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From: sakkinen@tukki.jyu.fi (Markku Sakkinen)
Newsgroups: comp.object
Subject: complex number example
Message-ID: <2904@tukki.jyu.fi>
Date: 1 Feb 90 13:01:30 GMT
Reply-To: sakkinen@jytko.jyu.fi (Markku Sakkinen)
          SAKKINEN@FINJYU.bitnet (alternative)
Organization: University of Jyvaskyla, Finland
Lines: 24

This is connected with a criticism of Grogono and Bennett's paper
"Polymorphism and Type Checking in Object-Oriented Languages"
in the November 1989 issue of SIGPLAN Notices, specifically
with their suggestion on handling alternative representations
of complex numbers.

I have read in some book or article an example in which a Complex object
(implementing complex numbers) contained both the Cartesian
and the polar representation and a validity indicator for each:
at every moment, at least one representation must be valid,
and even both can be. If memory serves, it was a well-done example.
The only problem is that I don't remember where it was.

My previous quest for a lost reference yielded very good results.
I am again asking for some kind person who does remember where
this example was presented, to mail me the exact reference.
Thank you in advance!

Markku Sakkinen
Department of Computer Science
University of Jyvaskyla (a's with umlauts)
Seminaarinkatu 15
SF-40100 Jyvaskyla (umlauts again)
Finland