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[edit]
Defined in header
(1)
float log2 ( float num );
double log2 ( double num ); long double log2 ( long double num ); (until C++23) /* floating-point-type */ log2 ( /* floating-point-type */ num ); (since C++23) (constexpr since C++26) float log2f( float num ); (2) (since C++11) (constexpr since C++26) long double log2l( long double num ); (3) (since C++11) (constexpr since C++26) Additional overloads (since C++11) Defined in header template double log2 ( Integer num ); (A) (constexpr since C++26) 1-3) Computes the binary (base-2) logarithm of num. The library provides overloads of std::log2 for all cv-unqualified floating-point types as the type of the parameter.(since C++23) A) Additional overloads are provided for all integer types, which are treated as double. (since C++11) Contents 1 Parameters 2 Return value 3 Error handling 4 Notes 5 Example 6 See also [edit] Parameters num - floating-point or integer value [edit] Return valueIf no errors occur, the base-2 logarithm of num (log2(num) or lb(num)) is returned. If a domain error occurs, an implementation-defined value is returned (NaN where supported). If a pole error occurs, -HUGE_VAL, -HUGE_VALF, or -HUGE_VALL is returned. [edit] Error handlingErrors are reported as specified in math_errhandling. Domain error occurs if num is less than zero. Pole error may occur if num is zero. If the implementation supports IEEE floating-point arithmetic (IEC 60559), If the argument is ±0, -∞ is returned and FE_DIVBYZERO is raised. If the argument is 1, +0 is returned. If the argument is negative, NaN is returned and FE_INVALID is raised. If the argument is +∞, +∞ is returned. If the argument is NaN, NaN is returned. [edit] NotesFor integer num, the binary logarithm can be interpreted as the zero-based index of the most significant 1 bit in the input. The additional overloads are not required to be provided exactly as (A). They only need to be sufficient to ensure that for their argument num of integer type, std::log2(num) has the same effect as std::log2(static_cast(num)). [edit] Example Run this code #include #include #include #include #include // #pragma STDC FENV_ACCESS ON int main() { std::cout |
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