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std::ranges::ref_view

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

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>;

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)