure-designator shall designate a subroutine. 20 R1219 procedure-designator is procedure-name 21 or data-ref % procedure-component-name 22 or data-ref % binding-name 23 C1223 (R1219) A procedure-name shall be the name of a procedure or procedure pointer. 24 C1224 (R1219) A procedure-component-name shall be the name of a procedure pointer component of 25 the declared type of data-ref . 26 C1225 (R1219) A binding-name shall be the name of a procedure binding (4.5.1.5) of the declared type 27 of data-ref . 28 For type-bound procedure references, the declared binding is the binding in the declared type of the 262 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 data-ref whose name is binding-name, and the dynamic binding is the binding in the dynamic type 2 of the data-ref with that name. 3 If the declared binding is nongeneric, the procedure identified by the dynamic binding is referenced. 4 If the declared binding is generic, then 5 (1) If the reference is consistent with one of the specific interfaces in the declared binding, the 6 corresponding specific interface in the dynamic binding is selected. 7 (2) Otherwise, the reference shall be consistent with an elemental reference to one of the spe- 8 cific interfaces in the declared binding; the corresponding specific interface in the dynamic 9 binding is selected. 10 The reference is to the procedure identified by that interface. 11 A function may also be referenced as a defined operation (12.3.2.1.1). A subroutine may also be referenced 12 as a defined assignment (12.3.2.1.2). 13 R1220 actual-arg-spec is [ keyword = ] actual-arg 14 R1221 actual-arg is expr 15 or variable 16 or procedure-name 17 or alt-return-spec 18 R1222 alt-return-spec is * label 19 C1226 (R1220) The keyword = shall not appear if the interface of the procedure is implicit in the 20 scoping unit. 21 C1227 (R1220) The keyword = may be omitted from an actual-arg-spec only if the keyword = has been 22 omitted from each preceding actual-arg-spec in the argument list. 23 C1228 (R1220) Each keyword shall be the name of a dummy argument in the explicit interface of the 24 procedure. 25 C1229 (R1221) A nonintrinsic elemental procedure shall not be used as an actual argument. 26 C1230 (R1221) A procedure-name shall be the name of an external procedure, a dummy procedure, a 27 module procedure, a procedure pointer, or a specific intrinsic function that is listed in 13.6 and 28 not marked with a bullet(·). NOTE 12.17 This standard does not allow internal procedures to be used as actual arguments, in part to simplify the problem of ensuring that internal procedures with recursive hosts access entities from the correct instance (12.5.2.3) of the host. If, as an extension, a processor allows internal procedures to be used as actual arguments, the correct instance in this case is the instance in which the procedure is supplied as an actual argument, even if the corresponding dummy argument is eventually invoked from a different instance. 29 C1231 (R1221) In a reference to a pure procedure, a procedure-name actual-arg shall be the name of a 30 pure procedure (12.6). NOTE 12.18 This constraint ensures that the purity of a procedure cannot be undermined by allowing it to call a nonpure procedure. 31 C1232 (R1222) The label used in the alt-return-spec shall be the statement label of a branch target statement that SEP 2002 COMMITTEE DRAFT 263 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 appears in the same scoping unit as the call-stmt . NOTE 12.19 Successive commas shall not be used to omit optional arguments. NOTE 12.20 Examples of procedure reference using procedure pointers: P => BESSEL WRITE (*, *) P(2.5) !-- BESSEL(2.5) S => PRINT_REAL CALL S(3.14) 2 12.4.1 Actual arguments, dummy arguments, and argument association 3 In either a subroutine reference or a function reference, the actual argument list identifies the corre- 4 spondence between the actual arguments supplied and the dummy arguments of the procedure. This 5 correspondence may be established either by keyword or by position. If an argument keyword appears, 6 the actual argument is associated with the dummy argument whose name is the same as the argument 7 keyword (using the dummy argument names from the interface accessible in the scoping unit containing 8 the procedure reference). In the absence of an argument keyword, an actual argument is associated 9 with the dummy argument occupying the corresponding position in the reduced dummy argument list; 10 that is, the first actual argument is associated with the first dummy argument in the reduced list, the 11 second actual argument is associated with the second dummy argument in the reduced list, etc. The 12 reduced dummy argument list is either the full dummy argument list or, if there is a passed-object 13 dummy argument (4.5.1.6), the dummy argument list with the passed object dummy argument omitted. 14 Exactly one actual argument shall be associated with each nonoptional dummy argument. At most one 15 actual argument may be associated with each optional dummy argument. Each actual argument shall 16 be associated with a dummy argument. NOTE 12.21 For example, the procedure defined by SUBROUTINE SOLVE (FUNCT, SOLUTION, METHOD, STRATEGY, PRINT) INTERFACE FUNCTION FUNCT (X) REAL FUNCT, X END FUNCTION FUNCT END INTERFACE REAL SOLUTION INTEGER, OPTIONAL :: METHOD, STRATEGY, PRINT ... may be invoked with CALL SOLVE (FUN, SOL, PRINT = 6) provided its interface is explicit; if the interface is specified by an interface block, the name of the last argument shall be PRINT. 264 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 12.4.1.1 The passed-object dummy argument and argument association 2 In a reference to a type-bound procedure that has a passed-object dummy argument (4.5.1.6), the data- 3 ref of the function-reference or call-stmt is associated, as an actual argument, with the passed-object 4 dummy argument. 5 12.4.1.2 Actual arguments associated with dummy data objects 6 A dummy argument shall be type compatible (5.1.1.8) with the associated actual argument unless the 7 dummy argument has INTENT(OUT) and is allocatable or a pointer. If the dummy argument is an 8 allocatable or pointer that does not have INTENT(IN), the associated actual argument shall be type 9 compatible with the dummy argument. If the dummy argument is allocatable or a pointer, the associated 10 actual argument shall be polymorphic if and only if the dummy argument is polymorphic. 11 The type parameter values of the actual argument shall agree with the corresponding ones of the dummy 12 argument that are not assumed or deferred, except for the case of the character length parameter of 13 an actual argument of type default character associated with a dummy argument that is not assumed 14 shape. 15 If a scalar dummy argument is of type default character, the length len of the dummy argument shall 16 be less than or equal to the length of the actual argument. The dummy argument becomes associated 17 with the leftmost len characters of the actual argument. If an array dummy argument is of type default 18 character and is not assumed shape, it becomes associated with the leftmost characters of the actual 19 argument element sequence (12.4.1.5) and it shall not extend beyond the end of that sequence. 20 The values of assumed type parameters of a dummy argument are assumed from the corresponding type 21 parameters of the associated actual argument. 22 An actual argument associated with a dummy argument that is allocatable or a pointer shall have 23 deferred the same type parameters as the dummy argument. 24 If the dummy argument is a pointer, the actual argument shall be a pointer and the nondeferred type 25 parameters and ranks shall agree. If a dummy argument is allocatable, the actual argument shall be 26 allocatable and the nondeferred type parameters and ranks shall agree. It is permissible for the actual 27 argument to have an allocation status of unallocated. 28 At the invocation of the procedure, the pointer association status of an actual argument associated with 29 a pointer dummy argument becomes undefined if the dummy argument has INTENT(OUT). 30 Except in references to intrinsic inquiry functions, if the dummy argument is not a pointer and the 31 corresponding actual argument is a pointer, the actual argument shall be associated with a target and 32 the dummy argument becomes argument associated with that target. 33 Except in references to intrinsic inquiry functions, if the dummy argument is not allocatable and the 34 actual argument is allocatable, the actual argument shall be allocated. 35 If the dummy argument has the VALUE attribute it becomes associated with a definable anonymous 36 data object whose initial value is that of the actual argument. Subsequent changes to the value or 37 definition status of the dummy argument do not affect the actual argument. NOTE 12.22 Fortran argument association is usually similar to call by reference and call by value-result. If the VALUE attribute is specified, the effect is as if the actual argument is assigned to a temporary, and the temporary is then argument associated with the dummy argument. The actual mechanism by which this happens is determined by the processor. SEP 2002 COMMITTEE DRAFT 265 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 If the dummy argument does not have the TARGET or POINTER attribute, any pointers associated 2 with the actual argument do not become associated with the corresponding dummy argument on in- 3 vocation of the procedure. If such a dummy argument is associated with an actual argument that is 4 a dummy argument with the TARGET attribute, whether any pointers associated with the original 5 actual argument become associated with the dummy argument with the TARGET attribute is processor 6 dependent. 7 If the dummy argument has the TARGET attribute, does not have the VALUE attribute, and is either 8 a scalar or an assumed-shape array, and the corresponding actual argument has the TARGET attribute 9 but is not an array section with a vector subscript then 10 (1) Any pointers associated with the actual argument become associated with the corresponding 11 dummy argument on invocation of the procedure and 12 (2) When execution of the procedure completes, any pointers that do not become undefined 13 (16.4.2.1.3) and are associated with the dummy argument remain associated with the actual 14 argument. 15 If the dummy argument has the TARGET attribute and is an explicit-shape array or is an assumed-size 16 array, and the corresponding actual argument has the TARGET attribute but is not an array section 17 with a vector subscript then 18 (1) On invocation of the procedure, whether any pointers associated with the actual argument 19 become associated with the corresponding dummy argument is processor dependent and 20 (2) When execution of the procedure completes, the pointer association status of any pointer 21 that is pointer associated with the dummy argument is processor dependent. 22 If the dummy argument has the TARGET attribute and the corresponding actual argument does not 23 have the TARGET attribute or is an array section with a vector subscript, any pointers associated with 24 the dummy argument become undefined when execution of the procedure completes. 25 If the dummy argument has the TARGET attribute and the VALUE attribute, any pointers associated 26 with the dummy argument become undefined when execution of the procedure completes. 27 If the actual argument is scalar, the corresponding dummy argument shall be scalar unless the actual 28 argument is of type default character, of type character with the C character kind (15.1), or is an element 29 or substring of an element of an array that is not an assumed-shape or pointer array. If the procedure 30 is nonelemental and is referenced by a generic name or as a defined operator or defined assignment, the 31 ranks of the actual arguments and corresponding dummy arguments shall agree. 32 If a dummy argument is an assumed-shape array, the rank of the actual argument shall be the same as 33 the rank of the dummy argument; the actual argument shall not be an assumed-size array (including an 34 array element designator or an array element substring designator). 35 Except when a procedure reference is elemental (12.7), each element of an array actual argument or of 36 a sequence in a sequence association (12.4.1.5) is associated with the element of the dummy array that 37 has the same position in array element order (6.2.2.2). NOTE 12.23 For type default character sequence associations, the interpretation of element is provided in 12.4.1.5. 38 A scalar dummy argument of a nonelemental procedure may be associated only with a scalar actual 39 argument. 40 If a nonpointer dummy argument has INTENT (OUT) or INTENT (INOUT), the actual argument shall 41 be definable. If a dummy argument has INTENT (OUT), the corresponding actual argument becomes 42 undefined at the time the association is established. If the dummy argument is not polymorphic and the 266 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 type of the actual argument is an extension type of the type of the dummy argument, only the part of 2 the actual argument that is of the same type as the dummy argument becomes undefined. 3 If the actual argument is an array section having a vector subscript, the dummy argument is not defin- 4 able and shall not have the INTENT (OUT), INTENT (INOUT), VOLATILE, or ASYNCHRONOUS 5 attributes. NOTE 12.24 Argument intent specifications serve several purposes. See Note 5.16. NOTE 12.25 For more explanatory information on argument association and evaluation, see section C.9.4. For more explanatory information on pointers and targets as dummy arguments, see section C.9.5. 6 C1233 (R1221) If an actual argument is an array section or an assumed-shape array, and the corre- 7 sponding dummy argument has either the VOLATILE or ASYNCHRONOUS attribute, that 8 dummy argument shall be an assumed-shape array. 9 C1234 (R1221) If an actual argument is a pointer array, and the corresponding dummy argument 10 has either the VOLATILE or ASYNCHRONOUS attribute, that dummy argument shall be an 11 assumed-shape array or a pointer array. NOTE 12.26 The constraints on actual arguments that correspond to a dummy argument with either the ASYN- CHRONOUS or VOLATILE attribute are designed to avoid forcing a processor to use the so-called copy-in/copy-out argument passing mechanism. Making a copy of actual arguments whose values are likely to change due to an asynchronous I/O operation completing or in some unpredictable manner will cause those new values to be lost when a called procedure returns and the copy-out overwrites the actual argument. 12 12.4.1.3 Actual arguments associated with dummy procedure entities 13 If a dummy argument is a procedure pointer, the associated actual argument shall be a procedure pointer, 14 a reference to a function that returns a procedure pointer, or a reference to the NULL intrinsic function. 15 If a dummy argument is a dummy procedure, the associated actual argument shall be the specific name 16 of an external, module, dummy, or intrinsic procedure, a procedure pointer, or a reference to a function 17 that returns a procedure pointer. The only intrinsic procedures permitted are those listed in 13.6 and 18 not marked with a bullet (·). If the specific name is also a generic name, only the specific procedure is 19 associated with the dummy argument. 20 If an external procedure name or a dummy procedure name is used as an actual argument, its interface 21 shall be explicit or it shall be explicitly declared to have the EXTERNAL attribute. 22 If the interface of the dummy argument is explicit, the characteristics listed in 12.2 shall be the same 23 for the associated actual argument and the corresponding dummy argument, except that a pure actual 24 argument may be associated with a dummy argument that is not pure and an elemental intrinsic actual 25 procedure may be associated with a dummy procedure (which is prohibited from being elemental). 26 If the interface of the dummy argument is implicit and either the name of the dummy argument is 27 explicitly typed or it is referenced as a function, the dummy argument shall not be referenced as a 28 subroutine and the actual argument shall be a function, function procedure pointer, or dummy procedure. 29 If the interface of the dummy argument is implicit and a reference to it appears as a subroutine reference, SEP 2002 COMMITTEE DRAFT 267 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 the actual argument shall be a subroutine, subroutine procedure pointer, or dummy procedure. 2 12.4.1.4 Actual arguments associated with alternate return indicators 3 If a dummy argument is an asterisk (12.5.2.2), the associated actual argument shall be an alternate return specifier (12.4). 4 12.4.1.5 Sequence association 5 An actual argument represents an element sequence if it is an array expression, an array element 6 designator, a scalar of type default character, or a scalar of type character with the C character kind 7 (15.1). If the actual argument is an array expression, the element sequence consists of the elements 8 in array element order. If the actual argument is an array element designator, the element sequence 9 consists of that array element and each element that follows it in array element order. 10 If the actual argument is of type default character or of type character with the C character kind, and is 11 an array expression, array element, or array element substring designator, the element sequence consists 12 of the storage units beginning with the first storage unit of the actual argument and continuing to the 13 end of the array. The storage units of an array element substring designator are viewed as array elements 14 consisting of consecutive groups of storage units having the character length of the dummy array. 15 If the actual argument is of type default character or of type character with the C character kind, and 16 is a scalar that is not an array element or array element substring designator, the element sequence 17 consists of the storage units of the actual argument. NOTE 12.27 Some of the elements in the element sequence may consist of storage units from different elements of the original array. 18 An actual argument that represents an element sequence and corresponds to a dummy argument that is 19 an array is sequence associated with the dummy argument if the dummy argument is an explicit-shape 20 or assumed-size array. The rank and shape of the actual argument need not agree with the rank and 21 shape of the dummy argument, but the number of elements in the dummy argument shall not exceed 22 the number of elements in the element sequence of the actual argument. If the dummy argument is 23 assumed-size, the number of elements in the dummy argument is exactly the number of elements in the 24 element sequence. 25 12.4.1.6 Restrictions on dummy arguments not present 26 A dummy argument or an entity that is host associated with a dummy argument is not present if the 27 dummy argument 28 (1) is not associated with an actual argument, or 29 (2) is associated with an actual argument that is not present. 30 Otherwise, it is present. A dummy argument that is not optional shall be present. An optional dummy 31 argument that is not present is subject to the following restrictions: 32 (1) If it is a data object, it shall not be referenced or be defined. If it is of a type for which 33 default initialization is specified for some component, the initialization has no effect. 34 (2) It shall not be used as the data-target or proc-target of a pointer assignment. 35 (3) If it is a procedure or procedure pointer, it shall not be invoked. 36 (4) It shall not be supplied as an actual argument corresponding to a nonoptional dummy 37 argument other than as the argument of the PRESENT intrinsic function or as an argument 38 of a function reference that meets the requirements of (6) or (8) in 7.1.7. 268 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 (5) A designator with it as the base object and with at least one subobject selector shall not 2 be supplied as an actual argument. 3 (6) If it is an array, it shall not be supplied as an actual argument to an elemental procedure 4 unless an array of the same rank is supplied as an actual argument corresponding to a 5 nonoptional dummy argument of that elemental procedure. 6 (7) If it is a pointer, it shall not be allocated, deallocated, nullified, pointer-assigned, or supplied 7 as an actual argument corresponding to an optional nonpointer dummy argument. 8 (8) If it is allocatable, it shall not be allocated, deallocated, or supplied as an actual argument 9 corresponding to an optional nonallocatable dummy argument. 10 (9) If it has nonkind type parameters, they shall not be the subject of an inquiry. 11 (10) It shall not be used as the selector in a SELECT TYPE or ASSOCIATE construct. 12 Except as noted in the list above, it may be supplied as an actual argument corresponding to an optional 13 dummy argument, which is then also considered not to be associated with an actual argument. 14 12.4.1.7 Restrictions on entities associated with dummy arguments 15 While an entity is associated with a dummy argument, the following restrictions hold: 16 (1) Action that affects the allocation status of the entity or a subobject thereof shall be taken 17 through the dummy argument. Action that affects the value of the entity or any subobject 18 of it shall be taken only through the dummy argument unless 19 (a) the dummy argument has the POINTER attribute or 20 (b) the dummy argument has the TARGET attribute, the dummy argument does not 21 have INTENT (IN), the dummy argument is a scalar object or an assumed-shape 22 array, and the actual argument is a target other than an array section with a vector 23 subscript. NOTE 12.28 In SUBROUTINE OUTER REAL, POINTER :: A (:) ... ALLOCATE (A (1:N)) ... CALL INNER (A) ... CONTAINS SUBROUTINE INNER (B) REAL :: B (:) ... END SUBROUTINE INNER SUBROUTINE SET (C, D) REAL, INTENT (OUT) :: C REAL, INTENT (IN) :: D C = D END SUBROUTINE SET END SUBROUTINE OUTER an assignment statement such as SEP 2002 COMMITTEE DRAFT 269 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 12.28 (cont.) A (1) = 1.0 would not be permitted during the execution of INNER because this would be changing A without using B, but statements such as B (1) = 1.0 or CALL SET (B (1), 1.0) would be allowed. Similarly, DEALLOCATE (A) would not be allowed because this affects the allocation of B without using B. In this case, DEALLOCATE (B) also would not be permitted. If B were declared with the POINTER attribute, either of the statements DEALLOCATE (A) and DEALLOCATE (B) would be permitted, but not both. NOTE 12.29 If there is a partial or complete overlap between the actual arguments associated with two different dummy arguments of the same procedure and the dummy arguments have neither the POINTER nor TARGET attribute, the overlapped portions shall not be defined, redefined, or become unde- fined during the execution of the procedure. For example, in CALL SUB (A (1:5), A (3:9)) A (3:5) shall not be defined, redefined, or become undefined through the first dummy argument because it is part of the argument associated with the second dummy argument and shall not be defined, redefined, or become undefined through the second dummy argument because it is part of the argument associated with the first dummy argument. A (1:2) remains definable through the first dummy argument and A (6:9) remains definable through the second dummy argument. NOTE 12.30 This restriction applies equally to pointer targets. In REAL, DIMENSION (10), TARGET :: A REAL, DIMENSION (:), POINTER :: B, C 270 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 12.30 (cont.) B => A (1:5) C => A (3:9) CALL SUB (B, C) ! The dummy arguments of SUB are neither pointers nor targets. B (3:5) cannot be defined because it is part of the argument associated with the second dummy argument. C (1:3) cannot be defined because it is part of the argument associated with the first dummy argument. A (1:2) [which is B (1:2)] remains definable through the first dummy argument and A (6:9) [which is C (4:7)] remains definable through the second dummy argument. NOTE 12.31 Since a nonpointer dummy argument declared with INTENT(IN) shall not be used to change the associated actual argument, the associated actual argument remains constant throughout the execution of the procedure. 1 (2) If the allocation status of the entity or a subobject thereof is affected through the dummy 2 argument, then at any time during the execution of the procedure, either before or after 3 the allocation or deallocation, it may be referenced only through the dummy argument. If 4 the value the entity or any subobject of it is affected through the dummy argument, then 5 at any time during the execution of the procedure, either before or after the definition, it 6 may be referenced only through that dummy argument unless 7 (a) the dummy argument has the POINTER attribute or 8 (b) the dummy argument has the TARGET attribute, the dummy argument does not 9 have INTENT (IN), the dummy argument is a scalar object or an assumed-shape 10 array, and the actual argument is a target other than an array section with a vector 11 subscript. NOTE 12.32 In MODULE DATA REAL :: W, X, Y, Z END MODULE DATA PROGRAM MAIN USE DATA ... CALL INIT (X) ... END PROGRAM MAIN SUBROUTINE INIT (V) USE DATA ... READ (*, *) V ... END SUBROUTINE INIT variable X shall not be directly referenced at any time during the execution of INIT because it is being defined through the dummy argument V. X may be (indirectly) referenced through V. W, Y, and Z may be directly referenced. X may, of course, be directly referenced once execution of INIT is complete. SEP 2002 COMMITTEE DRAFT 271 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 12.33 The restrictions on entities associated with dummy arguments are intended to facilitate a variety of optimizations in the translation of the subprogram, including implementations of argument association in which the value of an actual argument that is neither a pointer nor a target is maintained in a register or in local storage. 1 12.4.2 Function reference 2 A function is invoked during expression evaluation by a function-reference or by a defined operation 3 (7.1.3). When it is invoked, all actual argument expressions are evaluated, then the arguments are 4 associated, and then the function is executed. When execution of the function is complete, the value 5 of the function result is available for use in the expression that caused the function to be invoked. The 6 characteristics of the function result (12.2.2) are determined by the interface of the function. A reference 7 to an elemental function (12.7) is an elemental reference if one or more actual arguments are arrays and 8 all array arguments have the same shape. 9 12.4.3 Subroutine reference 10 A subroutine is invoked by execution of a CALL statement or defined assignment statement (7.4.1.4). 11 When a subroutine is invoked, all actual argument expressions are evaluated, then the arguments are 12 associated, and then the subroutine is executed. When the actions specified by the subroutine are 13 completed, execution of the CALL statement or defined assignment statement is also completed. If a 14 CALL statement includes one or more alternate return specifiers among its arguments, control may be transferred to 15 one of the statements indicated, depending on the action specified by the subroutine. A reference to an elemental 16 subroutine (12.7) is an elemental reference if there is at least one actual argument corresponding to an 17 INTENT(OUT) or INTENT(INOUT) dummy argument, all such actual arguments are arrays, and all 18 actual arguments are conformable. 19 12.4.4 Resolving procedure references 20 The rules for interpreting a procedure reference depend on whether the procedure name in the reference 21 is established by the available declarations and specifications to be generic in the scoping unit containing 22 the reference, is established to be specific only in the scoping unit containing the reference, or is not 23 established. 24 (1) A procedure name is established to be generic in a scoping unit 25 (a) if that scoping unit contains an interface block with that name; 26 (b) if that scoping unit contains an INTRINSIC attribute specification for that name and 27 it is the name of a generic intrinsic procedure; 28 (c) if that scoping unit contains a USE statement that makes that procedure name ac- 29 cessible and the corresponding name in the module is established to be generic; or 30 (d) if that scoping unit contains no declarations of that name, that scoping unit has a 31 host scoping unit, and that name is established to be generic in the host scoping unit. 32 (2) A procedure name is established to be specific only in a scoping unit if it is established to 33 be specific and not established to be generic. It is established to be specific 34 (a) if that scoping unit contains a module subprogram, internal subprogram, or statement 35 function that defines a procedure with that name; 36 (b) if that scoping unit contains an INTRINSIC attribute specification for that name and 37 if it is the name of a specific intrinsic procedure; 38 (c) if that scoping unit contains an explicit EXTERNAL attribute specification (5.1.2.6) 39 for that name; 272 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 (d) if that scoping unit contains a USE statement that makes that procedure name ac- 2 cessible and the corresponding name in the module is established to be specific; or 3 (e) if that scoping unit contains no declarations of that name, that scoping unit has a 4 host scoping unit, and that name is established to be specific in the host scoping unit. 5 (3) A procedure name is not established in a scoping unit if it is neither established to be generic 6 nor established to be specific. 7 12.4.4.1 Resolving procedure references to names established to be generic 8 (1) If the reference is consistent with a nonelemental reference to one of the specific interfaces of 9 a generic interface that has that name and either is in the scoping unit in which the reference 10 appears or is made accessible by a USE statement in the scoping unit, the reference is to 11 the specific procedure in the interface block that provides that interface. The rules in 16.2.3 12 ensure that there can be at most one such specific procedure. 13 (2) If (1) does not apply, if the reference is consistent with an elemental reference to one of the 14 specific interfaces of a generic interface that has that name and either is in the scoping unit 15 in which the reference appears or is made accessible by a USE statement in the scoping unit, 16 the reference is to the specific elemental procedure in the interface block that provides that 17 interface. The rules in 16.2.3 ensure that there can be at most one such specific elemental 18 procedure. NOTE 12.34 These rules allow particular instances of a generic function to be used for particular array ranks and a general elemental version to be used for other ranks. Given an interface block such as: INTERFACE RANF ELEMENTAL FUNCTION SCALAR_RANF(X) REAL X END FUNCTION SCALAR_RANF FUNCTION VECTOR_RANDOM(X) REAL X(:) REAL VECTOR_RANDOM(SIZE(X)) END FUNCTION VECTOR_RANDOM END INTERFACE RANF and a declaration such as: REAL A(10,10), AA(10,10) then the statement A = RANF(AA) is an elemental reference to SCALAR RANF. The statement A = RANF(AA(6:10,2)) is a nonelemental reference to VECTOR RANDOM. 19 (3) If (1) and (2) do not apply, if the scoping unit contains either an INTRINSIC attribute 20 specification for that name or a USE statement that makes that name accessible from a 21 module in which the corresponding name is specified to have the INTRINSIC attribute, and 22 if the reference is consistent with the interface of that intrinsic procedure, the reference is 23 to that intrinsic procedure. SEP 2002 COMMITTEE DRAFT 273 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 12.35 In the USE statement case, it is possible, because of the renaming facility, for the name in the reference to be different from the name of the intrinsic procedure. 1 (4) If (1), (2), and (3) do not apply, if the scoping unit has a host scoping unit, if the name 2 is established to be generic in that host scoping unit, and if there is agreement between 3 the scoping unit and the host scoping unit as to whether the name is a function name or 4 a subroutine name, the name is resolved by applying the rules in this section to the host 5 scoping unit. 6 12.4.4.2 Resolving procedure references to names established to be specific 7 (1) If the scoping unit contains an interface body or EXTERNAL attribute specification for the 8 name, if the scoping unit is a subprogram, and if the name is the name of a dummy argument 9 of that subprogram, the dummy argument is a dummy procedure and the reference is to 10 that dummy procedure. That is, the procedure invoked by executing that reference is the 11 procedure supplied as the actual argument corresponding to that dummy procedure. 12 (2) If the scoping unit contains an interface body or EXTERNAL attribute specification for the 13 name and if (1) does not apply, the reference is to an external procedure with that name. 14 (3) If the scoping unit contains a module subprogram, internal subprogram, or statement function 15 that defines a procedure with the name, the reference is to the procedure so defined. 16 (4) If the scoping unit contains an INTRINSIC attribute specification for the name, the reference 17 is to the intrinsic with that name. 18 (5) If the scoping unit contains a USE statement that makes a procedure accessible by the 19 name, the reference is to that procedure. NOTE 12.36 Because of the renaming facility of the USE statement, the name in the reference may be different from the original name of the procedure. 20 (6) If none of the above apply, the scoping unit shall have a host scoping unit, and the reference 21 is resolved by applying the rules in this section to the host scoping unit. 22 12.4.4.3 Resolving procedure references to names not established 23 (1) If the scoping unit is a subprogram and if the name is the name of a dummy argument 24 of that subprogram, the dummy argument is a dummy procedure and the reference is to 25 that dummy procedure. That is, the procedure invoked by executing that reference is the 26 procedure supplied as the actual argument corresponding to that dummy procedure. 27 (2) If (1) does not apply, if the name is the name of an intrinsic procedure, and if there is 28 agreement between the reference and the status of the intrinsic procedure as being a function 29 or subroutine, the reference is to that intrinsic procedure. 30 (3) If (1) and (2) do not apply, the reference is to an external procedure with that name. 31 12.5 Procedure definition 32 12.5.1 Intrinsic procedure definition 33 Intrinsic procedures are defined as an inherent part of the processor. A standard-conforming processor 34 shall include the intrinsic procedures described in Section 13, but may include others. However, a 35 standard-conforming program shall not make use of intrinsic procedures other than those described in 36 Section 13. 274 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 12.5.2 Procedures defined by subprograms 2 When a procedure defined by a subprogram is invoked, an instance (12.5.2.3) of the subprogram is 3 created and executed. Execution begins with the first executable construct following the FUNCTION, 4 SUBROUTINE, or ENTRY statement specifying the name of the procedure invoked. 5 12.5.2.1 Function subprogram 6 A function subprogram is a subprogram that has a FUNCTION statement as its first statement. 7 R1223 function-subprogram is function-stmt 8 [ specification-part ] 9 [ execution-part ] 10 [ internal-subprogram-part ] 11 end-function-stmt 12 R1224 function-stmt is [ prefix ] FUNCTION function-name 13 ( [ dummy-arg-name-list ] ) 14 [, proc-language-binding-spec] [ RESULT ( result-name ) ] 15 C1235 (R1224) If RESULT is specified, result-name shall not be the same as function-name and shall 16 not be the same as the entry-name in any ENTRY statement in the subprogram. 17 C1236 (R1224) If RESULT is specified, the function-name shall not appear in any specification state- 18 ment in the scoping unit of the function subprogram. 19 R1225 proc-language-binding-spec is language-binding-spec 20 C1237 (R1225) A proc-language-binding-spec with a NAME= specifier shall not be specified in the 21 function-stmt or subroutine-stmt of an interface body for an abstract interface or a dummy 22 procedure. 23 C1238 (R1225) A proc-language-binding-spec shall not be specified for an internal procedure. 24 C1239 (R1225) If proc-language-binding-spec is specified for a procedure, each of the procedure's dummy 25 arguments shall be a nonoptional interoperable variable (15.2.4, 15.2.5) or an interoperable 26 procedure (15.2.6). If proc-language-binding-spec is specified for a function, the function result 27 shall be an interoperable variable. 28 R1226 dummy-arg-name is name 29 C1240 (R1226) A dummy-arg-name shall be the name of a dummy argument. 30 R1227 prefix is prefix-spec [ prefix-spec ] ... 31 R1228 prefix-spec is declaration-type-spec 32 or RECURSIVE 33 or PURE 34 or ELEMENTAL 35 C1241 (R1227) A prefix shall contain at most one of each prefix-spec. 36 C1242 (R1227) A prefix shall not specify both ELEMENTAL and RECURSIVE. 37 C1243 (R1227) A prefix shall not specify ELEMENTAL if proc-language-binding-spec appears in the 38 function-stmt or subroutine-stmt . 39 R1229 end-function-stmt is END [ FUNCTION [ function-name ] ] 40 C1244 (R1229) FUNCTION shall appear in the end-function-stmt of an internal or module function. SEP 2002 COMMITTEE DRAFT 275 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 C1245 (R1223) An internal function subprogram shall not contain an ENTRY statement. 2 C1246 (R1223) An internal function subprogram shall not contain an internal-subprogram-part . 3 C1247 (R1229) If a function-name appears in the end-function-stmt , it shall be identical to the function- 4 name specified in the function-stmt . 5 The type and type parameters (if any) of the result of the function defined by a function subprogram 6 may be specified by a type specification in the FUNCTION statement or by the name of the result 7 variable appearing in a type declaration statement in the declaration part of the function subprogram. 8 They shall not be specified both ways. If they are not specified either way, they are determined by 9 the implicit typing rules in force within the function subprogram. If the function result is an array, 10 allocatable, or a pointer, this shall be specified by specifications of the name of the result variable within 11 the function body. The specifications of the function result attributes, the specification of dummy 12 argument attributes, and the information in the procedure heading collectively define the characteristics 13 of the function (12.2). 14 The prefix-spec RECURSIVE shall appear if the function directly or indirectly invokes itself or a function 15 defined by an ENTRY statement in the same subprogram. Similarly, RECURSIVE shall appear if a 16 function defined by an ENTRY statement in the subprogram directly or indirectly invokes itself, another 17 function defined by an ENTRY statement in that subprogram, or the function defined by the FUNCTION 18 statement. 19 The name of the function is function-name. 20 If RESULT is specified, the name of the result variable of the function is result-name and all occurrences 21 of the function name in execution-part statements in the scoping unit refer to the function itself. If 22 RESULT is not specified, the result variable is function-name and all occurrences of the function name 23 in execution-part statements in the scoping unit are references to the result variable. The characteristics 24 (12.2.2) of the function result are those of the result variable. On completion of execution of a function, 25 the value returned is the value of its result variable. If the function result is a pointer, the shape of 26 the value returned by the function is determined by the shape of the result variable when the execution 27 of the function is completed. If the result variable is not a pointer, its value shall be defined by the 28 function. If the function result is a pointer, the function shall either associate a target with the result 29 variable pointer or cause the association status of this pointer to become defined as disassociated. NOTE 12.37 The result variable is similar to any other variable local to a function subprogram. Its existence begins when execution of the function is initiated and ends when execution of the function is terminated. However, because the final value of this variable is used subsequently in the evaluation of the expression that invoked the function, an implementation may wish to defer releasing the storage occupied by that variable until after its value has been used in expression evaluation. 30 If the prefix-spec PURE or ELEMENTAL appears, the subprogram is a pure subprogram and shall meet 31 the additional constraints of 12.6. 32 If the prefix-spec ELEMENTAL appears, the subprogram is an elemental subprogram and shall meet 33 the additional constraints of 12.7.1. NOTE 12.38 An example of a recursive function is: RECURSIVE FUNCTION CUMM_SUM (ARRAY) RESULT (C_SUM) 276 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 12.38 (cont.) REAL, INTENT (IN), DIMENSION (:) :: ARRAY REAL, DIMENSION (SIZE (ARRAY)) ::C_SUM INTEGER N N = SIZE (ARRAY) IF (N <= 1) THEN C_SUM = ARRAY ELSE N = N / 2 C_SUM (:N) = CUMM_SUM (ARRAY (:N)) C_SUM (N+1:) = C_SUM (N) + CUMM_SUM (ARRAY (N+1:)) END IF END FUNCTION CUMM_SUM NOTE 12.39 The following is an example of the declaration of an interface body with the BIND attribute, and a reference to the procedure declared. USE, INTRINSIC :: ISO_C_BINDING INTERFACE FUNCTION JOE (I, J, R), BIND(C,NAME="FrEd") USE, INTRINSIC :: ISO_C_BINDING INTEGER(C_INT) :: JOE INTEGER(C_INT), VALUE :: I, J REAL(C_FLOAT), VALUE :: R END FUNCTION JOE END INTERFACE INT = JOE(1_C_INT, 3_C_INT, 4.0_C_FLOAT) END PROGRAM The invocation of the function JOE results in a reference to a function with a binding label "FrEd". FrEd may be a C function described by the C prototype int FrEd(int n, int m, float x); 1 12.5.2.2 Subroutine subprogram 2 A subroutine subprogram is a subprogram that has a SUBROUTINE statement as its first statement. 3 R1230 subroutine-subprogram is subroutine-stmt 4 [ specification-part ] 5 [ execution-part ] 6 [ internal-subprogram-part ] 7 end-subroutine-stmt 8 R1231 subroutine-stmt is [ prefix ] SUBROUTINE subroutine-name 9 [ ( [ dummy-arg -list ] ) ] [, proc-language-binding-spec ] 10 C1248 (R1231) The prefix of a subroutine-stmt shall not contain a declaration-type-spec. 11 R1232 dummy-arg is dummy-arg-name SEP 2002 COMMITTEE DRAFT 277 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 or * 2 R1233 end-subroutine-stmt is END [ SUBROUTINE [ subroutine-name ] ] 3 C1249 (R1233) SUBROUTINE shall appear in the end-subroutine-stmt of an internal or module sub- 4 routine. 5 C1250 (R1230) An internal subroutine subprogram shall not contain an ENTRY statement. 6 C1251 (R1230) An internal subroutine subprogram shall not contain an internal-subprogram-part . 7 C1252 (R1233) If a subroutine-name appears in the end-subroutine-stmt , it shall be identical to the 8 subroutine-name specified in the subroutine-stmt . 9 The name of the subroutine is subroutine-name. 10 The prefix-spec RECURSIVE shall appear if the subroutine directly or indirectly invokes itself or a 11 subroutine defined by an ENTRY statement in the same subprogram. Similarly, RECURSIVE shall 12 appear if a subroutine defined by an ENTRY statement in the subprogram directly or indirectly invokes 13 itself, another subroutine defined by an ENTRY statement in that subprogram, or the subroutine defined 14 by the SUBROUTINE statement. 15 If the prefix-spec PURE or ELEMENTAL appears, the subprogram is a pure subprogram and shall meet 16 the additional constraints of 12.6. 17 If the prefix-spec ELEMENTAL appears, the subprogram is an elemental subprogram and shall meet 18 the additional constraints of 12.7.1. 19 12.5.2.3 Instances of a subprogram 20 When a function or subroutine defined by a subprogram is invoked, an instance of that subprogram is 21 created. When a statement function is invoked, an instance of that statement function is created. 22 Each instance has an independent sequence of execution and an independent set of dummy arguments 23 and local unsaved data objects. If an internal procedure or statement function in the subprogram is invoked 24 directly from an instance of the subprogram or from an internal subprogram or statement function that 25 has access to the entities of that instance, the created instance of the internal subprogram or statement 26 function also has access to the entities of that instance of the host subprogram. 27 All other entities are shared by all instances of the subprogram. NOTE 12.40 The value of a saved data object appearing in one instance may have been defined in a previous instance or by initialization in a DATA statement or type declaration statement. 28 12.5.2.4 ENTRY statement 29 An ENTRY statement permits a procedure reference to begin with a particular executable statement 30 within the function or subroutine subprogram in which the ENTRY statement appears. 31 R1234 entry-stmt is ENTRY entry-name [ ( [ dummy-arg -list ] ) 32 [, proc-language-binding-spec ] 33 [ RESULT ( result-name ) ] ] 34 or ENTRY entry-name 35 , proc-language-binding-spec [ RESULT ( result-name ) ] 36 C1253 (R1234) If RESULT is specified, the entry-name shall not appear in any specification or type- 278 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 declaration statement in the scoping unit of the function program. 2 C1254 (R1234) An entry-stmt may appear only in an external-subprogram or module-subprogram. An 3 entry-stmt shall not appear within an executable-construct . 4 C1255 (R1234) RESULT may appear only if the entry-stmt is in a function subprogram. 5 C1256 (R1234) Within the subprogram containing the entry-stmt , the entry-name shall not appear 6 as a dummy argument in the FUNCTION or SUBROUTINE statement or in another ENTRY 7 statement nor shall it appear in an EXTERNAL, INTRINSIC, or PROCEDURE statement. 8 C1257 (R1234) A dummy-arg may be an alternate return indicator only if the ENTRY statement is in a subroutine 9 subprogram. 10 C1258 (R1234) If RESULT is specified, result-name shall not be the same as the function-name in the 11 FUNCTION statement and shall not be the same as the entry-name in any ENTRY statement 12 in the subprogram. 13 Optionally, a subprogram may have one or more ENTRY statements. 14 If the ENTRY statement is in a function subprogram, an additional function is defined by that subpro- 15 gram. The name of the function is entry-name and the name of its result variable is result-name or 16 is entry-name if no result-name is provided. The characteristics of the function result are specified by 17 specifications of the result variable. The dummy arguments of the function are those specified in the 18 ENTRY statement. If the characteristics of the result of the function named in the ENTRY statement 19 are the same as the characteristics of the result of the function named in the FUNCTION statement, 20 their result variables identify the same variable, although their names need not be the same. Otherwise, 21 they are storage associated and shall all be scalars without the POINTER attribute and one of the types: 22 default integer, default real, double precision real, default complex, or default logical. 23 If the ENTRY statement is in a subroutine subprogram, an additional subroutine is defined by that 24 subprogram. The name of the subroutine is entry-name. The dummy arguments of the subroutine are 25 those specified in the ENTRY statement. 26 The order, number, types, kind type parameters, and names of the dummy arguments in an ENTRY 27 statement may differ from the order, number, types, kind type parameters, and names of the dummy 28 arguments in the FUNCTION or SUBROUTINE statement in the containing subprogram. 29 Because an ENTRY statement defines an additional function or an additional subroutine, it is referenced 30 in the same manner as any other function or subroutine (12.4). 31 In a subprogram, a name that appears as a dummy argument in an ENTRY statement shall not appear 32 in an executable statement preceding that ENTRY statement, unless it also appears in a FUNCTION, 33 SUBROUTINE, or ENTRY statement that precedes the executable statement. 34 In a subprogram, a name that appears as a dummy argument in an ENTRY statement shall not appear in the expression 35 of a statement function unless the name is also a dummy argument of the statement function, appears in a FUNCTION 36 or SUBROUTINE statement, or appears in an ENTRY statement that precedes the statement function statement. 37 If a dummy argument appears in an executable statement, the execution of the executable statement is 38 permitted during the execution of a reference to the function or subroutine only if the dummy argument 39 appears in the dummy argument list of the procedure name referenced. 40 If a dummy argument is used in a specification expression to specify an array bound or character length 41 of an object, the appearance of the object in a statement that is executed during a procedure reference 42 is permitted only if the dummy argument appears in the dummy argument list of the procedure name 43 referenced and it is present (12.4.1.6). SEP 2002 COMMITTEE DRAFT 279 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 A scoping unit containing a reference to a procedure defined by an ENTRY statement may have access to 2 an interface body for the procedure. The procedure header for the interface body shall be a FUNCTION 3 statement for an entry in a function subprogram and shall be a SUBROUTINE statement for an entry 4 in a subroutine subprogram. 5 The keyword RECURSIVE is not used in an ENTRY statement. Instead, the presence or absence of 6 RECURSIVE in the initial SUBROUTINE or FUNCTION statement controls whether the procedure 7 defined by an ENTRY statement is permitted to reference itself. 8 The keyword PURE is not used in an ENTRY statement. Instead, the procedure defined by an ENTRY 9 statement is pure if and only if PURE or ELEMENTAL is specified in the SUBROUTINE or FUNCTION 10 statement. 11 The keyword ELEMENTAL is not used in an ENTRY statement. Instead, the procedure defined by 12 an ENTRY statement is elemental if and only if ELEMENTAL is specified in the SUBROUTINE or 13 FUNCTION statement. 14 12.5.2.5 RETURN statement 15 R1235 return-stmt is RETURN [ scalar-int-expr ] 16 C1259 (R1235) The return-stmt shall be in the scoping unit of a function or subroutine subprogram. 17 C1260 (R1235) The scalar-int-expr is allowed only in the scoping unit of a subroutine subprogram. 18 Execution of the RETURN statement completes execution of the instance of the subprogram in which 19 it appears. If the expression appears and has a value n between 1 and the number of asterisks in the dummy argument 20 list, the CALL statement that invoked the subroutine transfers control to the statement identified by the nth alternate 21 return specifier in the actual argument list. If the expression is omitted or has a value outside the required range, there is 22 no transfer of control to an alternate return. 23 Execution of an end-function-stmt or end-subroutine-stmt is equivalent to executing a RETURN state- 24 ment with no expression. 25 12.5.2.6 CONTAINS statement 26 R1236 contains-stmt is CONTAINS 27 The CONTAINS statement separates the body of a main program, module, or subprogram from any 28 internal or module subprograms it may contain, or it introduces the type-bound procedure part of a 29 derived-type definition (4.5.1). The CONTAINS statement is not executable. 30 12.5.3 Definition and invocation of procedures by means other than Fortran 31 A procedure may be defined by means other than Fortran. The interface of a procedure defined by means 32 other than Fortran may be specified in an interface block. If the interface of such a procedure does not 33 have a proc-language-binding-spec, the means by which the procedure is defined are processor dependent. 34 A reference to such a procedure is made as though it were defined by an external subprogram. 35 If the interface of a procedure has a proc-language-binding-spec, the procedure is interoperable (15.4). 36 Interoperation with C functions is described in 15.4. NOTE 12.41 For explanatory information on definition of procedures by means other than Fortran, see section C.9.2. 280 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 12.5.4 Statement function 2 A statement function is a function defined by a single statement. 3 R1237 stmt-function-stmt is function-name ( [ dummy-arg-name-list ] ) = scalar-expr 4 C1261 (R1237) The primaries of the scalar-expr shall be constants (literal and named), references to variables, references 5 to functions and function dummy procedures, and intrinsic operations. If scalar-expr contains a reference to a 6 function or a function dummy procedure, the reference shall not require an explicit interface, the function shall 7 not require an explicit interface unless it is an intrinsic, the function shall not be a transformational intrinsic, 8 and the result shall be scalar. If an argument to a function or a function dummy procedure is an array, it shall 9 be an array name. If a reference to a statement function appears in scalar-expr , its definition shall have been 10 provided earlier in the scoping unit and shall not be the name of the statement function being defined. 11 C1262 (R1237) Named constants in scalar-expr shall have been declared earlier in the scoping unit or made accessible 12 by use or host association. If array elements appear in scalar-expr , the array shall have been declared as an array 13 earlier in the scoping unit or made accessible by use or host association. 14 C1263 (R1237) If a dummy-arg-name, variable, function reference, or dummy function reference is typed by the implicit 15 typing rules, its appearance in any subsequent type declaration statement shall confirm this implied type and 16 the values of any implied type parameters. 17 C1264 (R1237) The function-name and each dummy-arg-name shall be specified, explicitly or implicitly, to be scalar. 18 C1265 (R1237) A given dummy-arg-name may appear only once in any dummy-arg-name-list. 19 C1266 (R1237) Each variable reference in scalar-expr may be either a reference to a dummy argument of the statement 20 function or a reference to a variable accessible in the same scoping unit as the statement function statement. 21 The definition of a statement function with the same name as an accessible entity from the host shall be preceded by the 22 declaration of its type in a type declaration statement. 23 The dummy arguments have a scope of the statement function statement. Each dummy argument has the same type and 24 type parameters as the entity of the same name in the scoping unit containing the statement function. 25 A statement function shall not be supplied as a procedure argument. 26 The value of a statement function reference is obtained by evaluating the expression using the values of the actual arguments 27 for the values of the corresponding dummy arguments and, if necessary, converting the result to the declared type and 28 type attributes of the function. 29 A function reference in the scalar expression shall not cause a dummy argument of the statement function to become 30 redefined or undefined. 31 12.6 Pure procedures 32 A pure procedure is 33 (1) A pure intrinsic function (13.1), 34 (2) A pure intrinsic subroutine (13.1), 35 (3) Defined by a pure subprogram, or 36 (4) A statement function that references only pure functions. 37 A pure subprogram is a subprogram that has the prefix-spec PURE or ELEMENTAL. The following 38 additional constraints apply to pure subprograms. SEP 2002 COMMITTEE DRAFT 281 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 C1267 The specification-part of a pure function subprogram shall specify that all dummy arguments 2 have INTENT (IN) except procedure arguments and arguments with the POINTER attribute. 3 C1268 The specification-part of a pure subroutine subprogram shall specify the intents of all dummy ar- 4 guments except procedure arguments, alternate return indicators, and arguments with the POINTER 5 attribute. 6 C1269 A local variable declared in the specification-part or internal-subprogram-part of a pure subpro- 7 gram shall not have the SAVE attribute. NOTE 12.42 Variable initialization in a type-declaration-stmt or a data-stmt implies the SAVE attribute; there- fore, such initialization is also disallowed. 8 C1270 The specification-part of a pure subprogram shall specify that all dummy arguments that are 9 procedure arguments are pure. 10 C1271 If a procedure that is neither an intrinsic procedure nor a statement function is used in a context 11 that requires it to be pure, then its interface shall be explicit in the scope of that use. The 12 interface shall specify that the procedure is pure. 13 C1272 All internal subprograms in a pure subprogram shall be pure. 14 C1273 In a pure subprogram any designator with a base object that is in common or accessed by 15 host or use association, is a dummy argument of a pure function, is a dummy argument with 16 INTENT (IN) of a pure subroutine, or an object that is storage associated with any such variable, 17 shall not be used in the following contexts: 18 (1) In a variable definition context(16.5.7); 19 (2) As the data-target in a pointer-assignment-stmt ; 20 (3) As the expr corresponding to a component with the POINTER attribute in a structure- 21 constructor . 22 (4) As the expr of an intrinsic assignment statement in which the variable is of a derived type 23 if the derived type has a pointer component at any level of component selection; or NOTE 12.43 This requires that processors be able to determine if entities with the PRIVATE attribute or with private components have a pointer component. 24 (5) As an actual argument associated with a dummy argument with INTENT (OUT) or IN- 25 TENT (INOUT) or with the POINTER attribute. 26 C1274 Any procedure referenced in a pure subprogram, including one referenced via a defined operation, 27 assignment, or finalization, shall be pure. 28 C1275 A pure subprogram shall not contain a print-stmt , open-stmt , close-stmt , backspace-stmt , endfile- 29 stmt , rewind-stmt , flush-stmt , wait-stmt , or inquire-stmt . 30 C1276 A pure subprogram shall not contain a read-stmt or write-stmt whose io-unit is a file-unit- 31 number or *. 32 C1277 A pure subprogram shall not contain a stop-stmt . 282 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 NOTE 12.44 The above constraints are designed to guarantee that a pure procedure is free from side effects (modifications of data visible outside the procedure), which means that it is safe to reference it in constructs such as a FORALL assignment-stmt where there is no explicit order of evaluation. The constraints on pure subprograms may appear complicated, but it is not necessary for a pro- grammer to be intimately familiar with them. From the programmer's point of view, these con- straints can be summarized as follows: a pure subprogram shall not contain any operation that could conceivably result in an assignment or pointer assignment to a common variable, a variable accessed by use or host association, or an INTENT (IN) dummy argument; nor shall a pure sub- program contain any operation that could conceivably perform any external file input/output or STOP operation. Note the use of the word conceivably; it is not sufficient for a pure subprogram merely to be side-effect free in practice. For example, a function that contains an assignment to a global variable but in a block that is not executed in any invocation of the function is nevertheless not a pure function. The exclusion of functions of this nature is required if strict compile-time checking is to be used. It is expected that most library procedures will conform to the constraints required of pure pro- cedures, and so can be declared pure and referenced in FORALL statements and constructs and within user-defined pure procedures. NOTE 12.45 Pure subroutines are included to allow subroutine calls from pure procedures in a safe way, and to allow forall-assignment-stmt s to be defined assignments. The constraints for pure subroutines are based on the same principles as for pure functions, except that side effects to INTENT (OUT), INTENT (INOUT), and pointer dummy arguments are permitted. 1 12.7 Elemental procedures 2 12.7.1 Elemental procedure declaration and interface 3 An elemental procedure is an elemental intrinsic procedure or a procedure that is defined by an 4 elemental subprogram. 5 An elemental subprogram has the prefix-spec ELEMENTAL. An elemental subprogram is a pure sub- 6 program. The PURE prefix-spec need not appear; it is implied by the ELEMENTAL prefix-spec. The 7 following additional constraints apply to elemental subprograms. 8 C1278 All dummy arguments of an elemental procedure shall be scalar dummy data objects and shall 9 not have the POINTER or ALLOCATABLE attribute. 10 C1279 The result variable of an elemental function shall be scalar and shall not have the POINTER or 11 ALLOCATABLE attribute. 12 C1280 In the scoping unit of an elemental subprogram, an object designator with a dummy argument 13 as the base object shall not appear in a specification-expr except as the argument to one of the 14 intrinsic functions BIT SIZE, KIND, LEN, or the numeric inquiry functions (13.5.6). NOTE 12.46 An elemental subprogram is a pure subprogram and all of the constraints for pure subprograms also apply. SEP 2002 COMMITTEE DRAFT 283 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 12.47 The restriction on dummy arguments in specification expressions is imposed primarily to facilitate optimization. An example of usage that is not permitted is ELEMENTAL REAL FUNCTION F (A, N) REAL, INTENT (IN) :: A INTEGER, INTENT (IN) :: N REAL :: WORK_ARRAY(N) ! Invalid ... END FUNCTION F An example of usage that is permitted is ELEMENTAL REAL FUNCTION F (A) REAL, INTENT (IN) :: A REAL (SELECTED_REAL_KIND (PRECISION (A)*2)) :: WORK ... END FUNCTION F 1 12.7.2 Elemental function actual arguments and results 2 If a generic name or a specific name is used to reference an elemental function, the shape of the result is 3 the same as the shape of the actual argument with the greatest rank. If there are no actual arguments 4 or the actual arguments are all scalar, the result is scalar. For those elemental functions that have more 5 than one argument, all actual arguments shall be conformable. In the array case, the values of the 6 elements, if any, of the result are the same as would have been obtained if the scalar function had been 7 applied separately, in any order, to corresponding elements of each array actual argument. NOTE 12.48 An example of an elemental reference to the intrinsic function MAX: if X and Y are arrays of shape (M, N), MAX (X, 0.0, Y) is an array expression of shape (M, N) whose elements have values MAX (X(I, J), 0.0, Y(I, J)), I = 1, 2, ..., M, J = 1,2, ..., N 8 12.7.3 Elemental subroutine actual arguments 9 An elemental subroutine is one that has only scalar dummy arguments, but may have array actual 10 arguments. In a reference to an elemental subroutine, either all actual arguments shall be scalar, or 11 all actual arguments associated with INTENT (OUT) and INTENT (INOUT) dummy arguments shall 12 be arrays of the same shape and the remaining actual arguments shall be conformable with them. In 13 the case that the actual arguments associated with INTENT (OUT) and INTENT (INOUT) dummy 14 arguments are arrays, the values of the elements, if any, of the results are the same as would be obtained 15 if the subroutine had been applied separately, in any order, to corresponding elements of each array 16 actual argument. 17 In a reference to the intrinsic subroutine MVBITS, the actual arguments corresponding to the TO and 18 FROM dummy arguments may be the same variable and may be associated scalar variables or associated 19 array variables all of whose corresponding elements are associated. Apart from this, the actual arguments 284 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 in a reference to an elemental subroutine must satisfy the restrictions of 12.4.1.7. SEP 2002 COMMITTEE DRAFT 285 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 286 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 Section 13: Intrinsic procedures and modules 2 There are four classes of intrinsic procedures: inquiry functions, elemental functions, transformational 3 functions, and subroutines. Some intrinsic subroutines are elemental. 4 There are three sets of standard intrinsic modules: a Fortran environment module (13.8.3), modules to 5 support exception handling and IEEE arithmetic, and a module to support interoperability with the C 6 programming language. The later two sets of modules are described in sections 14 and 15, respectively. 7 13.1 Classes of intrinsic procedures 8 An inquiry function is one whose result depends on the properties of one or more of its arguments 9 instead of their values; in fact, these argument values may be undefined. Unless the description of an 10 inquiry function states otherwise, these arguments are permitted to be unallocated or pointers that are 11 not associated. An elemental intrinsic function is one that is specified for scalar arguments, but may 12 be applied to array arguments as described in 12.7. All other intrinsic functions are transformational 13 functions; they almost all have one or more array arguments or an array result. All standard intrinsic 14 functions are pure. 15 The elemental subroutine MVBITS is pure. No other standard intrinsic subroutine is pure. NOTE 13.1 As with user-written elemental subroutines, an elemental intrinsic subroutine is pure. The nonele- mental intrinsic subroutines all have side effects (or reflect system side effects) and thus are not pure. 16 Generic names of standard intrinsic procedures are listed in 13.5. In most cases, generic functions 17 accept arguments of more than one type and the type of the result is the same as the type of the 18 arguments. Specific names of standard intrinsic functions with corresponding generic names are listed 19 in 13.6. 20 If an intrinsic function is used as an actual argument to a procedure, its specific name shall be used and 21 it may be referenced in the called procedure only with scalar arguments. If an intrinsic function does 22 not have a specific name, it shall not be used as an actual argument (12.4.1.3). 23 Elemental intrinsic procedures behave as described in 12.7. 24 13.2 Arguments to intrinsic procedures 25 All intrinsic procedures may be invoked with either positional arguments or argument keywords (12.4). 26 The descriptions in 13.5 through 13.7 give the argument keyword names and positional sequence for 27 standard intrinsic procedures. 28 Many of the intrinsic procedures have optional arguments. These arguments are identified by the notation 29 "optional" in the argument descriptions. In addition, the names of the optional arguments are enclosed 30 in square brackets in description headings and in lists of procedures. The valid forms of reference for 31 procedures with optional arguments are described in 12.4.1. SEP 2002 COMMITTEE DRAFT 287 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 NOTE 13.2 The text CMPLX (X [, Y, KIND]) indicates that Y and KIND are both optional arguments. Valid reference forms include CMPLX(x ), CMPLX(x, y), CMPLX(x, KIND=kind ), CMPLX(x, y, kind ), and CMPLX(KIND=kind, X=x, Y=y). NOTE 13.3 Some intrinsic procedures impose additional requirements on their optional arguments. For exam- ple, SELECTED REAL KIND requires that at least one of its optional arguments be present, and RANDOM SEED requires that at most one of its optional arguments be present. 1 The dummy arguments of the specific intrinsic procedures in 13.6 have INTENT(IN). The dummy 2 arguments of the generic intrinsic procedures in 13.7 have INTENT(IN) if the intent is not stated 3 explicitly. 4 The actual argument associated with an intrinsic function dummy argument named KIND shall be a 5 scalar integer initialization expression and its value shall specify a representation method for the function 6 result that exists on the processor. 7 Intrinsic subroutines that assign values to arguments of type character do so in accordance with the 8 rules of intrinsic assignment (7.4.1.3). 9 13.2.1 The shape of array arguments 10 Unless otherwise specified, the inquiry intrinsic functions accept array arguments for which the shape 11 need not be defined. The shape of array arguments to transformational and elemental intrinsic functions 12 shall be defined. 13 13.2.2 Mask arguments 14 Some array intrinsic functions have an optional MASK argument of type logical that is used by the 15 function to select the elements of one or more arguments to be operated on by the function. Any 16 element not selected by the mask need not be defined at the time the function is invoked. 17 The MASK affects only the value of the function, and does not affect the evaluation, prior to invoking 18 the function, of arguments that are array expressions. 19 13.3 Bit model 20 The bit manipulation procedures are ten elemental functions and one elemental subroutine. Logical 21 operations on bits are provided by the elemental functions IOR, IAND, NOT, and IEOR; shift operations 22 are provided by the elemental functions ISHFT and ISHFTC; bit subfields may be referenced by the 23 elemental function IBITS and by the elemental subroutine MVBITS; single-bit processing is provided 24 by the elemental functions BTEST, IBSET, and IBCLR. 25 For the purposes of these procedures, a bit is defined to be a binary digit w located at position k of a 26 nonnegative integer scalar object based on a model nonnegative integer defined by z-1 j = wk × 2k k=0 27 and for which wk may have the value 0 or 1. An example of a model number compatible with the 28 examples used in 13.4 would have z = 32, thereby defining a 32-bit integer. 288 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 An inquiry function BIT SIZE is available to determine the parameter z of the model. 2 Effectively, this model defines an integer object to consist of z bits in sequence numbered from right 3 to left from 0 to z - 1. This model is valid only in the context of the use of such an object as the 4 argument or result of one of the bit manipulation procedures. In all other contexts, the model defined 5 for an integer in 13.4 applies. In particular, whereas the models are identical for wz-1 = 0, they do not 6 correspond for wz-1 = 1 and the interpretation of bits in such objects is processor dependent. 7 13.4 Numeric models 8 The numeric manipulation and inquiry functions are described in terms of a model for the representation 9 and behavior of numbers on a processor. The model has parameters that are determined so as to make 10 the model best fit the machine on which the program is executed. 11 The model set for integer i is defined by q-1 i = s × wk × rk k=0 12 where r is an integer exceeding one, q is a positive integer, each wk is a nonnegative integer less than r, 13 and s is +1 or ­1. 14 The model set for real x is defined by 0 or p x = s × be × fk × b-k , k=1 15 where b and p are integers exceeding one; each fk is a nonnegative integer less than b, with f1 nonzero; s 16 is +1 or ­1; and e is an integer that lies between some integer maximum emax and some integer minimum 17 emin inclusively. For x = 0, its exponent e and digits fk are defined to be zero. The integer parameters 18 r and q determine the set of model integers and the integer parameters b, p, emin, and emax determine 19 the set of model floating point numbers. The parameters of the integer and real models are available 20 for each integer and real type implemented by the processor. The parameters characterize the set of 21 available numbers in the definition of the model. The floating-point manipulation functions (13.5.10) 22 and numeric inquiry functions (13.5.6) provide values of some parameters and other values related to 23 the models. NOTE 13.4 Examples of these functions in 13.7 use the models 30 i = s × wk × 2k k=0 and 24 1 x = 0 or s × 2e × + fk × 2-k , - 126 e 127 2 k=2 SEP 2002 COMMITTEE DRAFT 289 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 13.5 Standard generic intrinsic procedures 2 For all of the standard intrinsic procedures, the arguments shown are the names that shall be used for 3 argument keywords if the keyword form is used for actual arguments. NOTE 13.5 For example, a reference to CMPLX may be written in the form CMPLX (A, B, M) or in the form CMPLX (Y = B, KIND = M, X = A). NOTE 13.6 Many of the argument keywords have names that are indicative of their usage. For example: KIND Describes the kind type parameter of the result STRING, STRING A An arbitrary character string BACK Controls the direction of string scan (forward or backward) MASK A mask that may be applied to the arguments DIM A selected dimension of an array argument 4 13.5.1 Numeric functions 5 ABS (A) Absolute value 6 AIMAG (Z) Imaginary part of a complex number 7 AINT (A [, KIND]) Truncation to whole number 8 ANINT (A [, KIND]) Nearest whole number 9 CEILING (A [, KIND]) Least integer greater than or equal to number 10 CMPLX (X [, Y, KIND]) Conversion to complex type 11 CONJG (Z) Conjugate of a complex number 12 DBLE (A) Conversion to double precision real type 13 DIM (X, Y) Positive difference 14 DPROD (X, Y) Double precision real product 15 FLOOR (A [, KIND]) Greatest integer less than or equal to number 16 INT (A [, KIND]) Conversion to integer type 17 MAX (A1, A2 [, A3,...]) Maximum value 18 MIN (A1, A2 [, A3,...]) Minimum value 19 MOD (A, P) Remainder function 20 MODULO (A, P) Modulo function 21 NINT (A [, KIND]) Nearest integer 22 REAL (A [, KIND]) Conversion to real type 23 SIGN (A, B) Transfer of sign 24 13.5.2 Mathematical functions 25 ACOS (X) Arccosine 26 ASIN (X) Arcsine 27 ATAN (X) Arctangent 28 ATAN2 (Y, X) Arctangent 29 COS (X) Cosine 30 COSH (X) Hyperbolic cosine 31 EXP (X) Exponential 32 LOG (X) Natural logarithm 33 LOG10 (X) Common logarithm (base 10) 34 SIN (X) Sine 290 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 SINH (X) Hyperbolic sine 2 SQRT (X) Square root 3 TAN (X) Tangent 4 TANH (X) Hyperbolic tangent 5 13.5.3 Character functions 6 ACHAR (I) Character in given position in ASCII collating 7 sequence 8 ADJUSTL (STRING) Adjust left 9 ADJUSTR (STRING) Adjust right 10 CHAR (I [, KIND]) Character in given position in processor collating 11 sequence 12 IACHAR (C) Position of a character in ASCII collating 13 sequence 14 ICHAR (C [, KIND]) Position of a character in processor collating 15 sequence INDEX (STRING, SUBSTRING [, BACK, Starting position of a substring 16 KIND]) 17 LEN TRIM (STRING [, KIND]) Length without trailing blank characters 18 LGE (STRING A, STRING B) Lexically greater than or equal 19 LGT (STRING A, STRING B) Lexically greater than 20 LLE (STRING A, STRING B) Lexically less than or equal 21 LLT (STRING A, STRING B) Lexically less than 22 MAX (A1, A2 [, A3,...]) Maximum value 23 MIN (A1, A2 [, A3,...]) Minimum value 24 REPEAT (STRING, NCOPIES) Repeated concatenation 25 SCAN (STRING, SET [, BACK, KIND]) Scan a string for a character in a set 26 TRIM (STRING) Remove trailing blank characters 27 VERIFY (STRING, SET [, BACK, KIND]) Verify the set of characters in a string 28 13.5.4 Kind functions 29 KIND (X) Kind type parameter value 30 SELECTED CHAR KIND (NAME) Character kind type parameter value, given 31 character set name 32 SELECTED INT KIND (R) Integer kind type parameter value, given range 33 SELECTED REAL KIND ([P, R]) Real kind type parameter value, given precision 34 and range 35 13.5.5 Miscellaneous type conversion functions 36 LOGICAL (L [, KIND]) Convert between objects of type logical with 37 different kind type parameters 38 TRANSFER (SOURCE, MOLD [, SIZE]) Treat first argument as if of type of second 39 argument 40 13.5.6 Numeric inquiry functions 41 DIGITS (X) Number of significant digits of the model 42 EPSILON (X) Number that is almost negligible compared to 43 one 44 HUGE (X) Largest number of the model 45 MAXEXPONENT (X) Maximum exponent of the model SEP 2002 COMMITTEE DRAFT 291 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 MINEXPONENT (X) Minimum exponent of the model 2 PRECISION (X) Decimal precision 3 RADIX (X) Base of the model 4 RANGE (X) Decimal exponent range 5 TINY (X) Smallest positive number of the model 6 13.5.7 Array inquiry functions 7 LBOUND (ARRAY [, DIM, KIND]) Lower dimension bounds of an array 8 SHAPE (SOURCE [, KIND]) Shape of an array or scalar 9 SIZE (ARRAY [, DIM, KIND]) total number of elements in an array 10 UBOUND (ARRAY [, DIM, KIND]) Upper dimension bounds of an array 11 13.5.8 Other inquiry functions ALLOCATED (ARRAY) or Allocation status 12 ALLOCATED (SCALAR) 13 ASSOCIATED (POINTER [, TARGET]) Association status inquiry or comparison 14 BIT SIZE (I) Number of bits of the model 15 EXTENDS TYPE OF (A, MOLD) Same dynamic type or an extension 16 LEN (STRING [, KIND]) Length of a character entity 17 PRESENT (A) Argument presence 18 SAME TYPE AS (A, B) Same dynamic type 19 13.5.9 Bit manipulation procedures 20 BTEST (I, POS) Bit testing 21 IAND (I, J) Bitwise AND 22 IBCLR (I, POS) Clear bit 23 IBITS (I, POS, LEN) Bit extraction 24 IBSET (I, POS) Set bit 25 IEOR (I, J) Exclusive OR 26 IOR (I, J) Inclusive OR 27 ISHFT (I, SHIFT) Logical shift 28 ISHFTC (I, SHIFT [, SIZE]) Circular shift MVBITS (FROM, FROMPOS, LEN, TO, Copies bits from one integer to another 29 TOPOS) 30 NOT (I) Bitwise complement 31 13.5.10 Floating-point manipulation functions 32 EXPONENT (X) Exponent part of a model number 33 FRACTION (X) Fractional part of a number 34 NEAREST (X, S) Nearest different processor number in given 35 direction 36 RRSPACING (X) Reciprocal of the relative spacing of model 37 numbers near given number 38 SCALE (X, I) Multiply a real by its base to an integer power 39 SET EXPONENT (X, I) Set exponent part of a number 40 SPACING (X) Absolute spacing of model numbers near given 41 number 292 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 13.5.11 Vector and matrix multiply functions DOT PRODUCT (VECTOR A, Dot product of two rank-one arrays 2 VECTOR B) 3 MATMUL (MATRIX A, MATRIX B) Matrix multiplication 4 13.5.12 Array reduction functions 5 ALL (MASK [, DIM]) True if all values are true 6 ANY (MASK [, DIM]) True if any value is true 7 COUNT (MASK [, DIM, KIND]) Number of true elements in an array MAXVAL (ARRAY, DIM [, MASK]) or Maximum value in an array 8 MAXVAL (ARRAY [, MASK]) MINVAL (ARRAY, DIM [, MASK]) or Minimum value in an array 9 MINVAL (ARRAY [, MASK]) PRODUCT (ARRAY, DIM [, MASK]) or Product of array elements 10 PRODUCT (ARRAY [, MASK]) SUM (ARRAY, DIM [, MASK]) or Sum of array elements 11 SUM (ARRAY [, MASK]) 12 13.5.13 Array construction functions 13 CSHIFT (ARRAY, SHIFT [, DIM]) Circular shift EOSHIFT (ARRAY, SHIFT [, BOUNDARY, End-off shift 14 DIM]) 15 MERGE (TSOURCE, FSOURCE, MASK) Merge under mask 16 PACK (ARRAY, MASK [, VECTOR]) Pack an array into an array of rank one under a 17 mask RESHAPE (SOURCE, SHAPE[, PAD, Reshape an array 18 ORDER]) 19 SPREAD (SOURCE, DIM, NCOPIES) Replicates array by adding a dimension 20 TRANSPOSE (MATRIX) Transpose of an array of rank two 21 UNPACK (VECTOR, MASK, FIELD) Unpack an array of rank one into an array under 22 a mask 23 13.5.14 Array location functions MAXLOC (ARRAY, DIM [, MASK, KIND]) Location of a maximum value in an array or MAXLOC (ARRAY [, MASK, 24 KIND]) MINLOC (ARRAY, DIM [, MASK, KIND]) Location of a minimum value in an array or MINLOC (ARRAY [, MASK, KIND]) 25 26 13.5.15 Null function 27 NULL ([MOLD]) Returns disassociated or unallocated result 28 13.5.16 Random number subroutines 29 RANDOM NUMBER (HARVEST) Returns pseudorandom number 30 RANDOM SEED ([SIZE, PUT, GET]) Initializes or restarts the pseudorandom number 31 generator SEP 2002 COMMITTEE DRAFT 293 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 13.5.17 System environment procedures 2 COMMAND ARGUMENT COUNT () Number of command arguments 3 CPU TIME (TIME) Obtain processor time DATE AND TIME ([DATE, TIME, ZONE, Obtain date and time 4 VALUES]) GET COMMAND ([COMMAND, Returns entire command 5 LENGTH, STATUS]) GET COMMAND ARGUMENT (NUMBER Returns a command argument 6 [, VALUE, LENGTH, STATUS]) GET ENVIRONMENT VARIABLE (NAME Obtain the value of an environment variable [, VALUE, LENGTH, STATUS, 7 TRIM NAME]) SYSTEM CLOCK ([COUNT, Obtain data from the system clock 8 COUNT RATE, COUNT MAX]) 9 13.6 Specific names for standard intrinsic functions 10 Except for AMAX0, AMIN0, MAX1, and MIN1, the result type of the specific function is the same as the 11 result type of the corresponding generic function would be if it were invoked with the same arguments 12 as the specific function. Specific Name Generic Name Argument Type ABS ABS default real ACOS ACOS default real AIMAG AIMAG default complex AINT AINT default real ALOG LOG default real ALOG10 LOG10 default real · AMAX0 (. . . ) REAL (MAX (. . . )) default integer · AMAX1 MAX default real · AMIN0 (. . . ) REAL (MIN (. . . )) default integer · AMIN1 MIN default real AMOD MOD default real ANINT ANINT default real ASIN ASIN default real ATAN ATAN default real ATAN2 ATAN2 default real CABS ABS default complex CCOS COS default complex CEXP EXP default complex CHAR CHAR default integer CLOG LOG default complex CONJG CONJG default complex COS COS default real COSH COSH default real CSIN SIN default complex CSQRT SQRT default complex DABS ABS double precision real DACOS ACOS double precision real DASIN ASIN double precision real DATAN ATAN double precision real DATAN2 ATAN2 double precision real DCOS COS double precision real 294 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 Specific Name Generic Name Argument Type DCOSH COSH double precision real DDIM DIM double precision real DEXP EXP double precision real DIM DIM default real DINT AINT double precision real DLOG LOG double precision real DLOG10 LOG10 double precision real · DMAX1 MAX double precision real · DMIN1 MIN double precision real DMOD MOD double precision real DNINT ANINT double precision real DPROD DPROD default real DSIGN SIGN double precision real DSIN SIN double precision real DSINH SINH double precision real DSQRT SQRT double precision real DTAN TAN double precision real DTANH TANH double precision real EXP EXP default real · FLOAT REAL default integer IABS ABS default integer · ICHAR ICHAR default character IDIM DIM default integer · IDINT INT double precision real IDNINT NINT double precision real · IFIX INT default real INDEX INDEX default character · INT INT default real ISIGN SIGN default integer LEN LEN default character · LGE LGE default character · LGT LGT default character · LLE LLE default character · LLT LLT default character · MAX0 MAX default integer · MAX1 (. . . ) INT (MAX (. . . )) default real · MIN0 MIN default integer · MIN1 (. . . ) INT (MIN (. . . )) default real MOD MOD default integer NINT NINT default real · REAL REAL default integer SIGN SIGN default real SIN SIN default real SINH SINH default real · SNGL REAL double precision real SQRT SQRT default real TAN TAN default real TANH TANH default real 1 A specific intrinsic function market with a bullet (·) shall not be used as an actual argument. SEP 2002 COMMITTEE DRAFT 295 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 13.7 Specifications of the standard intrinsic procedures 2 Detailed specifications of the standard generic intrinsic procedures are provided here in alphabetical 3 order. 4 The types and type parameters of standard intrinsic procedure arguments and function results are de- 5 termined by these specifications. The "Argument(s)" paragraphs specify requirements on the actual 6 arguments of the procedures. The result characteristics are sometimes specified in terms of the charac- 7 teristics of dummy arguments. A program is prohibited from invoking an intrinsic procedure under cir- 8 cumstances where a value to be returned in a subroutine argument or function result is outside the range 9 of values representable by objects of the specified type and type parameters, unless the intrinsic module 10 IEEE ARITHMETIC (section 14) is accessible and there is support for an infinite or a NaN result, as 11 appropriate. If an infinite result is returned, the flag IEEE OVERFLOW or IEEE DIVIDE BY ZERO 12 shall signal; if a NaN result is returned, the flag IEEE INVALID shall signal. If all results are normal, 13 these flags shall have the same status as when the intrinsic procedure was invoked. 14 13.7.1 ABS (A) 15 Description. Absolute value. 16 Class. Elemental function. 17 Argument. A shall be of type integer, real, or complex. 18 Result Characteristics. The same as A except that if A is complex, the result is real. 19 Result Value. If A is of type integer or real, the value of the result is |A|; if A is complex with 20 value (x, y), the result is equal to a processor-dependent approximation to x2 + y2. 21 Example. ABS ((3.0, 4.0)) has the value 5.0 (approximately). 22 13.7.2 ACHAR (I) 23 Description. Returns the character in a specified position of the ASCII collating sequence. It 24 is the inverse of the IACHAR function. 25 Class. Elemental function. 26 Argument. I shall be of type integer. 27 Result Characteristics. Default character of length one. 28 Result Value. If I has a value in the range 0 I 127, the result is the character in position I 29 of the ASCII collating sequence, provided the processor is capable of representing that character; 30 otherwise, the result is processor dependent. ACHAR (IACHAR (C)) shall have the value C for 31 any character C capable of representation in the processor. 32 Example. ACHAR (88) has the value 'X'. 33 13.7.3 ACOS (X) 34 Description. Arccosine (inverse cosine) function. 35 Class. Elemental function. 36 Argument. X shall be of type real with a value that satisfies the inequality |X| 1. 37 Result Characteristics. Same as X. 296 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 Result Value. The result has a value equal to a processor-dependent approximation to arc- 2 cos(X), expressed in radians. It lies in the range 0 ACOS(X) . 3 Example. ACOS (0.54030231) has the value 1.0 (approximately). 4 13.7.4 ADJUSTL (STRING) 5 Description. Adjust to the left, removing leading blanks and inserting trailing blanks. 6 Class. Elemental function. 7 Argument. STRING shall be of type character. 8 Result Characteristics. Character of the same length and kind type parameter as STRING. 9 Result Value. The value of the result is the same as STRING except that any leading blanks 10 have been deleted and the same number of trailing blanks have been inserted. 11 Example. ADJUSTL (' WORD') has the value 'WORD '. 12 13.7.5 ADJUSTR (STRING) 13 Description. Adjust to the right, removing trailing blanks and inserting leading blanks. 14 Class. Elemental function. 15 Argument. STRING shall be of type character. 16 Result Characteristics. Character of the same length and kind type parameter as STRING. 17 Result Value. The value of the result is the same as STRING except that any trailing blanks 18 have been deleted and the same number of leading blanks have been inserted. 19 Example. ADJUSTR ('WORD ') has the value ' WORD'. 20 13.7.6 AIMAG (Z) 21 Description. Imaginary part of a complex number. 22 Class. Elemental function. 23 Argument. Z shall be of type complex. 24 Result Characteristics. Real with the same kind type parameter as Z. 25 Result Value. If Z has the value (x, y), the result has the value y. 26 Example. AIMAG ((2.0, 3.0)) has the value 3.0. 27 13.7.7 AINT (A [, KIND]) 28 Description. Truncation to a whole number. 29 Class. Elemental function. 30 Arguments. 31 A shall be of type real. 32 KIND (optional) shall be a scalar integer initialization expression. SEP 2002 COMMITTEE DRAFT 297 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 Result Characteristics. The result is of type real. If KIND is present, the kind type parameter 2 is that specified by the value of KIND; otherwise, the kind type parameter is that of A. 3 Result Value. If |A| < 1, AINT (A) has the value 0; if |A| 1, AINT (A) has a value equal 4 to the integer whose magnitude is the largest integer that does not exceed the magnitude of A 5 and whose sign is the same as the sign of A. 6 Examples. AINT (2.783) has the value 2.0. AINT (­2.783) has the value ­2.0. 7 13.7.8 ALL (MASK [, DIM]) 8 Description. Determine whether all values are true in MASK along dimension DIM. 9 Class. Transformational function. 10 Arguments. 11 MASK shall be of type logical. It shall not be scalar. DIM (optional) shall be scalar and of type integer with value in the range 1 DIM n, where n is the rank of MASK. The corresponding actual argument shall not 12 be an optional dummy argument. 13 Result Characteristics. The result is of type logical with the same kind type parameter as 14 MASK. It is scalar if DIM is absent; otherwise, the result has rank n - 1 and shape (d1, d2, 15 ..., dDIM-1, dDIM+1, ..., dn) where (d1, d2, ..., dn) is the shape of MASK. 16 Result Value. 17 Case (i): The result of ALL (MASK) has the value true if all elements of MASK are true 18 or if MASK has size zero, and the result has value false if any element of MASK 19 is false. 20 Case (ii): If MASK has rank one, ALL(MASK,DIM) is equal to ALL(MASK). Otherwise, 21 the value of element (s1, s2, . . . , sDIM-1, sDIM+1, . . . , sn) of ALL (MASK, DIM) 22 is equal to ALL (MASK (s1, s2, . . . , sDIM-1, :, sDIM+1, ..., sn)). 23 Examples. 24 Case (i): The value of ALL ((/ .TRUE., .FALSE., .TRUE. /)) is false. 1 3 5 0 3 5 Case (ii): If B is the array and C is the array then ALL (B /= C, 25 2 4 6 7 4 8 26 DIM = 1) is [true, false, false] and ALL (B /= C, DIM = 2) is [false, false]. 27 13.7.9 ALLOCATED (ARRAY) or ALLOCATED (SCALAR) 28 Description. Indicate whether an allocatable variable is allocated. 29 Class. Inquiry function. 30 Arguments. 31 ARRAY shall be an allocatable array. 32 SCALAR shall be an allocatable scalar. 33 Result Characteristics. Default logical scalar. 34 Result Value. The result has the value true if the argument (ARRAY or SCALAR) is allocated 35 and has the value false if the argument is unallocated. 298 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 13.7.10 ANINT (A [, KIND]) 2 Description. Nearest whole number. 3 Class. Elemental function. 4 Arguments. 5 A shall be of type real. 6 KIND (optional) shall be a scalar integer initialization expression. 7 Result Characteristics. The result is of type real. If KIND is present, the kind type parameter 8 is that specified by the value of KIND; otherwise, the kind type parameter is that of A. 9 Result Value. The result is the integer nearest A, or if there are two integers equally near A, 10 the result is whichever such integer has the greater magnitude. 11 Examples. ANINT (2.783) has the value 3.0. ANINT (­2.783) has the value ­3.0. 12 13.7.11 ANY (MASK [, DIM]) 13 Description. Determine whether any value is true in MASK along dimension DIM. 14 Class. Transformational function. 15 Arguments. 16 MASK shall be of type logical. It shall not be scalar. DIM (optional) shall be scalar and of type integer with a value in the range 1 DIM n, where n is the rank of MASK. The corresponding actual argument shall not 17 be an optional dummy argument. 18 Result Characteristics. The result is of type logical with the same kind type parameter as 19 MASK. It is scalar if DIM is absent; otherwise, the result has rank n - 1 and shape (d1, d2, 20 ..., dDIM-1, dDIM+1, ..., dn) where (d1, d2, ..., dn) is the shape of MASK. 21 Result Value. 22 Case (i): The result of ANY (MASK) has the value true if any element of MASK is true 23 and has the value false if no elements are true or if MASK has size zero. 24 Case (ii): If MASK has rank one, ANY(MASK,DIM) is equal to ANY(MASK). Otherwise, 25 the value of element (s1, s2, . . . , sDIM-1, sDIM+1, . . . , sn) of ANY(MASK, DIM) 26 is equal to ANY(MASK (s1, s2, . . . , sDIM-1, :, sDIM+1, . . . , sn)). 27 Examples. 28 Case (i): The value of ANY ((/ .TRUE., .FALSE., .TRUE. /)) is true. 1 3 5 0 3 5 Case (ii): If B is the array and C is the array then ANY(B /= C, 29 2 4 6 7 4 8 30 DIM = 1) is [true, false, true] and ANY(B /= C, DIM = 2) is [true, true]. 31 13.7.12 ASIN (X) 32 Description. Arcsine (inverse sine) function. 33 Class. Elemental function. SEP 2002 COMMITTEE DRAFT 299 ISO/IEC 1539-1 COMMITTEE DRAFT SEP 2002 1 Argument. X shall be of type real. Its value shall satisfy the inequality |X| 1. 2 Result Characteristics. Same as X. 3 Result Value. The result has a value equal to a processor-dependent approximation to arc- 4 sin(X), expressed in radians. It lies in the range -/2 ASIN(X) /2. 5 Example. ASIN (0.84147098) has the value 1.0 (approximately). 6 13.7.13 ASSOCIATED (POINTER [, TARGET]) 7 Description. Returns the association status of its pointer argument or indicates whether the 8 pointer is associated with the target. 9 Class. Inquiry function. 10 Arguments. POINTER shall be a pointer. It may be of any type or may be a procedure pointer. Its 11 pointer association status shall not be undefined. TARGET shall be allowable as the data-target or proc-target in a pointer assignment (optional) statement (7.4.2) in which POINTER is pointer-object . If TARGET is a 12 pointer then its pointer association status shall not be undefined. 13 Result Characteristics. Default logical scalar. 14 Result Value. 15 Case (i): If TARGET is absent, the result is true if POINTER is associated with a target 16 and false if it is not. 17 Case (ii): If TARGET is present and is a procedure, the result is true if POINTER is 18 associated with TARGET. 19 Case (iii): If TARGET is present and is a procedure pointer, the result is true if POINTER 20 and TARGET are associated with the same procedure. If either POINTER or 21 TARGET is disassociated, the result is false. 22 Case (iv): If TARGET is present and is a scalar target, the result is true if TARGET is not a 23 zero-sized storage sequence and the target associated with POINTER occupies the 24 same storage units as TARGET. Otherwise, the result is false. If the POINTER 25 is disassociated, the result is false. 26 Case (v): If TARGET is present and is an array target, the result is true if the target 27 associated with POINTER and TARGET have the same shape, are neither of 28 size zero nor arrays whose elements are zero-sized storage sequences, and occupy 29 the same storage units in array element order. Otherwise, the result is false. If 30 POINTER is disassociated, the result is false. 31 Case (vi): If TARGET is present and is a scalar pointer, the result is true if the target 32 associated with POINTER and the target associated with TARGET are not zero- 33 sized storage sequences and they occupy the same storage units. Otherwise, the 34 result is false. If either POINTER or TARGET is disassociated, the result is 35 false. 36 Case (vii): If TARGET is present and is an array pointer, the result is true if the target 37 associated with POINTER and the target associated with TARGET have the 38 same shape, are neither of size zero nor arrays whose elements are zero-sized 39 storage sequences, and occupy the same storage units in array element order. 40 Otherwise, the result is false. If either POINTER or TARGET is disassociated, 41 the result is false. 300 COMMITTEE DRAFT SEP 2002 SEP 2002 COMMITTEE DRAFT ISO/IEC 1539-1 1 Examples. ASSOCIATED (CURRENT, HEAD) is true if CURRENT is as