NAME    [Toc]    [Back]

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

LIBRARY    [Toc]    [Back]

     Math Library (libm, -lm)

SYNOPSIS    [Toc]    [Back]

     #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);

DESCRIPTION                _
     lgamma(x) returns ln|| (x)|.
                                                       _
     The external integer signgam returns the sign of | (x).

     lgamma_r() is a reentrant interface that _erforms 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.

IDIOSYNCRASIES    [Toc]    [Back]

     D_ 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    [Toc]    [Back]

     lgamma() returns appropriate values unless an argument is out of range.
     Overflow will occur for sufficiently large positive values, and non-positive
 integers.  On the VAX, the reserved operator is returned, and errno
     is set to ERANGE.

SEE ALSO    [Toc]    [Back]

     math(3)

HISTORY    [Toc]    [Back]

     The lgamma function appeared in 4.3BSD.

BSD                            December 3, 1992                            BSD