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std::ranges::ref_view

From cppreference.com
< cpp‎ | ranges
 
 
 
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.

Contents

[edit] Data members

std::ranges::ref_view::r_

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

pointer to the referenced range

[edit] 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_); }

[edit] 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.

[edit] Deduction guides

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

[edit] Example

[edit] See also

CopyConstructible and CopyAssignable reference wrapper
(class template) [edit]
a view that includes all elements of a range
(alias template) (range adaptor object) [edit]