TRS: { sum(0()) -> 0(), sum(s(x)) -> +(sum(x), s(x)), +(x, 0()) -> x, +(x, s(y)) -> s(+(x, y))} POP*: Quasi-Precedence: + > s, sum > + empty Normal: pi(+) = [2], pi(sum) = [1] Safe: pi(s) = [1], pi(+) = [1] Predicative System: { sum(0();) -> 0(), sum(s(;x);) -> +(s(;x);sum(x;)), +(0();x) -> x, +(s(;y);x) -> s(;+(y;x))} Qed