#[global]
Instance CR_of_Q_morph_T
  : forall {R : ConstructiveReals}, CMorphisms.Proper
      (CMorphisms.respectful Qeq (CReq R)) (CR_of_Q R).

Lemma CR_of_Q_opp : forall {R : ConstructiveReals} (q : Q), CR_of_Q R (-q) == - CR_of_Q R q.