Newsgroups: comp.lang.c++,comp.object,comp.theory,comp.lang.smalltalk
From: mfinney@lynchburg.net
Subject: Re: Opinions on Ellipse-Circle dilemma?
Reply-To: mfinney@lynchburg.net
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In <5dtcui$bik@bagan.srce.hr>, kmajor@jagor.srce.hr (Kazimir Majorinc) writes:

>: For details in theorectic aspects, language descriptions, and
>: more examples, the following papers are available:
>
>:  1. Covariant Deep Subtype Reconsidered
>:     ACM Sigplan Notices, May, 1995.

There are many more available than that, and the opinion expressed 
in that paper about covariant parameters is far from being undisputed.
And as far as the assertion that covariant specifications are unsound
there has been a good deal of work showing how the formalisms can
be made sound.  In particular, the book...

   A Theory of Objects
      Martin Abadi & Luca Cardelli
      0-387-94775-2

which was recently published, considers theories for both first and
second order constraints (such as covariance), where the theories
are sound for the second order constraints.


Michael Lee Finney

