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

NAME
       std::countl_one - std::countl_one

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

	  Returns  the number of consecutive 1 ("one") bits in the value of x,
       starting	from
	  the most significant bit ("left").

	  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  consecutive 1 bits in the value of x, starting from
       the most
	  significant bit.

Notes
	  Feature-test macro: __cpp_lib_bitops

Example
       // Run this code

	#include <bit>
	#include <bitset>
	#include <cstdint>
	#include <iostream>

	int main()
	{
	    for	 (const	 std::uint8_t  i  :  {	0,   0b11111111,   0b01111111,
       0b11100011 }) {
		std::cout << "countl_one( " << std::bitset<8>(i) << " )	= "
			  << std::countl_one(i)	<< '\n';
	    }
	}

Output:
	countl_one( 00000000 ) = 0
	countl_one( 11111111 ) = 8
	countl_one( 01111111 ) = 0
	countl_one( 11100011 ) = 3

See also
	  countl_zero	  counts  the  number  of consecutive 0	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)
	  popcount	 counts	the number of 1	bits in	an unsigned integer
	  (C++20)	 (function template)
	  has_single_bit checks	if a number is an integral power of two
	  (C++20)	 (function template)
	  count		 returns the number of bits set	to true
			 (public member	function of std::bitset<N>)
	  all
	  any		 checks	if all,	any or none of the  bits  are  set  to
       true
	  none		 (public member	function of std::bitset<N>)
	  (C++11)

http://cppreference.com		  2022.07.31		    std::countl_one(3)

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