Difference between revisions of "cpp/numeric/popcount"
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===Notes=== | ===Notes=== | ||
| − | {{feature test macro|__cpp_lib_bitops}} | + | {{feature test macro|__cpp_lib_bitops|std=C++20|value=201907L|[[cpp/numeric#Bit_manipulation (since C++20)|Bit operations]]}} |
=== Example === | === Example === | ||
Revision as of 13:20, 5 October 2022
| 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, or an extended unsigned integer type).
Contents |
Parameters
| x | - | value of unsigned integer type |
Return value
The number of 1 bits in the value of x.
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() { for (const std::uint8_t i : { 0, 0b11111111, 0b00011101 }) { std::cout << "popcount( " << std::bitset<8>(i) << " ) = " << std::popcount(i) << '\n'; } }
Output:
popcount( 00000000 ) = 0 popcount( 11111111 ) = 8 popcount( 00011101 ) = 4
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>)
|
