proposition: Lemma indicT : \1_[set: T] = cst (1 : R).
proof: Proof. by apply/funext=> x; rewrite indicE in_setT. Qed.
imports: HB(structures) mathcomp(all_ssreflect ssralg ssrnum ssrint interval finmap) mathcomp(mathcomp_extra boolp classical_sets fsbigop) mathcomp(functions cardinality set_interval) signed reals ereal topology normedtype sequences