```/*****************************************************************************
* Project: RooFit                                                           *
* Package: RooFitModels                                                     *
*    File: \$Id: RooBreitWigner.cc,v 1.13 2005/06/20 15:51:06 wverkerke Exp \$
* Authors:                                                                  *
*   AS, Abi Soffer, Colorado State University, abi@slac.stanford.edu        *
*   TS, Thomas Schietinger, SLAC, schieti@slac.stanford.edu                 *
*                                                                           *
* Copyright (c) 2000-2005, Regents of the University of California          *
*                                                                           *
* Redistribution and use in source and binary forms,                        *
* with or without modification, are permitted according to the terms        *
*****************************************************************************/

// -- CLASS DESCRIPTION [PDF] --

#include "RooFit.h"

#include "Riostream.h"
#include "Riostream.h"
#include <math.h>

#include "RooBreitWigner.h"
#include "RooAbsReal.h"
#include "RooRealVar.h"
// #include "RooFitTools/RooRandom.h"

ClassImp(RooBreitWigner)

RooBreitWigner::RooBreitWigner(const char *name, const char *title,
RooAbsReal& _x, RooAbsReal& _mean,
RooAbsReal& _width) :
RooAbsPdf(name,title),
x("x","Dependent",this,_x),
mean("mean","Mean",this,_mean),
width("width","Width",this,_width)
{
}

RooBreitWigner::RooBreitWigner(const RooBreitWigner& other, const char* name) :
RooAbsPdf(other,name), x("x",this,other.x), mean("mean",this,other.mean),
width("width",this,other.width)
{
}

Double_t RooBreitWigner::evaluate() const
{
Double_t arg= x - mean;
return 1. / (arg*arg + 0.25*width*width);
}

Int_t RooBreitWigner::getAnalyticalIntegral(RooArgSet& allVars, RooArgSet& analVars, const char* /*rangeName*/) const
{
if (matchArgs(allVars,analVars,x)) return 1 ;
return 0 ;
}

Double_t RooBreitWigner::analyticalIntegral(Int_t code, const char* rangeName) const
{
switch(code) {
case 1:
{
Double_t c = 2./width;
return c*(atan(c*(x.max(rangeName)-mean)) - atan(c*(x.min(rangeName)-mean)));
}
}

assert(0) ;
return 0 ;
}

```

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