proposition: Lemma Qcplus_neg_nonpos (x y : Qc) : x < 0 → y ≤ 0 → x + y < 0.
proof: Proof. intros. apply Qcle_lt_trans with (x + 0); [|by rewrite Qcplus_0_r]. by apply Qcplus_le_mono_l. Qed.
imports: Coq(QArith Qcanon) stdpp(well_founded) stdpp(options)