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Defined in header <ranges> | ||
template<ranges::view V> requiresranges::input_range<V> | (1) | (since C++23) |
namespace views{ inlineconstexpr/* unspecified */ as_rvalue=/* unspecified */; | (2) | (since C++23) |
Call signature | ||
template<ranges::viewable_range R> requires/* see below */ | (since C++23) | |
view whose elements are rvalues.T bedecltype((e)). Then the expressionviews::as_rvalue(e) isexpression-equivalent to:T modelsinput_range, andstd::same_as<ranges::range_rvalue_reference_t<T>,ranges::range_reference_t<T>> istrue;Contents |
| Member | Description |
Vbase_(private) | the underlying view (exposition-only member object*) |
constructs anas_rvalue_view(public member function) | |
returns the underlying viewV(public member function) | |
returns the beginning iterator of theas_rvalue_view(public member function) | |
returns the end iterator of theas_rvalue_view(public member function) | |
| returns the size of the view if it is bounded (public member function) | |
(C++26) | returns the approximate size of the underlyingapproximately_sized_range(public member function) |
Inherited fromstd::ranges::view_interface | |
returns whether the derived view is empty, provided only if it satisfiessized_range orforward_range(public member function of std::ranges::view_interface<D>)[edit] | |
(C++23) | returns a constant iterator to the beginning of the range (public member function of std::ranges::view_interface<D>)[edit] |
(C++23) | returns a sentinel for the constant iterator of the range (public member function of std::ranges::view_interface<D>)[edit] |
| returns whether the derived view is not empty, provided only ifranges::empty is applicable to it (public member function of std::ranges::view_interface<D>)[edit] | |
returns the first element in the derived view, provided if it satisfiesforward_range(public member function of std::ranges::view_interface<D>)[edit] | |
returns the last element in the derived view, provided only if it satisfiesbidirectional_range andcommon_range(public member function of std::ranges::view_interface<D>)[edit] | |
returns thenth element in the derived view, provided only if it satisfiesrandom_access_range(public member function of std::ranges::view_interface<D>)[edit] | |
as_rvalue_view() requiresstd::default_initializable<V>=default; | (1) | (since C++23) |
constexprexplicit as_rvalue_view( V base); | (2) | (since C++23) |
| base | - | a view |
constexpr V base()const& requiresstd::copy_constructible<V>; | (1) | (since C++23) |
constexpr V base()&&; | (2) | (since C++23) |
Returns the underlying view.
base_ ;.base_ );.constexprauto begin() requires(!/*simple-view*/<V>); | (1) | (since C++23) |
constexprauto begin()const requiresranges::range<const V>; | (2) | (since C++23) |
Returnsstd::move_iterator(ranges::begin(base_ )).
constexprauto end() requires(!/*simple-view*/<V>); | (1) | (since C++23) |
constexprauto end()const requiresranges::range<const V>; | (2) | (since C++23) |
Returnsstd::move_iterator(ranges::end(base_ )) if(1)V or(2)const V modelscommon_range.
Returnsstd::move_sentinel(ranges::end(base_ )) otherwise.
constexprauto size() requiresranges::sized_range<V>; | (1) | (since C++23) |
constexprauto size()const requiresranges::sized_range<const V>; | (2) | (since C++23) |
Returns the size of the view if the view is bounded. Equivalent toreturnranges::size(base_ );.
constexprauto reserve_hint() requires ranges::approximately_sized_range<V>; | (1) | (since C++26) |
constexprauto reserve_hint()const requires ranges::approximately_sized_range<const V>; | (2) | (since C++26) |
Returnsranges::reserve_hint(base_ ).
template<class R> as_rvalue_view( R&&)-> as_rvalue_view<views::all_t<R>>; | (since C++23) | |
template<class T> constexprbool enable_borrowed_range<std::ranges::as_rvalue_view<T>>= | (since C++23) | |
This specialization ofranges::enable_borrowed_range makesas_rvalue_view satisfyborrowed_range when the underlying view satisfies it.
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_ranges_as_rvalue | 202207L | (C++23) | std::ranges::as_rvalue_view |
__cpp_lib_ranges_reserve_hint | 202502L | (C++26) | ranges::approximately_sized_range andreserve_hint |
#include <algorithm>#include <iostream>#include <ranges>#include <string>#include <vector> int main(){std::vector<std::string> words={"Quick","red","\N{FOX FACE}","jumped","over","a","pterodactyl"};std::vector<std::string> new_words; std::ranges::copy( words| std::views::as_rvalue,std::back_inserter(new_words));// move string from words into new_words auto quoted= std::views::transform([](auto&& s){return"“"+ s+"”";}); std::cout<<"Old words: ";for(auto&& word: words| std::views::as_rvalue| quoted)std::cout<< word<<' '; std::cout<<"\nNew words: ";for(auto&& word: new_words| std::views::as_rvalue| quoted)std::cout<< word<<' ';}
Possible output:
Old words: “” “” “” “” “” “” “” New words: “Quick” “red” “🦊” “jumped” “over” “a” “pterodactyl”
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 4083 | C++23 | views::as_rvalue used to accept non-input ranges | made rejected |
(C++20) | casts the result of dereferencing an object to its associated rvalue reference type (customization point object)[edit] |
(C++11) | iterator adaptor which dereferences to an rvalue (class template)[edit] |
(C++20) | sentinel adaptor forstd::move_iterator (class template)[edit] |
converts aview into aconstant_range(class template)(range adaptor object)[edit] |
