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From: Adam Beneschan <adam@irvine.com>
Newsgroups: comp.lang.ada
Subject: Re: Dispatch on the result still does not work?
Date: Mon, 13 Jul 2009 11:46:54 -0700 (PDT)
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Date: 2009-07-13T11:46:54-07:00
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On Jul 13, 8:13=A0am, Adam Beneschan <a...@irvine.com> wrote:
> I think this also works:
>
> =A0 =A0 =A0X : T'Class :=3D S'(Value);
> =A0 begin
> =A0 =A0 =A0declare
> =A0 =A0 =A0 =A0 function T_Value return T renames Pak1.Value;
> =A0 =A0 =A0begin
> =A0 =A0 =A0 =A0 X :=3D T_Value;
> =A0 =A0 =A0end;
>
> Again, the rename helps the compiler determine unambiguously which
> Value subprogram is intended, but it doesn't change the fact that the
> call to it is tag-indeterminate. =A0I'd need to pore over the rules more
> closely to make sure of this, however.

OK, I think I got this part wrong.  The AARM says that whether a call
on a subprogram rename is a dispatching operation depends on where the
renaming operation is declared, not on what it renames; here, the
rename is not a primitive subprogram (even though the thing it renames
*is* primitive), so the call on T_Value is not a dispatching operation
and thus can't be tag-indeterminate, and therefore the assignment
statement is illegal.  GNAT might be getting this wrong.

                                  -- Adam


>
> Anyway, the important thing to remember is that the compiler first has
> to determine which declaration is meant by every identifier in a
> statement, and only *then* can it think about whether a call is
> dispatching or not.
>
> Hope this helps,
>
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0-- Adam- Hide quoted text -
>
> - Show quoted text -