intros x x' y y' H' H'0; try assumption.
simpl in |- *.
red in |- *; auto with algebra.
Qed.
Hint Resolve Build_Ctype_comp: algebra.

(* Specifications: *)
Lemma real_comp : forall x x' : Cset, Equal x x' -> Equal (real x) (real x').
simpl in |- *.