FreeBSD Manual Pages
std::bit_floor(3) C++ Standard Libary std::bit_floor(3) NAME std::bit_floor - std::bit_floor Synopsis Defined in header <bit> template< class T > (since C++20) constexpr T bit_floor( T x ) noexcept; If x is not zero, calculates the largest integral power of two that is not greater than 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, the largest integral power of two that is not greater than x. Notes Feature-test macro: __cpp_lib_int_pow2 Possible implementation template <std::unsigned_integral T> requires !std::same_as<T, bool> && !std::same_as<T, char> && !std::same_as<T, char8_t> && !std::same_as<T, char16_t> && !std::same_as<T, char32_t> && !std::same_as<T, wchar_t> constexpr T bit_floor(T x) noexcept { if (x != 0) return T{1} << (std::bit_width(x) - 1); return 0; } Example // Run this code #include <bit> #include <bitset> #include <iostream> int main() { using bin = std::bitset<8>; for (unsigned x = 0; x != 10; ++x) { auto const z = std::bit_floor(x); // `floor2` before P1956R1 std::cout << "bit_floor( " << bin(x) << " ) = " << bin(z) << '\n'; } } Output: bit_floor( 00000000 ) = 00000000 bit_floor( 00000001 ) = 00000001 bit_floor( 00000010 ) = 00000010 bit_floor( 00000011 ) = 00000010 bit_floor( 00000100 ) = 00000100 bit_floor( 00000101 ) = 00000100 bit_floor( 00000110 ) = 00000100 bit_floor( 00000111 ) = 00000100 bit_floor( 00001000 ) = 00001000 bit_floor( 00001001 ) = 00001000 See also bit_ceil finds the smallest integral power of two not less than the given (C++20) value (function template) rotr computes the result of bitwise right-rotation (C++20) (function template) bit_width finds the smallest number of bits needed to represent the given value (C++20) (function template) has_single_bit checks if a number is an integral power of two (C++20) (function template) http://cppreference.com 2022.07.31 std::bit_floor(3)
NAME | Synopsis | Parameters | Return value | Notes | Possible implementation | Example | Output: | See also
Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=std::bit_floor&sektion=3&manpath=FreeBSD+Ports+15.0>