YES (VAR x0 x1 x y z) (RULES R(x0) -> x0 t(x0) -> x0 r(x0) -> x0 S(x0) -> x0 T(x0) -> x0 s(x0) -> x0 i(f(x1,x0)) -> f(i(x0),i(x1)) i(i(x0)) -> x0 f(x1,f(i(x1),x0)) -> x0 f(i(x1),f(x1,x0)) -> x0 i(e()) -> e() f(x,e()) -> x f(e(),x) -> x f(i(x),x) -> e() f(x,i(x)) -> e() f(f(x,y),z) -> f(x,f(y,z)) ) (COMMENT Termination is shown by EKBO with interpretations on natural numbers f_A(x1,x2) = x1 + x2 + 1 i_A(x1) = x1 e_A = 1 T_A(x1) = x1 r_A(x1) = x1 t_A(x1) = x1 R_A(x1) = x1 s_A(x1) = x1 S_A(x1) = x1 e#_A = 0 weights w0 = 1 w(f) = 0 w(i) = 0 w(e) = 1 w(T) = 6 w(r) = 22 w(t) = 21 w(R) = 56 w(s) = 3 w(S) = 4 and precedence: i > t > s > r > R > S > T > f > e )