proposition: Lemma mx_ball_center x (e : R) : 0 < e -> mx_ball x e x.
proof: Proof. by move=> ???; apply: ballxx. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed