std::ranges::borrowed_iterator_t, std::ranges::borrowed_subrange_t
来自cppreference.com
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) |
2) 若
R
实现 borrowed_range
则为 std::ranges::subrange<std::ranges::iterator_t<R>> ,否则为 std::ranges::dangling 。某些受约束算法用此二模板别名避免返回潜在悬垂的迭代器或视图。
可能的实现
版本一 |
---|
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>; |
版本二 |
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>; |
参阅
(C++20) |
占位类型,指示不应返回迭代器或子范围,因为它可能悬垂 (类) |