Date: Nov 20, 2012 3:39 AM
Author: Graham Cooper
Subject: PROLOG does SO have NOT() !!

Exactly the same way we use not().

Failure to return a result can be programmed for ANY PREDICATE

*WITH A FINITE DOMAIN*

e.g. Boolean Predicates


if(X,Y) :- true(X) , true(Y)
if(X,Y) :- not(X) , true(Y)
if(X,Y) :- not(X) , not(Y)
not(if(X,Y)) :- true(X) , not(Y)

---------------

A predicate with more than 2 values!

gender(m). 1
gender(f). 2
not(gender(X)). 3

Prolog searches for a match from top to bottom,
it will return
--> gender(m)

or
--> not(gender(t)).

for any value other than m or f!

You can PROGRAM the predicate NOT(...)

for any predicate with a FINITE SET OF ARGUMENT VALUES!


Herc
--
www.microPROLOG.com

if( if(t(S),f(R)) , if(t(R),f(S)) ).
if it's sunny then it's not raining
ergo
if it's raining then it's not sunny