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From: Robert A Duff <bobduff@world.std.com>
Subject: Re: Subverting 'Access for Sub-programs
Date: 1999/08/04
Message-ID: <wccbtcnfzr3.fsf@world.std.com>#1/1
X-Deja-AN: 508764351
Sender: bobduff@world.std.com (Robert A Duff)
References: <37A71EF1.2201@dera.gov.uk> <37A7FDE8.4F5@dera.gov.uk>
Organization: The World Public Access UNIX, Brookline, MA
Newsgroups: comp.lang.ada
Date: 1999-08-04T00:00:00+00:00
List-Id: <comp.lang.ada>

Anton Gibbs <agibbs@dera.gov.uk> writes:

> Here, the problem is retaining visibility of the parameter F within the
> procedure whose 'Access I am trying to pass to the Perform operation. If
> I move Print_If_Multiple out to its own package (ie. out of the scope of
> Not_Main) then the only way I can see F is by using global data. I know
> this will work but I am reluctant to adopt this approach because I have
> often found that non-re-entrant code bites back in years to come when it
> gets re-used (usually by me) in a way the author never originally
> intended.

There is no good solution to this problem: no solution that is portable,
concise, reentrant, &c.

One thing you can do is declare a tagged type, and use an extension as
the environment of the procedure you want to pass -- then instead of
passing a procedure as a parameter, pass an object of the class-wide
type.

> "The Information contained in this E-Mail and any 
> subsequent correspondence is private and is intended
> solely for the intended recipient(s). ...

 :-) :-) :-)

- Bob
-- 
Change robert to bob to get my real email address.  Sorry.