lgamma(3) [osf1 man page]

lgamma(3)						     Library Functions Manual							 lgamma(3)

NAME

       lgamma, gamma - Compute the logarithm of the gamma function

LIBRARY

       Math Library (libm.a)

SYNOPSIS

       #include <math.h>

       double lgamma  (double x); float  lgammaf (float  x); long double lgammal  (long double x);

STANDARDS

       Interfaces documented on this reference page conform to industry standards as follows:

       lgamma():  XPG4

       gamma():  XPG4

       Refer to the standards(5) reference page for more information about industry standards and associated tags.

DESCRIPTION

       The  lgamma(),  lgammaf(),  and lgammal() functions return the logarithm of the absolute value of gamma of x, or ln(|G(x)|), where G is the
       gamma function. The sign of gamma of x is returned in the external integer variable signgam.  The x parameter cannot be	0  or  a  negative
       integer.

       The gamma() function returns the natural log of the gamma function and so is functionally equivalent to lgamma().  Because of this, gamma()
       is marked TO BE WITHDRAWN in the X/Open Portability Guide, Revision 4 (XPG4).

       The following table describes function behavior in response to exceptional arguments:

       -------------------------------------------------------------------------
       Function 		       Exceptional Argument    Routine Behavior
       -------------------------------------------------------------------------
       lgamma(), lgammaf(), lgamma()   |x| = infinity	       Invalid argument
       lgamma(), lgammaf(), lgamma()   x = 0, -1, -2, -3,...   Invalid argument
       lgamma(), lgammaf(), lgamma()   x > lgamma_max_float    Overflow
       -------------------------------------------------------------------------

       The following table lists boundary values used by these functions:

       -------------------------------------------------------------------------
       Value		  Data	     Hexadecimal Value	 Decimal Value
       Name		  Type
       -------------------------------------------------------------------------
       lgamma_max_float   S_FLOAT    7BC650F9		 2.0594342e36
			  T_FLOAT    7F475ABDC501F55F	 1.2812545499066958e305
       -------------------------------------------------------------------------
       delim off

																	 lgamma(3)

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