proposition: Lemma Qball_Qabs : forall e a b, Qball e a b <-> Qabs (a - b) <= e.
proof: Proof. split; apply AbsSmall_Qabs. Qed.
imports: CoRN.metric2.Metric CoRN.metric2.Prelength CoRN.metric2.Classification CoRN.model.totalorder.QMinMax CoRN.model.totalorder.QposMinMax Coq.QArith.Qabs CoRN.metric2.UniformContinuity MathClasses.implementations.stdlib_rationals