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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Limited_Controlled, orthogonality and related issues
Newsgroups: comp.lang.ada
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Date: Fri, 19 Jan 2007 19:26:00 +0100
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Date: 2007-01-19T19:25:48+01:00
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On Fri, 19 Jan 2007 11:36:57 -0500, Robert A Duff wrote:

> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:
> 
>> On Fri, 19 Jan 2007 10:29:35 -0500, Robert A Duff wrote:
>>
>>> Make all types tagged.  For efficiency, this would require a different
>>> run-time model than what Ada compilers currently do -- you don't want
>>> to store a tag field with every Boolean variable!  To enable the
>>> non-stored-tag model, eliminate the rule that all tagged parameter
>>> are aliased (and allow "aliased" keyword).
>>> 
>>> None of the above are likely to happen, I suspect.
>>
>> Even if we, all the Ada community, really wanted it? 
> 
> The Ada community wants compatibility with older versions of the
> language.  What I described above is not compatible.

I don't directly see what and why.

We could make all types "tagged" with non-stored tags. The keyword "tagged"
would mean a stored tag + by-reference semantics. This looks fully backward
compatible to me, at first glance.

As for legacy exceptions, we should choose a model first. Is End_Error a
type (derived from Root_Exception) or a value of Root_Exception?

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