proposition: Lemma hornerX x : 'X.[x] = x.
proof: Proof. by rewrite /horner polyseqX /= !simp. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)