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

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

 

Ranges library

Range access
begincbegin endcend	rbegincrbegin rendcrend	size empty datacdata
Range primitives
iterator_tsentinel_t	range_difference_trange_value_t	range_reference_trange_rvalue_reference_t
Dangling iterator handling
dangling	borrowed_iterator_t	borrowed_subrange_t
Range concepts
range borrowed_range sized_range	common_range view viewable_range	input_range output_range forward_range	bidirectional_range random_access_range contiguous_range
Views
view_interface	subrange
Semiregular wrapper
Factories
empty_viewviews::empty	single_viewviews::single	iota_viewviews::iota	views::counted
Adaptors
all_viewviews::all join_viewviews::join take_viewviews::take basic_istream_viewistream_view	ref_view                                split_viewviews::split take_while_viewviews::take_while elements_viewviews::elements	common_viewviews::common transform_viewviews::transform drop_viewviews::drop keys_viewviews::keys	reverse_viewviews::reverse filter_viewviews::filter drop_while_viewviews::drop_while values_viewviews::values

 

Defined in header <ranges>
template<ranges::range R> using borrowed_iterator_t = std::conditional_t<ranges::borrowed_range<R>,     ranges::iterator_t<R>, ranges::dangling>;	(1)	(since C++20)
template<ranges::range R> using borrowed_subrange_t = std::conditional_t<ranges::borrowed_range<R>,     ranges::subrange<ranges::iterator_t<R>>, ranges::dangling>;	(2)	(since C++20)

1) Same as ranges::iterator_t when R models borrowed_range, 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

dangling

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