YES (VAR x0 x x1 y z) (RULES R(x0) -> x0 t(x) -> x r(x0) -> x0 s(x0) -> x0 S(x0) -> x0 T(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 KBO with weight w0 = 1 w(f) = 0 w(i) = 0 w(e) = 1 w(T) = 42 w(r) = 2 w(t) = 1 w(R) = 24 w(s) = 4 w(S) = 3 and precedence: i > T > R > t > S > s > r > f > e )