Empty Matrix DLD question

[Andy+Alison Adler]

I'd like to return an empty matrix from
an *oct file.

Initially I hoped that when cx==0

    X["ridx"]= ridxX.extract( 0, cx-1);

would return an empty matrix.
No luck. x.ridx is a two element column vector.

Next, I tried

   if ( cx > 0 ) {
      X["ridx"]= ridxX.extract( 0, cx-1);
   } else {
      ColumnVector nullvec(0);
      X["ridx"]= nullvec;
   }

But this segfaults octave.

I couldn't find any examples of how to do this
in the source.

Is there an approved way to create empty matrices?

andy,