NAME¶

std::rotl - std::rotl

Synopsis¶

Defined in header <bit>
template< class T > (since C++20)
[[nodiscard]] constexpr T rotl( T x, int s ) noexcept;

Computes the result of bitwise left-rotating the value of x by s positions. This
operation is also known as a left circular shift.

Formally, let N be std::numeric_limits<T>::digits, r be s % N.

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

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).

Parameters¶

x - value of unsigned integer type
s - number of positions to shift

Return value¶

The result of bitwise left-rotating x by s positions.

Notes¶

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

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 << "rotl(i,0) = " << std::bitset<8>(std::rotl(i, 0)) << '\n';
std::cout << "rotl(i,1) = " << std::bitset<8>(std::rotl(i, 1)) << '\n';
std::cout << "rotl(i,4) = " << std::bitset<8>(std::rotl(i, 4)) << '\n';
std::cout << "rotl(i,9) = " << std::bitset<8>(std::rotl(i, 9)) << '\n';
std::cout << "rotl(i,-1) = " << std::bitset<8>(std::rotl(i, -1)) << '\n';
}

Output:¶

i = 00011101
rotl(i,0) = 00011101
rotl(i,1) = 00111010
rotl(i,4) = 11010001
rotl(i,9) = 00111010
rotl(i,-1) = 10001110

See also¶

rotr computes the result of bitwise right-rotation
(C++20) (function template)
operator<<=
operator>>= performs binary shift left and shift right
operator<< (public member function of std::bitset<N>)
operator>>