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From: "Nick Roberts" <nickroberts@adaos.worldonline.co.uk>
Newsgroups: comp.lang.ada
Subject: Re: Ada95 language design question (accessibility rules and type
 extensions)
Date: Thu, 20 Dec 2001 22:13:05 -0000
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Date: 2001-12-20T22:13:05+00:00
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I think the answer to your question, Mark, is that something like what you
suggest would have worked, but (the designers feared?) it would have ended
up with a lot of code with dynamic checks in it. I guess the designers felt
uncomfortable with this happening, and that the existing rules were not a
problem in practice (and they generally aren't).

But IANALL (I Am Not A Language Lawyer ;-) and a comment from one of the 9X
design team would be interesting.

--
Nick Roberts

"Mark Lundquist" <no.spam@getalife.com> wrote in message
news:dULT7.2153$NM4.98008@rwcrnsc53...
> The invocation of accessibility rules in RM 3.9.1(3) is designed to
prevent
> dangling dispatch.  It seems to me that another way would have been to
> disallow assignment of a tagged type to the classwide type of a statically
> shallower parent.  Does anyone know why that would not have worked?
>
> What got me started thinking on this was the common complaint about the
> implementation of controlledness, and the ramification of this rule that
> controlled types can't be declared deeper than library-level...