proposition: Lemma polyCB : {morph (@polyC R) : a b / a - b}.
proof: Proof. by move=> a b; rewrite polyCD polyCN. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)