NAME¶

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

Synopsis¶

Defined in header <ranges>
template< ranges::range R > (1) (since C++20)
using borrowed_iterator_t = /* see below */;
template< ranges::range R > (2) (since C++20)
using borrowed_subrange_t = /* see below */;

1) std::ranges::iterator_t<R> if R models borrowed_range, std::ranges::dangling
otherwise.
2) std::ranges::subrange<std::ranges::iterator_t<R>> if R models borrowed_range,
std::ranges::dangling otherwise.

These two alias templates are used by some constrained algorithms to avoid returning
potentially dangling iterators or views.

Possible implementation¶

First version¶

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>;

Second version¶

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>;

See also¶

ranges::dangling a placeholder type indicating that an iterator or a subrange should
(C++20) not be returned since it would be dangling
(class)