lgammaf man page on ElementaryOS

```LGAMMA(3)		   Linux Programmer's Manual		     LGAMMA(3)

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);

extern int signgam;

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

lgamma():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
or cc -std=c99
lgammaf(), lgammal():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 ||
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99
lgamma_r(), lgammaf_r(), lgammal_r():
_BSD_SOURCE || _SVID_SOURCE
signgam:
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE

DESCRIPTION
For the definition of the Gamma function, see tgamma(3).

The lgamma() function returns 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 func‐
tions lgamma_r() etc. 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 math‐
ematical 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	float‐
ing-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 and POSIX.1-2001.   signgam
is specified in POSIX.1-2001, 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.

tgamma(3)

COLOPHON
This page is part of release 3.54 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/.

2010-09-11			     LGAMMA(3)
```
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