proposition: Lemma prod_ball_center x (eps : R) : 0 < eps -> prod_ball x eps x.
proof: Proof. by move=> /posnumP[?]. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed