Maxima Function
get_lu_factors (x)
When x = lu_factor (A), then get_lu_factors returns a list of the form [P, L, U], where P is a permutation matrix, L is lower triangular with ones on the diagonal, and U is upper triangular, and A = P L U.
x = lu_factor (A)
get_lu_factors
[P, L, U]
A = P L U