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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Ada 2005 OOP : newbie questions
Newsgroups: comp.lang.ada
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References: <C9673789.51E3%news@findlayw.plus.com>
Date: Thu, 27 Jan 2011 16:15:20 +0100
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Date: 2011-01-27T16:15:25+01:00
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On Thu, 27 Jan 2011 14:54:01 +0000, Bill Findlay wrote:

> I have a package P that declares
> 
>    type R is new Limited_Controlled with private;
> 
> The private extension of R contains a number of fields that I want to be
> common to future derived types S, T, etc; P declares a number of primitive
> operation signatures of R that I want S, T, etc, to override; and there are
> some operations on R'Class in P as well.
> 
> 1. Can I prevent objects of type P.R from being declared,
>    while allowing objects of types S, T, etc?

A type with no instances is abstract:

   type R is abstract new Limited_Controlled with private;

> 2. Can I prevent a useless primitive of P.R, say P.Op from being called?

Useless in which sense? If the operation cannot be implemented in R, it
should be abstract to be implemented in S and T.

   procedure Foo (Object : in out R) is abstract;

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