type suite = char list;;

type code = bool list;;

type cle = (char * code) list;;

let coder (s:suite) (c:cle)=
  let rec code_of_char t cl = match cl with
    | [] -> failwith "Erreur dans coder"
    | (x,l)::r -> if x=t then l

    else code_of_char t r

    and coder_aux ss = match ss with
    |  [] -> []
    | t::q -> (code_of_char t c)@(coder_aux q)
in coder_aux s ;;