(* Algebraic integers. *)
Definition Aint : pred_class :=
fun x : algC => minCpoly x \is a polyOver Cint.
Fact Aint_key : pred_key Aint. Proof. by []. Qed.
Canonical Aint_keyed := KeyedPred Aint_key.

Lemma Aint_int x : x%:~R \in Aint.