YES We show the termination of the TRS R: f(c(s(x),y)) -> f(c(x,s(y))) g(c(x,s(y))) -> g(c(s(x),y)) g(s(f(x))) -> g(f(x)) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: f#(c(s(x),y)) -> f#(c(x,s(y))) p2: g#(c(x,s(y))) -> g#(c(s(x),y)) p3: g#(s(f(x))) -> g#(f(x)) and R consists of: r1: f(c(s(x),y)) -> f(c(x,s(y))) r2: g(c(x,s(y))) -> g(c(s(x),y)) r3: g(s(f(x))) -> g(f(x)) The estimated dependency graph contains the following SCCs: {p1} {p3} {p2} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: f#(c(s(x),y)) -> f#(c(x,s(y))) and R consists of: r1: f(c(s(x),y)) -> f(c(x,s(y))) r2: g(c(x,s(y))) -> g(c(s(x),y)) r3: g(s(f(x))) -> g(f(x)) The set of usable rules consists of (no rules) Take the reduction pair: lexicographic combination of reduction pairs: 1. weighted path order base order: matrix interpretations: carrier: N^2 order: lexicographic order interpretations: f#_A(x1) = ((1,0),(1,1)) x1 c_A(x1,x2) = x1 + (1,1) s_A(x1) = x1 + (2,3) precedence: f# = c = s partial status: pi(f#) = [] pi(c) = [] pi(s) = [] 2. weighted path order base order: matrix interpretations: carrier: N^2 order: lexicographic order interpretations: f#_A(x1) = x1 + (2,2) c_A(x1,x2) = x1 + (2,2) s_A(x1) = x1 + (3,3) precedence: f# = c > s partial status: pi(f#) = [1] pi(c) = [] pi(s) = [] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains. -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: g#(s(f(x))) -> g#(f(x)) and R consists of: r1: f(c(s(x),y)) -> f(c(x,s(y))) r2: g(c(x,s(y))) -> g(c(s(x),y)) r3: g(s(f(x))) -> g(f(x)) The set of usable rules consists of r1 Take the reduction pair: lexicographic combination of reduction pairs: 1. weighted path order base order: matrix interpretations: carrier: N^2 order: lexicographic order interpretations: g#_A(x1) = x1 + (1,1) s_A(x1) = ((1,0),(1,1)) x1 + (2,2) f_A(x1) = (0,0) c_A(x1,x2) = x1 + (1,1) precedence: g# > s = f = c partial status: pi(g#) = [1] pi(s) = [1] pi(f) = [] pi(c) = [1] 2. weighted path order base order: matrix interpretations: carrier: N^2 order: lexicographic order interpretations: g#_A(x1) = x1 s_A(x1) = ((1,0),(1,0)) x1 + (4,2) f_A(x1) = (2,3) c_A(x1,x2) = ((1,0),(0,0)) x1 + (3,1) precedence: s = f = c > g# partial status: pi(g#) = [1] pi(s) = [] pi(f) = [] pi(c) = [] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains. -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: g#(c(x,s(y))) -> g#(c(s(x),y)) and R consists of: r1: f(c(s(x),y)) -> f(c(x,s(y))) r2: g(c(x,s(y))) -> g(c(s(x),y)) r3: g(s(f(x))) -> g(f(x)) The set of usable rules consists of (no rules) Take the reduction pair: lexicographic combination of reduction pairs: 1. weighted path order base order: matrix interpretations: carrier: N^2 order: lexicographic order interpretations: g#_A(x1) = x1 + (3,1) c_A(x1,x2) = x2 + (1,1) s_A(x1) = x1 + (2,3) precedence: g# = c = s partial status: pi(g#) = [] pi(c) = [] pi(s) = [] 2. weighted path order base order: matrix interpretations: carrier: N^2 order: lexicographic order interpretations: g#_A(x1) = x1 c_A(x1,x2) = x2 s_A(x1) = x1 + (1,1) precedence: g# > c = s partial status: pi(g#) = [1] pi(c) = [] pi(s) = [] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.