let pxor ?(loc=Lexing.dummy_pos,Lexing.dummy_pos) (p1, p2) =
match p1.content, p2.content with
Ptrue, Ptrue -> unamed ~loc Pfalse
| Ptrue, _ -> p1
| _, Ptrue -> p2
| Pfalse, _ -> p2
| _, Pfalse -> p1
| _,_ -> unamed ~loc (Pxor (p1,p2))