LGAMMA(3) BSD Programmer's Manual LGAMMA(3)
NAME
lgamma gamma  log gamma function, gamma function
SYNOPSIS
#include <<math.h>>
extern int signgam;
double
lgamma(double x);
double
gamma(double x);
DESCRIPTION _
Lgamma(x) returns ln (x).
_
The external integer signgam returns the sign of  (x).
_
Gamma(x) returns  (x), with no effect on signgam.
IDIOSYNCRASIES
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.
For arguments in its range, gamma() is preferred, as for positive argu
ments it is accurate to within one unit in the last place. Exponentia
tion of lgamma() will lose up to 10 significant bits.
RETURN VALUES
Gamma() and lgamma() return appropriate values unless an argument is out
of range. Overflow will occur for sufficiently large positive values,
and nonpositive integers. On the VAX, the reserved operator is re
turned, and errno is set to ERANGE For large noninteger negative values,
gamma() will underflow.
SEE ALSO
math(3), infnan(3)
HISTORY
The lgamma function appeared in 4.3BSD. The gamma function appeared in
4.4BSD. The name gamma() was originally dedicated to the lgamma() func
tion, so some old code may no longer be compatible.
4.3 Berkeley Distribution December 11, 1993 1
