proposition: Lemma unity_rootP n z : reflect (z ^+ n = 1) (n.-unity_root z).
proof: Proof. by rewrite unity_rootE; apply: eqP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)