Section MapMatrixSpaces.
Variables (aF rF : fieldType) (f : {rmorphism aF -> rF}).
Local Notation "A ^f" := (map_mx f A) : ring_scope.

Lemma rank_mxdiag (V_ : forall i, 'M[F]_(p_ i)) :
(\rank (\mxdiag_i V_ i) = \sum_i \rank (V_ i))%N.