YES O(n^2) TRS: {f(c(s(x), y)) -> f(c(x, s(y))), g(c(x, s(y))) -> g(c(s(x), y))} DUP: We consider a non-duplicating system. Trs: {f(c(s(x), y)) -> f(c(x, s(y))), g(c(x, s(y))) -> g(c(s(x), y))} Matrix Interpretation: Interpretation class: triangular [X1] [1 3][X1] [0] [g]([X0]) = [0 0][X0] + [0] [X1] [1 0][X1] [0] [s]([X0]) = [0 1][X0] + [2] [X3] [X1] [1 2][X3] [1 1][X1] [0] [c]([X2], [X0]) = [0 0][X2] + [0 1][X0] + [0] [X1] [1 0][X1] [0] [f]([X0]) = [0 0][X0] + [0] Qed