table of contents
ilogb(3) | Library Functions Manual | ilogb(3) |
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);
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).
Interface | Attribute | Value |
ilogb (), ilogbf (), ilogbl () | Thread safety | MT-Safe |
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¶
2024-05-02 | Linux man-pages 6.8 |