proposition: Lemma infinite_hlength_itv i : hlength [set` i] = +oo -> (exists s r, i = Interval -oo%O (BSide s r) \/ i = Interval (BSide s r) +oo%O) \/ i = `]-oo, +oo[.
proof: Proof. rewrite hlength_itv; case: i => -[ba a|[]] [bb b|[]] //= => [|_|_|]. - by case: ifPn. - by left; exists ba, a; right. - by left; exists bb, b; left. - by right. 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