Language Reference

INTENT

Purpose

The INTENT attribute specifies the intended use of dummy arguments.

Format

>>-INTENT--(--+-IN----+--)--+----+--dummy_arg_name_list--------><
              +-OUT---+     '-::-'
              '-INOUT-'
 
 

dummy_arg_name

is the name of a dummy argument, which cannot be a dummy procedure

Rules

If you specify a nonpointer, nonallocatable dummy argument, the INTENT attribute will have the following characteristics:

• INTENT(IN) specifies that the dummy argument must not be redefined or become undefined during the execution of the subprogram.
• INTENT(OUT) specifies that the dummy argument must be defined before it is referenced within the subprogram. Such a dummy argument might not become undefined on invocation of the subprogram.
• INTENT(INOUT) specifies that the dummy argument can both receive and return data to the invoking subprogram.

If you specify a pointer dummy argument, the INTENT attribute will have the following characteristics:

• INTENT(IN) specifies that during the execution of the procedure, the association status of the pointer dummy argument cannot be changed, except if the target of the pointer is deallocated. If the target of the pointer is deallocated, the association status of the pointer dummy argument becomes undefined.

  You cannot use an INTENT(IN) pointer dummy argument as a pointer object in a pointer assignment statement. You cannot allocate, deallocate, or nullify an INTENT(IN) pointer dummy argument

  You cannot specify an INTENT(IN) pointer dummy argument as an actual argument to a procedure if the associated dummy argument is a pointer with INTENT(OUT) or INTENT(INOUT) attribute.

• INTENT(OUT) specifies that at the execution of the procedure, the association status of the pointer dummy argument is undefined
• INTENT(INOUT) specifies that the dummy argument can both receive and return data to the invoking subprogram.

If you specify an allocatable dummy argument, the INTENT attribute will have the following characteristics:

• INTENT(IN) specifies that during the execution of the procedure, the allocation status of the dummy argument cannot be changed, and it must not be redefined or become undefined.
• INTENT(OUT) specifies that at the execution of the procedure, if the associated actual argument is currently allocated it will be deallocated.
• INTENT(INOUT) specifies that the dummy argument can both receive and return data to the invoking subprogram.

If you do not specify the INTENT attribute for a pointer or allocatable dummy argument, its use is subject to the limitations and restrictions of the associated actual argument.

An actual argument that becomes associated with a dummy argument with an intent of OUT or INOUT must be definable. Hence, a dummy argument with an intent of IN, or an actual argument that is a constant, a subobject of a constant, or an expression, cannot be passed as an actual argument to a subprogram expecting an argument with an intent of OUT or INOUT.

An actual argument that is an array section with a vector subscript cannot be associated with a dummy array that is defined or redefined (that is, with an intent of OUT or INOUT).

+-------------------------------IBM Extension--------------------------------+

The %VAL built-in function, used for interlanguage calls, can only be used for an actual argument that corresponds to a dummy argument with an intent of IN, or that has no intent specified. This constraint does not apply to the %REF built-in function.

+----------------------------End of IBM Extension----------------------------+

Examples

      PROGRAM MAIN
        DATA R,S /12.34,56.78/
        CALL SUB(R+S,R,S)
      END PROGRAM
 
      SUBROUTINE SUB (A,B,C)
        INTENT(IN) A
        INTENT(OUT) B
        INTENT(INOUT) C
        C=C+A+ABS(A)            ! Valid references to A and C
                                ! Valid redefinition of C
        B=C**2                  ! Valid redefinition of B
      END SUBROUTINE

Related Information

• Intent of Dummy Arguments
• Argument Association
• %VAL and %REF, for details on interlanguage calls
• Dummy Arguments