std::ranges::ref_view

 

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>     requires std::is_object_v<R> class ref_view : public ranges::view_interface<ref_view<R>>		(since C++20)

ref_­view is a View of the elements of some other Range. It wraps a reference to that Range.

Data members

std::ranges::ref_view::r_

R* r_ = nullptr; /* exposition-only */

pointer to the referenced range

Member functions

std::ranges::ref_view::ref_view

constexpr ref_view() noexcept = default;	(1)
template<__NotSameAs<ref_view> T>     requires /* see below */ constexpr ref_view(T&& t);	(2)

1) Initializes r_ with nullptr. A default-initialized ref_view references no Range.

2) Initializes r_ with std::addressof(static_­cast<R&>(std::forward<T>(t))).

__NotSameAs is an exposition-only helper concept.

The expression in the requires-clause of (2) is equivalent to ConvertibleTo<T, R&> && requires { FUN(declval<T>()); }, where the exposition-only functions FUN are declared as void FUN(R&); void FUN(R&&) = delete;.

Parameters

t

-

range to reference

std::ranges::rev_view::base

constexpr R& base() const;

Equivalent to return *r_;

std::ranges::ref_view::begin

constexpr iterator_t<R> begin() const;

Equivalent to return ranges::begin(*r_);

std::ranges::ref_view::end

constexpr sentinel_t<R> end() const;

Equivalent to return ranges::end(*r_);

std::ranges::ref_view::empty

constexpr bool empty() const     requires requires { ranges::empty(*r_); };

Equivalent to return ranges::empty(*r_);

std::ranges::ref_view::size

constexpr auto size() const     requires SizedRange<R> { return ranges::size(*r_); }

std::ranges::ref_view::data

constexpr auto data() const     requires ContiguousRange<R> { return ranges::data(*r_); }

Non-member functions

begin, end(std::ranges::ref_view)

friend constexpr iterator_t<R> begin(ref_view r);	(1)
friend constexpr sentinel_t<R> end(ref_view r);	(2)

1) Equivalent to return r.begin();

2) Equivalent to return r.end();

These functions are not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when std::ranges::ref_view<R> is an associated class of the arguments.

Deduction guides

template<class R> ref_view(R&) -> ref_view<R>;

See also

reference_wrapper (C++11)	CopyConstructible and CopyAssignable reference wrapper (class template)
all_viewview::all	a View that includes all elements of a Range (alias template) (range adaptor object)