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From: gjr@hplgr2.hpl.hp.com (Guillermo (Bill) J. Rozas)
Subject: Re: null? vs zero?
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In-Reply-To: spot@sandoz.slip.cs.cmu.edu's message of 18 Mar 1996 20:05:04 GMT
Date: Tue, 19 Mar 1996 01:34:33 GMT
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	<SPOT.96Mar18170504@sandoz.slip.cs.cmu.edu>
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In article <SPOT.96Mar18170504@sandoz.slip.cs.cmu.edu> spot@sandoz.slip.cs.cmu.edu (Scott Draves) writes:

|   NULL? is not a type predicate, that would be LIST?.

You don't believe in singleton types?

|   both NULL? and ZERO? test if the object is a distinguished and useful
|   object.  in both cases that object is the `identity'.

This is not true of ZERO?  There are potentially many objects that
satisfy it.  For example, in many implementations the exact integer 0
and the inexact integer (exact->inexact 0) will satisfy it yet they
are not the same object (nor is it required that every instance of
either be the same object as any other instance).
