Manual Pages for UNIX Operating System command usage for man gammaf

Mathematical Library Functions                         lgamma(3M)



NAME
     lgamma, lgammaf, lgammal,  lgamma_r,  lgammaf_r,  lgammal_r,
     gamma,  gammaf,  gammal,  gamma_r,  gammaf_r, gammal_r - log
     gamma function

SYNOPSIS
     c99 [ flag... ] file... -lm [ library... ]
     #include 

     extern int signgam;

     double lgamma(double x);


     float lgammaf(float x);


     long double lgammal(long double x);


     double gamma(double x);


     float gammaf(float x);


     long double gammal(long double x);


     double lgamma_r(double x, int *signgamp);


     float lgammaf_r(float x, int *signgamp);


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


     double gamma_r(double x, int *signgamp);


     float gammaf_r(float x, int *signgamp);


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


DESCRIPTION
     These functions return

     ln||~(x)|




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Mathematical Library Functions                         lgamma(3M)



     where

     |~(x) = integral from 0 to +Infinity  of  pow(t,x-1)*exp(-t)
     dt


     for x > 0 and

     |~(x) = n/(|~(1-x)sin(nx))


     for x < 1.


     These functions use the external integer signgam  to  return
     the  sign  of  |~(x)  while lgamma_r() and gamma_r() use the
     user-allocated space addressed by signgamp.

RETURN VALUES
     Upon successful completion, these functions return the loga-
     rithmic gamma of x.


     If x is a non-positive integer,  a  pole  error  occurs  and
     these    functions   return   +HUGE_VAL,   +HUGE_VALF,   and
     +HUGE_VALL, respectively.


     If x is NaN, a NaN is returned.


     If x is 1 or 2, +0 shall be returned.


     If x is +_Inf, +Inf is returned.

ERRORS
     These functions will fail if:

     Pole Error    The x argument is a negative integer or 0.

                   If the integer expression (math_errhandling  &
                   MATH_ERREXCEPT)  is non-zero, then the divide-
                   by-zero floating-point exception is raised.


USAGE
     An application wanting to check for exceptions  should  call
     feclearexcept(FE_ALL_EXCEPT) before calling these functions.
     On  return,  if  fetestexcept(FE_INVALID  |  FE_DIVBYZERO  |
     FE_OVERFLOW  |  FE_UNDERFLOW)  is non-zero, an exception has
     been raised. An application should either examine the return



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Mathematical Library Functions                         lgamma(3M)



     value  or check the floating point exception flags to detect
     exceptions.


     In  the  case  of  lgamma(),  do  not  use  the   expression
     signgam*exp(lgamma(x)) to compute

     `g  := |~(x)'


     Instead compute lgamma() first:


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


     only after lgamma() has returned  can  signgam  be  correct.
     Note that |~(x) must overflow when x is large enough, under-
     flow when -x is large enough, and generate a division  by  0
     exception at the singularities x a nonpositive integer.

ATTRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:



     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Interface Stability         | Committed                   |
    |_____________________________|_____________________________|
    | MT-Level                    | See below.                  |
    |_____________________________|_____________________________|
    | Standard                    | See below.                  |
    |_____________________________|_____________________________|



     The lgamma(), lgammaf(), lgammal(), gamma(),  gammaf(),  and
     gammal() functions are Unsafe in multithreaded applications.
     The   lgamma_r(),   lgammaf_r(),   lgammal_r(),   gamma_r(),
     gammaf_r(),  and gammal_r() functions are MT-Safe and should
     be used instead.


     For lgamma(), lgammaf(), lgammal(), and gamma(),  see  stan-
     dards(5).

SEE ALSO
     exp(3M),  feclearexcept(3M),  fetestexcept(3M),   isnan(3M),
     math.h(3HEAD), attributes(5), standards(5)



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Mathematical Library Functions                         lgamma(3M)



NOTES
     When compiling multithreaded  applications,  the  _REENTRANT
     flag  must be defined on the compile line.  This flag should
     only be used in multithreaded applications.



















































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