lgamma(3m) [bsd man page]

LGAMMA(3M)																LGAMMA(3M)

NAME

       lgamma - log gamma function

SYNOPSIS

       #include <math.h>

       double lgamma(x)
       double x;

DESCRIPTION
		  _
       Lgamma returns ln|| (x)|.
							 _
       The external integer signgam returns the sign of | (x) .

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  has  returned  can signgam be correct.  Note too that | (x) must overflow when x is large enough, underflow when -x is
       large enough, and spawn a division by zero when x is a nonpositive integer.
										  _
       Only in the UNIX m_th library for C was the na_e gamma ever attached to ln| .  Elsewhere, for instance in IBM's FORTRAN library,  the  name
       GAMMA belongs to |  and the name ALGAMA to ln|  in single precision; in double the names are DGAMMA and DLGAMA.	Why should C be different?
									      _
       Archaeological records suggest that C's gamma originally delivered ln(| (|x|)).	Later, the program gamma was changed to cope with negative
       arguments x in a more conventional way, but the documentation did _ot reflect that change correctly.  The most recent change corrects inac-
       curate  values  when  x	is  almost a negative integer, and lets | (x) be computed without conditional expressions.  Programmers should not
       assume that lgamma has settled down.

       At some time in the future, the name gamma will be rehabilitated and used for the gamma function, just as is done in FORTRAN.   The  reason
       for  this is not so much compatibility with FORTRAN as a desire to achieve greater speed for smaller values of |x| and greater accuracy for
       larger values.

       Meanwhile, programmers who have to use the name gamma in its former sense, for what is now lgamma, have two choices:

       1) Use the old math library, libom.

       2) Add the following program to your others:
	  #include <math.h>
	  double gamma(x)
	  double x;
	  {
		 return (lgamma(x));
	  }

DIAGNOSTICS

       The reserved operand is returned on a VAX for negative integer arguments, errno is set to ERANGE; for very large arguments  over/underflows
       will occur inside the lgamma routine.

SEE ALSO

       math(3M), infnan(3M)

4.3 Berkeley Distribution					   May 12, 1986 							LGAMMA(3M)

Check Out this Related Man Page

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

NAME

     lgamma, lgammaf, lgamma_r, lgammaf_r, gamma, gammaf, gamma_r, gammaf_r, tgamma, tgammaf -- log gamma function

LIBRARY

     Math Library (libm, -lm)

SYNOPSIS

     #include <math.h>

     extern int signgam;

     double
     lgamma(double x);

     float
     lgammaf(float x);

     double
     lgamma_r(double x, int *sign);

     float
     lgammaf_r(float x, int *sign);

     double
     gamma(double x);

     float
     gammaf(float x);

     double
     gamma_r(double x, int *sign);

     float
     gammaf_r(float x, int *sign);

     double
     tgamma(double x);

     float
     tgammaf(float x);

DESCRIPTION
		   _
     lgamma(x) returns ln|| (x)|.
						       _
     The external integer signgam returns the sign of | (x).
													       _
     lgamma_r() is a reentrant interface that performs identically to lgamma(), differing in that the sign of | (x) is stored in the location
     pointed to by the sign argument and signgam is not modified.
						    _
     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() has returned can signgam be correct.

RETURN VALUES

     lgamma() returns 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.  On the VAX, the reserved operator is returned, and errno
     is set to ERANGE.

SEE ALSO

     math(3)

HISTORY

     The lgamma function appeared in 4.3BSD.  The tgamma() function appeared in NetBSD 6.0.

BSD
								    May 4, 2012 							       BSD

Linux and UNIX Man Pages

lgamma(3m) [bsd man page]

Check Out this Related Man Page