std::flat_map::rbegin,(3)

🎀 std::flat_map::rbegin,(3) 🎀

Okay bestie, this page is from the C++ Standard Libary manual, and it's all about std::flat_map::rbegin, — reverse iterator energy for std::flat_map, plus the const twin crbegin(). Let's go 💅

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💖 NAME 💖

std::flat_map::rbegin, — that's the name, comma and all. The original NAME line literally reads std::flat_map::rbegin, - std::flat_map::rbegin, ✨

🌸 Synopsis 🌸

reverse_iterator rbegin() noexcept;              (1) (since C++23)
const_reverse_iterator rbegin() const noexcept;  (2) (since C++23)
const_reverse_iterator crbegin() const noexcept; (3) (since C++23)

Three overloads, all noexcept, all since C++23: regular rbegin() is (1), the const rbegin() is (2), and crbegin() is (3). Slay 🫶

Returns a reverse iterator to the first element of the reversed flat_map. It corresponds to the last element of the non-reversed flat_map. If the flat_map is empty, the returned iterator is equal to rend().

There's also a diagram named range-rbegin-rend.svg in the original — very visual, very range-rbegin-to-rend 🌈

🫶 Parameters 🫶

(none) — literally nothing to pass, bestie 🎀

✨ 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.

⚠️ Translation: this reverse iterator is riding on the end iterator, so if the end iterator gets invalidated, your returned iterator gets invalidated too. Don't ignore that, bestie 😭

🦋 Example 🦋

The original page says // Run this code before the snippet, so here's the snippet:

#include <iomanip>
#include <iostream>
#include <string_view>
#include <flat_map>

int main()
{
    const std::flat_map<int, std::string_view> coins
    {
        {10, "dime"},
        {100, "dollar"},
        {50, "half dollar"},
        {5, "nickel"},
        {1, "penny"},
        {25, "quarter"}
    }; // initializer entries in name alphabetical order

    std::cout << "US coins in circulation, largest to smallest denomination:\n";
    for (auto it = coins.crbegin(); it != coins.crend(); ++it)
        std::cout << std::setw(11) << it->second << " = ¢" << it->first << '\n';
}

🌈 Output 🌈

US coins in circulation, largest to smallest denomination:
     dollar = ¢100
half dollar = ¢50
    quarter = ¢25
       dime = ¢10
     nickel = ¢5
      penny = ¢1

👑 See also 👑

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

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Byeee 🫶 — source/version is http://cppreference.com, dated 2024.06.10, for the page std::flat_map::rbegin,(3). Mwah 💋