Man page - ilogbf(3)

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Manual

ilogb

NAME
LIBRARY
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
ATTRIBUTES
STANDARDS
HISTORY
BUGS
SEE ALSO

NAME

ilogb, ilogbf, ilogbl - get integer exponent of a floating-point value

LIBRARY

Math library ( libm , -lm )

SYNOPSIS

#include <math.h>

int ilogb(double x );
int ilogbf(float x );
int ilogbl(long double x );

Feature Test Macro Requirements for glibc (see feature_test_macros (7)):

ilogb ():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| _XOPEN_SOURCE >= 500
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

ilogbf (), ilogbl ():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

These functions return the exponent part of their argument as a signed integer. When no error occurs, these functions are equivalent to the corresponding logb (3) functions, cast to int .

RETURN VALUE

On success, these functions return the exponent of x , as a signed integer.

If x is zero, then a domain error occurs, and the functions return FP_ILOGB0 .

If x is a NaN, then a domain error occurs, and the functions return FP_ILOGBNAN .

If x is negative infinity or positive infinity, then a domain error occurs, and the functions return INT_MAX .

ERRORS

See math_error (7) for information on how to determine whether an error has occurred when calling these functions.

The following errors can occur:
Domain error: x is 0 or a NaN

An invalid floating-point exception ( FE_INVALID ) is raised, and errno is set to EDOM (but see BUGS).

Domain error: x is an infinity

An invalid floating-point exception ( FE_INVALID ) is raised, and errno is set to EDOM (but see BUGS).

ATTRIBUTES

For an explanation of the terms used in this section, see attributes (7).

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STANDARDS

C11, POSIX.1-2008.

HISTORY

C99, POSIX.1-2001.

BUGS

Before glibc 2.16, the following bugs existed in the glibc implementation of these functions:

•

The domain error case where x is 0 or a NaN did not cause errno to be set or (on some architectures) raise a floating-point exception.

•

The domain error case where x is an infinity did not cause errno to be set or raise a floating-point exception.

SEE ALSO

log (3), logb (3), significand (3)