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: matrix interpretations: carrier: N^4 order: lexicographic order interpretations: f#_A(x1) = ((1,0,0,0),(0,1,0,0),(0,1,1,0),(1,0,0,0)) x1 c_A(x1,x2) = ((1,0,0,0),(0,1,0,0),(0,1,0,0),(1,1,0,0)) x1 + ((1,0,0,0),(0,1,0,0),(0,0,1,0),(0,1,0,0)) x2 s_A(x1) = ((1,0,0,0),(0,1,0,0),(0,0,0,0),(1,1,1,0)) x1 + (1,2,1,1) 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: matrix interpretations: carrier: N^4 order: lexicographic order interpretations: g#_A(x1) = ((1,0,0,0),(0,1,0,0),(0,1,0,0),(1,1,0,0)) x1 s_A(x1) = ((1,0,0,0),(0,0,0,0),(0,1,0,0),(1,1,1,0)) x1 + (1,2,1,1) f_A(x1) = ((1,0,0,0),(1,1,0,0),(0,0,0,0),(0,0,0,0)) x1 + (1,1,0,1) c_A(x1,x2) = ((1,0,0,0),(1,0,0,0),(1,0,0,0),(0,0,0,0)) x1 + x2 + (0,1,1,1) 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: matrix interpretations: carrier: N^4 order: lexicographic order interpretations: g#_A(x1) = ((1,0,0,0),(1,1,0,0),(1,0,1,0),(1,0,1,1)) x1 c_A(x1,x2) = ((1,0,0,0),(0,1,0,0),(0,0,0,0),(1,0,0,0)) x1 + ((1,0,0,0),(0,1,0,0),(1,1,1,0),(0,0,1,1)) x2 + (0,1,1,1) s_A(x1) = ((1,0,0,0),(0,1,0,0),(1,1,1,0),(1,1,1,1)) x1 + (1,0,0,0) The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.