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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: API design problem - buffer scatter I/O
Newsgroups: comp.lang.ada
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Date: Tue, 25 Nov 2008 09:34:16 +0100
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Date: 2008-11-25T09:34:16+01:00
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On Mon, 24 Nov 2008 21:59:41 -0800 (PST), christoph.grein@eurocopter.com
wrote:

>> Sure it is. �How a compiler represents data types (including access
>> types) is an implementation detail.
> 
> What I meant is the incompatibility between pointers to constrained
> and unconstrained:

I agree with you. Pointer to a subtype is not necessarily a subtype of the
pointer to the base. That is not an implementation detail. It should be per
programmer's choice. Unfortunately Ada lacks means to propagate type
constraints between related types, which is the issue here. We need a way
to say whether the constraint has to be moved from the target to the
pointer, making the later unconstrained. That does not necessary imply that
the pointer's representation must become "fat." That indeed would be an
implementation detail, as Robert says. But the decision is not a detail.

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