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// $Id: G4BlineEquation.hh,v 1.2 2006/06/29 17:14:53 gunter Exp $
// GEANT4 tag $Name: geant4-09-03-cand-01 $
//
// 
// --------------------------------------------------------------------
//
// G4BlineEquation
//
// Class description:
//
// This class defines the equation of motion needed to trace magnetic
// field lines in the simulation. 

// --------------------------------------------------------------------
// Author: Laurent Desorgher (desorgher@phim.unibe.ch)
//         Created - 2003-10-06
// --------------------------------------------------------------------
#ifndef G4BlineEquation_h
#define G4BlineEquation_h 1

#include "G4Mag_EqRhs.hh"
#include "G4MagneticField.hh"

class G4BlineEquation : public G4Mag_EqRhs
{
  public:  // with description

    G4BlineEquation( G4MagneticField* MagField );
    ~G4BlineEquation();
      // Constructor and destructor.

    void EvaluateRhsGivenB( const G4double y[],
                            const G4double B[3],
                                  G4double dydx[] ) const;
      // Given the value of the magnetic field B, this function 
      // calculates the value of the derivative dydx.

    void SetBackwardDirectionOfIntegration(G4bool abool);  

  private:

    G4bool backward_direction;
    G4double direction;
};

#endif