proposition: Lemma hlength_itv_ge0 i : 0 <= hlength [set` i].
proof: Proof. rewrite hlength_itv; case: ifPn => //; case: (i.1 : \bar _) => [r| |]. - by rewrite suber_ge0//; exact: ltW. - by rewrite ltNge leey. - by move=> i2gtNy; rewrite addey//; case: (i.2 : \bar R) i2gtNy. 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