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Path: utzoo!utgpu!water!watnot!watmath!clyde!rutgers!im4u!milano!varghese
From: varghese@milano.UUCP
Newsgroups: comp.lang.prolog
Subject: Re: 91 function
Message-ID: <3832@milano.UUCP>
Date: Tue, 17-Feb-87 18:21:17 EST
Article-I.D.: milano.3832
Posted: Tue Feb 17 18:21:17 1987
Date-Received: Wed, 18-Feb-87 21:28:35 EST
References: <3782@milano.UUCP>
Sender: varghese@milano.UUCP
Organization: MCC, Austin, TX
Lines: 29
Summary: Typo in prolog version

In article <3782@milano.UUCP>, varghese@milano.UUCP writes:
> 
> A "fix" to make it converge to 91:
> 
> (defun f91 (x) 
>   (cond ((= x 91) 91)
> 	((> x 111) (f91 (f91 (- x 10))))
> 	((> x 100) (f91 (- x 10)))
> 	(t (f91 (f91 (+ x 11))))))
> 
> or, if you don't speak LISP, a Prolog version:
> 
> f91(91,91) :- !.
> f91(X,Y) :- X > 111, !, Z is X - 10, f91(Z,W), f91(W,Y).
> f91(X,Y) :- X > 100, !, Z is X - 10, f91(Z,Y).
> f91(X,Y) :- Z is X + 10, f91(Z,W), f91(W,Y).
> 

The last line of the prolog version should be

f91(X,Y) :- Z is X + 11, f91(Z,W), f91(W,Y).

to make it correspond to the Lisp version. I
work on Lisp machines and the Prolog version is 
a translation of the Lisp program. Sorry about that.

--------------------
Joe Varghese
varghese@mcc.com