public function join(string $combiner, self $expr): self
    {
        $path = $this->__toString().$combiner;

        if ('*/' !== $expr->path) {
            $path .= $expr->path;
        }

        $this->path = $path;
        $this->element = $expr->element;
        $this->condition = $expr->condition;

        return $this;
    }