gamma(3) [redhat man page]

GAMMA(3)							libc math functions							  GAMMA(3)

NAME

       gamma - logarithm of the gamma function

SYNOPSIS

       #include <math.h>

       double gamma (double x);

       float gammaf (float x);

       long double gammal (long double x);

DESCRIPTION

       The  gamma() functions exist for compatibility reasons.	They are equivalent to lgamma() etc. Use these. Use of the name gamma() is confus-
       ing, since these functions do not compute the Gamma function, but the natural logarithm of the Gamma function.

CONFORMING TO

       Nonstandard. Compatible with previous mistakes.

SEE ALSO

       lgamma(3), signgam(3), tgamma(3)

GNU
								    2002-08-10								  GAMMA(3)

GAMMA(3)						     Linux Programmer's Manual							  GAMMA(3)

NAME

       gamma, gammaf, gammal - (logarithm of the) gamma function

SYNOPSIS

       #include <math.h>

       double gamma(double x);
       float gammaf(float x);
       long double gammal(long double x);

       Link with -lm.

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

       gamma():
	   _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE
       gammaf(), gammal():
	   _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600

DESCRIPTION

       These functions are deprecated: instead, use either the tgamma(3) or the lgamma(3) functions, as appropriate.

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

   *BSD version
       The libm in 4.4BSD and some versions of FreeBSD had a gamma() function that computes the Gamma function, as one would expect.

   glibc version
       Glibc has a gamma() function that is equivalent to lgamma(3) and computes the natural logarithm of the Gamma function.

RETURN VALUE

       See lgamma(3).

ERRORS

       See lgamma(3).

CONFORMING TO

       Because of historical variations in behavior across systems, this function is not specified in any standard.

NOTES

   History
       4.2BSD  had  a  gamma() that computed ln(|Gamma(|x|)|), leaving the sign of Gamma(|x|) in the external integer signgam.	In 4.3BSD the name
       was changed to lgamma(3), and the man page promises

	   "At some time in the future the name gamma will be rehabilitated and used for the Gamma function"

       This did indeed happen in 4.4BSD, where gamma() computes the Gamma function (with no effect on signgam).  However, this came too late,  and
       we now have tgamma(3), the "true gamma" function.

SEE ALSO

       lgamma(3), signgam(3), 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/.

GNU
								    2008-08-05								  GAMMA(3)