proposition: Lemma Zabs_div_lft : forall a : Z, (Z.abs a / a)%Z = Z.sgn a.
proof: Proof. intro a. rewrite Zmult_sgn_eq_abs. case (Zdec a). intro Ha. rewrite Ha. simpl in |- *. auto with zarith. apply Zdiv_mult_cancel_rht. Qed.
imports: CoRN.model.Zmod.ZBasics