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From: Dmitry A. Kazakov <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Anybody in US using ADA ? One silly idea..
Date: Wed, 29 Jan 2003 09:37:02 +0100
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Date: 2003-01-29T09:37:02+01:00
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On Tue, 28 Jan 2003 12:11:50 -0500, Hyman Rosen <hyrosen@mail.com>
wrote:

>Dmitry A. Kazakov wrote:
>> But that's another thing. Here, Circle cannot use (inherit) the
>> methods of Ellipse. It inherits only the abstract methods of
>> EliipseInterface and thus, have to implement all of them for scratch.
>> This kills the whole idea of inheritance for code reuse.
>
>It's just the way I wrote it here, because I figured Circle
>didn't need to store two doubles, just one. It could have
>inherited directly from Ellipse if I'd wanted it that way:

That's the whole point. We want to inherit from Ellipse (non-abstract)
some of its methods, but we do not want to inherit the representation
(two doubles). Of course, if you change the representation, you lose
view conversions and thus an ability to pass Circle by-reference where
an Ellipse is required. You have to pass it by-copy instead. C++
cannot this, it lacks in out parameters, but Ada well can.

---
Regards,
Dmitry Kazakov
www.dmitry-kazakov.de