YES We show the termination of the TRS R: g(s(x)) -> f(x) f(|0|()) -> s(|0|()) f(s(x)) -> s(s(g(x))) g(|0|()) -> |0|() -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: g#(s(x)) -> f#(x) p2: f#(s(x)) -> g#(x) and R consists of: r1: g(s(x)) -> f(x) r2: f(|0|()) -> s(|0|()) r3: f(s(x)) -> s(s(g(x))) r4: g(|0|()) -> |0|() The estimated dependency graph contains the following SCCs: {p1, p2} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: g#(s(x)) -> f#(x) p2: f#(s(x)) -> g#(x) and R consists of: r1: g(s(x)) -> f(x) r2: f(|0|()) -> s(|0|()) r3: f(s(x)) -> s(s(g(x))) r4: g(|0|()) -> |0|() The set of usable rules consists of (no rules) Take the reduction pair: lexicographic combination of reduction pairs: 1. weighted path order base order: max/plus interpretations on natural numbers: g#_A(x1) = x1 + 4 s_A(x1) = x1 + 4 f#_A(x1) = x1 + 3 precedence: g# = s = f# partial status: pi(g#) = [] pi(s) = [] pi(f#) = [] 2. weighted path order base order: max/plus interpretations on natural numbers: g#_A(x1) = max{3, x1 + 2} s_A(x1) = x1 + 1 f#_A(x1) = x1 + 2 precedence: g# = s = f# partial status: pi(g#) = [] pi(s) = [1] pi(f#) = [1] The next rules are strictly ordered: p1, p2 We remove them from the problem. Then no dependency pair remains.