Section Elt.
Variable elt:Type.
Implicit Types m r : t elt.
(** * Basic results about [MapsTo], [In], [lt_tree], [gt_tree], [height] *)
(** Facts about [MapsTo] and [In]. *)
Hint Resolve MapsTo_In : core.
Hint Immediate MapsTo_1 : core.
(** Results about [lt_tree] and [gt_tree] *)
Hint Resolve lt_leaf gt_leaf lt_tree_node gt_tree_node : core.
Hint Resolve lt_left lt_right gt_left gt_right : core.
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.
(** * Emptyness test *)
(** * Membership *)

Lemma find_in : forall m x, find x m <> None -> In x m.