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LGAMMA(3) FreeBSD Library Functions Manual LGAMMA(3)
NAME
lgamma, lgamma_r, lgammaf, lgammaf_r, lgammal, lgammal_r, gamma, gamma_r,
gammaf, gammaf_r, tgamma, tgammaf, tgammal, - log gamma functions, gamma
function
LIBRARY
Math Library (libm, -lm)
SYNOPSIS
#include <math.h>
extern int signgam;
double
lgamma(double x);
double
lgamma_r(double x, int *signgamp);
float
lgammaf(float x);
float
lgammaf_r(float x, int *signgamp);
long double
lgammal(long double x);
long double
lgammal_r(long double x, int *signgamp);
double
gamma(double x);
double
gamma_r(double x, int *signgamp);
float
gammaf(float x);
float
gammaf_r(float x, int *signgamp);
long double
tgamma(double x);
float
tgammaf(float x);
long double
tgammal(long double x);
DESCRIPTION
lgamma(x), lgammaf(x), and lgammal(x) return ln|<Gamma>(x)|. The
external integer signgam returns the sign of <Gamma>(x).
lgamma_r(x, signgamp), lgammaf_r(x, signgamp), and lgammal_r(x, signgamp)
lgamma(), lgammaf(), lgamma_r(), and lgammaf_r(), respectively.
IDIOSYNCRASIES
Do not use the expression "signgam*exp(lgamma(x))" to compute g :=
<Gamma>(x). Instead use a program like this (in C):
lg = lgamma(x); g = signgam*exp(lg);
Only after lgamma() or lgammaf() has returned can signgam be correct.
For arguments in its range, tgamma() is preferred, as for positive
arguments it is accurate to within one unit in the last place.
Exponentiation of lgamma() will lose up to 10 significant bits.
RETURN VALUES
gamma(), gammaf(), gammal(), gamma_r(), gammaf_r(), gammal_r(), lgamma(),
lgammaf(), lgammal(), lgamma_r(), lgammaf_r(), and lgammal_r() return
appropriate values unless an argument is out of range. Overflow will
occur for sufficiently large positive values, and non-positive integers.
For large non-integer negative values, tgamma() will underflow.
BUGS
To conform with newer C/C++ standards, a stub implementation for tgammal
was committed to the math library, where tgammal is mapped to tgamma.
Thus, the numerical accuracy is at most that of the 53-bit double
precision implementation.
SEE ALSO
math(3)
STANDARDS
The lgamma(), lgammaf(), lgammal(), tgamma(), tgammaf(), and tgammal()
functions are expected to conform to ISO/IEC 9899:1999 ("ISO C99").
HISTORY
The lgamma() function appeared in 4.3BSD. The gamma() function appeared
in 4.4BSD as a function which computed <Gamma>(x). This version was used
in FreeBSD 1.1. The name gamma() was originally dedicated to the
lgamma() function, and that usage was restored by switching to Sun's
fdlibm in FreeBSD 1.1.5. The tgamma() function appeared in FreeBSD 5.0.
FreeBSD 14.0-RELEASE-p11 December 8, 2017 FreeBSD 14.0-RELEASE-p11