Module Import PX := KeyDecidableType X.Definition key := X.t.Definition t (elt:Type) := list (X.t * elt).Notation eqk := (eqk (elt:=elt)).Notation eqke := (eqke (elt:=elt)).Notation MapsTo := (MapsTo (elt:=elt)).Notation In := (In (elt:=elt)).Notation NoDupA := (NoDupA eqk).(** * [empty] *)

Definition empty : t elt := nil.Definition Empty m := forall (a : key)(e:elt), ~ MapsTo a e m.

Lemma empty_NoDup : NoDupA empty.