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From: lady0065@sable.ox.ac.uk (David Hopwood)
Subject: Ada terminology (was Re: Real OO)
Date: 1996/05/07
Message-ID: <4mn0vd$7o9@news.ox.ac.uk>#1/1
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sender: david.hopwood@lmh.ox.ac.uk
references: <4j9p3a$uo5@watnews1.watson.ibm.com>
 <4kbqun$iiv@watnews1.watson.ibm.com> <6850x6pV3RB@herold.franken.de>
 <4mls4h$sau@watnews1.watson.ibm.com>
organization: Oxford University, England
newsgroups: comp.lang.eiffel,comp.lang.ada,comp.object
Date: 1996-05-07T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <4mls4h$sau@watnews1.watson.ibm.com>,
Norman H. Cohen <ncohen@watson.ibm.com> wrote:
>
>In Ada, a class is not a type, but a SET OF TYPES.  In particular, the
>set of tagged types directly or indirectly derived from a common root
>forms a "derivation class".  ("Deriving" from a type means defining a
>descendant type.)  For each type T at the root of a tree or
>subtree in the derivation hierarchy, there is a "classwide type",
>T'Class, whose values are taken from the discriminated union of the types
>in the class.  One cannot derive from a classwide type.
>(By "discriminated union," we mean that for each value V of each type in
>the class, there is a corresponding value in T'Class, and that the
>corresponding value in T'Class includes a "tag" identifying the type of
>the original value V.)

Maybe it's just me, but...
Why does Ada use the words 'type' and 'class' in the opposite sense
to everyone else?

David Hopwood
david.hopwood@lmh.ox.ac.uk