Section BlockMatrixRec.
Local Notation e := (mxsize_recl, mxsize_recl).
Local Notation l0 := (lift ord0).
Context {T : Type}.

Lemma mxEmxcol m n (A : 'M[T]_(m, n)) :
A = castmx (big_ord1 _ (fun=> m), erefl) (\mxcol__ A).