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std::ranges::views::as_rvalue, std::ranges::as_rvalue_view

Defined in header <ranges> 
template< ranges::view V >
    requires ranges::input_range<V>
class as_rvalue_view :
    public ranges::view_interface<as_rvalue_view<V>>
 (1) (since C++23) 
namespace views {
    inline constexpr /* unspecified */ as_rvalue = /* unspecified */;
}
 (2) (since C++23)
Call signature 
template< ranges::viewable_range R >
    requires /* see below */
constexpr ranges::view auto as_rvalue( R&& r );
 (since C++23)
1) A range adaptor that represents a view of underlying view whose elements are rvalues.
2) RangeAdaptorObject. Let e be a subexpression and let T be decltype((e)). Then the expression views::as_rvalue(e) is expression-equivalent to:

Data members

Typical implementations of as_rvalue_view only hold one non-static data member:

  • the underlying view of type V (shown here as base_, the name is exposition only).

Member functions

(C++23)
 constructs an as_rvalue_view
(public member function)
(C++23)
 returns the underlying view V
(public member function)
(C++23)
 returns the beginning iterator of the as_rvalue_view
(public member function)
(C++23)
 returns the end iterator of the as_rvalue_view
(public member function)
(C++23)
 returns the size of the view if it is bounded
(public member function)
Inherited from std::ranges::view_interface
(C++20)
 returns whether the derived view is empty. Provided if it satisfies sized_range or forward_range.
(public member function of std::ranges::view_interface<D>)
(C++23)
 returns a constant iterator to the beginning of the range.
(public member function of std::ranges::view_interface<D>)
(C++23)
 returns a sentinel for the constant iterator of the range.
(public member function of std::ranges::view_interface<D>)
(C++20)
 returns whether the derived view is not empty. Provided if ranges::empty is applicable to it.
(public member function of std::ranges::view_interface<D>)
(C++20)
 returns the first element in the derived view. Provided if it satisfies forward_range.
(public member function of std::ranges::view_interface<D>)
(C++20)
 returns the last element in the derived view. Provided if it satisfies bidirectional_range and common_range.
(public member function of std::ranges::view_interface<D>)
(C++20)
 returns the nth element in the derived view. Provided if it satisfies random_access_range.
(public member function of std::ranges::view_interface<D>)

std::ranges::as_rvalue_view::as_rvalue_view

as_rvalue_view() requires std::default_initializable<V> = default;
 (1) (since C++23) 
constexpr explicit as_rvalue_view( V base );
 (2) (since C++23)
1) Value-initializes base_ via its default member initializer (= V()).
2) Initializes base_ with std::move(base).

Parameters

base - a view

std::ranges::as_rvalue_view::base

constexpr V base() const& requires std::copy_constructible<V>;
 (1) (since C++23) 
constexpr V base() &&;
 (2) (since C++23)

Returns the underlying view.

1) Copy-constructs the result from the underlying view. Equivalent to return base_;.
2) Move-constructs the result from the underlying view. Equivalent to return std::move(base_);.

std::ranges::as_rvalue_view::begin

constexpr auto begin() requires (!__simple_view<V>);
 (1) (since C++23) 
constexpr auto begin() const requires ranges::range<const V>;
 (2) (since C++23)
1,2) Returns std::move_iterator(ranges::begin(base_)).

std::ranges::as_rvalue_view::end

constexpr auto end() requires (!__simple_view<V>);
 (1) (since C++23) 
constexpr auto end() const requires ranges::range<const V>;
 (2) (since C++23)
1) Returns std::move_iterator(ranges::end(base_)) if V models common_range, otherwise std::move_sentinel(ranges::end(base_)).
2) Returns std::move_iterator(ranges::end(base_)) if const V models common_range, otherwise std::move_sentinel(ranges::end(base_)).

std::ranges::as_rvalue_view::size

constexpr auto size() requires ranges::sized_range<V>;
 (1) (since C++23) 
constexpr auto size() const requires ranges::sized_range<const V>;
 (2) (since C++23)

Returns the size of the view if the view is bounded.

1,2) Equivalent to return ranges::size(base_);

Deduction guides

template< class R >
as_rvalue_view( R&& ) -> as_rvalue_view<views::all_t<R>>;
 (since C++23)

Helper templates

template< class T >
inline constexpr bool enable_borrowed_range<std::ranges::as_rvalue_view<T>> =
    std::ranges::enable_borrowed_range<T>;
 (since C++23)

This specialization of std::ranges::enable_borrowed_range makes as_rvalue_view satisfy borrowed_range when the underlying view satisfies it.

Notes

Feature-test macro Value Std Comment
__cpp_lib_ranges_as_rvalue 202207L (C++23) std::ranges::as_rvalue_view

Example

See also

(C++11)
 iterator adaptor which dereferences to an rvalue reference
(class template)
(C++20)
 sentinel adaptor for use with std::move_iterator
(class template)
(C++23)
 converts a view into a constant_range
(class template) (range adaptor object)

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