Import Geant4 0.0.0 source tree

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+// This code implementation is the intellectual property of
+// neutron_hp -- header file
+// J.P. Wellisch, Nov-1996
+// A prototype of the low energy neutron transport model.
+//
+// By copying, distributing or modifying the Program (or any work
+// based on the Program) you indicate your acceptance of this statement,
+// and all its terms.
+//
+// $Id: G4NeutronHPFissionSpectrum.hh,v 2.4 1998/11/07 11:21:16 hpw Exp $
+// GEANT4 tag $Name: geant4-00 $
+//
+#ifndef G4NeutronHPFissionSpectrum_h
+#define G4NeutronHPFissionSpectrum_h 1
+
+#include "globals.hh"
+#include "G4NeutronHPVector.hh"
+#include "Randomize.hh"
+#include "G4ios.hh"
+#include <fstream.h>
+#include "G4VNeutronHPEDis.hh"
+
+// we will need a List of these .... one per term.
+
+class G4NeutronHPFissionSpectrum : public G4VNeutronHPEDis
+{
+  public:
+  G4NeutronHPFissionSpectrum()
+  {
+    expm1 = exp(-1.);
+  }
+  ~G4NeutronHPFissionSpectrum()
+  {
+  }
+  
+  inline void Init(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);
+    // here we need to sample Maxwells distribution, if 
+    // need be.
+    G4double result, cut;
+    G4double range =50*MeV;
+    G4double max = Maxwell((theta*eV)/2., theta);
+    G4double value;
+    do
+    {
+      result = range*G4UniformRand();
+      value = Maxwell(result, theta);
+      cut = G4UniformRand();
+    }
+    while(cut > value/max);
+    return result;
+  }
+  
+  private:
+ 
+  // this is the function to sample from. 
+  inline G4double Maxwell(G4double anEnergy, G4double theta)
+  {
+    G4double result = sqrt(anEnergy/eV)*exp(-anEnergy/eV/theta);
+    return result;
+  }
+  
+  private:
+  
+  G4double expm1;
+  
+  G4NeutronHPVector theFractionalProb;
+  
+  G4NeutronHPVector theThetaDist;
+  
+};
+
+#endif