LGAMMA

Section: Linux Programmer's Manual (3)
Updated: 2002-08-10
Index Return to Main Contents

NAME

lgamma, lgammaf, lgammal, lgamma_r, lgammaf_r, lgammal_r - log gamma function

SYNOPSIS

#include <math.h>

double lgamma(double x);


float lgammaf(float x);


long double lgammal(long double x);

double lgamma_r(double x, int *signp);


float lgammaf_r(float x, int *signp);


long double lgammal_r(long double x, int *signp);

Compile with -std=c99; link with -lm.

DESCRIPTION

For the definition of the Gamma function, see tgamma(3).

The lgamma() function returns the natural logarithm of the absolute value of the Gamma function. The sign of the Gamma function is returned in the external integer signgam declared in <math.h>. It is 1 when the Gamma function is positive or zero, -1 when it is negative.

Since using a constant location signgam is not thread-safe, the functions lgamma_r() etc. have been introduced; they return this sign via the parameter signp.

For nonpositive integer values of x, lgamma() returns HUGE_VAL, sets errno to ERANGE and raises the zero divide exception. (Similarly, lgammaf() returns HUGE_VALF and lgammal() returns HUGE_VALL.)

ERRORS

In order to check for errors, set errno to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.

A range error occurs if x is too large. A pole error occurs if x is a negative integer or zero.

CONFORMING TO

C99, SVID 3, BSD 4.3

This document was created by man2html, using the manual pages.
Time: 00:12:38 GMT, May 13, 2005