proposition: Lemma hornerXn x n : ('X^n).[x] = x ^+ n.
proof: Proof. by rewrite horner_exp_comm /comm_poly hornerX. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)