Nov 7, 2003
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- Final touches with Prolog
	- not operator
		- be careful when using it
		- can produce counter-intuitive results

- Interactions for today:

/* try the difference between the following two */
?- human(X).
?- not(not(human(X))).

/* and these two */
?- X=0, not(X=1). /* instantiates X to zero */
?- not(X=1), X=0. /* returns false. why? */