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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Ada OOP syntax
Newsgroups: comp.lang.ada
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Date: Wed, 18 Jun 2008 14:30:55 +0200
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On Wed, 18 Jun 2008 00:48:22 -0700 (PDT), markus034@gmail.com wrote:

> Especially, package types and package subtypes are very interesting.
> That syntax seems to be clearer than tagged types. I don't understand
> why it was rejected?

I don't know it. But in my eyes the drawbacks of the proposal are:

1. Impure (not all types have classes, there are methods and non-methods)
2. No multiple inheritance
3. No multiple dispatch
4. Conflating classes and packages (sets of types vs. visibility)
5. Self
6. Operators (multi-methods) are clumsy and have no access to the
implementation (a consequence of 1,3,4,5) 
7. Re-dispatch (inconsistent, performance hit)
8. Entries are confused with procedures (it is unclear when and if the
queue appear)
9. It is unclear (to me) how generic (class-wide) programming is
accomplished.

Though the Ada 95 model also has some of these problems (and many others
too), yet it did not damage the language, because there seem to be ways to
fix it. Tagged types are rather an outbuilding. The proposal would be a
total rebuild (IMO on the fundament of sand).

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