1GAMMA(3)                      libc math functions                     GAMMA(3)
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NAME

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

9       #include <math.h>
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11       double gamma(double x);
12       float gammaf(float x);
13       long double gammal(long double x);
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15       Link with -lm.
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DESCRIPTION

18       For the definition of the Gamma function, see tgamma(3).
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20   *BSD version
21       4.4BSD and FreeBSD libm have a gamma() function that computes the Gamma
22       function, as one would expect.
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24   glibc version
25       Glibc has a gamma() function that is equivalent to  lgamma()  and  com‐
26       putes  the  natural logarithm of the Gamma function.  (This is for com‐
27       patibility reasons only. Don't use this function.)
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HISTORY

30       4.2BSD had a gamma() that computed ln(|Gamma(|x|)|), leaving  the  sign
31       of  Gamma(|x|) in the external integer signgam.  In 4.3BSD the name was
32       changed to lgamma(), and the man page promises
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34          "At some time in the future the name gamma will be rehabilitated and
35          used for the Gamma function"
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37       This  did  indeed  happen  in  4.4BSD, where gamma() computes the Gamma
38       function (with no effect on signgam).  However, this came too late, and
39       we now have tgamma(), the "true gamma" function.
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CONFORMING TO

42       4.2BSD. Compatible with previous mistakes.
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SEE ALSO

45       lgamma(3), signgam(3), tgamma(3)
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49GNU                               2002-08-10                          GAMMA(3)