5.2 ALLOCATABLE Attribute and Statement

The ALLOCATABLE attribute specifies that an array is an allocatable array with a deferred shape. The shape of an allocatable array is determined when an ALLOCATE statement is executed, dynamically allocating space for the array.

The ALLOCATABLE attribute can be specified in a type declaration statement or an ALLOCATABLE statement, and takes one of the following forms:

Type Declaration Statement:

 type, [att-ls,] ALLOCATABLE [,att-ls] :: a[(d-spec)] [,a[(d-spec)]]...

Statement:

 ALLOCATABLE [::] a[(d-spec)] [,a[(d-spec)]]...

type

Is a data type specifier.

att-ls

Is an optional list of attribute specifiers.

a

Is the name of the allocatable array; it must not be a dummy argument or function result.

d-spec

Is a deferred-shape specification (: [,:]...). Each colon represents a dimension of the array.

Rules and Behavior

If the array is given the DIMENSION attribute elsewhere in the program, it must be declared as a deferred-shape array.

When the allocatable array is no longer needed, it can be deallocated by execution of a DEALLOCATE statement.

An allocatable array cannot be specified in a COMMON, EQUIVALENCE, DATA, or NAMELIST statement.

Examples

The following example shows a type declaration statement specifying the ALLOCATABLE attribute:

REAL, ALLOCATABLE :: Z(:, :, :)

The following is an example of the ALLOCATABLE statement:

REAL A, B(:)
ALLOCATABLE :: A(:,:), B

For More Information:

• On type declaration statements, see Section 5.1.

• On the ALLOCATE statement, see Section 6.1.

• On the DEALLOCATE statement, see Section 6.2.

• On allocation status, see Section 6.1.1.

• On compatible attributes, see Table 5-1.