Help building a matrix-calculus package

One more thing: Maybe it be helpful to be able to do things like:

  kron_delta(k,l) . m . kron_delta(k,l) --> matrix_element(m,k,l) * kron_delta(k,l)

Maxima does have a simplifying multiple-indexed Kronecker delta, but there is no 
simplifying function similar to matrix_element (I think).

--Barton