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 );

Arguments:

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

Library:

libm

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

Description:

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

logr |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:

Returns:

The exponent part of x, in integer format.

If x is: These functions return: Errors:
0.0 FP_ILOGB0
NaN FP_ILOGBNAN
±Inf INT_MAX

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

Classification:

ANSI, POSIX 1003.1

Safety:  
Cancellation point No
Interrupt handler No
Signal handler No
Thread Yes