static ColumnVector
nozeros (const ColumnVector v0, const double tol = 0.0)
{
  ColumnVector v (v0.length ());
  register int i, j;
  for (i = j = 0; i < v.length (); i++)
    if (tol < abs (v0 (i)))
    if (tol < std::abs (v0 (i)))
      {
	v (j) = v0 (i);
	j++;
      }
  if (0 == j)
    {
      return *new ColumnVector ();