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Date: Sat, 11 Jul 2009 20:54:05 +0200
From: Georg Bauhaus <rm.tsoh.plus-bug.bauhaus@maps.futureapps.de>
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Newsgroups: comp.lang.ada
Subject: Re: Dispatch on the result still does not work?
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Date: 2009-07-11T20:54:07+02:00
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Dmitry A. Kazakov wrote:
> Considering this one:

> I would expect it rather dispatching on the tag of X, i.e. selecting Value,
> which returns S.
> 

Another one, I don't like to call this a solution,
and the running program differs per compiler
used. But both compilers compile the units without errors:

package P is

   type T is tagged null record;

   function Value return T;
   function Dispatched(X, V: T) return T'Class;

   type S is new T with null record;

   function Value return S;
   function Dispatched(X, V: S) return T'Class;

end P;

with Ada.Text_IO;
package body P is

   function Dispatched(X, V: T) return T'Class is
   begin
      return V;
   end Dispatched;

   function Dispatched(X, V: S) return T'Class is
   begin
      return V;
   end Dispatched;

   function Value return T is
   begin
      Ada.Text_IO.Put_Line("Value returns a T");
      return T'(null record);
   end Value;

   function Value return S is
   begin
      Ada.Text_IO.Put_Line("Value returns an S");
      return S'(T with null record);
   end Value;

end P;


with P;
procedure Run_P is

   use P;

   X: T'Class := S'(Value);
begin
   X := Dispatched(X, Value);
end Run_P;