proposition: Lemma mfun_subring_closed : subring_closed (@mfun _ aT rT).
proof: Proof. split=> [|f g|f g]; rewrite !inE/=. - exact: measurable_cst. - exact: measurable_funB. - exact: measurable_funM. Qed.
imports: HB(structures) mathcomp(all_ssreflect ssralg ssrnum ssrint interval finmap) mathcomp(mathcomp_extra boolp classical_sets functions) mathcomp(cardinality fsbigop ) signed reals ereal topology normedtype sequences real_interval esum measure lebesgue_measure numfun