Section QintPred.
Definition Qint := [qualify a x : rat | denq x == 1].
Fact Qint_key : pred_key Qint. Proof. by []. Qed.
Canonical Qint_keyed := KeyedQualifier Qint_key.

Lemma Qint_def x : (x \is a Qint) = (denq x == 1). Proof. by []. Qed.