YES O(n^2) TRS: { r1(empty(), a) -> a, r1(cons(x, k), a) -> r1(k, cons(x, a)), rev(ls) -> r1(ls, empty()) } DUP: We consider a non-duplicating system. Trs: { r1(empty(), a) -> a, r1(cons(x, k), a) -> r1(k, cons(x, a)), rev(ls) -> r1(ls, empty()) } Matrix Interpretation: Interpretation class: triangular [X3] [X1] [1 0][X3] [1 0][X1] [0] [cons]([X2], [X0]) = [0 0][X2] + [0 1][X0] + [1] [X1] [1 1][X1] [1] [rev]([X0]) = [0 1][X0] + [1] [0] [empty] = [1] [X3] [X1] [1 1][X3] [1 0][X1] [0] [r1]([X2], [X0]) = [0 1][X2] + [0 1][X0] + [0] Qed