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std::list<T,Allocator>::rbegin, std::list<T,Allocator>::crbegin

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< cpp‎ | container‎ | list
Revision as of 12:13, 4 May 2012 by P12bot (Talk | contribs)

 
 
 
 
reverse_iterator rbegin();
(1) (noexcept since C++11)
const_reverse_iterator rbegin() const;
(2) (noexcept since C++11)
const_reverse_iterator crbegin() const noexcept;
(3) (since C++11)

Returns a reverse iterator to the first element of the reversed list. It corresponds to the last element of the non-reversed list. If the list is empty, the returned iterator is equal to rend().

range-rbegin-rend.svg

Contents

Parameters

(none)

Return value

Reverse iterator to the first element.

Complexity

Constant.

Notes

The underlying iterator of the returned reverse iterator is the end iterator. Hence the returned iterator is invalidated if and when the end iterator is invalidated.

libc++ backports crbegin() to C++98 mode.

Example

#include <algorithm>
#include <iostream>
#include <numeric>
#include <string>
#include <list>
 
int main()
{
    std::list<int> nums{1, 2, 4, 8, 16};
    std::list<std::string> fruits{"orange", "apple", "raspberry"};
    std::list<char> empty;
 
    // Print list.
    std::for_each(nums.rbegin(), nums.rend(), [](const int n) { std::cout << n << ' '; });
    std::cout << '\n';
 
    // Sums all integers in the list nums (if any), printing only the result.
    std::cout << "Sum of nums: "
              << std::accumulate(nums.rbegin(), nums.rend(), 0) << '\n';
 
    // Prints the first fruit in the list fruits, checking if there is any.
    if (!fruits.empty())
        std::cout << "First fruit: " << *fruits.rbegin() << '\n';
 
    if (empty.rbegin() == empty.rend())
        std::cout << "list 'empty' is indeed empty.\n";
}

Output:

16 8 4 2 1
Sum of nums: 31
First fruit: raspberry
list 'empty' is indeed empty.

See also

(C++11)
returns a reverse iterator to the end
(public member function) [edit]
returns a reverse iterator to the beginning of a container or array
(function template) [edit]