Name
logb, logbf, logbl — get exponent of a floating-point value
Synopsis
#include <math.h>
double
logb( |
double x); |
float
logbf( |
float x); |
long double
logbl( |
long double x); |
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DESCRIPTION
These 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 VALUE
On success, these functions return the exponent of
x.
If x is a NaN, a
NaN is returned.
If x is zero, then
a pole error occurs, and the functions return -HUGE_VAL, -HUGE_VALF, or -HUGE_VALL, respectively.
If x is negative
infinity or positive infinity, then positive infinity is
returned.
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:
- Pole error:
xis 0 -
A divide-by-zero floating-point exception (
FE_DIVBYZERO) is raised.
These functions do not set errno.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
| Interface | Attribute | Value |
logb(), logbf(), logbl() |
Thread safety | MT-Safe |
COLOPHON
This page is part of release 4.07 of the Linux man-pages project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.
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Copyright 2004 Andries Brouwer <aebcwi.nl>. and Copyright 2008, Linux Foundation, written by Michael Kerrisk <mtk.manpagesgmail.com> %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END Inspired by a page by Walter Harms created 2002-08-10 |