proposition: Lemma poly_unitE p : (p \in GRing.unit) = (size p == 1) && (p`_0 \in GRing.unit).
proof: Proof. by []. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)