std::has_single_bit

Since C++20

Header: <bit>

Checks if x is an integral power of two.

# Declarations

template< class T >
constexpr bool has_single_bit( T x ) noexcept;

(since C++20)

# Parameters

# Return value

true if x is an integral power of two; otherwise false.

# Notes

Prior to P1956R1, the proposed name for this function template was ispow2.

# Example

#include <bit>
#include <bitset>
#include <cmath>
#include <iostream>
 
int main()
{
    for (auto u{0u}; u != 0B1010; ++u)
    {
        std::cout << "u = " << u << " = " << std::bitset<4>(u);
        if (std::has_single_bit(u))
            std::cout << " = 2^" << std::log2(u) << " (is power of two)";
        std::cout << '\n';
    }
}

# See also