Visible to Intel only — GUID: GUID-638CE46F-977E-42BB-B1E4-852C7753ED82
Visible to Intel only — GUID: GUID-638CE46F-977E-42BB-B1E4-852C7753ED82
NULLIFY
Statement: Disassociates a pointer from a target.
NULLIFY (pointer-object[,pointer-object]...)
pointer-object |
Is a structure component, the name of a variable, or the name of a procedure pointer. It must have the POINTER attribute. Each pointer-object may not depend on the value, bounds or association of another pointer object in the same NULLIFY statement. |
Description
The initial association status of a pointer is undefined. You can use NULLIFY to initialize an undefined pointer, giving it disassociated status. Then the pointer can be tested using the intrinsic function ASSOCIATED.
When a polymorphic pointer is nullified, its dynamic type becomes its declared type.
Example
The following is an example of the NULLIFY statement:
REAL, TARGET :: TAR(0:50) REAL, POINTER :: PTR_A(:), PTR_B(:) PTR_A => TAR PTR_B => TAR ... NULLIFY(PTR_A)
After these statements are executed, PTR_A will have disassociated status, while PTR_B will continue to be associated with variable TAR.
The following shows another example:
! POINTER2.F90 Pointing at a Pointer and Target !DIR$ FIXEDFORMLINESIZE:80 REAL, POINTER :: arrow1 (:) REAL, POINTER :: arrow2 (:) REAL, ALLOCATABLE, TARGET :: bullseye (:) ALLOCATE (bullseye (7)) bullseye = 1. bullseye (1:7:2) = 10. WRITE (*,'(/1x,a,7f8.0)') 'target ',bullseye arrow1 => bullseye WRITE (*,'(/1x,a,7f8.0)') 'pointer',arrow1 arrow2 => arrow1 IF (ASSOCIATED(arrow2)) WRITE (*,'(/a/)') ' ARROW2 is pointed.' WRITE (*,'(1x,a,7f8.0)') 'pointer',arrow2 NULLIFY (arrow2) IF (.NOT.ASSOCIATED(arrow2)) WRITE (*,'(/a/)') ' ARROW2 is not pointed.' WRITE (*,'( 1x,a,7f8.0)') 'pointer',arrow1 WRITE (*,'(/1x,a,7f8.0)') 'target ',bullseye END