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From: Tucker Taft <stt@averstar.com>
Subject: Re: meaning of "current instance"
Date: 1999/11/15
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Date: 1999-11-15T00:00:00+00:00
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Robert A Duff wrote:
> 
> "Matthew Heaney" <matthew_heaney@acm.org> writes:
> 
> > I have some code below that I thought had a bug (um, I mean "error"),
> 
> ;-)
> 
> > but now I'm not so sure.
> >
> > Suppose I have this:
> >
> >   type T is tagged private;
> > ...
> >   function Init (O : access T'Class)
> >
> >   type T is
> >     tagged record
> >       I : Integer := Init (T'Access);
> >     end record;
> 
> I think you want T to be limited, or else use 'Unchecked_Access.

This is illegal, even if you use 'Unchecked_Access, unless T is limited,
because only if T is limited is the "view from the inside" aliased
(see 3.10(9) and 3.10.2(24)).  Just making it tagged is not enough.

> ...
-- 
-Tucker Taft   stt@averstar.com   http://www.averstar.com/~stt/
Technical Director, Distributed IT Solutions  (www.averstar.com/tools)
AverStar (formerly Intermetrics, Inc.)   Burlington, MA  USA