TGAMMA(3) libc math functions TGAMMA(3)
NAME
tgamma, tgammaf, tgammal - true gamma function
SYNOPSIS
#include <math.h>
double tgamma(double x);
float tgammaf(float x);
long double tgammal(long double x);
Link with -lm.
DESCRIPTION
The Gamma function is defined by
Gamma(x) = integral from 0 to infinity of t^(x-1) 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)
For x < 0.5 one can use
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() that returns something else.
ERRORS
In order to check for errors, set(7,n,1 builtins) errno to zero and call feclearex-
cept(FE_ALL_EXCEPT) before calling these functions. On return, if(3,n) errno
is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW |
FE_UNDERFLOW) is non-zero, an error(8,n) has occurred.
A range error(8,n) occurs if(3,n) x is too large. A pole error(8,n) occurs if(3,n) x is
zero. A domain error(8,n) (or a pole error(8,n)) occurs if(3,n) x is a negative inte-
ger.
CONFORMING TO
C99.
SEE ALSO
gamma(3), lgamma(3)
GNU 2002-08-10 TGAMMA(3)