proposition: Lemma pexprn_eq1 x n : 0 <= x -> (x ^+ n == 1) = (n == 0) || (x == 1).
proof: Proof. by case: n => [|n] xge0; rewrite ?eqxx // pexpr_eq1 ?gtn_eqF. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)