std::multimap::rbegin,(3)

💅 std::multimap::rbegin,(3)

okay bestie, welcome to this page from the C++ Standard Libary manual — yes, that’s the manual name, and the title up there is std::multimap::rbegin,(3). This whole page is about the reverse-begin vibes of std::multimap. 🫶

✨ NAME ✨

std::multimap::rbegin, - std::multimap::rbegin,

no cap, that trailing comma is literally in the name and we are respecting it 💀

🧾 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)

Okay so this returns a reverse iterator to the first element of the reversed multimap. It corresponds to the last element of the non-reversed multimap. And if the multimap is empty, the returned iterator is equal to rend(). 🌀

there’s also a diagram situation: range-rbegin-rend.svg — that’s the visual bestie for this exact range-rbegin-rend energy.

🫶 Parameters

(none)

🎁 Return value

Reverse iterator to the first element.

⚡ Complexity

Constant. periodt. ⚡

🧠 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.

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

🍓 Example

// Run this code

#include <algorithm>
#include <iostream>
#include <string>
#include <map>

int main()
{
    std::multimap<std::string, int> map
    {
        {"█", 1},
        {"▒", 5},
        {"░", 3},
        {"▓", 7},
        {"▓", 8},
        {"░", 4},
        {"▒", 6},
        {"█", 2}
    };

    std::cout << "Print out in reverse order using const reverse iterators:\n";
    std::for_each(map.crbegin(), map.crend(),
        [](std::pair<const std::string, int> const& e)
        {
            std::cout << "{ \"" << e.first << "\", " << e.second << " };\n";
        });

    map.rbegin()->second = 42; // OK: non-const value is modifiable
//  map.crbegin()->second = 42; // Error: cannot modify the const value
}

🌈 Possible output

Print out in reverse order using const reverse iterators:
{ "▓", 8 };
{ "▓", 7 };
{ "▒", 6 };
{ "▒", 5 };
{ "░", 4 };
{ "░", 3 };
{ "█", 2 };
{ "█", 1 };

👀 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)

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source: http://cppreference.com · version/date: 2024.06.10 · page: std::multimap::rbegin,(3) — mwah, go reverse-iterate responsibly 💋✨