proposition: Lemma mpoly_mul_revwE p q kp kq : msize p <= kp -> msize q <= kq -> p *M q = [mpoly \sum_(m : 'X_{1..n < kq, kp}) p *M_[(m.2, m.1)] q].
proof: Proof. by move=> lep leq; rewrite big_pairA exchange_big pair_bigA -mpoly_mulwE. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finfun bigop finset binomial) mathcomp(order fingroup perm ssralg zmodp poly ssrint) mathcomp(matrix vector) mathcomp(bigenough) ssrcomplements freeg