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From: William Elliot <ma...@panix.com>
Newsgroups: sci.logic,sci.math,comp.lang.prolog,comp.ai.philosophy
Subject: Re: PROLOG THEORY BUG!
Date: Tue, 30 Oct 2012 02:56:24 -0700
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On Tue, 30 Oct 2012, Hercules ofZeus wrote:

> f(0).
> t(1).
> 
> wff(X) :- t(X).
> wff(X) :- f(X).
> what(X,true) :- t(X).
> what(X,false) :- f(X).
> 
> if(X,Y) :- t(X), t(Y).
> if(X,Y) :- f(X), f(Y).
> if(X,Y) :- f(X), t(Y).
> 
> f(if(X,Y)) :- t(X),f(Y).
> 
What's f?

> t(if(X,Y)) :- if(X,Y).
 
t(X) :- X

What's :- supposed to mean?

> OK, X should be any Boolean Predicate Formula, just if(x,y) at this
> stage.
> 
> ?-  wff(  if(1,1) )
> YES
> 
> ?- wff(  if(1,0) )
> *HANGS*
> 
You got a problem with a lynching?

> It should complete matching the WFF(X) :- t(X) without success and
> proceed onto WFF(X) :- f(X).

Why?