std::ranges::borrowed_iterator_t,std::ranges::borrowed_subrange_t(3)

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)