(** * Conversions between maps and association lists. *)

  Definition uncurry {U V W : Type} (f : U -> V -> W) : U*V -> W :=
   fun p => f (fst p) (snd p).Definition of_list :=
    List.fold_right (uncurry (@add _)) (empty elt).Definition to_list := elements.

Lemma fold_Empty : forall m i, Empty m -> eqA (fold f m i) i.