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.

Lemma In_1 :
forall m x y, X.eq x y -> In x m -> In y m.