proposition: Lemma poly_invE p : p ^-1 = if p \in GRing.unit then (p`_0)^-1%:P else p.
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)