proposition: Lemma phi_invK : cancel phi_inv phi.
proof: Proof. by move=> p; rewrite /phi -map_poly_comp_id0 // map_poly_id. 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)