std::countl_zero

 

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countl_zero (C++20)

countl_one (C++20)

countr_zero (C++20)

countr_one (C++20)

popcount (C++20)

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endian (C++20)

 

Defined in header <bit>
template<class T > constexprint countl_zero( T x )noexcept;		(since C++20)

Returns the number of consecutive ​0​ 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, unsignedchar, unsignedshort, unsignedint, unsignedlong, unsignedlonglong, or an extended unsigned integer type).

Parameters

x

-

value of unsigned integer type

Return value

The number of consecutive ​0​ bits in the value of x, starting from the most significant bit.

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(conststd::uint8_t i :{0, 0b11111111, 0b11110000, 0b00011110})std::cout<<"countl_zero( "<<std::bitset<8>(i)<<" ) = "<< std::countl_zero(i)<<'\n';}

Output:

countl_zero( 00000000 ) = 8 countl_zero( 11111111 ) = 0 countl_zero( 11110000 ) = 0 countl_zero( 00011110 ) = 3

See also

countl_one (C++20)	counts the number of consecutive 1 bits, starting from the most significant bit (function template)
countr_zero (C++20)	counts the number of consecutive ​0​ bits, starting from the least significant bit (function template)
countr_one (C++20)	counts the number of consecutive 1 bits, starting from the least significant bit (function template)
popcount (C++20)	counts the number of 1 bits in an unsigned integer (function template)
allanynone	checks if all, any or none of the bits are set to true (public member function of std::bitset<N>)
C documentation for stdc_leading_zeros