TYPE Statement (Derived Types)

Syntax

TYPE [[,type-attr-spec-list] :: ] name

component-definition

   [component-definition]. . .

END TYPE [ name ]

type-attr-spec-list	Is access-spec or BIND (C).
access-spec	Is the PUBLIC or PRIVATE keyword. The keyword can only be specified if the derived-type definition is in the specification part of a module.
name	Is the name of the derived data type. It must not be the same as the name of any intrinsic type, or the same as the name of a derived type that can be accessed from a module.
component-definition	Is one or more type declaration statements defining the component of derived type. The first component definition can be preceded by an optional PRIVATE or SEQUENCE statement. (Only one PRIVATE or SEQUENCE statement can appear in a given derived-type definition.) If SEQUENCE is present, all derived types specified in component definitions must be sequence types. A component definition takes the following form: type[ [, attr] :: ] component[( a-spec)] [ *char-len] [ init-ex] type Is a type specifier. It can be an intrinsic type or a previously defined derived type. (If the POINTER attribute follows this specifier, the type can also be any accessible derived type, including the type being defined.) attr Is an optional POINTER attribute for a pointer component, or an optional DIMENSION or ALLOCATABLE attribute for an array component. You cannot specify both the ALLOCATABLE and POINTER attribute. If DIMENSION is specified, it can be followed by an array specification. Each attribute can only appear once in a given component-definition. component Is the name of the component being defined. a-spec Is an optional array specification, enclosed in parentheses. If POINTER or ALLOCATABLE is specified, the array is deferred shape; otherwise, it is explicit shape. In an explicit-shape specification, each bound must be a constant scalar integer expression. If the array bounds are not specified here, they must be specified following the DIMENSION attribute. char-len Is an optional scalar integer literal constant; it must be preceded by an asterisk (*). This parameter can only be specified if the component is of type CHARACTER. init-ex Is an initialization expression, or for pointer components, => NULL( ). This is a Fortran 95 feature. If init-ex is specified, a double colon must appear in the component definition. The equals assignment symbol (=) can only be specified for nonpointer components. The initialization expression is evaluated in the scoping unit of the type definition.

Description

If a name is specified following the END TYPE statement, it must be the same name that follows TYPE in the derived type statement.

A derived type can be defined only once in a scoping unit. If the same derived-type name appears in a derived-type definition in another scoping unit, it is treated independently.

A component name has the scope of the derived-type definition only. Therefore, the same name can be used in another derived-type definition in the same scoping unit.

Two data entities have the same type if they are both declared to be of the same derived type (the derived-type definition can be accessed from a module or a host scoping unit).

If the entities are in different scoping units, they can also have the same derived type if they are declared with reference to different derived-type definitions, and if both derived-type definitions have all of the following:

• The same name

• A SEQUENCE statement (they both have sequence type)

• Components that agree in name, order, and attributes; components cannot be private

If BIND (C) is specified, the following rules apply:

• The derived type cannot be a SEQUENCE type.

• The derived type must have type parameters.

• Each component of the derived type must be a nonpointer, nonallocatable data component with interoperable type and type parameters.

Example

! DERIVED.F90

! Define a derived-type structure,

! type variables, and assign values

TYPE member

INTEGER age

CHARACTER (LEN = 20) name

END TYPE member

TYPE (member) :: george

TYPE (member) :: ernie

george = member( 33, 'George Brown' )

ernie%age = 56

ernie%name = 'Ernie Brown'

WRITE (*,*) george

WRITE (*,*) ernie

END

The following shows another example of a derived type:

TYPE mem_name

SEQUENCE

CHARACTER (LEN = 20) lastn

CHARACTER (LEN = 20) firstn

CHARACTER (len = 3) cos ! this works because COS is a component name

END TYPE mem_name

TYPE member

TYPE (mem_name) :: name

SEQUENCE

INTEGER age

CHARACTER (LEN = 20) specialty

END TYPE member

In the following example, a and b are both variable arrays of derived type pair:

TYPE (pair)

INTEGER i, j

END TYPE

TYPE (pair), DIMENSION (2, 2) :: a, b(3)

The following example shows how you can use derived-type objects as components of other derived-type objects:

TYPE employee_name

CHARACTER(25) last_name

CHARACTER(15) first_name

END TYPE

TYPE employee_addr

CHARACTER(20) street_name

INTEGER(2) street_number

INTEGER(2) apt_number

CHARACTER(20) city

CHARACTER(2) state

INTEGER(4) zip

END TYPE

Objects of these derived types can then be used within a third derived-type specification, such as:

TYPE employee_data

TYPE (employee_name) :: name

TYPE (employee_addr) :: addr

INTEGER(4) telephone

INTEGER(2) date_of_birth

INTEGER(2) date_of_hire

INTEGER(2) social_security(3)

LOGICAL(2) married

INTEGER(2) dependents

END TYPE