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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);

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() and lgammaf() 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  TO BE WITHDRAWN in the X/Open Portability Guide, Revision 4 (XPG4).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()	|x| = infinity		Invalid argument
  lgamma(), lgammaf()	x = 0, -1, -2, -3,...	Invalid argument
  lgamma(), lgammaf()	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
  ________________________________________________________________________