proposition: Lemma ltn_modp p q : (size (p %% q) < size q) = (q != 0).
proof: Proof. rewrite /modp unlock redivp_def /=; case: ifP=> ulcq; rewrite ?ltn_rmodp //=. rewrite size_scale ?ltn_rmodp // -exprVn expf_neq0 // invr_eq0. by case: eqP ulcq => // ->; rewrite unitr0. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop ssralg poly)