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. weighted path order base order: matrix interpretations: carrier: N^2 order: lexicographic order interpretations: copy#_A(x1,x2,x3) = ((1,0),(0,0)) x1 s_A(x1) = x1 + (4,1) cons_A(x1,x2) = ((1,0),(1,1)) x2 + (3,2) f_A(x1) = x1 + (5,2) nil_A() = (1,2) copy_A(x1,x2,x3) = x1 + (2,1) n_A() = (0,0) precedence: copy# > s = nil > copy > cons = f = n partial status: pi(copy#) = [] pi(s) = [] pi(cons) = [2] pi(f) = [1] pi(nil) = [] pi(copy) = [1] pi(n) = [] 2. weighted path order base order: matrix interpretations: carrier: N^2 order: lexicographic order interpretations: copy#_A(x1,x2,x3) = (0,0) s_A(x1) = (5,5) cons_A(x1,x2) = ((1,0),(1,1)) x2 + (6,2) f_A(x1) = (4,4) nil_A() = (2,2) copy_A(x1,x2,x3) = x1 + (2,2) n_A() = (1,1) precedence: nil > cons > copy# = s = f = copy = n partial status: pi(copy#) = [] pi(s) = [] pi(cons) = [2] pi(f) = [] pi(nil) = [] pi(copy) = [1] pi(n) = [] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.