proposition: Lemma mxvec_delta m n i j : mxvec (delta_mx i j) = delta_mx 0 (mxvec_index i j) :> 'rV_(m * n).
proof: Proof. by rewrite -vec_mx_delta vec_mxK. 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)