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From: bruniau@cenatls.cena.dgac.fr (Christophe Bruniau)
Subject: Re: Ada 9X _has_ "class"
Message-ID: <1993Mar25.102730.10202@cenatls.cena.dgac.fr>
Originator: bruniau@piano
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Organization: Centre d'Etudes de la Navigation Aerienne
References: <1993Mar19.213439.2342@evb.com> <1993Mar24.164424@lglsun.epfl.ch>
Date: Thu, 25 Mar 1993 10:27:30 GMT
Date: 1993-03-25T10:27:30+00:00
List-Id: <comp.lang.ada>


In article <1993Mar24.164424@lglsun.epfl.ch>, magnus@lglsun.epfl.ch (Magnus Kempe) writes:
|> jgg@evb.com (John Goodsen) quotes a lot and writes:
|> : 
|> : The 'CLASS attribute is not what you will see in marketing literature.
|> : What you will see in Marketing literature is "tagged types".
|> 
|> I have seen a lot of marketing literature touting "inheritance" and
|> "polymorphism", although the programming languages involved did not have
|> such keywords.  In addition, I have never seen any ad revolving around
|> "int" for C, "VAR" for Pascal, or "!" for PROLOG.
|> 
...
|> The primary goal w.r.t. Ada's syntax is to have a readable and
|> understandable language.  It has been explained several times that Ada
|> 9X provides both specific types and classes (a set of related types).
|> These constructs are _so_ different that they should each be subsumed
|> by a specific concept, and these concepts should not be randomly
|> mixed.
|> 
|> Since a specific type is _not_ a class, it is quite reasonable to _not_
|> call it a "class".  If you think the distinction does not matter, or is
|> "merely technical", think twice.  A tagged type T is _not_ a class: it
|> is _in_ a class (T'class) as well as in the superclasses of T'class
|> (e.g. T_First'class).
|> 

If find this quite amazing (if not disturbing).
What does an instance of a class look like ?

It seems to me that, in order to agree with the object paradigm,
 a class instance should be an object. I don't think this is true in
 that case, if a class is some kind of a type set.


|> -- 
|> Magnus Kempe                "No nation was ever drunk when wine was cheap."
|> magnus@lglsun.epfl.ch                                   -- Thomas Jefferson

Christophe BRUNIAU   bruniau@cenatls.cena.dgac.fr