/*
 * call-seq:
 *   node.nd_file => String or nil
 *
 * Returns the file the node is associated with
 */
static VALUE node_nd_file(VALUE self)
{
  NODE * n;
  Data_Get_Struct(self, NODE, n);
  if(n->nd_file)
  {
    return rb_str_new2(n->nd_file);
  }
  else
  {
    return Qnil;
  }
}