std::rotr(3)

💅 std::rotr(3) — C++ Standard Library

okay bestie, welcome to the std::rotr page — yes, that's the C++ Standard Library, and yes, this little icon is about to make bit rotation make sense. buckle up 🎀

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✨ NAME ✨

std::rotr — literally std::rotr. that's the name, that's the vibe, no notes 💖

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🌸 SYNOPSIS 🌸

Defined in header <bit> — that's where you go to find it, mwah.

template< class T >                                     (since C++20)
[[nodiscard]] constexpr T rotr( T x, int s ) noexcept;

So what does it actually do? It computes the result of bitwise right-rotating the value of x by s positions. This operation is also known as a right circular shift 🔄✨ (circular! like a little hamster wheel of bits, iykyk).

Formally — and bestie, we love a formal definition — let N be std::numeric_limits<T>::digits, and let r be s % N. Then:

• If r is 0, it returns x;
• if r is positive, it returns (x >> r) | (x << (N - r));
• if r is negative, it returns std::rotl(x, -r).

🫶 lowkey important: this overload participates in overload resolution only if T is an unsigned integer type (that is, unsigned char, unsigned short, unsigned int, unsigned long, unsigned long long, or an extended unsigned integer type). no signed shenanigans, we don't do that here 💅

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🦋 PARAMETERS 🦋

• x — value of unsigned integer type (the bit baddie in question 👑)
• s — number of positions to shift (how many spins we're doing)

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⭐ RETURN VALUE ⭐

The result of bitwise right-rotating x by s positions. that's it, that's the whole gift 🎁

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💜 NOTES 💜

Feature-test macro check, periodt — here's the table, done as a list because we're cute like that:

• Feature-test macro: __cpp_lib_bitops
• Value: 201907L
• Std: (C++20)
• Feature: Bit operations

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🌈 EXAMPLE 🌈

// Run this code

#include <bit>
#include <bitset>
#include <cstdint>
#include <iostream>

int main()
{
    const std::uint8_t i = 0b00011101;
    std::cout << "i          = " << std::bitset<8>(i) << '\n';
    std::cout << "rotr(i,0)  = " << std::bitset<8>(std::rotr(i, 0)) << '\n';
    std::cout << "rotr(i,1)  = " << std::bitset<8>(std::rotr(i, 1)) << '\n';
    std::cout << "rotr(i,9)  = " << std::bitset<8>(std::rotr(i, 9)) << '\n';
    std::cout << "rotr(i,-1) = " << std::bitset<8>(std::rotr(i, -1)) << '\n';
}

🍓 Output

i          = 00011101
rotr(i,0)  = 00011101
rotr(i,1)  = 10001110
rotr(i,9)  = 10001110
rotr(i,-1) = 00111010

look at that. 9 and 1 give the same answer because 9 % 8 == 1 — she's consistent, she's iconic, she ate 🔥

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🧚 SEE ALSO 🧚

• rotl — computes the result of bitwise left-rotation (C++20) (function template) — the mirror twin, obsessed 😭
• operator<<=, operator>>=, operator<<, operator>> — performs binary shift left and shift right (public member function of std::bitset<N>)

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and that's the page, bestie! 🌟 brought to you by http://cppreference.com, dated 2024.06.10, filed under std::rotr(3) — go rotate some bits responsibly, ily, bye 💅🎀💖