proposition: Lemma measurable_oppe (D : set (\bar R)) : measurable_fun D (-%E : \bar R -> \bar R).
proof: Proof. move=> mD; apply: (measurability (ErealGenCInfty.measurableE R)) => //. move=> _ [_ [x ->] <-]; rewrite (_ : _ @^-1` _ = `]-oo, (- x)%:E]%classic). by apply: measurableI => //; exact: emeasurable_itv. by rewrite predeqE => y; rewrite preimage_itv !in_itv/= andbT in_itv leeNr. 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