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
iteartor_tsentinel_t	range_difference_trange_value_t	range_reference_trange_rvalue_reference_t
Dangling iterator handling
dangling	safe_iterator_t	safe_subrange_t
Range concepts
range sized_range view	input_range output_range forward_range	bidirectional_range random_access_range contiguous_range	common_range viewable_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>     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 std::convertible_to<T, R&> && requires { _FUN(std::declval<T>()); } 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))).

Names __NotSameAs and _FUN are exposition-only. __NotSameAs<T, U> is satisfied if and only if !std::same_as<std::remove_cvref_t<T>, std::remove_cvref_t<U>>. The function _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 ranges::iterator_t<R> begin() const;

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

std::ranges::ref_view::end

constexpr ranges::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 ranges::sized_range<R> { return ranges::size(*r_); }

std::ranges::ref_view::data

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

Non-member functions

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

friend constexpr ranges::iterator_t<R> begin(ref_view r);	(1)
friend constexpr ranges::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_viewviews::all	a view that includes all elements of a range (alias template) (range adaptor object)