proposition: Lemma funeneg_ge0 f x : 0 <= f^\- x.
proof: Proof. by rewrite /funeneg le_maxr lexx orbT. 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