proposition: Lemma mxsub_cast m1 m2 n1 n2 (eq_m : m1 = m2) (eq_n : n1 = n2) A : mxsub (cast_ord eq_m) (cast_ord eq_n) A = castmx (esym eq_m, esym eq_n) A.
proof: Proof. by rewrite mxsubrc rowsub_cast colsub_cast castmx_comp/= etrans_id. 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)