|LOGB(3)||Linux Programmer's Manual||LOGB(3)|
NAMElogb, logbf, logbl - get exponent of a floating-point value
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;or cc -std=c99
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;or cc -std=c99
DESCRIPTIONThese functions extract the exponent from the internal floating-point representation of x and return it as a floating-point value. The integer constant FLT_RADIX, defined in <float.h>, indicates the radix used for the system's floating-point representation. If FLT_RADIX is 2, logb( x ) is equal to floor(log2( x )), except that it is probably faster.
If x is subnormal, logb() returns the exponent x would have if it were normalized.
RETURN VALUEOn success, these functions return the exponent of x.
ERRORSSee math_error(7) for information on how to determine whether an error has occurred when calling these functions.
The following errors can occur:
- Pole error: x is 0
- A divide-by-zero floating-point exception ( FE_DIVBYZERO) is raised.
These functions do not set errno.
CONFORMING TOC99, POSIX.1-2001.
SEE ALSOilogb(3), log(3)
COLOPHONThis page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.