proposition: Lemma adde_gt0 x y : 0 < x -> 0 < y -> 0 < x + y.
proof: Proof. by move: x y => [x| |] [y| |] //; rewrite !lte_fin; exact: addr_gt0. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap) mathcomp(mathcomp_extra) signed