proposition: Lemma filter_from_ballE {R : numDomainType} {M : pseudoMetricType R} x : @filter_from R _ [set x : R | 0 < x] (@ball R M x) = nbhs x.
proof: Proof. by rewrite -nbhs_ballE. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed