proposition: Lemma N_cast_diff: forall n m, n <> m -> N_cast n m = None.
proof: Proof. intros [ |n] [ |m]; auto; intro Heq. - elim Heq; reflexivity. - simpl. rewrite positive_cast_diff; auto. intro H. apply Heq. rewrite H. reflexivity. Qed.
imports: Bool Int63 Psatz PArray BinNat BinPos ZArith SMT_classes_instances Misc State BVList