I have just checked in code which computes the state variable
equations for a linear electric circuit.
It was developed with the commercial macsyma, and will not work
with maxima unless the m..n operator is implemented which provides
a matlab sequence of integers from m thru n.
There is code which is used to deal with empty matrixes not being
compatible in one direction or another. That is, it should be possible
to combine a matrix of zero columns and n rows, to a matrix of n rows,
and likewise with columns.
Dan Stanger