proposition: Lemma expr_rev (x : R) k : (x : R^c) ^+ k = x ^+ k.
proof: Proof. by elim:k=> // k IHk; rewrite exprS exprSr IHk. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq path) mathcomp(ssralg fintype finfun perm matrix bigop zmodp mxalgebra) mathcomp(choice poly polydiv mxpoly binomial)