In the absence of iterators, `visit_all` is provided as an alternative way to process all the elements in the container:
In the absence of iterators, `visit_all` is provided as an alternative way to process all the elements in the container:在缺乏迭代器的情况下， `visit++_++all` 提供处理容器内全部元素的替代方案：
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In the absence of iterators, `visit_all` is provided as an alternative way to process all the elements in the container:在缺乏迭代器的情况下， `visit++_++all` 提供处理容器内全部元素的替代方案：