proposition: Lemma nodes_preserved_trans : forall cfg1 cfg2 cfg3 : BDDconfig, nodes_preserved cfg1 cfg2 -> nodes_preserved cfg2 cfg3 -> nodes_preserved cfg1 cfg3.
proof: Proof. unfold nodes_preserved in |- *; intros. apply H0. apply H. assumption. Qed.
imports: Bool Sumbool Arith ZArith NArith Nnat Ndec Ndigits IntMap(Allmaps) Wf_nat BDDvar_ad_nat bdd1 bdd2 bdd3 bdd4 bdd5_1 bdd5_2