ASSOCIATED - The GNU Fortran Compiler
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### 8.20 `ASSOCIATED` — Status of a pointer or pointer/target pair

Description:
  `ASSOCIATED(POINTER [, TARGET])` determines the status of the pointer POINTER or if POINTER is associated with the target TARGET.
Standard:
  Fortran 95 and later
Class:
  Inquiry function
Syntax:
  `RESULT = ASSOCIATED(POINTER [, TARGET])`
Arguments:

  POINTER | POINTER shall have the `POINTER` attribute and it can be of any type.
  TARGET | (Optional) TARGET shall be a pointer or a target. It must have the same type, kind type parameter, and array rank as POINTER.

  The association status of neither POINTER nor TARGET shall be undefined.
Return value:
  `ASSOCIATED(POINTER)` returns a scalar value of type `LOGICAL(4)`. There are several cases:
  (A) When the optional TARGET is not present then
    `ASSOCIATED(POINTER)` is true if POINTER is associated with a target; otherwise, it returns false.
  (B) If TARGET is present and a scalar target, the result is true if
    TARGET is not a zero-sized storage sequence and the target associated with POINTER occupies the same storage units. If POINTER is disassociated, the result is false.
  (C) If TARGET is present and an array target, the result is true if
    TARGET and POINTER have the same shape, are not zero-sized arrays, are arrays whose elements are not zero-sized storage sequences, and TARGET and POINTER occupy the same storage units in array element order. As in case(B), the result is false, if POINTER is disassociated.
  (D) If TARGET is present and an scalar pointer, the result is true
    if TARGET is associated with POINTER, the target associated with TARGET are not zero-sized storage sequences and occupy the same storage units. The result is false, if either TARGET or POINTER is disassociated.
  (E) If TARGET is present and an array pointer, the result is true if
    target associated with POINTER and the target associated with TARGET have the same shape, are not zero-sized arrays, are arrays whose elements are not zero-sized storage sequences, and TARGET and POINTER occupy the same storage units in array element order. The result is false, if either TARGET or POINTER is disassociated.
Example:

                program test_associated
                   implicit none
                   real, target  :: tgt(2) = (/1., 2./)
                   real, pointer :: ptr(:)
                   ptr => tgt
                   if (associated(ptr)     .eqv. .false.) call abort
                   if (associated(ptr,tgt) .eqv. .false.) call abort
                end program test_associated

See also:
  NULL