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From: Lutz Donnerhacke <lutz@iks-jena.de>
Newsgroups: comp.lang.ada
Subject: Re: Q: Endless loop by dispatching
Date: Tue, 22 Jul 2003 15:11:15 +0000 (UTC)
Organization: IKS GmbH Jena
Message-ID: <slrnbhql0g.oa.lutz@taranis.iks-jena.de>
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* Dmitry A Kazakov wrote:
> On Tue, 22 Jul 2003 12:18:57 +0000 (UTC), Lutz Donnerhacke
>>If publicly defined tagged types are fixed at the private syntax element,
>>there is no possibility to define dispatching procedures and functions
>>afterwards. Of course, it's not a choice, because it will break existing
>>programs.
>
> But what if I need to extend the interface by adding some new
> primitive operations?

Not possible in the private part. Plain and simple.

package X is
   type T is tagged private;
   function Foo return T; -- Ok.
private -- fix T
   procedure Bar(o : T); -- Fails.
   type T is new Ada.Finalization.Controlled with null record; -- Fails.
end X;

but

package X is
   type T is tagged private;
   function Foo return T;
private -- fix T
   type T is ...
end X;

with X;
package Y is
   type T is new X.T with private;
   procedure Bar(o : T); -- Ok.
private
   type T is new X.T with null record;
end Y;

with X;
package Z is
   [...]
private
   type T is new X.T with null record;
   procedure Bar(o : T); -- Ok.
end Z;



> Or do you mean some sort of interface freezing like Java's "final"?

No.