proposition: Lemma L_strext: (fun_strext L).
proof: Proof. simpl. unfold fun_strext. simpl. unfold Astar. intros x. induction x. intro y. case y. simpl. unfold ap_nat. intuition. simpl. intuition. intro y. case y. simpl. intuition. simpl. intros c l H. right. apply IHx. unfold ap_nat in H |- *. intuition. Qed.
imports: CoRN.algebra.CMonoids CoRN.model.monoids.Nmonoid