Add Parametric Morphism : CReal_abs
with signature CRealEq ==> CRealEq
as CReal_abs_morph.

(* The proof by cases on the signs of x and y applies constructively, because of the positivity hypotheses. *)
Lemma CReal_abs_mult : forall x y : CReal,
CReal_abs (x * y) == CReal_abs x * CReal_abs y.