FreeBSD Manual Pages
std::bit_width(3) C++ Standard Libary std::bit_width(3) NAME std::bit_width - std::bit_width Synopsis Defined in header <bit> template< class T > (since C++20) constexpr int bit_width( T x ) noexcept; If x is not zero, calculates the number of bits needed to store the value x, that is, \(1 + \lfloor \log_2(x) \rfloor\)1 + floor(log 2(x)). If x is zero, returns zero. 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 - unsigned integer value Return value Zero if x is zero; otherwise, one plus the base-2 logarithm of x, with any fractional part discarded. Notes This function is equivalent to return std::numeric_limits<T>::digits - std::countl_zero(x);. Feature-test macro: __cpp_lib_int_pow2 Example // Run this code #include <bit> #include <bitset> #include <iostream> int main() { for (unsigned x{0}; x != 8; ++x) { std::cout << "bit_width( " << std::bitset<4>{x} << " ) = " << std::bit_width(x) << '\n'; } } Output: bit_width( 0000 ) = 0 bit_width( 0001 ) = 1 bit_width( 0010 ) = 2 bit_width( 0011 ) = 2 bit_width( 0100 ) = 3 bit_width( 0101 ) = 3 bit_width( 0110 ) = 3 bit_width( 0111 ) = 3 Defect reports The following behavior-changing defect reports were applied retroac- tively to previously published C++ standards. DR Applied to Behavior as published Correct behavior LWG 3656 C++20 the return type of bit_width is the same as the made it int type of its function argument See also countl_zero counts the number of consecutive 0 bits, starting from the most (C++20) significant bit (function template) http://cppreference.com 2022.07.31 std::bit_width(3)
NAME | Synopsis | Parameters | Return value | Notes | Example | Output: | See also
Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=std::bit_width&sektion=3&manpath=FreeBSD+Ports+15.0>