proposition: Lemma col_0mx m n (M : 'M[R]_(m, n)) : col_mx (0 :'M_(0%N, _)) M = M.
proof: Proof. apply/matrixP=> i j; rewrite !mxE. case: splitP => [[] //|k eq_i_k]; congr (M _ _). by apply: val_inj; rewrite /= eq_i_k. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq path) mathcomp(ssralg fintype finfun perm matrix bigop zmodp mxalgebra) mathcomp(choice poly polydiv mxpoly binomial)