proposition: Lemma mxcol_recu {T : Type} {p : nat} {p_ : 'I_p.+1 -> nat} m (B_ : forall j, 'M[T]_(p_ j, m)) : \mxcol_j B_ j = castmx (mxsize_recl, erefl) (col_mx (B_ 0) (\mxcol_j B_ (lift ord0 j))).
proof: Proof. by apply: trmx_inj; rewrite trmx_cast tr_col_mx !tr_mxcol mxrow_recl. 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)