public function getExpression(AbstractPlatform $platform)
    {
        $len = count($this->expressions);
        $con = '';
        $i   = 0;

        if (empty($this->expressions)) {
            return $this->isInverse ? '1 = 0' : '1 = 1';
        }

        foreach ($this->expressions as $key => $expr) {
            $con.= $expr->getExpression($platform);
            $con.= ($i == $len - 1) ? '' : ' ' . $expr->getConjunction() . ' ';

            $i++;
        }

        return ($this->isInverse ? '!' : '') . '(' . $con . ')';
    }