proposition: Lemma emeasurable_neq y : measurable (D `&` [set x | f x != y]).
proof: Proof. rewrite (_ : [set x | f x != y] = f @^-1` (setT `\ y)). exact/mf/measurableD. rewrite predeqE => t; split; last by rewrite /preimage /= => -[_ /eqP]. by rewrite /= => ft0; rewrite /preimage /=; split => //; exact/eqP. 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