proposition: Lemma ball_center {R : numDomainType} (M : pseudoMetricType R) (x : M) (e : {posnum R}) : ball x e%:num x.
proof: Proof. exact: ball_center_subproof. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed