proposition: Lemma mem_spec m x {Hm:Ok m} : mem x m = true <-> In x m.
proof: Proof. induction m as [|(k,e') m IH]; simpl. - split. discriminate. inversion 1. inversion_clear H0. - inversion_clear Hm. rewrite In_cons; simpl. case X.compare_spec; intros. + intuition. + split. discriminate. intros [E|(e,IN)]. MX.order. SortLt. MX.order. + rewrite IH; trivial. split; auto. intros [E|IN]; trivial. MX.order. Qed.
imports: Coq(OrdersFacts OrdersLists)