std::map::rend,std::map::crend(3)

NAME
std::map::rend,std::map::crend - std::map::rend,std::map::crend

Synopsis
   reverse_iterator rend(); (until C++11)
   reverse_iterator rend() noexcept; (since C++11)
   const_reverse_iterator rend() const; (until C++11)
   const_reverse_iterator rend() const noexcept; (since C++11)
   const_reverse_iterator crend() const noexcept; (since C++11)
   Returns a reverse iterator to the element following the last element of the reversed
   map. It corresponds to the element preceding the first element of the non-reversed
   map. This element acts as a placeholder, attempting to access it results in
   undefined behavior.
   range-rbegin-rend.svg

Parameters
   (none)

Return value
   Reverse iterator to the element following the last element.

Complexity
   Constant.

Example
// Run this code
 #include <iostream>
 #include <iomanip>
 #include <chrono>
 #include <map>
 #include <string_view>
 using namespace std::chrono;
 // until C++20 chrono operator<< ready
 std::ostream& operator<<(std::ostream& os, const year_month_day& ymd) {
     return os << std::setfill('0') << static_cast<int>(ymd.year()) << '/'
               << std::setw(2) << static_cast<unsigned>(ymd.month()) << '/'
               << std::setw(2) << static_cast<unsigned>(ymd.day());
 }
 int main()
 {
     const std::map<year_month_day, int> messages {
         { February/17/2023 , 10 },
         { February/17/2023 , 20 },
         { February/16/2022 , 30 },
         { October/22/2022 , 40 },
         { June/14/2022 , 50 },
         { November/23/2021 , 60 },
         { December/10/2022 , 55 },
         { December/12/2021 , 45 },
         { April/1/2020 , 42 },
         { April/1/2020 , 24 },
     };
     std::cout << "Messages received, reverse date order:\n";
     for (auto it = messages.crbegin(); it != messages.crend(); ++it) {
         std::cout << it->first << " : " << it->second << '\n';
     }
 }

Possible output:
 Messages received, reverse date order:
 2023/02/17 : 10
 2022/12/10 : 55
 2022/10/22 : 40
 2022/06/14 : 50
 2022/02/16 : 30
 2021/12/12 : 45
 2021/11/23 : 60
 2020/04/01 : 42

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