End MatrixStructural.
Arguments const_mx {R m n}.
Arguments row_mxA {R m n1 n2 n3 A1 A2 A3}.
Arguments col_mxA {R m1 m2 m3 n A1 A2 A3}.
Arguments block_mxA
{R m1 m2 m3 n1 n2 n3 A11 A12 A13 A21 A22 A23 A31 A32 A33}.
Prenex Implicits castmx trmx trmxK lsubmx rsubmx usubmx dsubmx row_mx col_mx.
Prenex Implicits block_mx ulsubmx ursubmx dlsubmx drsubmx.
Prenex Implicits mxvec vec_mx mxvec_indexP mxvecK vec_mxK.
Arguments trmx_inj {R m n} [A1 A2] eqA12t : rename.
Notation "A ^T" := (trmx A) : ring_scope.
(* Matrix parametricity. *)
Section MapMatrix.
Variables (aT rT : Type) (f : aT -> rT).
Fact map_mx_key : unit. Proof. by []. Qed.
Definition map_mx m n (A : 'M_(m, n)) := \matrix[map_mx_key]_(i, j) f (A i j).
Notation "A ^f" := (map_mx A) : ring_scope.
Section OneMatrix.
Variables (m n : nat) (A : 'M[aT]_(m, n)).

Lemma map_trmx : A^f^T = A^T^f.