J3/00-326

To: J3
From: Malcolm Cohen
Subject: Issue 272
Date: 27 November 2000

1. Introduction

Issue 272 says
  "It ought to be possible to assign a procedure to a procedure pointer
   with explicit interface from within itself."

I disagree that this should always be possible.  Within a procedure, the
result variable name should always refer to the result variable, never to
the procedure itself.

2. Proposal

2.1 Specifications and Syntax

That a non-RECURSIVE procedure should be able to assign "itself" to a
procedure pointer (when there is no possible confusion between it and
the result variable).

The same syntax to be used as if it were a RECURSIVE procedure.

2.2 Discussion

Arguments for and against:
 - unlike passing itself as an actual argument, assignment to a procedure
   pointer can be useful
 - it would be irregular to require the RECURSIVE keyword when no recursion
   is being involved
 - the functionality is already available, but only clumsily, by using a
   "helper" procedure.
 - it may be inconvenient (or impossible) to make the procedure RECURSIVE,
   due to external constraints.

3. Edits to 00-007r3

[245:8] Delete "recursive" twice.
{Remove the RECURSIVE keyword requirement - makes the procedure interface
 explicit.}

[245:13-21] Delete J3 note 272.

[267:24] Change "are recursive function references"
         to "refer to the function itself".
{Not all occurrences of the function name are function references: in
 particular, appearance on the right-hand-side of a procedure pointer
 assignment is not.}

[269:10] Change "If RECURSIVE is specified, the"
         to "The".
{There is no need to invoke recursion just to make the interface explicit.}

[270:14-15] Delete "and RECURSIVE is specified in the FUNCTION statement".
{No need for recursion.}

[270:20] Replace "If RECURSIVE ... , the"
         by "The"
{No need for recursion.}

[270:20] Replace "the subroutine" by "a subroutine".
{Wording improvement.}

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