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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Implementing Rust's borrow checked pointers
Date: Tue, 24 Sep 2019 11:57:04 +0200
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Xref: reader01.eternal-september.org comp.lang.ada:57178
Date: 2019-09-24T11:57:04+02:00
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On 2019-09-24 11:05, Lucretia wrote:

> Been talking to someone on Telegraph and he was saying Ada should implement this, just wondering whether Ada could? I posed a slight change to access type specification to do this, what do people think?
> 
> type P is restricted access X;
> 
> Restricted in this case would mean that once assigned it cannot be re-assigned into or out of with out some sort of move operation, which could be implemented as an attribute on the access type.
> 
> A : P := L'Access;
> B : P := A'Move; --  A cannot no longer be used.
> 
> begin
>     A.all ... ; -- raises exception.
> 
> 
> I don't know enough about all this to put a complete proposal together, but I think I've got the basics understood.

Since run-time checks are involved the whole idea does not make sense to me.

Semantically it makes no sense either. Why copying should have this 
effect on pointer when, as in your example, unrelated to scopes (or 
unchecked deallocation)?

A more realistic example might help.

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