NULL

Transformational Intrinsic Function (Generic): Initializes a pointer as disassociated when it is declared. This is a new intrinsic function in Fortran 95.

Syntax

result = NULL ([ mold ])

mold
(Optional) Must be a pointer; it can be of any type. Its pointer association status can be associated, disassociated, or undefined. If its status is associated, the target does not have to be defined with a value.

Results

The result type is the same as mold, if present; otherwise, it is determined as follows:

If NULL ( ) Appears...	Type is Determined From...
On the right side of pointer assignment	The pointer on the left side
As initialization for an object in a declaration	The object
As default initialization for a component	The component
In a structure constructor	The corresponding component
As an actual argument	The corresponding dummy argument
In a DATA statement	The corresponding pointer object

The result is a pointer with disassociated association status.

Caution

If you use module IFWIN or IFWINTY, you will have a name conflict if you use the NULL intrinsic. To avoid this problem, rename the integer parameter constant NULL to something else; for example:

   USE IFWIN, NULL0 => NULL

This example lets you use both NULL0 and NULL( ) in the same program unit with no conflict.

Examples

Consider the following:

  INTEGER, POINTER :: POINT1 => NULL( )

This statement defines the initial association status of POINT1 to be disassociated.