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