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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: discriminant questions
Date: Sat, 17 Sep 2011 19:19:40 +0200
Organization: cbb software GmbH
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Date: 2011-09-17T19:19:40+02:00
List-Id: <comp.lang.ada>

On Sat, 17 Sep 2011 09:30:46 -0700 (PDT), ytomino wrote:

> I would like to write smart pointer and make that it is able to assign-
> able type, as follows:
> 
> declare
>    a : the_smart_pointer (element => wrap (new Integer'(100)));
>    b : the_smart_pointer (element => wrap (new Integer'(200)));
> begin
>    a.element.all.all := 300; -- a.all := 300; (if compiler supported
> Implicit_Dereference)
>    b := a; -- it frees element of b on Finalize and add reference
> count of a on Assign
> end;

Given:

   with Object.Handle;

   type Integer_Object is new Object.Entity with record
      Value : Integer;
   end record;
   type Integer_Object_Ptr is access Integer_Object'Class;

   package Integer_Handles is
      new Object.Handle (Integer_Object, Integer_Object_Ptr);
   use Integer_Handles;

   function Wrap (Value : Integer) return Handle is
   begin
      return Ref (new Integer_Object'(Object.Entity with Value));
   end Wrap;

You write:

   use Integer_Handles;

   A : Handle := Wrap (100);
   B : Handle := Wrap (200);
begin
   A.Ptr.Value := 300;
   B := A; -- Frees B.Ptr, increases the count of A.Ptr

For the sample sources see:

http://www.dmitry-kazakov.de/ada/components.htm#Objects_etc

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de