MirOS Manual: gamma(3), gammaf(3), gammaf_r(3), gamma_r(3), lgamma(3), lgammaf(3), lgammaf_r(3), lgamma_r(3)

LGAMMA(3)                  BSD Programmer's Manual                   LGAMMA(3)

NAME

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

LIBRARY

     libm

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);

DESCRIPTION

     lgamma(x) returns ln|I̅(x)|.

     The external integer signgam returns the sign of I̅(x).

     lgamma_r() is a reentrant interface that performs identically to lgam-
     ma(), differing in that the sign of I̅(x) is stored in the location point-
     ed to by the sign argument and signgam is not modified.

IDIOSYNCRASIES

     Do not use the expression "signgam*exp(lgamma(x))" to compute g := I̅(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. On the VAX, the reserved operator is returned, and
     errno is set to ERANGE.

SEE ALSO

     math(3)

HISTORY

     The lgamma function appeared in 4.3BSD.

MirOS BSD #10-current          December 3, 1992                              1

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