proposition: Lemma nbhs_ballP {R : numDomainType} {M : pseudoMetricType R} (x : M) P : nbhs x P <-> nbhs_ball x P.
proof: Proof. by rewrite nbhs_simpl. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed