proposition: Lemma fold_init : forall i i' s, eqA i i' -> eqA (fold f s i) (fold f s i').
proof: Proof. intros. apply fold_rel with (R:=eqA); auto. intros; apply Comp; auto with relations. Qed.
imports: MSetInterface PeanoNat DecidableTypeEx OrdersLists MSetFacts MSetDecide