proposition: Lemma CRdistance_comm (x y: CR): CRdistance x y == CRdistance y x.
proof: Proof. unfold CRdistance. intros. CRring_replace (x - y) (-(y - x)). apply CRabs_opp. Qed.
imports: CoRN.algebra.RSetoid CoRN.metric2.Metric CoRN.metric2.UniformContinuity CoRN.model.totalorder.QposMinMax CoRN.reals.fast.CRArith CoRN.model.metric2.Qmetric Coq.QArith.Qabs CoRN.model.totalorder.QMinMax CoRN.logic.Stability