# gamma(3) [freebsd man page]

```LGAMMA(3)						   BSD 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 arguments it is accurate to within one unit in the last place.	Exponenti-
ation of lgamma() will lose up to 10 significant bits.

RETURN VALUES
gamma(), gammaf(), gammal(), gamma_r(), gammaf_r(), gammal_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 negative 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 FreeBSD 5.0.

BSD								September 12, 2014							       BSD```

## Check Out this Related Man Page

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

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

LIBRARY
Math Library (libm, -lm)

SYNOPSIS
#include <math.h>

extern int signgam;

double
lgamma(double x);

float
lgammaf(float x);

double
lgamma_r(double x, int *sign);

float
lgammaf_r(float x, int *sign);

double
gamma(double x);

float
gammaf(float x);

double
gamma_r(double x, int *sign);

float
gammaf_r(float x, int *sign);

double
tgamma(double x);

float
tgammaf(float x);

DESCRIPTION		   _
lgamma(x) returns ln|| (x)|.
_
The external integer signgam returns the sign of | (x).
_
lgamma_r() is a reentrant interface that performs identically to lgamma(), differing in that the sign of | (x) is stored in the location
pointed to by the sign argument and signgam is not modified.
_
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() has returned can signgam be correct.

RETURN VALUES
lgamma() returns 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 negative values, tgamma() will underflow.  On the VAX, the reserved operator is returned, and errno
is set to ERANGE.