proposition: Lemma Zmult_gt_0_le_0_compat n m : n > 0 -> 0 <= m -> 0 <= m * n.
proof: Proof. Z.swap_greater. intros. apply Z.mul_nonneg_nonneg. - trivial. - now apply Z.lt_le_incl. Qed.
imports: BinPos BinInt Decidable Zcompare Arith_base