Language Reference

COMPLEX

Purpose

A COMPLEX type declaration statement specifies the length and attributes of objects and functions of type complex. Initial values can be assigned to objects.

Format

>>-COMPLEX--+---------------+--+-+----+----------------+-------->
            '-kind_selector-'  | '-::-'                |
                               '-,--attr_spec_list--::-'
 
>--entity_decl_list--------------------------------------------><
 
 

where:

kind_selector

>>-+-(--+-----------+--int_initialization_expr--)-+------------>< | '-KIND-- = -' | | (1) | '- * --int_literal_constant--------------------' Notes: IBM Extension.

 

specifies the length of complex entities:

+-------------------------------IBM Extension--------------------------------+

• If int_initialization_expr is specified, the valid values are 4, 8 and 16. These values represent the precision and range of each part of the complex entity.
• If the *int_literal_constant form is specified, the valid values are 8, 16 and 32. These values represent the length of the whole complex entity, and correspond to the values allowed for the alternative form. int_literal_constant cannot specify a kind type parameter.

+----------------------------End of IBM Extension----------------------------+

attr_spec

For detailed information on rules about a particular attribute, refer to the statement of the same name.

intent_spec

is either IN, OUT, or INOUT

::

is the double colon separator. It is required if attributes are specified, = initialization_expr or NULL() is used.

array_spec

is a list of dimension bounds.

entity_decl

>>-a--+-+---------------+--+------------------+-+---------------> | | (1) | '-(--array_spec--)-' | | '- * --len------' | | (2) | '-(--array_spec--)-- * --len--------------' >--+-----------------------------------+----------------------->< | (3) | '-+-/--initial_value_list--/------+-' +- = --initialization_expr------+ | (4) | '- => --NULL()------------------' Notes: IBM Extension. IBM Extension. IBM Extension. Fortran 95.

 

a

is an object name or function name. array_spec cannot be specified for a function name.

+-------------------------------IBM Extension--------------------------------+

len

overrides the length as specified in kind_selector, and cannot specify a kind type parameter. The entity length must be an integer literal constant that represents one of the permissible length specifications.

+----------------------------End of IBM Extension----------------------------+

+-------------------------------IBM Extension--------------------------------+

initial_value

provides an initial value for the entity specified by the immediately preceding name

+----------------------------End of IBM Extension----------------------------+

initialization_expr

provides an initial value, by means of an initialization expression, for the entity specified by the immediately preceding name

+---------------------------------Fortran 95---------------------------------+

=> NULL()

provides an initial value for the pointer object

+-----------------------------End of Fortran 95------------------------------+

Rules

+---------------------------------Fortran 95---------------------------------+

Within the context of a derived type definition:

• If => appears in a component initialization, the POINTER attribute must appear in the attr_spec_list.
• If = appears in a component initialization, the POINTER attribute cannot appear in the component attr_spec_list.
• The compiler will evaluate initialization_expr within the scoping unit of the type definition.

If => appears for a variable, the object must have the POINTER attribute.

+-----------------------------End of Fortran 95------------------------------+

If initialization_expr appears for a variable, the object cannot have the POINTER attribute.

Entities in type declaration statements are constrained by the rules of any attributes specified for the entities, as detailed in the corresponding attribute statements.

The type declaration statement overrides the implicit type rules in effect. You can use a type declaration statement that confirms the type of an intrinsic function. The appearance of a generic or specific intrinsic function name in a type declaration statement does not cause the name to lose its intrinsic property.

An object cannot be initialized in a type declaration statement if it is a dummy argument, an allocatable object, a pointer, a function result, an object in blank common, an integer pointer, an external name, an intrinsic name, or an automatic object. Nor can an object be initialized if it has the AUTOMATIC attribute. The object may be initialized if:

• it appears in a named common block in a block data program unit.

  +-------------------------------IBM Extension--------------------------------+

  
  
• if it appears in a named common block in a module.

  +----------------------------End of IBM Extension----------------------------+

+---------------------------------Fortran 95---------------------------------+

In Fortran 95, a pointer can be initialized. Pointers can only be initialized by the use of => NULL().

+-----------------------------End of Fortran 95------------------------------+

The specification expression of an array_spec can be a nonconstant expression if the specification expression appears in an interface body or in the specification part of a subprogram. Any object being declared that uses this nonconstant expression and is not a dummy argument or a pointee is called an automatic object.

An attribute cannot be repeated in a given type declaration statement, nor can an entity be explicitly given the same attribute more than once in a scoping unit.

initialization_expr must be specified if the statement contains the PARAMETER attribute. If initialization_expr or NULL() is specified, and the entity you are declaring:

• is a variable, the variable is initially defined.

  +---------------------------------Fortran 95---------------------------------+

  
  
• is a derived type component, the derived type has default initialization.

  +-----------------------------End of Fortran 95------------------------------+

A variable or variable subobject cannot be initialized more than once. If a is a variable, the presence of initialization_expr or NULL() implies that a is a saved object, except for an object in a named common block. The initialization of an object could affect the fundamental storage class of an object.

An array_spec specified in the entity_decl takes precedence over the array_spec in the DIMENSION attribute.

An array function result that does not have the POINTER attribute must have an explicit-shape array specification.

If the entity declared is a function, it must not have an accessible explicit interface unless it is an intrinsic function.

+-------------------------------IBM Extension--------------------------------+

If T or F, defined previously as the name of a constant, appears in a type declaration statement, it is no longer an abbreviated logical constant but the name of the named constant.

+----------------------------End of IBM Extension----------------------------+

Examples

      COMPLEX, DIMENSION (2,3) :: ABC(3) ! ABC has 3 (not 6) array elements

Related Information

• Complex
• Initialization Expressions
• How Type Is Determined, for details on the implicit typing rules
• Array Declarators
• Automatic Objects
• Storage Classes for Variables
• DATA, for details on initial values