proposition: Lemma lead_coef_eq0 p : (lead_coef p == 0) = (p == 0).
proof: Proof. rewrite -nil_poly /lead_coef nth_last. by case: p => [[|x s] /= /negbTE // _]; rewrite eqxx. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)