# signgam(3m) [ultrix man page]

```gamma(3m)																 gamma(3m)

Name
gamma, lgamma, signgam - log gamma function

Syntax
#include <math.h>

double gamma(x)
double x;

double lgamma(x)
double x;

extern int

Description			 _			_
The fu_ction returns ln || (|x|)|.  The sign of | (|x|) is returned in the external integer The following C program might be used to calcu-
late | :

y = gamma(x);
if (y > 88.0)
error();
y = exp(y);
if(signgam)
y = -y;

The function is another name for the function.

Return Values
The and functions return NaN when x is NaN or when it is an integer value less than or equal to zero.  On  overflow  and  functions  return
HUGE_VAL.

Environment
When your program is compiled using the System V environment for nonpositive integer values, HUGE is returned, and errno is set to EDOM.  A
message indicating DOMAIN error is printed on the standard error output.

If the correct value would overflow, returns HUGE and sets errno to ERANGE.

These error-handling procedures may be changed with the function

matherr(3m)

RISC								 gamma(3m)```

## 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.