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gamma, gammaf, gammal - (logarithm of the) gamma function
#include
<math.h>
double gamma(double x);
float gammaf(float x);
long double gammal(long
double x);
For the definition of the Gamma function, see tgamma(3)
.
4.4BSD and FreeBSD libm have a gamma() function that computes
the Gamma function, as one would expect.
Glibc has a gamma()
function that is equivalent to lgamma() and computes the natural logarithm
of the Gamma function. (This is for compatibility reasons only. Don’t use
this function.)
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.
4.2BSD. Compatible with
previous mistakes.
lgamma(3)
, signgam(3)
, tgamma(3)
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