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 of x and return it as a
floating-point value. If FLT_RADIX is two, logb(x) is equal to
floor(log2(x)),
except that it is probably faster.
If x is
de-normalized, logb() returns
the exponent x would
have if it were normalized.
If x is zero,
−HUGE_VAL (resp.
−HUGE_VALF,
−HUGE_VALL) is returned,
and a pole error occurs. If x is infinite, plus infinity is
returned. If x is
NaN, NaN is returned.
ERRORS
In order to check for errors, set errno to zero and call feclearexcept(FE_ALL_EXCEPT)
before calling these functions. On return, if errno is nonzero or fetestexcept(FE_INVALID | FE_DIVBYZERO |
FE_OVERFLOW | FE_UNDERFLOW) is nonzero, an error
has occurred.
If an error occurs and (math_errhandling & MATH_ERRNO) is nonzero, then errno is set to ERANGE. If an error occurs and (math_errhandling & MATH_ERREXCEPT) is nonzero, then the divide-by-zero floating-point exception is raised.
A pole error occurs when x is zero.
COLOPHON
This page is part of release 2.79 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/.
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Copyright 2004 Andries Brouwer <aebcwi.nl>. 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 Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date.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. Inspired by a page by Walter Harms created 2002-08-10 |