ALLOCATE

Statement: Dynamically creates storage for allocatable arrays and pointer targets. The storage space allocated is uninitialized.

Syntax

ALLOCATE (object [(s-spec)] [, object [(s-spec [, s-spec...])] ] ...[, STAT=sv])

object
Is the object to be allocated. It is a variable name or structure component, and must be a pointer or allocatable array. The object can be of type character with zero length.

s-spec
Is a shape specification in the form [lower-bound:]upper-bound. Each bound must be a scalar integer expression. The number of shape specifications must be the same as the rank of the object.

sv
(Output) Is a scalar integer variable in which the status of the allocation is stored.

Description

A bound in s-spec must not be an expression containing an array inquiry function whose argument is any allocatable object in the same ALLOCATE statement; for example, the following is not permitted:

  INTEGER ERR
  INTEGER, ALLOCATABLE :: A(:), B(:)
  ...
  ALLOCATE(A(10:25), B(SIZE(A)), STAT=ERR)  ! A is invalid as an argument
                                            !   to function SIZE

If a STAT variable is specified, it must not be allocated in the ALLOCATE statement in which it appears. If the allocation is successful, the variable is set to zero. If the allocation is not successful, an error condition occurs, and the variable is set to a positive integer value (representing the run-time error). If no STAT variable is specified and an error condition occurs, program execution terminates.

To release the storage for an allocated array, use DEALLOCATE.

To determine whether an allocatable array is currently allocated, use the ALLOCATED intrinsic function.

To determine whether a pointer is currently associated with a target, use the ASSOCIATED intrinsic function.

See Also: ALLOCATABLE, ALLOCATED, DEALLOCATE, ASSOCIATED, POINTER, Dynamic Allocation, Pointer Assignments

Examples

  !Method for creating and allocating deferred shape arrays.
  INTEGER,ALLOCATABLE::matrix(:,:)
  REAL, ALLOCATABLE:: vector(:)
  . . .
  ALLOCATE (matrix(3,5),vector(-2:N+2))
  . . .

The following shows another example of the ALLOCATE statement:

  INTEGER J, N, ALLOC_ERR
  REAL, ALLOCATABLE :: A(:), B(:,:)
  ...
  ALLOCATE(A(0:80), B(-3:J+1, N), STAT = ALLOC_ERR)