proposition: Theorem Zplus_cmp_compat_r : ∀ n m p, (n ?= m)%Z = (n + p ?= m + p)%Z.
proof: Proof. intros. rewrite Zplus_comm. replace (m + p)%Z with (p + m)%Z by apply Zplus_comm. symmetry; apply Zcompare_plus_compat. Qed.
imports: Utf8 QArith NPeano Sorted Psatz