std::log2,std::log2f,std::log2l (3) - Linux Man Pages
Defined in header <cmath>
float log2 ( float arg ); (1) (since C++11)
float log2f( float arg );
double log2 ( double arg ); (2) (since C++11)
long double log2 ( long double arg ); (3) (since C++11)
long double log2l( long double arg );
double log2 ( IntegralType arg ); (4) (since C++11)
1-3) Computes the binary (base-2) logarithm of arg.
4) A set of overloads or a function template accepting an argument of any integral_type. Equivalent to 2) (the argument is cast to double).
arg - value of floating-point or Integral_type
If no errors occur, the base-2 logarithm of arg (log
2(arg) or lb(arg)) 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.
Errors are reported as specified in math_errhandling.
Domain error occurs if arg is less than zero.
Pole error may occur if arg 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
For integer arg, the binary logarithm can be interpreted as the zero-based index of the most significant 1 bit in the input.
// Run this code
logl computes natural (base e) logarithm (ln(x))
log10l computes common (base 10) logarithm (log10(x))
log1pl natural logarithm (to base e) of 1 plus the given number (ln(1+x))
exp2l returns 2 raised to the given power (2x)