/**
  * setupForm
  *
  * @param xxx $mform (passed by reference)
  */
 function setupForm(&$mform)
 {
     $objs = array($mform->createElement('select', $this->_name . '_op', null, $this->get_operators()), $mform->createElement('duration', $this->_name, null, array('optional' => 0, 'defaultunit' => 1)));
     $mform->addElement('group', $this->_name . '_grp', $this->_label, $objs, '', false);
     $mform->disabledIf($this->_name . '_grp', $this->_name . '_op', 'eq', 0);
     $mform->setType($this->_name . '_op', PARAM_INT);
     $mform->setType($this->_name . '[number]', PARAM_INT);
     $mform->setType($this->_name . '[timeunit]', PARAM_INT);
     if (!is_null($this->_default)) {
         $mform->setDefault($this->_name, $this->_default);
     }
     if ($this->_advanced) {
         $mform->setAdvanced($this->_name . '_grp');
     }
 }