J3/05-141

Date:    21 Jan 2005
To:      J3
From:    Rob James
Subject: Questions about internal files

NUMBER:
TITLE: Questions about internal files
KEYWORDS: internal file, data transfer
DEFECT TYPE:
STATUS: J3 consideration in progress

QUESTION:

Question 1:

Fortran 2003 does not seem to prohibit this kind of recursive internal
I/O.  Was this program intended to be standard-conforming?  If so,
then what does the program print?

MODULE m1
  CHARACTER(20) :: ifile = ''
CONTAINS
  CHARACTER(3) FUNCTION foo()
    WRITE(ifile, *) 'QWERTY'
    foo = 'abc'
  END FUNCTION
END MODULE

PROGRAM ex1
  USE m1
  WRITE(ifile, *) 'xyz', foo(), 'zyx'
  PRINT *, ifile
END PROGRAM


Question 2:

Fortran 2003 does not seem to prohibit this kind of recursive internal
I/O.  Was this program intended to be standard-conforming?  If so,
then what does the program print?

MODULE m2
  CHARACTER(20) :: ifile = 'abc def ghi jkl mno '
  CHARACTER(3) :: char
CONTAINS
  CHARACTER(3) FUNCTION foo()
    READ(ifile, *) char
    foo = 'abc'
  END FUNCTION
END MODULE

PROGRAM ex2
  USE m2
  WRITE(ifile, *) 'xyz', foo(), 'zyx'
  PRINT *, ifile
  PRINT *, char
END PROGRAM


Question 3:

Fortran 2003 does not appear to prohibit modifying a character
variable when it is being used as an internal file in a data transfer
statement that is currently executing.  Was this program intended to
be standard-conforming?  If so, then what does the program print?

MODULE m3
  CHARACTER(20) :: ifile = ''
CONTAINS
  CHARACTER(3) FUNCTION foo()
    ifile = 'bad thing to do?'
    foo = 'abc'
  END FUNCTION
END MODULE

PROGRAM ex3
  USE m3
  WRITE(ifile, *) 'xyz', foo(), 'zyx'
  PRINT *, ifile
  PRINT *, flag
END PROGRAM


Question 4:

Fortran 2003 does not appear to prohibit referencing a character
variable when it is being used as an internal file in a data transfer
statement that is currently executing.  Was this program intended to
be standard-conforming?  If so, then what does the program print?

MODULE m4
  CHARACTER(20) :: ifile = ''
  LOGICAL :: flag = .FALSE.
CONTAINS
  CHARACTER(3) FUNCTION foo()
    IF (ifile == ' xyz') THEN
      flag = .TRUE.
    END IF
    foo = 'abc'
  END FUNCTION
END MODULE

PROGRAM ex4
  USE m4
  WRITE(ifile, *) 'xyz', foo(), 'zyx'
  PRINT *, ifile
  PRINT *, flag
END PROGRAM


ANSWER:

TBD.


EDITS:

TBD.


SUBMITTED BY: Rob James

HISTORY: J3/05-141   m171 Submitted