YES We show the termination of the TRS R: f(cons(nil(),y)) -> y f(cons(f(cons(nil(),y)),z)) -> copy(n(),y,z) copy(|0|(),y,z) -> f(z) copy(s(x),y,z) -> copy(x,y,cons(f(y),z)) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: f#(cons(f(cons(nil(),y)),z)) -> copy#(n(),y,z) p2: copy#(|0|(),y,z) -> f#(z) p3: copy#(s(x),y,z) -> copy#(x,y,cons(f(y),z)) p4: copy#(s(x),y,z) -> f#(y) and R consists of: r1: f(cons(nil(),y)) -> y r2: f(cons(f(cons(nil(),y)),z)) -> copy(n(),y,z) r3: copy(|0|(),y,z) -> f(z) r4: copy(s(x),y,z) -> copy(x,y,cons(f(y),z)) The estimated dependency graph contains the following SCCs: {p3} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: copy#(s(x),y,z) -> copy#(x,y,cons(f(y),z)) and R consists of: r1: f(cons(nil(),y)) -> y r2: f(cons(f(cons(nil(),y)),z)) -> copy(n(),y,z) r3: copy(|0|(),y,z) -> f(z) r4: copy(s(x),y,z) -> copy(x,y,cons(f(y),z)) The set of usable rules consists of r1, r2 Take the reduction pair: lexicographic combination of reduction pairs: 1. lexicographic path order with precedence: precedence: nil > s > copy# > f > cons > n > copy argument filter: pi(copy#) = [1, 2, 3] pi(s) = [1] pi(cons) = [1, 2] pi(f) = [1] pi(nil) = [] pi(copy) = 2 pi(n) = [] 2. matrix interpretations: carrier: N^4 order: lexicographic order interpretations: copy#_A(x1,x2,x3) = ((1,0,0,0),(0,1,0,0),(0,0,0,0),(0,1,1,0)) x1 + ((1,0,0,0),(1,1,0,0),(0,0,0,0),(1,0,1,0)) x3 s_A(x1) = ((0,0,0,0),(1,0,0,0),(1,0,0,0),(0,0,0,0)) x1 + (1,1,2,0) cons_A(x1,x2) = ((1,0,0,0),(0,1,0,0),(0,0,1,0),(0,1,1,1)) x1 + ((1,0,0,0),(0,1,0,0),(1,0,1,0),(0,1,1,1)) x2 f_A(x1) = ((1,0,0,0),(0,1,0,0),(0,0,1,0),(1,0,0,1)) x1 + (2,1,0,1) nil_A() = (1,1,0,1) copy_A(x1,x2,x3) = (6,0,0,10) n_A() = (1,1,1,1) The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.