(* Implementation avec listes *)
(* Exercice 1 *)
(* 1. *)
type ('a, 'b) dict = ('a * 'b) list

(* 2. *)			       
let dict_empty = []

(* Exercice 2 *)
(* 3. *)
let rec dict_add key value dict =
  let rec aux dict ndict =
    match dict with
      [] -> (key, value)::ndict
    | (k, y)::d -> aux d (if k = key
			  then (k, value) :: ndict
			  else (k, y) :: ndict)
  in aux dict []

(* Exercice 3 *)
(* 4. *)
let rec dict_find key dict =
  match dict with
    [] -> None
  | (k, value)::l -> if k = key then Some value else dict_find key l

(* Exercice 4 *)						       
(* 5. *)
let dict_remove key dict =
  let rec aux dict ndict =
    match dict with
      [] -> ndict
    | (k, y)::d -> aux d (if k = key then ndict else (k,y) :: ndict)
  in aux dict []