std::ranges::views::as_rvalue, std::ranges::as_rvalue_view
<ranges>
requires ranges::input_range <V>
class as_rvalue_view
inline constexpr /* unspecified */ as_rvalue = /* unspecified */;
requires /* see below */
view
whose elements are rvalues.T
be decltype((e)). Then the expression views::as_rvalue(e) is expression-equivalent to:
- views::all (e), if it is a well-formed expression,
T
modelsinput_range
, and std::same_as <ranges::range_rvalue_reference_t <T>, ranges::range_reference_t <T>> is true; - as_rvalue_view{e} otherwise.
Contents
[edit] Data members
V
base_
(private)
the underlying view(exposition-only member object*)
[edit] Member functions
approximately_sized_range
(public member function)
Inherited from std::ranges::view_interface
sized_range
or forward_range
(public member function of
std::ranges::view_interface<D>
) [edit]
(public member function of
std::ranges::view_interface<D>
) [edit]
(public member function of
std::ranges::view_interface<D>
) [edit]
(public member function of
std::ranges::view_interface<D>
) [edit]
forward_range
(public member function of
std::ranges::view_interface<D>
) [edit]
bidirectional_range
and common_range
(public member function of
std::ranges::view_interface<D>
) [edit]
n
th element in the derived view, provided only if it satisfies random_access_range
(public member function of
std::ranges::view_interface<D>
) [edit]
std::ranges::as_rvalue_view::as_rvalue_view
Parameters
std::ranges::as_rvalue_view::base
Returns the underlying view.
base_
;.base_
);.
std::ranges::as_rvalue_view::begin
Returns std::move_iterator (ranges::begin (base_
)).
std::ranges::as_rvalue_view::end
Returns std::move_iterator (ranges::end (base_
)) if (1) V
or (2) const V models common_range
.
Returns std::move_sentinel (ranges::end (base_
)) otherwise.
std::ranges::as_rvalue_view::size
Returns the size of the view if the view is bounded. Equivalent to return ranges::size (base_
);.
std::ranges::as_rvalue_view::reserve_hint
requires ranges::approximately_sized_range<V>;
requires ranges::approximately_sized_range<const V>;
Returns ranges::reserve_hint(base_
).
[edit] Deduction guides
as_rvalue_view( R&& ) -> as_rvalue_view<views::all_t <R>>;
[edit] Helper templates
constexpr bool enable_borrowed_range<std::ranges::as_rvalue_view<T>> =
This specialization of ranges::enable_borrowed_range makes as_rvalue_view
satisfy borrowed_range
when the underlying view satisfies it.
[edit] Notes
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 and reserve_hint
|
[edit] Example
#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"
[edit] Defect reports
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 |
[edit] See also
(customization point object)[edit]