proposition: Lemma suber_lt0 x y : y \is a fin_num -> (x - y < 0) = (x < y).
proof: Proof. by move=> ?; rewrite lte_subl_addl// adde0. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap) mathcomp(mathcomp_extra) signed