Definition C_AbsRing_mixin :=
  AbsRing.Mixin _ _ Cmod_0 Cmod_m1 Cmod_triangle (fun x y => Req_le _ _ (Cmod_mult x y)) Cmod_eq_0.Canonical C_AbsRing :=
  AbsRing.Pack C (AbsRing.Class _ _ C_AbsRing_mixin) C.

Lemma Cmod_R : forall x : R, Cmod x = Rabs x.