public static function doUnaryOperation($operator, &$value)
    {
        if (self::$unaryOperations === null) {
            self::$unaryOperations = [
                    self::BITWISE_NOT   => function (&$i) { return ~$i; },
                    self::NOT           => function (&$i) { return !$i; },
                    self::INCREMENT     => function (&$i) { return $i++; },
                    self::DECREMENT     => function (&$i) { return $i--; },
                    self::PRE_INCREMENT => function (&$i) { return ++$i; },
                    self::PRE_DECREMENT => function (&$i) { return --$i; },
                    self::NEGATION      => function (&$i) { return -$i; },
                    self::PLUS          => function (&$i) { return +$i; },
            ];
        }

        if (!isset(self::$unaryOperations[$operator])) {
            throw new PinqException('Unary operator \'%s\' is not supported', $operator);
        }

        $operation = self::$unaryOperations[$operator];

        return $operation($value);
    }