proposition: Lemma fold_1b : forall s (A : Type)(i : A) (f : elt -> A -> A), Empty s -> (fold f s i) = i.
proof: Proof. intros. rewrite FM.fold_1. rewrite elements_Empty in H; rewrite H; simpl; auto. Qed.
imports: MSetInterface PeanoNat DecidableTypeEx OrdersLists MSetFacts MSetDecide