YES(O(1),O(n^1)) We are left with following problem, upon which TcT provides the certificate YES(O(1),O(n^1)). Strict Trs: { terms(N) -> cons(recip(sqr(N))) , sqr(0()) -> 0() , sqr(s()) -> s() , dbl(0()) -> 0() , dbl(s()) -> s() , add(0(), X) -> X , add(s(), Y) -> s() , first(0(), X) -> nil() , first(s(), cons(Y)) -> cons(Y) } Obligation: innermost runtime complexity Answer: YES(O(1),O(n^1)) We use the processor 'Small Polynomial Path Order (PS,1-bounded)' to orient following rules strictly. Trs: { terms(N) -> cons(recip(sqr(N))) , sqr(0()) -> 0() , sqr(s()) -> s() , dbl(0()) -> 0() , dbl(s()) -> s() , add(0(), X) -> X , add(s(), Y) -> s() , first(0(), X) -> nil() , first(s(), cons(Y)) -> cons(Y) } The induced complexity on above rules (modulo remaining rules) is YES(?,O(n^1)) . These rules are moved into the corresponding weak component(s). Sub-proof: ---------- The input was oriented with the instance of 'Small Polynomial Path Order (PS,1-bounded)' as induced by the safe mapping safe(terms) = {1}, safe(cons) = {1}, safe(recip) = {1}, safe(sqr) = {1}, safe(0) = {}, safe(s) = {}, safe(dbl) = {}, safe(add) = {}, safe(first) = {1}, safe(nil) = {} and precedence terms > sqr, add > dbl, first > sqr, terms ~ first . Following symbols are considered recursive: {terms, first} The recursion depth is 1. For your convenience, here are the satisfied ordering constraints: terms(; N) > cons(; recip(; sqr(; N))) sqr(; 0()) > 0() sqr(; s()) > s() dbl(0();) > 0() dbl(s();) > s() add(0(), X;) > X add(s(), Y;) > s() first(X; 0()) > nil() first(cons(; Y); s()) > cons(; Y) We return to the main proof. We are left with following problem, upon which TcT provides the certificate YES(O(1),O(1)). Weak Trs: { terms(N) -> cons(recip(sqr(N))) , sqr(0()) -> 0() , sqr(s()) -> s() , dbl(0()) -> 0() , dbl(s()) -> s() , add(0(), X) -> X , add(s(), Y) -> s() , first(0(), X) -> nil() , first(s(), cons(Y)) -> cons(Y) } Obligation: innermost runtime complexity Answer: YES(O(1),O(1)) Empty rules are trivially bounded Hurray, we answered YES(O(1),O(n^1))