proposition: Lemma isok_iff : forall l, sort X.lt l <-> Ok l.
proof: Proof. intro l; split; intro H. - elim H. + constructor; fail. + intros y ys Ha Hb Hc. change (inf y ys && isok ys = true). rewrite inf_iff in Hc. rewrite andb_true_iff; tauto. - induction l as [|x xs]. + constructor. + change (inf x xs && isok xs = true) in H. rewrite andb_true_iff, <- inf_iff in H. destruct H; constructor; tauto. Qed.
imports: MSetInterface OrdersFacts OrdersLists