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From: ncohen@watson.ibm.com (Norman H. Cohen)
Subject: Re: Type extension questions
Date: 1995/03/27
Message-ID: <3l6q0i$12kj@watnews1.watson.ibm.com>#1/1
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distribution: world
references: <D5wyp1.Fsv@ennews.eas.asu.edu> <3l0frd$b9t@lang8.cs.nyu.edu>
organization: IBM T.J. Watson Research Center
reply-to: ncohen@watson.ibm.com
newsgroups: comp.lang.ada
Date: 1995-03-27T00:00:00+00:00
List-Id: <comp.lang.ada>

In article <3l0frd$b9t@lang8.cs.nyu.edu>, comar@cs.nyu.edu (Cyrille Comar)
writes: 
|> koehnema@enuxsa.eas.asu.edu (Harry Koehnemann) writes: 
...
|> :                                                             What I
|> : really want is private inheritance ala C++.
|>
|> 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

No, there is a direct Ada analog to a C++ class with a private base
class, namely a private type implemented as a tagged derived type: 

   package Base_Type_Package is
      type Base_Type is tagged ...;
      ...
   end Base_Type_Package;

   with Base_Type_Package;
   package Derived_Type_Package is
      type Derived_Type is private;
      procedure Some_Operation (X: in out Derived_Type);
      ...
   private
      type Derived_Type is new Base_Type_Package.Base_Type with ...;
   end Derived_Type_Package;

--
Norman H. Cohen    ncohen@watson.ibm.com