YES O(n^3) 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 [X5] [X2] [1 0 0][X5] [1 0 0][X2] [0] [cons]([X4], [X1]) = [0 0 0][X4] + [0 1 0][X1] + [1] [X3] [X0] [0 0 0][X3] [0 0 1][X0] [1] [X2] [1 1 1][X2] [1] [rev]([X1]) = [0 1 1][X1] + [1] [X0] [0 0 1][X0] [0] [0] [empty] = [1] [0] [X5] [X2] [1 1 1][X5] [1 0 0][X2] [0] [r1]([X4], [X1]) = [0 1 0][X4] + [0 1 0][X1] + [0] [X3] [X0] [0 0 1][X3] [0 0 1][X0] [0] Qed