std::multimap::rend,(3)

✨ std::multimap::rend 💅

okay bestie, so this is the std::multimap::rend page from the C++ Standard Library — and it's literally the reverse-end iterator of a multimap. iconic behavior, no cap.

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🌸 SYNOPSIS 🌸

reverse_iterator rend();                       (1) (noexcept since C++11)
const_reverse_iterator rend() const;           (2) (noexcept since C++11)
const_reverse_iterator crend() const noexcept; (3) (since C++11)

So what is it giving? It returns a reverse iterator to the element following the last element of the reversed multimap. Think about it like the mirror-world version of your map — and this iterator corresponds to the element preceding the first element of the non-reversed multimap. 😭

Now the important part, bestie: this element acts as a placeholder. That means attempting to access it results in undefined behavior. fr fr, do not dereference it. It's giving "look but don't touch" energy. 🙈

range-rbegin-rend.svg

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🎀 PARAMETERS 🎀

none. (none.) you want a parameter? there isn't one. periodt. ✨

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🦋 RETURN VALUE 🦋

Reverse iterator to the element following the last element. That's it, that's the whole vibe. 🫶

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⭐ COMPLEXITY ⭐

Constant. lowkey the easiest thing ever. 💅

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💖 NOTES 💖

libc++ backports crend() to C++98 mode. cute of them, honestly. 🌸

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🌈 EXAMPLE 🌈

// Run this code

#include <chrono>
#include <iomanip>
#include <iostream>
#include <string_view>
#include <map>

using namespace std::chrono;

int main()
{
    const std::multimap<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 (date order is reversed):\n";
    for (auto it = messages.crbegin(); it != messages.crend(); ++it)
        std::cout << it->first << " : " << it->second << '\n';
}

💀 Possible output 💀

Messages received (date order is reversed):
2023-02-17 : 20
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 : 24
2020-04-01 : 42

see how it's walking backwards through the dates? main character energy, honestly. and note the duplicate April/1/2020 entries — it's a multimap, bestie, duplicates are its whole thing. slay. 🔥

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👑 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)

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bestie reminder: rend() points past the last element of the reversed view. dereferencing it = undefined behavior = we don't do that here. 🫶

signing off from cppreference.com, version 2024.06.10 — go forth and reverse-iterate responsibly, love u, mwah 💜