proposition: Lemma list_Q_spec_neg : forall a b c d, Z.abs_nat c <= Z.abs_nat a -> Z.abs_nat (Zneg d) <= Z.abs_nat b -> In (Qmake c d) (list_Q a b).
proof: Proof. intros a b c d. apply list_Q_spec_pos. Qed.
imports: Zring Qring Q_can