GAMMA(3) libc math functions 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.
DESCRIPTION For the definition of the Gamma function, see tgamma(3).
*BSD version 4.4BSD and FreeBSD libm have a gamma() function that computes the Gamma function, as one would expect.
glibc version Glibc has a gamma() function that is equivalent to lgamma() and com- putes the natural logarithm of the Gamma function. (This is for com- patibility reasons only. Dont use this function.)
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(), 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(), the "true gamma" function.
CONFORMING TO 4.2BSD. Compatible with previous mistakes.
SEE ALSO lgamma(3), signgam(3), tgamma(3)
GNU 2002-08-10 GAMMA(3)