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lgammaf (3)

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BSD mandoc

NAME



lgamma

 
lgamma_r

 
lgammaf

 
lgammaf_r

 
gamma

 
gamma_r

 
gammaf

 
gammaf_r

 
tgamma

 - log gamma functions, gamma function

LIBRARY

Lb libm

SYNOPSIS

#include <math.h>
extern int Fa signgam ;

double lgamma (double x);
double lgamma_r (double x int *signgamp);
float lgammaf (float x);
float lgammaf_r (float 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);
double tgamma (double x);

DESCRIPTION

lgamma (x);
and lgammaf (x);
return ln|Gamma(x)|.

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

lgamma_r (x signgamp);
and lgammaf_r (x signgamp);
provide the same functionality as lgamma (x);
and lgammaf (x);
but the caller must provide an integer to store the sign of Gamma(x).

gamma (,);
gammaf (,);
gamma_r (,);
and gammaf_r ();
are deprecated aliases for lgamma (,);
lgammaf (,);
lgamma_r (,);
and lgammaf_r (,);
respectively. tgamma (x);
returns Gamma(x), with no effect on Fa signgam .

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 (,);
gamma_r (,);
gammaf (,);
gammaf_r (,);
lgamma (,);
lgamma_r (,);
lgammaf (,);
and lgammaf_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.

STANDARDS

The lgamma ();
and tgamma ();
functions are expected to conform to St -isoC-99 .

HISTORY

The lgamma ();
function appeared in BSD 4.3 The gamma ();
function appeared in BSD 4.4 as a function which computed Gamma(x). This version was used in Fx 1.1 . The name gamma ();
was originally dedicated to the lgamma ();
function, and that usage was restored by switching to Sun's fdlibm in Fx 1.1.5 . The tgamma ();
function appeared in Fx 5.0 .