MAYBE We are left with following problem, upon which TcT provides the certificate MAYBE. Strict Trs: { rev(nil()) -> nil() , rev(cons(x, l)) -> cons(rev1(x, l), rev2(x, l)) , rev1(x, cons(y, l)) -> rev1(y, l) , rev1(0(), nil()) -> 0() , rev1(s(x), nil()) -> s(x) , rev2(x, nil()) -> nil() , rev2(x, cons(y, l)) -> rev(cons(x, rev2(y, l))) } Obligation: innermost runtime complexity Answer: MAYBE The input cannot be shown compatible Arrrr..