proposition: Lemma Z_div_0_l_pos x : 0 / Z.pos x = 0.
proof: Proof. reflexivity. Qed.
imports: Coq.ZArith.ZArith Coq.Lists.List Coq.Setoids.Setoid Coq.Classes.Morphisms Coq.QArith.QArith_base Coq.QArith.Qreduction Coq.QArith.Qround