YES (VAR x0 x1 y x z) (RULES f(i(x0),f(x0,x1)) -> x1 f(i(x0),x0) -> e() i(i(x0)) -> x0 f(x1,f(i(x1),x0)) -> x0 i(e()) -> e() i(f(y,x)) -> f(i(x),i(y)) f(e(),x) -> x f(x,e()) -> x 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 and precedence: i > f > e )