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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: APQ
Date: Wed, 22 Dec 2004 14:15:42 +0100
Organization: cbb software GmbH
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Date: 2004-12-22T14:15:42+01:00
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On Wed, 22 Dec 2004 11:07:44 +0100, Martin Krischik wrote:

> Warren W. Gay VE3WWG wrote:
> 
>> I can't imagine it making a practical difference here, but
>> perhaps I lack imagination on this point.
> 
> http://en.wikibooks.org/wiki/Programming:Ada:Types:access#access_vs._access_all

Pool-specific access types do not do well:

1. Upcast/downcast conversions do not work. You'll need
Unchecked_Conversion of pointers. It is nasty and dangerous.

2. '[Unchecked_]Access does not work (otherwise, (1) would be a minor
problem).

3. Rosen's trick does not work. Very bad. Move it to Initialize? That won't
work either, because of 2.

4. Construction/destruction is headache. Wished to insert a newly created
object into a list? Not from Initialize! To delete it from there upon
destruction? Nay!

5. Access discriminants cannot be pool-specific. Converting to general
access to specific one is again an Unchecked_Conversion of worst kind.

6. There is no way to restrict objects allocations to a definite set of
pools. "type X (<>) is ..." does not count.

In general, I think that the issue should be thoroughly reworked.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de