proposition: Lemma ball_splitr (z x y : M) (e : R) : ball z (e / 2) x -> ball z (e / 2) y -> ball x e y.
proof: Proof. by move=> /ball_sym /ball_split; apply. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed