std::span::...span::crend(3)

🎀 std::span::rend, std::span::crend — C++ Standard Libary

okay bestie, welcome to the std::span::...span::crend(3) page from the C++ Standard Libary. this is the reverse-iterator end-boss squad, and it is lowkey iconic. 💅

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🌸 NAME 🌸

std::span::rend,std::span::crend — std::span::rend,std::span::crend

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✨ Synopsis ✨

constexpr reverse_iterator rend() const noexcept;        (1) (since C++20)
constexpr const_reverse_iterator crend() const noexcept; (2) (since C++23)

So here's the vibe: these functions return a reverse iterator to the element following the last element of the reversed span. It corresponds to the element preceding the first element of the non-reversed span. That element is literally just a placeholder, and attempting to access it results in undefined behavior. not cute, bestie. 😭

The original docs also drop a diagram called range-rbegin-rend.svg, which is very demure, very cppreference. 🦋

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🍓 Parameters 🍓

(none)

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💖 Return value 💖

Reverse iterator to the element following the last element. periodt. ✨

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⭐ Complexity ⭐

Constant.

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🧚 Example 🧚

// Run this code

#include <algorithm>
#include <iostream>
#include <span>
#include <string_view>

void ascending(const std::span<const std::string_view> data,
               const std::string_view term)
{
    std::for_each(data.begin(), data.end(),
        [](const std::string_view x) { std::cout << x << ' '; });
    std::cout << term;
}

void descending(const std::span<const std::string_view> data,
                const std::string_view term)
{
    std::for_each(data.rbegin(), data.rend(),
        [](const std::string_view x) { std::cout << x << ' '; });
    std::cout << term;
}

int main()
{
    constexpr std::string_view bars[]{"▁","▂","▃","▄","▅","▆","▇","█"};
    ascending(bars, " ");
    descending(bars, "\n");
}

Output:

▁ ▂ ▃ ▄ ▅ ▆ ▇ █  █ ▇ ▆ ▅ ▄ ▃ ▂ ▁

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🌈 See also 🌈

• rbegin — returns a reverse iterator to the beginning
• crbegin — (public member function) (C++23)
• rend — returns a reverse end iterator for a container or array
• crend — (function template) (C++14)

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mwah 💋 that's the whole page. source: http://cppreference.com, version/date: 2024.06.10, manual page: std::span::...span::crend(3). stay safe, and remember: that placeholder is for looking, not touching — undefined behavior is not the moment. 🎀🫶