TGAMMA(3) Linux Programmers Manual TGAMMA(3)
NAME
tgamma, tgammaf, tgammal  true gamma function
SYNOPSIS
#include
double tgamma(double x);
float tgammaf(float x);
long double tgammal(long double x);
Link with lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
tgamma(), tgammaf(), tgammal(): _XOPEN_SOURCE >= 600  _ISOC99_SOURCE;
or cc std=c99
DESCRIPTION
The Gamma function is defined by
Gamma(x) = integral from 0 to infinity of t^(x1) e^t dt
It is defined for every real number except for nonpositive integers.
For nonnegative integral m one has
Gamma(m+1) = m!
and, more generally, for all x:
Gamma(x+1) = x * Gamma(x)
Furthermore, the following is valid for all values of x outside the
poles:
Gamma(x) * Gamma(1  x) = PI / sin(PI * x)
This function returns the value of the Gamma function for the argument
x. It had to be called "true gamma function" since there is already a
function gamma(3) that returns something else.
ERRORS
In order to check for errors, set errno to zero and call feclearex
cept(FE_ALL_EXCEPT) before calling these functions. On return, if
errno is nonzero or fetestexcept(FE_INVALID  FE_DIVBYZERO  FE_OVER
FLOW  FE_UNDERFLOW) is nonzero, an error has occurred.
A range error occurs if x is too large. A pole error occurs if x is
zero. A domain error (or a pole error) occurs if x is a negative inte
ger.
CONFORMING TO
C99.
SEE ALSO
gamma(3), lgamma(3)
COLOPHON
This page is part of release 3.05 of the Linux manpages project. A
description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/manpages/.
GNU 20070726 TGAMMA(3)
