module ComparableIntPair  = 
    struct
     type t =  int * int 
     (* analogue du compareTo de java *)
     let compare (x1,y1) (x2,y2) = 
          if x1 < x2 then -1
          else if x1 > x2 then 1
          else if y1 < y2 then -1
          else if y1 > y2 then 1
          else 0
     end
;;