code: public double num()
      throws javax.xml.transform.TransformerException
    {
  
  	throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NUM_NOT_SUPPORTED_XRTREEFRAGSELECTWRAPPER, null)); //"num() not supported by XRTreeFragSelectWrapper!");
    }
docs: Cast result object to a number.
  
  @return The result tree fragment as a number or NaN