YES (VAR x x0 x1 y z) (RULES s(x) -> x S(x0) -> x0 R(x0) -> x0 T(x) -> x t(x0) -> x0 r(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 ELPO with interpretations on natural numbers f_A(x1,x2) = x1 + x2 + 1 i_A(x1) = x1 e_A = 1 T_A(x1) = x1 + 2 r_A(x1) = x1 + 8 t_A(x1) = x1 + 6 R_A(x1) = x1 s_A(x1) = x1 + 21 S_A(x1) = x1 + 2 i#_A(x1) = 0 e#_A = 0 r#_A(x1) = x1 and precedence: i > f > e > t > r > S > T > s > R )