#[local]
Hint Resolve lt_tree_not_in lt_tree_trans gt_tree_not_in gt_tree_trans : core.
(** * Empty map *)
Definition Empty m := forall (a:key)(e:elt) , ~ MapsTo a e m.

Lemma find_mapsto_equiv : forall m m' x, bst m -> bst m' ->
(find x m = find x m' <->
(forall d, MapsTo x d m <-> MapsTo x d m')).