(* OK !! *)

(* Specifications: *)
Lemma betweene_bottom_x_top: forall(m:fmap)(x:dart),
inv_hmap m -> succ m zero x ->
betweene m (bottom m zero x) x (top m zero x).
Lemma between_bottom_x_top: forall(m:fmap)(x:dart),
inv_hmap m -> succ m zero x ->
betweene m (bottom m zero x) x (top m zero x).