protected function joinClause(
        /*# : string */ $prefix,
        /*# : string */ $seperator,
        array $clause,
        array $settings
    )/*# : string */ {
        if (empty($clause)) {
            return '';
        } else {
            $sepr = $settings['seperator'];
            $join = $settings['join'];
            $pref = empty($prefix) ? $join : ($sepr . $prefix . $join);
            return $pref . join($seperator . $join, $clause);
        }
    }