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man pages->Tru64 Unix man pages -> lgamma (3)
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lgamma(3)

```
```

NAME[Toc][Back]

```       lgamma,  gamma  - Compute the logarithm of the gamma function

```

SYNOPSIS[Toc][Back]

```       #include <math.h>

double lgamma(
double x ); float lgammaf(
float x ); long double lgammal(
long double x );
```

LIBRARY[Toc][Back]

```       Math Library (libm)
```

STANDARDS[Toc][Back]

```       Interfaces documented on this reference  page  conform  to
industry standards as follows:

lgamma():  XPG4

gamma():  XPG4

about industry standards and associated tags.
```

DESCRIPTION[Toc][Back]

```       The lgamma(), lgammaf(), and  lgammal()  functions  return
the  logarithm  of  the  absolute  value of gamma of x, or
ln(|G(x)|), where G is the gamma  function.  The  sign  of
gamma  of  x  is returned in the external integer variable
signgam. The x parameter cannot be 0 or a  negative  integer.

The  gamma() function returns the natural log of the gamma
function and so is functionally  equivalent  to  lgamma().
Because  of this, gamma() is marked TO BE WITHDRAWN in the
X/Open Portability Guide, Revision 4 (XPG4).

The  following  table  describes  function   behavior   in
response to exceptional arguments:

----------------------------------------------------------------------------
Function                         Exceptional Argument      Routine Behavior
----------------------------------------------------------------------------
lgamma(), lgammaf(), lgamma()    |x| = infinity            Invalid argument
lgamma(), lgammaf(), lgamma()    x = 0, -1, -2, -3,...     Invalid argument
lgamma(), lgammaf(), lgamma()    x > lgamma_max_float      Overflow
----------------------------------------------------------------------------

The  following  table  lists boundary values used by these
functions:

--------------------------------------------------------------------------
Value Name         Data Type   Hexadecimal Value   Decimal Value
--------------------------------------------------------------------------
lgamma_max_float   S_FLOAT     7BC650F9            2.0594342e36
T_FLOAT     7F475ABDC501F55F    1.2812545499066958e305
--------------------------------------------------------------------------

lgamma(3)
```
[ Back ]
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