YES We show the termination of the TRS R: f(|0|()) -> s(|0|()) f(s(|0|())) -> s(s(|0|())) f(s(|0|())) -> *(s(s(|0|())),f(|0|())) f(+(x,s(|0|()))) -> +(s(s(|0|())),f(x)) f(+(x,y)) -> *(f(x),f(y)) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: f#(s(|0|())) -> f#(|0|()) p2: f#(+(x,s(|0|()))) -> f#(x) p3: f#(+(x,y)) -> f#(x) p4: f#(+(x,y)) -> f#(y) and R consists of: r1: f(|0|()) -> s(|0|()) r2: f(s(|0|())) -> s(s(|0|())) r3: f(s(|0|())) -> *(s(s(|0|())),f(|0|())) r4: f(+(x,s(|0|()))) -> +(s(s(|0|())),f(x)) r5: f(+(x,y)) -> *(f(x),f(y)) The estimated dependency graph contains the following SCCs: {p2, p3, p4} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: f#(+(x,s(|0|()))) -> f#(x) p2: f#(+(x,y)) -> f#(y) p3: f#(+(x,y)) -> f#(x) and R consists of: r1: f(|0|()) -> s(|0|()) r2: f(s(|0|())) -> s(s(|0|())) r3: f(s(|0|())) -> *(s(s(|0|())),f(|0|())) r4: f(+(x,s(|0|()))) -> +(s(s(|0|())),f(x)) r5: f(+(x,y)) -> *(f(x),f(y)) 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: f#_A(x1) = max{2, x1 + 1} +_A(x1,x2) = max{1, x1, x2} s_A(x1) = max{1, x1} |0|_A = 0 precedence: f# = + = s = |0| partial status: pi(f#) = [1] pi(+) = [1, 2] pi(s) = [1] pi(|0|) = [] 2. weighted path order base order: max/plus interpretations on natural numbers: f#_A(x1) = x1 + 2 +_A(x1,x2) = max{x1 + 1, x2 + 1} s_A(x1) = x1 |0|_A = 0 precedence: f# = + = s = |0| partial status: pi(f#) = [] pi(+) = [2] pi(s) = [1] pi(|0|) = [] The next rules are strictly ordered: p1, p2, p3 We remove them from the problem. Then no dependency pair remains.