proposition: Lemma castmx_const m' n' (eq_mn : (m = m') * (n = n')) a : castmx eq_mn (const_mx a) = const_mx a.
proof: Proof. by case: eq_mn; case: m' /; case: n' /. 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)