Re: Qs re 'Write & 'Read

["David C. Hoos" <david.c.hoos.sr@ada95.com>]

<tmoran@acm.org> wrote in message news:nOtFa.1188350$F1.139910@sccrnsc04...
> >Maybe my mind's just in a fog today, but please explain why there'd be
> >a problem with any kind of access type -- general, or not, using my
> >approach.
>   Aliasing.
>   type phs is access integer;
>   type pgs is access all integer;
>   type r is record
>     i : aliased integer;
>     ph : phs;
>     pg : pgs;
>   end record;
>   x : r;
> begin
>   x.ph := new integer;
>   x.pg := x.i'access;
> but on reading it back in, you can tell both x.ph and x.pg are non-null,
> but you don't know whether x.pg should allocate from the heap or point
> to some existing (stack) object.

Well, for the life of me, I can't see why anyone would need to do what
your example does.  If, indeed, an access component of a record designates
an aliased component, then it seems to me that one would need an overridden
set of stream attributes for the whole record.  Writing r.pg to the stream
would be meaningless, since it designates data already written to the
stream.

The read attribute would simply make the assignment r.pg = r.i'access, after
having read r.i from the stream.

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