Namespaces
Variants

    std::ranges::borrowed_iterator_t, std::ranges::borrowed_subrange_t

    来自 zh.cppreference.net
     
    C++
     
    范围库
    范围适配器
     
    定义于头文件 <ranges> 
    template< ranges::range R >
using borrowed_iterator_t = /* see below */;
    		(1) (C++20 起) 
    template< ranges::range R >
using borrowed_subrange_t = /* see below */;
    		(2) (C++20 起)
    1) std::ranges::iterator_t<R> 如果 R 满足 borrowed_range, std::ranges::dangling 否则.
    2) std::ranges::subrange<std::ranges::iterator_t<R>> 如果 R 满足 borrowed_range, std::ranges::dangling 否则.

    这两个别名模板被一些 约束算法 用来避免返回可能悬垂的迭代器或视图.

    可能实现

    borrowed_iterator_t 
    template< std::ranges::range R >
using borrowed_iterator_t = std::conditional_t<std::ranges::borrowed_range<R>,
    std::ranges::iterator_t<R>, std::ranges::dangling>;
    borrowed_subrange_t 
    template< std::ranges::range R >
using borrowed_subrange_t = std::conditional_t<std::ranges::borrowed_range<R>,
    std::ranges::subrange<std::ranges::iterator_t<R>>, std::ranges::dangling>;

    参见

    (C++20)
    		用于指示迭代器或 subrange 不应被返回的占位符类型，因为返回会导致悬空引用
    (类)