std::deque::rbegin,std::deque::crbegin(3)

NAME
std::deque::rbegin,std::deque::crbegin - std::deque::rbegin,std::deque::crbegin

Synopsis
   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 deque. It
   corresponds to the last element of the non-reversed deque. If the deque is empty,
   the returned iterator is equal to rend().
   range-rbegin-rend.svg

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

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

See also
   rend returns a reverse iterator to the end
   crend (public member function)
   (C++11)
   rbegin returns a reverse iterator to the beginning of a container or array
   crbegin (function template)
   (C++14)