X3J3/96-131r1

From: Loren P. Meissner
Subject: Extend Character Intrinsics
Meeting 138

<FORTREQ>

<NUMBER>

<TITLE>   Extend Max, Min, etc. to Character Data Type

<KEYWORDS>   Intrinsic functions, Character type

<STATUS>   Registered

<TARGET>

<SUBGROUP>

<VERSION>   3

<REQUIREMENT>
Extend the intrinsic functions Max, Min, MaxLoc, MinLoc, MaxVal, and
MinVal to accept arguments of character data type.
</REQUIREMENT>

<JUSTIFICATION>
Regularity is the primary reason for this requirement. These intrinsic
functions now accept arguments of the other two ordered intrinsic 
types, integer and real. This proposal recognizes character data type 
as a first-class type and extends the ordering intrinsics so that they 
accept all types for which they make sense. This extension will 
facilitate constuction of families of similar routines in applications 
such as sorting for integer, real, and character data.
</JUSTIFICATION>

<SUGGESTED IMPLEMENTATION>
Add text to the specifications of the intrinsic functions mentioned.
Intrinsic functions for ordering character arguments should be 
consistent with character relational operators: for example, when A and 
B are character strings Max( A, B ) should return a string equivalent 
to A if the relational expression A > B is true.

This suggested implementation applies character comparisons for Max and
Min with padding as for relational operators.

For integer or real arrays with no elements (after masking), the 
Standard currently defines MaxVal as "the negative number of the 
largest magnitude supported by the processor" and MinVal as "the 
positive number of the largest magnitude supported by the processor" 
{and not as Huge, the largest model number}. A similar concept is 
needed for character arrays with no elements. For the implementation 
suggested here, the "most negative" value corresponds to a string of 
characters all equal to Char( 0 ) and the "most positive" value 
corresponds to a string of characters all equal to Char( n - 1) where n
is the number of characters in the collating sequence for the kind type
parameter of the argument array. Similar terminology appears in the 
current definition of Char.

Max, Min:
 Change "Result Characteristics" to:
 Result Characteristics. Type and kind type parameter are the same as 
 the arguments. For arguments of character type, the length of the 
 result is the length of the longest argument.

MaxLoc, MinLoc:
 Change "shall be of type integer or real" to "shall be of type 
 integer, real, or character"

MaxVal:
 Change "shall be of type integer or real" to "shall be of type
 integer, real, or character"

 Change "The result is of the same type and kind type parameter as 
 Array" to "The result is of the same type and type parameters as 
 Array"

 Replace Result Value Case(i) and Case (ii) as follows (no change to
 Case(iii)):

 Case(i):	  If the size of Array is not zero, the result of 
 MaxVal( Array ) has a value equal to the maximum value of all the 
 elements of Array. If Array has size zero and type integer or real,
 the result of MaxVal( Array ) has the value of the negative number of
 the largest magnitude supported by the processor for numbers of the
 type and kind type parameter of Array. If Array has size zero and type
 character, the result of MaxVal( Array ) has the value of a string of
 characters of length Len( Array ) with each character equal to
 Char( 0, Kind = Kind( Array ) ).

 Case(ii):  The result of MaxVal( Array, Mask = Mask ), if Mask has at
 least one true element, has a value equal to the maximum value of the
 elements of Array corresponding to true elements of Mask. If Mask has
 no true elements and the type of Array is integer or real, the result
 of MaxVal( Array, Mask = Mask ) has the value of the negative number
 of the largest magnitude supported by the processor for numbers of the
 type and kind type parameter of Array. If Mask has no true elements
 and the type of Array is character, the result of
 MaxVal( Array, Mask = Mask ) has the value of a string of characters
 of length Len( Array ) with each character equal to
 Char( 0, Kind = Kind( Array ) ).

MinVal:
 Change "shall be of type integer or real" to "shall be of type 
 integer, real, or character"

 Change "The result is of the same type and kind type parameter as
 Array" to "The result is of the same type and type parameters as
 Array"

 Replace Result Value Case(i) and Case (ii) as follows (no change to
 Case(iii)):

 Case(i):	  If the size of Array is not zero, the result of
 MinVal( Array ) has a value equal to the minimum value of all the
 elements of Array. If Array has size zero and type integer or real,
 the result of MinVal( Array ) has the value of the positive number of
 the largest magnitude supported by the processor for numbers of the
 type and kind type parameter of Array. If Array has size zero and type
 character, the result of MinVal( Array ) has the value of a string of
 characters of length Len( Array ) with each character equal to
 Char( n - 1, Kind = Kind( Array ) ) where n is the number of
 characters in the collating sequence for characters with the kind type
 parameter of Array.

 Case(ii):  The result of MinVal( Array, Mask = Mask ), if Mask has at
 least one true element, has a value equal to the minimum value of the
 elements of Array corresponding to true elements of Mask. If Mask has
 no true elements and the type of Array is integer or real, the result
 of MinVal( Array, Mask = Mask ) has the value of the negative number
 of the largest magnitude supported by the processor for numbers of the
 type and kind type parameter of Array. If Mask has no true elements
 and the type of Array is character, the result of
 MinVal( Array, Mask = Mask ) has the value of a string of characters
 of length Len( Array ) with each character equal to
 Char( n - 1, Kind = Kind( Array ) ) where n is the number of
 characters in the collating sequence for characters with the kind type
 parameter of Array.
</SUGGESTED IMPLEMENTATION>

<ESTIMATED IMPACT>
Regularizes, simplifies, and increases reliability of many application
programs that involve ordering of character data.
</ESTIMATED IMPACT>

<SUBMITTED BY>
   Loren Meissner
   2 Kerr Ave
   Kensington CA 94707
   LPMeissner@msn.com
</SUBMITTED BY>

<HISTORY>
<EVENT>   February 1996, meeting 136; submitted 96-042
<EVENT>   May 1996, meeting 137
<EVENT>   August 1996, meeting 138; X3J3 approved
</HISTORY>

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