std::bitset::operator[](3)

🌸 std::bitset::operator[](3) 🌸

okay so this page is from the C++ Standard Libary manual, and it’s literally all about indexing into a std::bitset — slay 💅✨

🎀 NAME 🎀

std::bitset::operator[] - std::bitset::operator[]

✨ Synopsis ✨

bool operator[]( std::size_t pos ) const; (1) (constexpr since C++11)
reference operator[]( std::size_t pos );  (2) (constexpr since C++23)

Bestie, here’s the vibe: this accesses the bit at position pos. Version (1) returns the value of the bit, and version (2) returns an object of type std::bitset::reference that allows modification of the value. 🫶

⚠️ Unlike test(), this does not throw exceptions: the behavior is undefined if pos is out of bounds. Not a cute look, so keep pos in range, okay? 😭

💖 Parameters 💖

• pos — position of the bit to return

🌈 Return value 🌈

1. The value of the requested bit.
2. An object of type std::bitset::reference, which allows writing to the requested bit.

🚫 Exceptions 🚫

• (none)

🍓 Example 🍓

// Run this code 👇

#include <bitset>
#include <cstddef>
#include <iostream>

int main()
{
    std::bitset<8> b1{0b00101010}; // binary literal for 42

    for (std::size_t i = 0; i < b1.size(); ++i)
        std::cout << "b1[" << i << "]: " << b1[i] << '\n';
    b1[0] = true; // modifies the first bit through bitset::reference

    std::cout << "After setting bit 0, b1 holds " << b1 << '\n';
}

Output

b1[0]: 0
b1[1]: 1
b1[2]: 0
b1[3]: 1
b1[4]: 0
b1[5]: 1
b1[6]: 0
b1[7]: 0
After setting bit 0, b1 holds 00101011

🧚 Defect reports 🧚

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

• DR LWG 11, applied to C++98 — behavior as published: 1. the description was missing in the C++ standard; 2. there was only the non-const overload. Correct behavior: 1. description added; 2. added the const overload. 💀✨
• DR LWG 907, applied to C++98 — behavior as published: the behavior of reading the bit at pos was equivalent to that of test(pos), but test() may throw exceptions. Correct behavior: avoids mentioning test(). 👑

👑 See also 👑

• test — accesses specific bit (public member function)

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mwah 💋 source/version: http://cppreference.com · date: 2024.06.10 — bye bestie, go index those bits responsibly 🫶✨