Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!comp.vuw.ac.nz!steve
From: steve@comp.vuw.ac.nz (Steve Cassidy)
Newsgroups: comp.lang.prolog
Subject: Re: HELP!!  Need a square root function/predicate in Prolog
Message-ID: <1990Aug08.230259.16224@comp.vuw.ac.nz>
Date: 8 Aug 90 23:02:59 GMT
References: <1990Aug08.001233.6587@hoss.unl.edu>
Sender: news@comp.vuw.ac.nz (News Admin)
Organization: Dept. of Comp. Sci., Victoria Uni. of Wellington, New Zealand.
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Sanjiv K. Bhatia writes:
>I am working on some experiments using Prolog and need a square root
>function. Will some kind soul mail me a copy of the same if you happen to
>have one handy? 


It's probably nothing like what you wanted but here's a version
of square/2 that is reversible - you can use it for square roots
as long as the root is integer.  Integers are represented as 
1 = s(0), 2 = s(s(0)) etc. Enjoy...

Steve 

square(N,M) :- times(N,N,M).

times(s(0),N,N).

times(N,M,P) :-
	add(N1,s(0),N),
	times(N1,M,P1),
	add(M,P1,P).

add(X,0,X).
add(X,s(Y),s(Z)) :- add(X,Y,Z).


succ(0,0) :- !.
succ(N,s(SM)) :- M is N - 1, succ(M,SM).