proposition: Lemma mxcol_mul n' m (C_ : forall i, 'M[R]_(p_ i, n')) (A : 'M[R]_(n', m)) : \mxcol_i C_ i *m A = \mxcol_i (C_ i *m A).
proof: Proof. by apply/matrixP=> i s; rewrite !mxE; under eq_bigr do rewrite !mxE. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype finfun bigop finset fingroup perm order) mathcomp(div prime binomial ssralg countalg finalg zmodp)