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// $Id: G4NeutronHPSimpleEvapSpectrum.hh,v 1.7 2002/12/12 19:18:17 gunter Exp $
// GEANT4 tag $Name: geant4-05-00 $
//
#ifndef G4NeutronHPSimpleEvapSpectrum_h
#define G4NeutronHPSimpleEvapSpectrum_h 1

#include "globals.hh"
#include "G4NeutronHPVector.hh"
#include "Randomize.hh"
#include "G4ios.hh"
#include "g4std/fstream"
#include "G4VNeutronHPEDis.hh"

// we will need a List of these .... one per term.

class G4NeutronHPSimpleEvapSpectrum : public G4VNeutronHPEDis
{
  public:
  G4NeutronHPSimpleEvapSpectrum()
  {
    expm1 = exp(-1.);
  }
  ~G4NeutronHPSimpleEvapSpectrum()
  {
  }
  
  inline void Init(G4std::ifstream & aDataFile)
  {
    theFractionalProb.Init(aDataFile,eV);
    theThetaDist.Init(aDataFile, eV);
  }
  
  inline G4double GetFractionalProbability(G4double anEnergy)
  {
    return theFractionalProb.GetY(anEnergy);
  }
  
  inline G4double Sample(G4double anEnergy) 
  {
    G4double theta = theThetaDist.GetY(anEnergy)*eV;
    G4double random, cut, max, result;
    max = 10.*theta;
    do
    {
      random = G4UniformRand();
      result = -theta*log(random); 
      cut = G4UniformRand();
    }
    while(cut>result/max); 
    return result;
  }
  
  private:
  
  inline G4double Evapo(G4double anEnergy, G4double theta)
  {
    G4double result = (anEnergy*eV)*exp(-anEnergy*eV/theta);
    return result;
  }
  
  private:
  
  G4double expm1;
  
  G4NeutronHPVector theFractionalProb;
  
  G4NeutronHPVector theThetaDist;
  
};

#endif