XOR and NOT Gates
XOR gate�s output is on when its inputs are different
(=> (Type ?g XOR)
(<=> (Signal (Out 1 ?g) On)
(not (Signal (In 1 ?g) (Signal (In 2 ?g))))))
NOT gate�s output is different from its inputs
(=> (Type ?g NOT)
(not (Signal (Out 1 ?g) (Signal (In 1 ?g)))))