> LENGTH(m) if the number of rows in the matrix m. But how to get the
> number of columns of the matrix?
Matrices in Maxima are thought of as a list of rows, so Length(m) gives
the number of rows. The first row is m[1], and its length,
Length(m[1]), gives you the number of columns.
Beware, though: Maxima allows a list [a,b,c] to function as the
matrix([a,b,c]) in many contexts. But Length(m) and Length(m[1]) will
give incorrect answers in that case.
-s