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From: adam@irvine.com
Subject: Re: Subverting 'Access for Sub-programs
Date: 1999/08/05
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Date: 1999-08-05T00:00:00+00:00
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I wrote:

> Couldn't it be made a property of the access type, instead of a
> property of the body?
>
> Was any solution like this considered, when Ada 95 was designed?  The
> inability to take an 'ACCESS of an inner subprogram seems like an
> obnoxious restriction, a step down from Pascal and Algol, and it seems
> like programmers should have an option to remove this restriction at
> the expense of adding restrictions elsewhere or perhaps adding runtime
> checks.  In fact, I kind of like the idea of allowing a different kind
> of subprogram access type declaration such that 3.10.2(28) wouldn't
> apply to that type, where the program must check to make sure the
> subprogram's ancestors are still on the stack when objects of the type
> get dereferenced.  I suspect that in the Integrate case, the compiler
> would even be able to tell that this runtime check is unnecessary.
>
> Comments?

Actually, posts on this thread that I read after writing the above,
along with some lookup in DejaNews, have mostly answered my question.
However, the discussions I found in DejaNews mentioned proposals to put
restrictions on assignment of these types, but not runtime checks.  Was
anything like this seriously considered?  Would it be simpler to
implement than the other solutions (for implementations that use
displays)?

				-- Adam


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