type 'a tr = {
  mutable taille : int;
  mutable donnees : 'a array
};;

let creer_tr capacity init_value = {
  taille = 0;
  donnees = Array.make (max capacity 1) init_value
};;

let taille_tr tr = tr.taille;;

let acces_tr tr i =
  if i >= tr.taille then
    invalid_arg "Index bigger than tr size"
  else
    tr.donnees.(i);;

let modif_tr tr i value =
  if i >= tr.taille then
    invalid_arg "Index bigger than tr size"
  else
    tr.donnees.(i) <- value;;

let append_tr tr value =
  let n = Array.length tr.donnees in

  if tr.taille >= n then
    tr.donnees <- Array.init
      (n*2)
      (fun i -> tr.donnees.(i mod n));

  tr.donnees.(tr.taille) <- value;
  tr.taille <- tr.taille + 1
;;

let pop_tr tr =
  if tr.taille <= 0 then
    invalid_arg "Empty tr"
  else
    tr.taille <- tr.taille - 1;
    tr.donnees.(tr.taille)
;;