f x y cond and isNat x isNat y x y cond tt x y f s x s y isNat s x isNat x isNat 0 tt and tt tt tt and ff x ff and x ff ff f 2 cond 3 and 2 isNat 1 tt 0 s 1 0 0 ff 0 FULL TRS//AProVE_10/andIsNat.trs