# DragonFly On-Line Manual Pages

```LGAMMA(3)	      DragonFly Library Functions Manual	     LGAMMA(3)

NAME
lgamma, lgamma_r, lgammaf, lgammaf_r, lgammal, lgammal_r, gamma, gamma_r,
gammaf, gammaf_r, tgamma, tgammaf -- log gamma functions, gamma function

LIBRARY
Math Library (libm, -lm)

SYNOPSIS
#include <math.h>

extern int signgam;

double
lgamma(double x);

double
lgamma_r(double x, int *signgamp);

float
lgammaf(float x);

float
lgammaf_r(float x, int *signgamp);

long double
lgammal(long double x);

long double
lgammal_r(long double x, int *signgamp);

double
gamma(double x);

double
gamma_r(double x, int *signgamp);

float
gammaf(float x);

float
gammaf_r(float x, int *signgamp);

long double
tgamma(double x);

float
tgammaf(float x);

DESCRIPTION					      _
lgamma(x), lgammaf(x), and lgammal(x)_return ln|| (x)|.  The external
integer signgam returns the sign of | (x).

lgamma_r(x, signgamp), lgammaf_r(x, signgamp), and lgammal_r(x, signgamp)
provide the same functionality as lgamma(x), lgammaf(x), and lgammal(x),
but the caller must provide an integer to store the sign of | (x).
_
The tgamma(x) and tgammaf(x) functions return | (x), with no effect on
signgam.

gamma(), gammaf(), gamma_r(), and gammaf_r() are deprecated aliases for
lgamma(), lgammaf(), lgamma_r(), and lgammaf_r(), respectively.

IDIOSYNCRASIES
Do not use the expression ``signgam*exp(lgamma(x))'' to compute g :=
| (x).  Instead use a program like this (in C):

lg = lgamma(x); g = signgam*exp(lg);

Only after lgamma() or lgammaf() has returned can signgam be correct.

For arguments in its range, tgamma() is preferred, as for positive argu-
ments it is accurate to within one unit in the last place.  Exponentia-
tion of lgamma() will lose up to 10 significant bits.

RETURN VALUES
gamma(), gammaf(), gamma_r(), gammaf_r(), lgamma(), lgammaf(), lgammal(),
lgamma_r(), lgammaf_r(), and lgammal_r() return appropriate values unless
an argument is out of range.  Overflow will occur for sufficiently large
positive values, and non-positive integers.  For large non-integer nega-
tive values, tgamma() will underflow.

math(3)

STANDARDS
The lgamma(), lgammaf(), lgammal(), tgamma(), and tgammaf() functions are
expected to conform to ISO/IEC 9899:1999 (``ISO C99'').

HISTORY
The lgamma() function appeared in 4.3BSD_	The gamma() function appeared
in 4.4BSD as a function which computed | (x).  This version was used in
FreeBSD 1.1.  The name gamma() was originally dedicated to the lgamma()
function, and that usage was restored by switching to Sun's fdlibm in
FreeBSD 1.1.5.  The tgamma() function appeared in DragonFly 2.13.

DragonFly 4.1		      September 12, 2014		 DragonFly 4.1
```