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std::popcount(3)	      C++ Standard Libary	      std::popcount(3)

NAME
       std::popcount - std::popcount

Synopsis
	  Defined in header <bit>
	  template< class T >			   (since C++20)
	  constexpr int	popcount( T x )	noexcept;

	  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
       // 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
	  countl_zero	 counts	the number of  consecutive  0  bits,  starting
       from the	most
	  (C++20)	 significant bit
			 (function template)
	  countl_one	  counts  the  number  of consecutive 1	bits, starting
       from the	most
	  (C++20)	 significant bit
			 (function template)
	  countr_zero	 counts	the number of  consecutive  0  bits,  starting
       from the	least
	  (C++20)	 significant bit
			 (function template)
	  countr_one	  counts  the  number  of consecutive 1	bits, starting
       from the	least
	  (C++20)	 significant bit
			 (function template)
	  has_single_bit checks	if a number is an integral power of 2
	  (C++20)	 (function template)
	  count		 returns the number of bits set	to true
			 (public member	function of std::bitset<N>)
	  all		 checks	if all,	any or none of the  bits  are  set  to
       true
	  any		 (public member	function of std::bitset<N>)
	  none

http://cppreference.com		  2024.06.10		      std::popcount(3)

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