freebsd man page for tgamma

LGAMMA(3)						   BSD Library Functions Manual 						 LGAMMA(3)

NAME
     lgamma, lgamma_r, lgammaf, lgammaf_r, lgammal, lgammal_r, gamma, gamma_r, gammaf, gammaf_r, tgamma, tgammaf -- 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);

DESCRIPTION
					      _ 							_
     lgamma(x), lgammaf(x), and lgammal(x) return ln|| (x)|.  The external integer signgam returns the sign of | (x).

     lgamma_r(x, signgamp), lgammaf_r(x, signgamp), and lgammal_r(x, signgamp)_provide the same functionality as lgamma(x), lgammaf(x), and
     lgammal(x), but the caller must provide an integer to store the sign of | (x).
						    _
     The tgamma(x) and tgammaf(x) functions return | (x), with no effect on signgam.

     gamma(), gammaf(), gamma_r(), and gammaf_r() are deprecated aliases for lgamma(), lgammaf(), lgamma_r(), and lgammaf_r(), respectively.

IDIOSYNCRASIES
								   _
     Do 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() 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.	Exponenti-
     ation 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.

SEE ALSO
     math(3)

STANDARDS
     The lgamma(), lgammaf(), lgammal(), tgamma(), and tgammaf() 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 | (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.

BSD
								September 12, 2014							       BSD