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From: AdaMagica <christoph.grein@eurocopter.com>
Newsgroups: comp.lang.ada
Subject: Re: A few Ada questions
Date: Fri, 24 Jul 2009 02:07:34 -0700 (PDT)
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Date: 2009-07-24T02:07:34-07:00
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Hu Ludovic,

that's dangerous what you proposed:
-----------------------------------
private with Ada.Finalization;

package Ludovic is

  type T is private;

  -- primitive operations here
  procedure Show (X: in T);

private

  type Controller (Enclosing: access T) is new
Ada.Finalization.Controlled with null record;

  overriding procedure Initialize (This: in out Controller);
  overriding procedure Adjust     (This: in out Controller);
  overriding procedure Finalize   (This: in out Controller);

  type T is record -- note: untagged record
    C: Controller (Enclosing => T'Access);
    I: Integer;
  end record;

end Ludovic;
with Ada.Text_IO;
use  Ada.Text_IO;

package body Ludovic is

  I: Integer := 0;

  overriding procedure Initialize (This: in out Controller) is
  begin
    I := I + 1;
    This.Enclosing.I := I;
  end Initialize;

  overriding procedure Adjust (This: in out Controller) is
  begin
    This.Enclosing.I := This.Enclosing.I + 1;
  end Adjust;

  overriding procedure Finalize (This: in out Controller) is
  begin
    null;
  end Finalize;

  procedure Show (X: in T) is
  begin
    Put_Line (Integer'Image (X.I) & Integer'Image (X.C.Enclosing.I));
  end Show;

end Ludovic;
with Ada.Text_IO;
use  Ada.Text_IO;

with Ludovic;

procedure Brenta is

  X, Y: Ludovic.T;

begin

  Ludovic.Show (X);
  Ludovic.Show (Y);
  New_Line;

  X := Y;
  Ludovic.Show (X);  -- X.C points to Y - that's surely not what you
want.
  Ludovic.Show (Y);
  New_Line;

end Brenta;