std::ranges::safe_iterator_t, std::ranges::safe_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_t	sentinel_t
Dangling iterator handling
dangling	safe_iterator_t	safe_subrange_t
Range concepts
Range SizedRange View	InputRange OutputRange ForwardRange	BidirectionalRange RandomAccessRange ContiguousRange	CommonRange ViewableRange
Views
view_interface	subrange
Semiregular wrapper
Factories
empty_viewview::empty	single_viewview::single	iota_viewview::iota	view::counted
Adaptors
all_viewview::all ref_view filter_viewview::filter	transform_viewview::transform                                take_viewview::take	join_viewview::join split_viewview::split	common_viewview::common reverse_viewview::reverse

 

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

dangling

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