#[global]
Instance CR_cv_morph
  : forall {R : ConstructiveReals} (un : nat -> CRcarrier R), CMorphisms.Proper
      (CMorphisms.respectful (CReq R) CRelationClasses.iffT) (CR_cv R un).

Lemma CR_cv_minus : forall {R : ConstructiveReals} (An Bn:nat -> CRcarrier R) (l1 l2:CRcarrier R), CR_cv R An l1 -> CR_cv R Bn l2 -> CR_cv R (fun i:nat => An i - Bn i) (l1 - l2).