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From: koehnema@enuxsa.eas.asu.edu (Harry Koehnemann)
Subject: Re: Type extension questions
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Reply-To: koehnema@enuxsa.eas.asu.edu (Harry Koehnemann)
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Date: Mon, 27 Mar 1995 17:29:07 GMT
References: <D5wyp1.Fsv@ennews.eas.asu.edu> <3l0frd$b9t@lang8.cs.nyu.edu>
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Date: 1995-03-27T17:29:07+00:00
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In article <3l0frd$b9t@lang8.cs.nyu.edu> comar@cs.nyu.edu (Cyrille Comar) writes:
>Don't try to be too close to C++, this doesn't fit Ada's
>model. "Private inheritance" is meaningless in Ada since "Private" is
>a caracteristic of packages and inheritance a characteristic of types
>but you can still do something very close from what you want :

Well, yes and no.  What I really want to do is restrict the interface
to a type.  It might help to see an example.  Let's pretend we have 2
abstract data types, where one is an extension of the other:

    class List {
	public:  Set (...) { ...}
	private: ...;
    };

    class Stack : private List {
	public:  Push() { ...}
	private: ...;
    };

It is not appropriate for a Stack to invoke Set.  One could argue that
Stack has-a List instead of Stack is-a list (I think Tucker Taft made
this argument earlier).  Bottom line - I guess there is no way to
perform private inheritance, as shown in the above example, in Ada95,
which was my question.  Thanks for the input.

BTW - I am by no means saying Ada95 should have included such a
feature (in fact, I am not a believer in restricting interfaces and
think that it clutters a design).  I'm just getting my Ada95 facts
straight.