ilogb(), ilogbf(), ilogbl()

Compute the integral part of a logarithm

Synopsis:

#include <math.h>

int ilogb( double x );

int ilogbf( float x );

int ilogbl( long double x );

x: The number for which you want to compute the integral part of the logarithm.

libm

Use the -l m option to qcc to link against this library.

The ilogb(), ilogbf(), and ilogbl() functions compute the integral part of:

log_r |x|

as a signed integral value, for nonzero finite x, where r is the radix of the machine's floating point arithmetic.

To check for error situations, use feclearexcept() and fetestexcept(). For example:

Call feclearexcept(FE_ALL_EXCEPT) before calling ilogb(), ilogbf(), or ilogbl().
On return, if fetestexcept(FE_ALL_EXCEPT) is nonzero, then an error has occurred.

The exponent part of x, in integer format.

These functions raise FE_INEXACT if the FPU reports that the result can't be exactly represented as a floating-point number.