(* We call this morphism slow to remind that it should only be used
   for proofs, not for computations. *)
Definition SlowConstructiveRealsMorphism {R1 R2 : ConstructiveReals}
  : @ConstructiveRealsMorphism R1 R2
  := Build_ConstructiveRealsMorphism
       R1 R2 SlowMorph CauchyMorph_rat
       SlowMorph_increasing.

Lemma CRmorph_abs : forall {R1 R2 : ConstructiveReals} (f : @ConstructiveRealsMorphism R1 R2) (x : CRcarrier R1), CRabs R2 (CRmorph f x) == CRmorph f (CRabs R1 x).