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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: A few questions
Date: Mon, 16 Nov 2015 21:50:26 +0000
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Date: 2015-11-16T21:50:26+00:00
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"Randy Brukardt" <randy@rrsoftware.com> writes:

> Since 'Unrestricted_Access is GNAT junk, it's doesn't have any value
> for a sample implementation (if you really need 'Unrestricted_Access,
> then the interface can't be implemented in Ada, and that would be a
> major problem.)  So far as I know, you might need to use
> 'Unchecked_Access, but that's necessary anytime one needs to get a
> pointer to save the evaluated version of something.

I can't of course speak for AdaCore, but I think that the problem is
to do with obtaining a writable view of an in parameter; for example, in
the Bounded Hashed Map (GCC 5) there is

   function Iterate
     (Container : Map) return Map_Iterator_Interfaces.Forward_Iterator'Class
   is
      B  : Natural renames Container'Unrestricted_Access.all.Busy;
   begin
      return It : constant Iterator :=
        (Limited_Controlled with
           Container => Container'Unrestricted_Access)
      do
         B := B + 1;
      end return;
   end Iterate;

I dare say something could be done with 'Address and Address To Access
Conversions.