Section Elt.
Variable elt : Type.
Notation eqk := (eqk (elt:=elt)).
Notation eqke := (eqke (elt:=elt)).
Notation ltk := (ltk (elt:=elt)).
Notation MapsTo := (MapsTo (elt:=elt)).
Notation In := (In (elt:=elt)).
Notation Sort := (sort ltk).
Notation Inf := (lelistA (ltk)).
(** * [empty] *)
Definition empty : t elt := nil.
Definition Empty m := forall (a : key)(e:elt) , ~ MapsTo a e m.
Hint Resolve empty_1 : core.

Lemma empty_sorted : Sort empty.