J3/04-226

Date:      2004-01-30
To:        J3
From:      fortran.com
Subject:   Allow forward type for allocatable components
Reference: Pub-116


This was submitted by Van Snyder  van.snyder@jpl.nasa.gov

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Number:

Title: Allow forward type for allocatable components

Submitted by: J3

Status: For Consideration

References: 03-007r2, Section 4.5.3

Basic Functionality: Allow the type of an allocatable component
to be one that isn't defined before the type containing
the allocatable component.


Rationale: Mutually recursive types can be related by
componenents having the POINTER attribute, which allows the
types of the components to be defined after the type in which
the components appear.  Some mutually recursive types could
be related by components having the ALLOCATABLE attribute,
except that is presently prohibited.  ALLOCATABLE is preferable
to POINTER whenever possible.  We should make every effort to
make ALLOCATABLE as widely usable as possible.


Estimated Impact: Easy to implement, improves performance, trivial
change in the standard.


Detailed Specification: In 03-007r2, revise Constraint 438:

C438 (R440) If neither the POINTER nor ALLOCATABLE attribute
     is specified for a component, the <declaration-type-spec>
     in the <component-def-stmt> shall specify an intrinsic
     type or a previously defined derived type.


History: Submitted as Pub-116