proposition: Lemma size_map_poly p : size p^f = size p.
proof: Proof. have [-> | nz_p] := eqVneq p 0; first by rewrite rmorph0 !size_poly0. by rewrite size_poly_eq // fmorph_eq0 // lead_coef_eq0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)