VALUE (Fortran 2003)

Purpose

The VALUE attribute specifies an argument association between a dummy and an actual argument. This association allows you to pass the dummy argument with the value of the actual argument. This Fortran 2003 pass by value implementation provides a standard conforming option to the %VAL built-in function.

An actual argument and the associated dummy argument can change independently. Changes to the value or definition status of the dummy argument do not affect the actual argument. A dummy argument with the VALUE attribute becomes associated with a temporary variable with an initial value identical to the value of the actual argument.

Syntax


>>-VALUE--+----+--dummy_argument_name_list---------------------><
          '-::-'

Rules

You must specify the VALUE attribute for dummy arguments only.

You must not use the %VAL or %REF built-in functions to reference a dummy argument with the VALUE attribute, or the associated actual argument.

A referenced procedure that has a dummy argument with the VALUE attribute must have an explicit interface.

A dummy argument with the VALUE attribute can be of character type .

You must not specify the VALUE attribute with the following:

Arrays
Dummy procedures
Polymorphic items

Table 1. Attributes compatible with the VALUE attribute
INTENT(IN)	OPTIONAL	TARGET

If a dummy argument has both the VALUE and TARGET attributes, any pointers associated with that dummy argument become undefined after the execution of the procedure.

Examples

Program validexm1
  integer :: x = 10, y = 20
  print *, 'before calling: ', x, y
  call intersub(x, y)
  print *, 'after calling: ', x, y

  contains
  subroutine intersub(x,y)
    integer, value ::  x
    integer y
    x = x + y
    y = x*y
    print *, 'in subroutine after changing: ', x, y
  end subroutine
end program validexm1

Expected output:

before calling: 10 20
in subroutine after changing: 30 600
after calling: 10 600

Related information

For more information, see the %VAL built-in function.