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

       Refer to the standards(5) reference page for more information
 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       Because  of this, gamma() is marked TO BE WITHDRAWN in the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)