Section (3) lgamma
Name
lgamma, lgammaf, lgammal, lgamma_r, lgammaf_r, lgammal_r, signgam — log gamma function
Synopsis
#include <math.h>
double
lgamma( |
double x) ; |
float
lgammaf( |
float x) ; |
long double
lgammal( |
long double x) ; |
double
lgamma_r( |
double x, |
int *signp) ; |
float
lgammaf_r( |
float x, |
int *signp) ; |
long double
lgammal_r( |
long double x, |
int *signp) ; |
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extern int signgam; Link with −lm.
DESCRIPTION
For the definition of the Gamma function, see tgamma(3).
The lgamma
(), lgammaf
(), and lgammal
() functions return the natural
logarithm of the absolute value of the Gamma function. The
sign of the Gamma function is returned in the external
integer signgam
declared in
<
math.h
>
It
is 1 when the Gamma function is positive or zero, −1
when it is negative.
Since using a constant location signgam
is not thread-safe, the functions
lgamma_r
(), lgammaf_r
(), and lgammal_r
() have been introduced; they
return the sign via the argument signp
.
RETURN VALUE
On success, these functions return the natural logarithm of Gamma(x).
If x
is a NaN, a
NaN is returned.
If x
is 1 or 2, +0
is returned.
If x
is positive
infinity or negative infinity, positive infinity is
returned.
If x
is a
nonpositive integer, a pole error occurs, and the functions
return +HUGE_VAL
, +HUGE_VALF
, or +HUGE_VALL
, respectively.
If the result overflows, a range error occurs, and the
functions return HUGE_VAL
,
HUGE_VALF
, or HUGE_VALL
, respectively, with the correct
mathematical sign.
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:
x
is a nonpositive integer -
errno
is set to ERANGE (but see BUGS). A divide-by-zero floating-point exception (FE_DIVBYZERO
) is raised. - Range error: result overflow
-
errno
is set to ERANGE. An overflow floating-point exception (FE_OVERFLOW
) is raised.
CONFORMING TO
The lgamma
() functions are
specified in C99, POSIX.1-2001, and POSIX.1-2008.
signgam
is specified in
POSIX.1-2001 and POSIX.1-2008, but not in C99. The
lgamma_r
() functions are
nonstandard, but present on several other systems.
BUGS
In glibc 2.9 and earlier, when a pole error occurs,
errno
is set to EDOM; instead of the POSIX-mandated
ERANGE. Since version 2.10,
glibc does the right thing.
COLOPHON
This page is part of release 4.16 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/.
Copyright 2002 Walter Harms (walter.harmsinformatik.uni-oldenburg.de) and Copyright 2008, Linux Foundation, written by Michael Kerrisk <mtk.manpagesgmail.com> %%%LICENSE_START(GPL_NOVERSION_ONELINE) Distributed under GPL %%%LICENSE_END based on glibc infopages |