YES We show the termination of the TRS R: f(s(x)) -> s(f(f(p(s(x))))) f(|0|()) -> |0|() p(s(x)) -> x -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: f#(s(x)) -> f#(f(p(s(x)))) p2: f#(s(x)) -> f#(p(s(x))) p3: f#(s(x)) -> p#(s(x)) and R consists of: r1: f(s(x)) -> s(f(f(p(s(x))))) r2: f(|0|()) -> |0|() r3: p(s(x)) -> x The estimated dependency graph contains the following SCCs: {p1, p2} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: f#(s(x)) -> f#(f(p(s(x)))) p2: f#(s(x)) -> f#(p(s(x))) and R consists of: r1: f(s(x)) -> s(f(f(p(s(x))))) r2: f(|0|()) -> |0|() r3: p(s(x)) -> x The set of usable rules consists of r1, r2, r3 Take the reduction pair: weighted path order base order: max/plus interpretations on natural numbers: f#_A(x1) = max{6, x1 + 4} s_A(x1) = max{12, x1 + 7} f_A(x1) = max{4, x1} p_A(x1) = max{5, x1 - 7} |0|_A = 5 precedence: s = f = p > f# = |0| partial status: pi(f#) = [1] pi(s) = [] pi(f) = [] pi(p) = [] pi(|0|) = [] The next rules are strictly ordered: p1 We remove them from the problem. -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: f#(s(x)) -> f#(p(s(x))) and R consists of: r1: f(s(x)) -> s(f(f(p(s(x))))) r2: f(|0|()) -> |0|() r3: p(s(x)) -> x The estimated dependency graph contains the following SCCs: {p1} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: f#(s(x)) -> f#(p(s(x))) and R consists of: r1: f(s(x)) -> s(f(f(p(s(x))))) r2: f(|0|()) -> |0|() r3: p(s(x)) -> x The set of usable rules consists of r3 Take the reduction pair: weighted path order base order: max/plus interpretations on natural numbers: f#_A(x1) = max{7, x1 + 4} s_A(x1) = x1 + 5 p_A(x1) = max{2, x1 - 3} precedence: f# = s = p partial status: pi(f#) = [] pi(s) = [1] pi(p) = [] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.