TRS:
 { f(0(), y) -> 0(),
  f(s(x), y) -> f(f(x, y), y)}
 POP* + Boolean Semantic Labelling:
  Normal positions:
  pi(f_sl=1) = [1,2], pi(f_sl=0) = [2]
  
Safe positions:
   pi(s_sl=1) = [1], pi(s_sl=0) = [1], pi(f_sl=0) = [1]
  
Precedence:
   f_sl=1 > f_sl=0
   empty
  
Interpretation:
   0^(0):
    | 1
   f^(2):
   00 | 1
   01 | 1
   10 | 1
   11 | 1
   s^(1):
   0 | 0
   1 | 0
   
  
Labelling:
   0^(0):
    | 0
   f^(2):
   00 | 1
   01 | 1
   10 | 0
   11 | 0
   s^(1):
   0 | 0
   1 | 0
   
  
Labelled predicative System:
   {   f_sl=0(y;0_sl=0()) -> 0_sl=0(),
       f_sl=0(y;0_sl=0()) -> 0_sl=0(),
    f_sl=1(s_sl=0(;x),y;) -> f_sl=0(y;f_sl=1(x,y;)),
    f_sl=1(s_sl=0(;x),y;) -> f_sl=0(y;f_sl=0(y;x)),
    f_sl=1(s_sl=0(;x),y;) -> f_sl=0(y;f_sl=1(x,y;)),
    f_sl=1(s_sl=0(;x),y;) -> f_sl=0(y;f_sl=0(y;x))}
  

  Qed