std::list::...st::crbegin(3)

💅 NAME 💅

std::list::rbegin, std::list::crbegin — that’s the name, bestie, and this is the C++ Standard Library manual page for it. The header is out here spelling the manual name as C++ Standard Libary and repeating the page title like std::list::rbegin,std::list::crbegin - std::list::rbegin,std::list::crbegin, and honestly? Commitment. 💅

---

🎀 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)

So rbegin() gives you a reverse iterator to the first element of the reversed list. That same iterator corresponds to the last element of the non-reversed list. And if the list is empty? The returned iterator is equal to rend(). Cute, consistent, no surprises. 💖

There’s also a diagram literally named range-rbegin-rend.svg in the original, doing the visual explanation thing.

---

🌸 Parameters 🌸

(none) — literally no parameters. Not a single one. 💀

---

✨ Return value ✨

Reverse iterator to the first element. That’s the return value, periodt.

---

🦋 Complexity 🦋

Constant. That’s the whole vibe.

---

💜 Notes 💜

The underlying iterator of the returned reverse iterator is the end iterator. So the returned iterator is invalidated if and when the end iterator is invalidated — that’s the caveat, bestie, keep it in mind. ⚠️

libc++ backports crbegin() to C++98 mode. Slay for backward compatibility. 💜

---

🍓 Example 🍓

Here’s the example from the page. It starts with the literal comment // Run this code, so we’re keeping that exactly:

// Run this code

#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 🌈

• 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) 🦋

---

source/version: http://cppreference.com • date: 2024.06.10 • page: std::list::...st::crbegin(3) — byeee, go reverse-iterate something cute. 🫶✨