matrix_type problems

[Vic Norton]

The idea of a matrix_type function makes a lot of sense to me, but what we have 
now doesn't seem to work in Octave 2.9.9.

For example:

   octave> A = eye(5)
   A =
   
      1   0   0   0   0
      0   1   0   0   0
      0   0   1   0   0
      0   0   0   1   0
      0   0   0   0   1

   octave> matrix_type(A)
   ans = Upper
   octave> A(2,1) = 1
   A =
   
      1   0   0   0   0
      1   1   0   0   0
      0   0   1   0   0
      0   0   0   1   0
      0   0   0   0   1
   
   octave> matrix_type(A)
   ans = Upper


It would be great if octave could take advantage of upper triangular structure, 
but the above exercise doesn't give me much confidence.

I would also like to see a simple test of whether a matrix is upper triangular. 
Obviously

   octave> strcmp(matrix_type(A), "Upper")
   ans =  1

doesn't work, because matrix_type (with one argument) doesn't work.

Regards,

Vic