proposition: Lemma zring_old_minus : forall i j, zring_old (i - j) [=] zring_old i[-]zring_old j.
proof: Proof. intros i j. unfold cg_minus in |- *. replace (i - j)%Z with (i + - j)%Z. Step_final (zring_old i[+]zring_old (- j)). auto. Qed.
imports: CoRN.tactics.CornTac CoRN.algebra.CSums CoRN.algebra.CAbMonoids Coq.Sorting.Permutation CoRN.util.SetoidPermutation Coq.Setoids.Setoid Coq.Classes.Morphisms Coq(Lia)