std::ranges::bidirectional_range

定义于头文件 `<ranges>`
template<class T> concept bidirectional_range = ranges::forward_range<T> && std::bidirectional_iterator<ranges::iterator_t<T>>;

bidirectional_range 概念是 range 的细化，对于实现的类型， ranges::begin 返回 bidirectional_iterator 的实现。

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