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,
unsigned
char
,
unsigned
short
,
unsigned
int
,
unsigned
long
,
unsigned
long
long
, 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>
)
|