map Cons x xs Cons f x map xs map Nil Nil goal xs map xs f x * x x +Full S x y +Full x S y +Full 0 y y * x S S y + x * x S y * x S 0 x * x 0 0 * 0 y 0 map 1 + 2 S 1 f 1 Cons 2 Nil 0 +Full 2 0 0 goal 1 * 2 INNERMOST