YES(?,O(n^2)) We are left with following problem, upon which TcT provides the certificate YES(?,O(n^2)). Strict Trs: { from(X) -> cons(X, n__from(s(X))) , from(X) -> n__from(X) , cons(X1, X2) -> n__cons(X1, X2) , 2ndspos(s(N), cons(X, n__cons(Y, Z))) -> rcons(posrecip(activate(Y)), 2ndsneg(N, activate(Z))) , 2ndspos(0(), Z) -> rnil() , activate(X) -> X , activate(n__from(X)) -> from(X) , activate(n__cons(X1, X2)) -> cons(X1, X2) , 2ndsneg(s(N), cons(X, n__cons(Y, Z))) -> rcons(negrecip(activate(Y)), 2ndspos(N, activate(Z))) , 2ndsneg(0(), Z) -> rnil() , pi(X) -> 2ndspos(X, from(0())) , plus(s(X), Y) -> s(plus(X, Y)) , plus(0(), Y) -> Y , times(s(X), Y) -> plus(Y, times(X, Y)) , times(0(), Y) -> 0() , square(X) -> times(X, X) } Obligation: innermost runtime complexity Answer: YES(?,O(n^2)) Arguments of following rules are not normal-forms: { 2ndspos(s(N), cons(X, n__cons(Y, Z))) -> rcons(posrecip(activate(Y)), 2ndsneg(N, activate(Z))) , 2ndsneg(s(N), cons(X, n__cons(Y, Z))) -> rcons(negrecip(activate(Y)), 2ndspos(N, activate(Z))) } All above mentioned rules can be savely removed. We are left with following problem, upon which TcT provides the certificate YES(?,O(n^2)). Strict Trs: { from(X) -> cons(X, n__from(s(X))) , from(X) -> n__from(X) , cons(X1, X2) -> n__cons(X1, X2) , 2ndspos(0(), Z) -> rnil() , activate(X) -> X , activate(n__from(X)) -> from(X) , activate(n__cons(X1, X2)) -> cons(X1, X2) , 2ndsneg(0(), Z) -> rnil() , pi(X) -> 2ndspos(X, from(0())) , plus(s(X), Y) -> s(plus(X, Y)) , plus(0(), Y) -> Y , times(s(X), Y) -> plus(Y, times(X, Y)) , times(0(), Y) -> 0() , square(X) -> times(X, X) } Obligation: innermost runtime complexity Answer: YES(?,O(n^2)) The input was oriented with the instance of 'Small Polynomial Path Order (PS,2-bounded)' as induced by the safe mapping safe(from) = {1}, safe(cons) = {1, 2}, safe(n__from) = {1}, safe(s) = {1}, safe(2ndspos) = {1, 2}, safe(0) = {}, safe(rnil) = {}, safe(n__cons) = {1, 2}, safe(rcons) = {1, 2}, safe(posrecip) = {1}, safe(activate) = {1}, safe(2ndsneg) = {}, safe(negrecip) = {1}, safe(pi) = {}, safe(plus) = {2}, safe(times) = {}, safe(square) = {} and precedence from > cons, from > plus, activate > from, activate > cons, activate > 2ndspos, activate > plus, 2ndsneg > from, 2ndsneg > cons, 2ndsneg > plus, 2ndsneg > times, pi > from, pi > cons, pi > 2ndspos, pi > plus, times > cons, times > plus, square > from, square > cons, square > 2ndspos, square > 2ndsneg, square > plus, square > times, cons ~ plus, activate ~ pi . Following symbols are considered recursive: {cons, plus, times} The recursion depth is 2. For your convenience, here are the satisfied ordering constraints: from(; X) > cons(; X, n__from(; s(; X))) from(; X) > n__from(; X) cons(; X1, X2) > n__cons(; X1, X2) 2ndspos(; 0(), Z) > rnil() activate(; X) > X activate(; n__from(; X)) > from(; X) activate(; n__cons(; X1, X2)) > cons(; X1, X2) 2ndsneg(0(), Z;) > rnil() pi(X;) > 2ndspos(; X, from(; 0())) plus(s(; X); Y) > s(; plus(X; Y)) plus(0(); Y) > Y times(s(; X), Y;) > plus(Y; times(X, Y;)) times(0(), Y;) > 0() square(X;) > times(X, X;) Hurray, we answered YES(?,O(n^2))