let double_pred = function x
    -> 2 * ( x - 1 );;

let double_pred x =
  2 * ( x - 1 );;

let carre_triple x = 
  9. *. x *. x;;

let carre_triple = function x
    -> 9. *. x *. x;;

let secondT (x, y, z) = 
  y;;

let ajoutL a l =
  a::l;;

(*
let est_nulle l = match l with
  [] -> true
  | _ -> false;;
*)

let est_nulle = function
  | [] -> true
  | _ -> false;;

let tete_L = function | [x; _] -> x;;