proposition: Lemma in_q_output : forall (d : data) (q : queue data), In_queue data d (first_out data q) -> In_queue data d q.
proof: Proof. simple induction q. simpl in |- *; trivial. intros d0 q0; case q0; simpl in |- *; intros. contradiction. elim H0; clear H0; intros. auto. right; apply H; auto. Qed.
imports: bibli