subsets Cons x xs subsets[Ite][True][Let] Cons x xs subsets xs subsets Nil Cons Nil Nil mapconsapp x' Cons x xs rest Cons Cons x' x mapconsapp x' xs rest mapconsapp x Nil rest rest notEmpty Cons x xs True notEmpty Nil False goal xs subsets xs subsets[Ite][True][Let] Cons x xs subs mapconsapp x subs subs subsets[Ite][True][Let] 2 True 0 subsets 1 Cons 2 Nil 0 mapconsapp 3 notEmpty 1 goal 1 False 0 INNERMOST