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From: wup@rpics.UUCP
Newsgroups: comp.lang.prolog
Subject: Re: Control Structures
Message-ID: <1093@rpics.RPI.EDU>
Date: Mon, 6-Apr-87 10:39:30 EST
Article-I.D.: rpics.1093
Posted: Mon Apr  6 10:39:30 1987
Date-Received: Thu, 9-Apr-87 00:08:40 EST
References: <2285@bigburd.PRC.Unisys.COM>
Lines: 17
Keywords: xor
Summary: Efficient XOR


Concerning xor(G1,G2)...
A "logic programming" approach is

   xor(G1,G2) :- G1,not(G2).
   xor(G1,G2) :- not(G1),G2.

To be efficient in computation, one may want to be somewhat imperative
in the "programming", I propose the following...

  xor(G1,G2) :- not(G1),G2.
  xor(G1,_)  :- G1.

This takes into account the possible "side effects" G1 and G2 may have.

Peter Y.F. Wu
wup@csv.rpi.edu