proposition: Lemma open_measurable (A : set R) : open A -> measurable A.
proof: Proof. move=>/open_bigcup_rat ->; rewrite bigcup_mkcond; apply: bigcupT_measurable_rat. move=> q; case: ifPn => // qfab; apply: is_interval_measurable => //. exact: is_interval_bigcup_ointsub. Qed.
imports: mathcomp(all_ssreflect ssralg ssrnum ssrint interval) mathcomp(finmap fingroup perm rat) mathcomp(mathcomp_extra boolp classical_sets functions) mathcomp(cardinality fsbigop) reals ereal signed topology numfun normedtype HB(structures) sequences esum measure real_interval realfun exp lebesgue_stieltjes_measure