proposition: Lemma pid_mx_minv m n r : pid_mx (minn m r) = pid_mx r :> 'M_(m, n).
proof: Proof. by apply/matrixP=> i j; rewrite !mxE leq_min ltn_ord. 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)