function _convertFunction($token, $num_args)
    {
        $args     = $this->_functions[$token][1];
        $volatile = $this->_functions[$token][3];

        // Fixed number of args eg. TIME($i,$j,$k).
        if ($args >= 0) {
            return pack("Cv", $this->ptg['ptgFuncV'], $this->_functions[$token][0]);
        }
        // Variable number of args eg. SUM($i,$j,$k, ..).
        if ($args == -1) {
            return pack("CCv", $this->ptg['ptgFuncVarV'], $num_args, $this->_functions[$token][0]);
        }
    }