(** * [fold] *)

(* Specifications: *)
Lemma fold_1 : forall m (A:Type)(i:A)(f:key->elt->A->A),
fold f m i = fold_left (fun a p => f (fst p) (snd p) a) (elements m) i.
Lemma fold_1 : forall m (A:Type)(i:A)(f:key->elt->A->A),
fold f m i = fold_left (fun a p => f (fst p) (snd p) a) (elements m) i.