[Octave-bug-tracker] [bug #60086] Matrix exponentiation fails for empty matrix

[Rik]

Follow-up Comment #3, bug #60086 (project octave):

This seems pretty easy to fix.  The code for powers of a matrix is in
libinterp/corefcn/xpow.cc.  There are many different cases, but the input
validation all looks like this:


  octave_value retval;

  octave_idx_type nr = a.rows ();
  octave_idx_type nc = a.cols ();

  if (nr == 0 || nc == 0 || nr != nc)
    err_nonsquare_matrix ();



It would be easy enough to check for an empty matrix (nr == 0 || nc == 0) and
immediately return an empty matrix.

Do we want to be fully Matlab compatible with respect to matrix dimensions? 
Matlab issues an error when the matrix is empty, but not square.  For
example,


zeros (0,2) ^ 2


I don't see the reasoning for that.  If the matrix is empty, then raising it
to a power is still always going to be an empty matrix.  We should decide on
this question before implementing a solution.  

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