proposition: Lemma exprzAC x m n : (x ^ m) ^ n = (x ^ n) ^ m.
proof: Proof. by rewrite !exprz_exp mulrC. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)