Canonical dvdC_opprPred x := OpprPred (dvdC_zmod x).
Canonical dvdC_addrPred x := AddrPred (dvdC_zmod x).
Canonical dvdC_zmodPred x := ZmodPred (dvdC_zmod x).

Lemma Crat0 : 0 \in Crat. Proof. by apply/CratP; exists 0; rewrite rmorph0. Qed.