proposition: Lemma mul_delta_mx m n p (j : 'I_n) (i : 'I_m) (k : 'I_p) : delta_mx i j *m delta_mx j k = delta_mx i k.
proof: Proof. by rewrite mul_delta_mx_cond eqxx. 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)