TRS:
 {f(x, y) -> h(x, y),
  f(x, y) -> h(y, x),
  h(x, x) -> x}
 POP*:
  Precedence:
  f > h
  empty
  
Normal:
   pi(f) = [1,2], pi(h) = [2]
  
Safe:
   pi(h) = [1]
  
Predicative System:
   {f(x,y;) -> h(y;x),
    f(x,y;) -> h(x;y),
     h(x;x) -> x}
  Qed