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From: stt@henning.camb.inmet.com (Tucker Taft)
Subject: Re: Ada terminology (was Re: Real OO)
Date: 1996/05/07
Message-ID: <Dr245J.MGD.0.-s@inmet.camb.inmet.com>#1/1
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Date: 1996-05-07T00:00:00+00:00
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David Hopwood (lady0065@sable.ox.ac.uk) wrote:

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

Various reasons:

   1) History -- Ada has used the terms "type" and "class of types"
      since 1979.

   2) "Class" is a synonym for "set" in mathematics, so at least
      we use "class" the same way mathematicians do.

   3) In many OOPs, the term "class" means 3 different things, depending
      on context:
       a) A syntactic construct that encapsulates the data and
          function component definitions;
       b) A particular type defined by a "class" construct;
       c) The set of types containing a type and all its descendants.

      In Ada, these three concepts have three different names:

       a) A package
       b) A type
       c) A (derivation) class (of types)

Your mileage may vary...

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

-Tucker Taft   stt@inmet.com   http://www.inmet.com/~stt/
Intermetrics, Inc.  Cambridge, MA  USA