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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Copy vector in Ada
Date: Mon, 5 Nov 2012 19:42:57 +0100
Organization: cbb software GmbH
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Date: 2012-11-05T19:42:57+01:00
List-Id: <comp.lang.ada>

On Mon, 05 Nov 2012 18:22:45 +0100, Yannick Duchêne (Hibou57) wrote:

> Le Mon, 05 Nov 2012 10:20:44 +0100, Dmitry A. Kazakov  
> <mailbox@dmitry-kazakov.de> a écrit:
>> There are lots of further questions about special treatment of copy
>> constructors, like whether one could introduce them later, e,g, promoting
>> limited types to non-limited
> Would make sense, with a derived type adding capabilities (similar comment  
> with unknown discriminant). The proof it would make sense is that in a  
> package spec, you can change a limited to a non‑limited, without breaking  
> anything.
> 
>> and demoting back.
> Back from non‑limited to limited? This one is not cool.

But "constant T" is cool? Note that constant does just this and also
disallows any other mutators. It is not that simple. However you bend a
type you inevitably break something. So it actually depends on whether
substitutability violations could be detected statically. If yes,
everything is cool. Any dynamic checks are evil per definition, only
permissible if the alternative is worse.

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