std::ranges::safe_iterator_t, std::ranges::safe_subrange_t

Defined in header <ranges>
template<Range R>
using safe_iterator_t = std::conditional_t<__ForwardingRange<R>,
    ranges::iterator_t<R>, ranges::dangling>;
(1) (since C++20)
template<Range R>
using safe_subrange_t = std::conditional_t<__ForwardingRange<R>,
    ranges::subrange<ranges::iterator_t<R>>, ranges::dangling>;
(2) (since C++20)
1) Same as ranges::iterator_t when R models exposition-only concept __ForwardingRange, otherwise yields ranges::dangling instead.
2) Similar to (1), but it yields a specialization of ranges::subrange when the the same condition is met.

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

See also

a placeholder type indicating that an iterator or a subrange should not be returned since it would be dangling

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