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From: "Prof. Dr. Carl Weierstrass" <carl.weierstrass@googlemail.com>
Newsgroups: comp.lang.ada
Subject: Use of abstract tagged types without access types -- again and
 complete
Date: Thu, 9 Jun 2011 10:50:12 -0700 (PDT)
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Date: 2011-06-09T10:50:12-07:00
List-Id: <comp.lang.ada>

Hi,

I have a question to all Ada gurus:

I want to do something like:

package Test is

   type Parent_Type is new Ada.Finalization.Controlled with private;
   type Child_Type is abstract new Ada.Finalization.Controlled with
private;
   type Child_Type_1 is new Child_Type with private;
   type Child_Type_N is new Child_Type with private;

private

   type Parent_Type is new Ada.Finalization.Controlled with record
         Child : Child_Type'Class;
   end record;
   type Child_Type is abstract new Ada.Finalization.Controlled with
null record;
   type Child_Type_1 is new Child_Type with null record;
   type Child_Type_N is new Child_Type with null record;

end Test;

This doesn't work, because:
class-wide subtype with unknown discriminants in component declaration

Of course I could use an access type to avoid the error but is there a
way to
do something like this without access types.


Regards