linux man page for lgammal_r

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;

       Link with -lm.

   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  nega-
       tive.

       Since  using  a	constant location signgam is not thread-safe, the functions 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
       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 and POSIX.1-2001.  signgam is specified in POSIX.1-2001, but not in C99.  The lgamma_r() func-
       tions 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.

SEE ALSO
       tgamma(3)

COLOPHON
       This  page is part of release 3.27 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)