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From: debray@arizona.UUCP
Newsgroups: comp.lang.prolog
Subject: Re: Prolog control structures
Message-ID: <1609@megaron.arizona.edu>
Date: Wed, 1-Apr-87 23:56:30 EST
Article-I.D.: megaron.1609
Posted: Wed Apr  1 23:56:30 1987
Date-Received: Sat, 4-Apr-87 19:48:18 EST
References: <10588@topaz.RUTGERS.EDU> <1608@megaron.arizona.edu>
Organization: U of Arizona CS Dept, Tucson
Lines: 19
Summary: even simpler solutions

I'd proposed the following solutions to Chomicki's problems:

> Assuming no side effects, the following works on most Prologs:
> 
> (1) 	xor(G1,G2) :- not(not(call(G1))) -> call(G1) ; call(G2).
> 
> (2)	P :- ( not(not( (A,B) )) -> (A -> B) ; (A, B) ), C, D.
> 
The following simplifications should now be obvious:

(1)	xor(X,Y) :- not(call(X)) -> call(Y) ; call(X).

(2)	P :- ( not( (A -> B) ) -> (A, B) ; (A -> B) ), C, D.

-- 
Saumya Debray		CS Department, University of Arizona, Tucson

     internet:   debray@arizona.edu
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