std::popcount
Defined in header <bit> | ||
|---|---|---|
template< class T > constexpr int popcount( T x ) noexcept; | (since C++20) |
Returns the number of 1 bits in the value of x.
This overload participates in overload resolution only if T is an unsigned integer type (that is, unsignedchar, unsignedshort, unsignedint, unsignedlong, unsignedlonglong, or an extended unsigned integer type).
Parameters
| x | - | value of unsigned integer type |
Return value
The number of 1 bits in the value of x.
Notes
The name popcount is a contraction for “population count”.
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_bitops | 201907L | (C++20) | Bit operations |
Example
#include <bit>
#include <bitset>
#include <cstdint>
#include <iostream>
static_assert(std::popcount(0xFULL) == 4);
int main()
{
for (const std::uint8_t x : {0, 0b00011101, 0b11111111})
std::cout << "popcount( " << std::bitset<8>(x) << " ) = "
<< std::popcount(x) << '\n';
}
Output:
popcount( 00000000 ) = 0 popcount( 00011101 ) = 4 popcount( 11111111 ) = 8
See also
|
(C++20) | counts the number of consecutive 0 bits, starting from the most significant bit (function template) |
|
(C++20) | counts the number of consecutive 1 bits, starting from the most significant bit (function template) |
|
(C++20) | counts the number of consecutive 0 bits, starting from the least significant bit (function template) |
|
(C++20) | counts the number of consecutive 1 bits, starting from the least significant bit (function template) |
|
(C++20) | checks if a number is an integral power of 2 (function template) |
returns the number of bits set to true (public member function of std::bitset<N>) |
|
checks if all, any or none of the bits are set to true (public member function of std::bitset<N>) |
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