Section Elt.
Variable elt:Type.
Definition Add x (e:elt) m m' := forall y, find y m' = find y (add x e m).
Notation eqke := (@eq_key_elt elt).
Notation eqk := (@eq_key elt).
Instance eqk_equiv : Equivalence eqk.
(** Complements about InA, NoDupA and findA *)
(** * Elements *)

Lemma elements_Empty : forall m:t elt, Empty m <-> elements m = nil.