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Re: [Axiom-developer] What is SubDomain (was: non extending category)

From: Scott Morrison
Subject: Re: [Axiom-developer] What is SubDomain (was: non extending category)
Date: Tue, 14 Feb 2006 07:28:41 -0800

>> SCM: Do you happen to remember what you wrote 20 years ago? :)

Well, not really.

I do remember that I never liked SubDomain.  We had all kinds of special-case code to deal with it, and it was only used for NonNegativeInteger and PositiveInteger.  I believe the original motivation for sub-domains was to share implementations, but not categories.  So PositiveInteger could share the all the implementation code from Integer, but not the categories of Integer, since they don't form a Group under addition, for example.  In the end it caused a lot more mork than it saved.

The concept of sub-domain never made it into Aldor, as far as I know, and that's a good thing.

-- SCM

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