std::popcount - cppreference.com (original) (raw)
| Defined in header | | | | -------------------------------------------------------------- | | ------------- | | 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, unsigned char, unsigned short, unsigned int, unsigned long, unsigned long long, or an extended unsigned integer type).
[edit] Parameters
| x | - | value of unsigned integer type |
|---|
[edit] Return value
The number of 1 bits in the value of x.
[edit] Notes
The name popcount is a contraction for “population count”.
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
| __cpp_lib_bitops | 201907L | (C++20) | Bit operations |
[edit] Example
#include #include #include #include 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
[edit] See also
| countl_zero(C++20) | counts the number of consecutive 0 bits, starting from the most significant bit (function template) [edit] |
|---|---|
| countl_one(C++20) | counts the number of consecutive 1 bits, starting from the most significant bit (function template) [edit] |
| countr_zero(C++20) | counts the number of consecutive 0 bits, starting from the least significant bit (function template) [edit] |
| countr_one(C++20) | counts the number of consecutive 1 bits, starting from the least significant bit (function template) [edit] |
| has_single_bit(C++20) | checks if a number is an integral power of 2 (function template) [edit] |
| count | returns the number of bits set to true (public member function of std::bitset) [edit] |
| allanynone | checks if all, any or none of the bits are set to true (public member function of std::bitset) [edit] |