let save_words flot  trie =

  let rec aux f keys = function
    | Leaf t -> f keys t
    | Node (t, l) ->
      f keys t; List.iter (fun (c, s) -> aux f (keys @ [c]) s) l
  in aux (fun keys -> parcours_aux (print_combine flot keys)) [] trie;;

save_words flot d;;