std::popcount
From cppreference.com
C++
Utilities library
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Bit manipulation
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(C++20)
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(C++20)
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(C++20)
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(C++20)
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popcount (C++20) |
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(C++20)
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Defined in header <bit>
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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
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
Run this code
#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
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(C++20)
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counts the number of consecutive 0 bits, starting from the most significant bit (function template) |
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(C++20)
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counts the number of consecutive 1 bits, starting from the most significant bit (function template) |
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(C++20)
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counts the number of consecutive 0 bits, starting from the least significant bit (function template) |
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(C++20)
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counts the number of consecutive 1 bits, starting from the least significant bit (function template) |
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(C++20)
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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>) |
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| checks if all, any or none of the bits are set to true
(public member function of std::bitset<N>)
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