std::ranges::view::reverse, std::ranges::reverse_view
template< View V > requires BidirectionalRange<V> |
(1) | (since C++20) |
namespace view { inline constexpr /*unspecified*/ reverse = /*unspecified*/; |
(2) | (since C++20) |
1) A range adaptor that represents a view of underlying
View
with reversed order.2) The expression view::reverse(E) is expression-equivalent to (has the same effect as) one of the following expressions, except that
E
is evaluated only once:
- E.base(), if the type of
E
is a (possibly cv-qualified) specialization ofreverse_view
; - otherwise, if the type of
E
is (possibly cv-qualified)ranges::subrange<std::reverse_iterator<I>, std::reverse_iterator<I>, K>
for some iterator typeI
and valueK
of typeranges::subrange_kind
:
- ranges::subrange<I, I, K>(E.end().base(), E.begin().base(), E.size()), if
K
isranges::subrange_kind::sized
; - otherwise ranges::subrange<I, I, K>(E.end().base(), E.begin().base());
- ranges::subrange<I, I, K>(E.end().base(), E.begin().base(), E.size()), if
- otherwise ranges::reverse_view{E}.
view::reverse
unwraps reversed views if possible.Data members
std::ranges::reverse_view::base_
V base_ = V(); /* exposition-only */ |
||
the underlying view
Member functions
std::ranges::reverse_view::reverse_view
reverse_view() = default; |
(1) | |
constexpr reverse_view(V base); |
(2) | |
template<ViewableRange R> requires BidirectionalRange<R> && Constructible<V, all_view<R>> |
(3) | |
1) Value-initializes
base_
2) Initializes
base_
with std::move(base).Parameters
r | - | range to reverse |
std::ranges::reverse_view::base
constexpr V base() const; |
||
Equivalent to return base_;
std::ranges::reverse_view::begin
constexpr std::reverse_iterator<ranges::iterator_t<V>> begin(); |
(1) | |
constexpr std::reverse_iterator<ranges::iterator_t<V>> begin() requires CommonRange<V>; |
(2) | |
constexpr std::reverse_iterator<ranges::iterator_t<const V>> begin() const requires CommonRange<const V>; |
(2) | |
1) Returns std::make_reverse_iterator(ranges::next(ranges::begin(base_), ranges::end(base_))). In order to provide the amortized constant time complexity required by the
Range
concept, this function caches the result within the reverse_view
object for use on subsequent calls.2) Equivalent to return std::make_reverse_iterator(ranges::end(base_));.
std::ranges::reverse_view::end
constexpr std::reverse_iterator<ranges::iterator_t<V>> end() requires CommonRange<V>; |
||
constexpr std::reverse_iterator<ranges::iterator_t<const V>> end() const requires CommonRange<const V>; |
||
Equivalent to return std::make_reverse_iterator(ranges::begin(base_));.
std::ranges::reverse_view::size
constexpr auto size() requires SizedRange<V> { return ranges::size(base_); |
||
constexpr auto size() const requires SizedRange<const V> { return ranges::size(base_); |
||
Returns the size of the view if the view is bounded.
Deduction guides
template<class R> reverse_view(R&&) -> reverse_view<all_view<R>>; |
||
Example
Run this code
#include <array> #include <ranges> #include <iostream> int main() { std::array<int, 6> il {3, 1, 4, 1, 5, 9}; std::ranges::reverse_view rv {il}; for (int i : rv) std::cout << i << ' '; }
Output:
9 5 1 4 1 3
See also
iterator adaptor for reverse-order traversal (class template) |