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From: duchier@cs.yale.edu (Denys Duchier)
Newsgroups: comp.lang.prolog
Subject: Re: not(X=Y) and side effects
Message-ID: <DUCHIER.90Dec12154306@albania.cs.yale.edu>
Date: 12 Dec 90 20:43:06 GMT
References: <5398@rex.cs.tulane.edu>
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In-reply-to: feldman@rex.cs.tulane.edu's message of 12 Dec 90 19:15:54 GMT

In article <5398@rex.cs.tulane.edu> feldman@rex.cs.tulane.edu (Damon Feldman) writes:
 >   I was writing a small prolog program, and I had use for the following
 >   predicate:
 >
 >   notequal(X,Y) :- nonvar(X),nonvar(Y),X=Y,!,fail.
 >   notequal(X,_) :- var(X),!,fail.
 >   notequal(_,Y) :- var(Y),!,fail.
 >   notequal(_,_).

Why not just:

notequal(X,Y) :- nonvar(X),nonvar(Y),X\=Y.

--Denys