Add Parametric Morphism : CReal_plus
    with signature CRealEq ==> CRealEq ==> CRealEq
      as CReal_plus_morph.#[global]
Instance CReal_plus_morph_T
  : CMorphisms.Proper
      (CMorphisms.respectful CRealEq (CMorphisms.respectful CRealEq CRealEq)) CReal_plus.

Lemma CReal_opp_plus_distr : forall r1 r2, - (r1 + r2) == - r1 + - r2.