proposition: Lemma dfin_numD x y : (x + y \is a fin_num) = (x \is a fin_num) && (y \is a fin_num).
proof: Proof. by move: x y => [x| |] [y| |]. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap) mathcomp(mathcomp_extra) signed