proposition: Lemma col_permM s t A : col_perm (s * t) A = col_perm s (col_perm t A).
proof: Proof. by apply/matrixP=> i j; rewrite !mxE permM. 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)