Difference between revisions of "cpp/numeric/countl one"
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{{cpp/title|countl_one}} | {{cpp/title|countl_one}} | ||
{{cpp/numeric/navbar}} | {{cpp/numeric/navbar}} | ||
| − | {{ddcl | header=bit | since=c++20 | | + | {{ddcl|header=bit|since=c++20| |
template< class T > | template< class T > | ||
constexpr int countl_one( T x ) noexcept; | constexpr int countl_one( T x ) noexcept; | ||
}} | }} | ||
| − | Returns the number of consecutive 1 ("one") bits in the value of {{ | + | Returns the number of consecutive {{c|1}} ("one") bits in the value of {{c|x}}, starting from the most significant bit ("left"). |
| − | {{cpp/enable_if|{{tt|T}} is an unsigned integer type (that is, {{c|unsigned char}}, {{c|unsigned short}}, {{c|unsigned int}}, {{c|unsigned long}}, {{c|unsigned long long}}, or an extended unsigned integer type)}}. | + | {{cpp/enable_if|{{tt|T}} is an unsigned integer type (that is, {{c/core|unsigned char}}, {{c/core|unsigned short}}, {{c/core|unsigned int}}, {{c/core|unsigned long}}, {{c/core|unsigned long long}}, or an extended unsigned integer type)}}. |
===Parameters=== | ===Parameters=== | ||
{{par begin}} | {{par begin}} | ||
| − | {{par | x | | + | {{par|x|value of unsigned integer type}} |
{{par end}} | {{par end}} | ||
===Return value=== | ===Return value=== | ||
| − | The number of consecutive 1 bits in the value of {{ | + | The number of consecutive {{c|1}} bits in the value of {{c|x}}, starting from the most significant bit. |
| − | === Example === | + | ===Notes=== |
| + | {{feature test macro|__cpp_lib_bitops|std=C++20|value=201907L|[[cpp/numeric#Bit_manipulation (since C++20)|Bit operations]]}} | ||
| + | |||
| + | ===Example=== | ||
{{example | {{example | ||
|code= | |code= | ||
| Line 28: | Line 31: | ||
int main() | int main() | ||
{ | { | ||
| − | for (const std::uint8_t i : { 0, 0b11111111, 0b01111111, 0b11100011 }) | + | for (const std::uint8_t i : {0, 0b11111111, 0b01111111, 0b11100011}) |
std::cout << "countl_one( " << std::bitset<8>(i) << " ) = " | std::cout << "countl_one( " << std::bitset<8>(i) << " ) = " | ||
<< std::countl_one(i) << '\n'; | << std::countl_one(i) << '\n'; | ||
| − | |||
} | } | ||
|output= | |output= | ||
| Line 40: | Line 42: | ||
}} | }} | ||
| − | === See also === | + | ===See also=== |
{{dsc begin}} | {{dsc begin}} | ||
| − | {{dsc inc | cpp/numeric/dsc countl_zero}} | + | {{dsc inc|cpp/numeric/dsc countl_zero}} |
| − | {{dsc inc | cpp/numeric/dsc countr_zero}} | + | {{dsc inc|cpp/numeric/dsc countr_zero}} |
| − | {{dsc inc | cpp/numeric/dsc countr_one}} | + | {{dsc inc|cpp/numeric/dsc countr_one}} |
| − | {{dsc inc | cpp/numeric/dsc popcount}} | + | {{dsc inc|cpp/numeric/dsc popcount}} |
| − | {{dsc inc | cpp/numeric/dsc has_single_bit}} | + | {{dsc inc|cpp/numeric/dsc has_single_bit}} |
| − | {{dsc inc | cpp/utility/bitset/dsc count}} | + | {{dsc inc|cpp/utility/bitset/dsc count}} |
| − | {{dsc inc | cpp/utility/bitset/dsc all_any_none}} | + | {{dsc inc|cpp/utility/bitset/dsc all_any_none}} |
{{dsc end}} | {{dsc end}} | ||
{{langlinks|es|ja|ru|zh}} | {{langlinks|es|ja|ru|zh}} | ||
Latest revision as of 14:10, 2 November 2024
| Defined in header <bit>
|
||
| template< class T > constexpr int countl_one( T x ) noexcept; |
(since C++20) | |
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).
Contents |
[edit] Parameters
| x | - | value of unsigned integer type |
[edit] Return value
The number of consecutive 1 bits in the value of x, starting from the most significant bit.
[edit] Notes
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_bitops |
201907L | (C++20) | Bit operations |
[edit] 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
[edit] 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 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) |
counts the number of 1 bits in an unsigned integer (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>)
|
