Execute the function. The function must return
a valid object.
// DTMIterator nl = m_arg0.asIterator(xctxt, xctxt.getCurrentNode());
// // We should probably make a function on the iterator for this,
// // as a given implementation could optimize.
// int i = 0;
//
// while (DTM.NULL != nl.nextNode())
// {
// i++;
// }
// nl.detach();
DTMIterator nl = m_arg0.asIterator(xctxt, xctxt.getCurrentNode());
int i = nl.getLength();
nl.detach();
return new XNumber((double) i);