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From: biep@cs.vu.nl (J A Biep Durieux)
Newsgroups: comp.lang.lisp
Subject: Re: Overloading of NIL (as empty list and logical falsity)
Message-ID: <2220@ski.cs.vu.nl>
Date: 28 Mar 89 17:31:36 GMT
References: <8903222013.AA00234@zooks.ads.com>
Reply-To: biep@cs.vu.nl (J A Biep Durieux)
Organization: VU Informatica, Amsterdam
Lines: 21

>If () was distinct to NIL (= FALSE)
>	then my little unifier would be a lot clearer to read.

But why does your empty list have to be NIL? let your bindings-list
end in T, and the problem is gone:

NIL		-->  unification failed
T		-->  unification succeeded with empty set of bindings
(--- . T)	-->  unification succeeded with given set of bindings

If your programs test for end-of-list with (ATOM &) instead of with
(NULL &), then everything should work OK.

After all, ending lists with the symbol for FALSE is only a choice,
not something imposed upon you by the language (except by the print-
functions, maybe..)
-- 
						Biep.  (biep@cs.vu.nl via mcvax)
	Who am I to doubt the existence of God?   I am
	  only a simple man,  I already have trouble
	enough doubting the existence of my neighbour!