proposition: Lemma widen_3: forall N1 N2, ble N2 N1 = false -> (measure (widen N1 N2) < measure N1)%nat.
proof: Proof. destruct N1, N2; cbn; intros; auto; try discriminate. unfold widen. cbn. rewrite H. cbn. lia. Qed.
imports: Coq(ZArith Psatz Bool String List FMaps) Coq(FunctionalExtensionality) CDF(Sequences IMP)