proposition: Theorem Zlt_Zopp : forall x y : Z, (x < y)%Z -> (- y < - x)%Z.
proof: Proof. intros x y; case x; case y; simpl in |- *; auto with zarith; intros p p0; unfold Z.lt in |- *; simpl in |- *; unfold Pos.compare; rewrite <- ZC4; auto. Qed.
imports: Reals ZArith List PeanoNat Psatz