proposition: Lemma Zabs_Qcabs : forall n d, Q2Qc (Z.abs n#d) = Qcabs (Q2Qc (n#d)).
proof: Proof. intros n d. apply Qc_is_canon. rewrite Qcabs_Q. repeat rewrite Q2Qc_correct. apply Qabs.Zabs_Qabs. Qed.
imports: Qreduction ClassicalRealizability.Qccomplement