proposition: Lemma find_2 : forall m x e, find x m = Some e -> MapsTo x e m.
proof: Proof. intros m x. unfold MapsTo. functional induction (find x m);simpl;intros e' eqfind; inversion eqfind; auto. Qed.
imports: SetoidList Bool OrderedType OrdersLists RelationPairs Orders RelationClasses