proposition: Lemma lte_dadd a b x y : a < b -> x < y -> a + x < b + y.
proof: Proof. rewrite !dual_addeE lteN2 -lteN2 -(lteN2 y); exact: lteD. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap) mathcomp(mathcomp_extra) signed