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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 09:28:02 +0100
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On Tue, 28 Jan 2003 12:14:43 -0500, Hyman Rosen <hyrosen@mail.com>
wrote:

>Dmitry A. Kazakov wrote:
>> Why do you think that making related types [Ellipse and Circle]
>> siblings (i.e. in fact unrelated) should provide the separation?
>
>Why do you think that the program objects Ellipse and Circle are
>related (as opposed to the mathematical objects, that is)?

Because program objects are used to model the mathematical ones. The
mathematical fact that circle is an ellipse makes possible
substitutability (limited of course) of the corresponding model
objects in programming language, which in turn is the basis of code
reuse.

>After all, mathematical objects are immutable.

So what? All values are immutable as well. If you think that
immutability implies absolute substitutability, then you are wrong. It
is a common delusion.

>You have a circle with
>a given radius, or an ellipse with given axes. They don't come
>with knobs.

If you do not like Circle and Ellipse, take int and float in C++.

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