(* Implementation avec fonctions *)
(* Exercice 9 *)
(* 10 *)
type ('a, 'b) dict = 'a -> 'b option

(* 11. *)
let dict_empty = fun k -> None

(* 12 *)
let dict_add key value dict =
  fun k -> if k = key then (Some value) else dict k

(* 13 *)			      
let dict_find key dict = dict key

(* 14 *)
let dict_remove key dict = fun k -> if k = key then None else dict k