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//
// G4ILawForceFreeFlight
//
// Class Description:
//
// A G4VBiasingInteractionLaw representing the "interaction" law
// for a force free flight, ie, a particle which does not interact.
// It is a limit case for which the non-interaction probability over
// a segment is always 1, and the effective cross-section always
// zero. This singular behavior is signaled by the IsSingular()
// method returning always true.
//
// Author: Marc Verderi, November 2013.
// --------------------------------------------------------------------
#ifndef G4ILawForceFreeFlight_hh
#define G4ILawForceFreeFlight_hh 1

#include "G4VBiasingInteractionLaw.hh"

class G4ILawForceFreeFlight : public G4VBiasingInteractionLaw
{
  public:

    G4ILawForceFreeFlight(const G4String& name = "forceFreeFlightLaw");
    virtual ~G4ILawForceFreeFlight();
  
    virtual G4double ComputeEffectiveCrossSectionAt(G4double length) const;
    virtual G4double ComputeNonInteractionProbabilityAt(G4double length) const;

    // -- sample the distribution
    virtual  G4double SampleInteractionLength();
    // -- move by true path length, this position becomes the new initial point
    virtual G4double UpdateInteractionLengthForStep(G4double truePathLength);
    virtual G4bool IsSingular() const { return true; }
};

#endif