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src
LogGamma.cc
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// -*- C++ -*-
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// $Id: LogGamma.cc,v 1.4 2003/10/10 17:40:39 garren Exp $
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// ---------------------------------------------------------------------------
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#include "
CLHEP/GenericFunctions/LogGamma.hh
"
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#include <cmath>
// for log()
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namespace
Genfun {
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FUNCTION_OBJECT_IMP
(LogGamma)
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const
double
LogGamma::_coefficient[6]={
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+76.18009172947146,
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-86.50532032941677,
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+24.01409824083091,
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-1.231739572450155,
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0.1208650973866179E-2,
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-0.5395239384953E-5};
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LogGamma::LogGamma
()
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{}
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LogGamma::LogGamma
(
const
LogGamma
& right) :
AbsFunction
(right)
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{}
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LogGamma::~LogGamma
() {
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}
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double
LogGamma::operator()
(
double
x)
const
{
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double
y=x,tmp=x+5.5,ser=1.000000000190015,c=2.5066282746310005;
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tmp -= (x+0.5)*log(tmp);
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for
(
int
j=0;j<6;j++) ser += _coefficient[j]/++y;
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return
-tmp+log(c*ser/x);
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}
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}
// namespace Genfun
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