proposition: Lemma set_induction_bis : forall P : t -> Type, (forall s s', s [=] s' -> P s -> P s') -> P empty -> (forall x s, ~In x s -> P s -> P (add x s)) -> forall s, P s.
proof: Proof. intros. apply (@fold_rec_bis _ (fun s _ => P s) (fun _ _ => tt) tt s); eauto. Qed.
imports: MSetInterface PeanoNat DecidableTypeEx OrdersLists MSetFacts MSetDecide