proposition: Lemma size_mul p q : p != 0 -> q != 0 -> size (p * q) = (size p + size q).-1.
proof: Proof. by move=> nz_p nz_q; rewrite -size_proper_mul ?mulf_neq0 ?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)