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From: "Jean-Pierre Rosen" <rosen.adalog@wanadoo.fr>
Newsgroups: comp.lang.ada
Subject: Re: controlled type in generic package?
Date: Wed, 7 Feb 2001 23:52:36 +0100
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"Ted Dennison" <dennison@telepath.com> a �crit dans le message news: 95rpj5$gq7$1@nnrp1.deja.com...
> I have to admit I'm a little unclear as to what nasty things could
> happen to me if I were allowed to declare a derived tagged type at a
> lower scope level than their parent type.
OK, let's go:

package body Pack is
   type Parent is tagged ...;
   procedure Proc (X : Parent) is ... end Proc;

   type Ptr is access Parent'Class;
   V : Ptr;

   procedure P is
      type Child is new Parent with...;
      procedure Proc (X : Child) is... end Proc;
   begin
      V := new Child;
   end P;

begin
   P;
-- Now, V.all points to an object of type P.Child
-- We can call Proc (V.all) which will result in a dispatching call to P.Proc, but P is out of scope at this point !!!