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_node_iff :
forall l x e r h y,
In y (Node l x e r h) <-> In y l \/ X.eq y x \/ In y r.