proposition: Lemma measurable_closed_ball (x : R) r : measurable (closed_ball x r).
proof: Proof. have [r0|r0] := leP r 0; first by rewrite closed_ball0. by rewrite closed_ball_itv. 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