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std::rend, std::crend

From cppreference.com
< cpp‎ | iterator
 
 
Iterator library
Iterator concepts
Iterator primitives
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Indirect callable concepts
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(C++20)
(C++20)
(C++20)
Utilities
(C++20)
Iterator adaptors
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Iterator operations
(C++11)    
(C++11)
Range access
(C++11)(C++14)
(C++14)(C++14)    
(C++11)(C++14)
rendcrend
(C++14)(C++14)    
(C++17)(C++20)
(C++17)
(C++17)
 
Defined in header <array>
Defined in header <deque>
Defined in header <flat_map>
Defined in header <flat_set>
Defined in header <forward_list>
Defined in header <iterator>
Defined in header <list>
Defined in header <map>
Defined in header <regex>
Defined in header <set>
Defined in header <span>
Defined in header <string>
Defined in header <string_view>
Defined in header <unordered_map>
Defined in header <unordered_set>
Defined in header <vector>
(1)
template< class C >
auto rend( C& c ) -> decltype(c.rend());
(since C++14)
(until C++17)
template< class C >
constexpr auto rend( C& c ) -> decltype(c.rend());
(since C++17)
(2)
template< class C >
auto rend( const C& c ) -> decltype(c.rend());
(since C++14)
(until C++17)
template< class C >
constexpr auto rend( const C& c ) -> decltype(c.rend());
(since C++17)
(3)
template< class T, std::size_t N >
std::reverse_iterator<T*> rend( T (&array)[N] );
(since C++14)
(until C++17)
template< class T, std::size_t N >
constexpr std::reverse_iterator<T*> rend( T (&array)[N] );
(since C++17)
(4)
template< class T >
std::reverse_iterator<const T*> rend( std::initializer_list<T> il );
(since C++14)
(until C++17)
template< class T >
constexpr std::reverse_iterator<const T*> rend( std::initializer_list<T> il );
(since C++17)
(5)
template< class C >
auto crend( const C& c ) -> decltype(std::rend(c));
(since C++14)
(until C++17)
template< class C >
constexpr auto crend( const C& c ) -> decltype(std::rend(c));
(since C++17)

Returns an iterator to the reverse-end of the given range.

1,2) Returns c.rend(), which is typically an iterator one past the reverse-end of the sequence represented by c.
1) If C is a standard Container, returns a C::reverse_iterator object.
2) If C is a standard Container, returns a C::const_reverse_iterator object.
3) Returns an std::reverse_iterator<T*> object to the reverse-end of array.
4) Returns an std::reverse_iterator<const T*> object to the reverse-end of il.
5) Returns std::end(c), with c always treated as const-qualified.
If C is a standard Container, returns a C::const_reverse_iterator object.

range-rbegin-rend.svg

Contents

[edit] Parameters

c - a container or view with a rend member function
array - an array of arbitrary type
il - an std::initializer_list

[edit] Return value

1,2) c.rend()
3) std::reverse_iterator<T*>(array)
4) std::reverse_iterator<const T*>(il.begin())
5) c.rend()

[edit] Exceptions

May throw implementation-defined exceptions.

[edit] Overloads

Custom overloads of rend may be provided for classes and enumerations that do not expose a suitable rend() member function, yet can be iterated.

Overloads of rend found by argument-dependent lookup can be used to customize the behavior of std::ranges::rend and std::ranges::crend.

(since C++20)

[edit] Notes

The overload for std::initializer_list is necessary because it does not have a member function rend.

[edit] Example

#include <algorithm>
#include <iostream>
#include <iterator>
#include <vector>
 
int main()
{
    int a[]{4, 6, -3, 9, 10};
    std::cout << "C-style array `a` backwards: ";
    std::copy(std::rbegin(a), std::rend(a), std::ostream_iterator<int>(std::cout, " "));
 
    auto il = {3, 1, 4};
    std::cout << "\nstd::initializer_list `il` backwards: ";
    std::copy(std::rbegin(il), std::rend(il), std::ostream_iterator<int>(std::cout, " "));
 
    std::vector<int> v{4, 6, -3, 9, 10};
    std::cout << "\nstd::vector `v` backwards: ";
    std::copy(std::rbegin(v), std::rend(v), std::ostream_iterator<int>(std::cout, " "));
    std::cout << '\n';
}

Output:

C-style array `a` backwards: 10 9 -3 6 4
std::initializer_list `il` backwards: 4 1 3
std::vector `v` backwards: 10 9 -3 6 4

[edit] See also

(C++11)(C++14)
returns an iterator to the end of a container or array
(function template) [edit]
returns a reverse iterator to the beginning of a container or array
(function template) [edit]
(C++11)(C++14)
returns an iterator to the beginning of a container or array
(function template) [edit]
returns a reverse end iterator to a range
(customization point object)[edit]
returns a reverse end iterator to a read-only range
(customization point object)[edit]