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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: How to stop inheritance in a good way?
Date: Wed, 15 Jan 2020 10:08:41 +0100
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Date: 2020-01-15T10:08:41+01:00
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On 2020-01-15 09:32, reinert wrote:
> Assume I define a tagged record (or interface) + derived types:
> 
>   type int1_t is interface;
>   function A(x : int1_t) return Integer is abstract;
> 
>   type object1_t is abstract new int1_t with private;
>   function A(x : object1_t) return Integer;
>   function B(x : object1_t) return Integer;
> 
>   type object2_1_t is new object1_t with private;
>   function C(x : object2_1_t) return Integer;
> 
>   type object2_2_t is new object1_t with private;
>   function D(x : object2_2_t) return Integer;
> 
> and I want object2_2_t *not* to inherit the function B (from type object1_t).
> I can make a dummy function B for object2_2_t (to override), but is it a more elegant/proper way? Or I here somehow break the concept of inheritance and enter a "dead end" ?

Inherit from object1_t privately?

    type int1_t is interface;
    function A(x : int1_t) return Integer is abstract;

    type int2_t is interface;
    function B(x : int2_t) return Integer is abstract;

    type object1_t is abstract new int1_t and int2_t with private;

    type object2_1_t is new int1_t and int2_t with private;
    overriding function A(x : object2_1_t) return Integer;
    overriding function B(x : object2_1_t) return Integer;
    function C(x : object2_1_t) return Integer;

    type object2_2_t is new int1_t with private;
    overriding function A(x : object2_2_t) return Integer;
    function D(x : object2_2_t) return Integer;

private
    type object2_1_t is new object1_t with ...;
    type object2_2_t is new object1_t with ...;

P.S. The suffix "_t" is really ugly.

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