lgamma, lgammaf, lgammal, lgamma_r, lgammaf_r, lgammal_r, signgam — log gamma function
||long double x
||long double x,|
extern int signgam; Link with −lm.
For the definition of the Gamma function, see tgamma(3).
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
signgam declared in
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
lgammal_r() have been introduced; they
return the sign via the argument
On success, these functions return the natural logarithm of Gamma(x).
x is a NaN, a
NaN is returned.
x is 1 or 2, +0
x is positive
infinity or negative infinity, positive infinity is
x is a
nonpositive integer, a pole error occurs, and the functions
HUGE_VALF, or +
If the result overflows, a range error occurs, and the
HUGE_VALL, respectively, with the correct
See math_error(7) for information on how to determine whether an error has occurred when calling these functions.
The following errors can occur:
xis a nonpositive integer
errno is set to
ERANGE (but see BUGS). A
divide-by-zero floating-point exception (
FE_DIVBYZERO) is raised.
errno is set to
ERANGE. An overflow
floating-point exception (
FE_OVERFLOW) is raised.
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.
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.
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
Copyright 2002 Walter Harms (walter.harmsinformatik.uni-oldenburg.de)
and Copyright 2008, Linux Foundation, written by Michael Kerrisk
Distributed under GPL
based on glibc infopages