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// $Id: G4Mag_UsualEqRhs.hh,v 1.7 2006/06/29 18:23:12 gunter Exp $
// GEANT4 tag $Name: geant4-09-02-cand-01 $
//
//
// class G4Mag_UsualEqRhs
//
// Class description:
//
// This is the standard right-hand side for equation of motion.
// The only case another is required is when using a moving reference
// frame ... or extending the class to include additional Forces,
// eg an electric field

// History:
// - Created: J. Apostolakis, January 13th 1997.
// --------------------------------------------------------------------

#ifndef G4MAG_USUAL_EQRHS
#define G4MAG_USUAL_EQRHS

#include "G4Mag_EqRhs.hh"

class G4MagneticField;

class G4Mag_UsualEqRhs : public G4Mag_EqRhs
{
   public:  // with description

     G4Mag_UsualEqRhs( G4MagneticField* MagField );
    ~G4Mag_UsualEqRhs();
       // Constructor and destructor. No actions.

     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.

     virtual void SetChargeMomentumMass( G4double particleCharge, // in e+ units
                                         G4double MomentumXc,
                                         G4double mass);
     
  private:

    G4double  fInvCurrentMomentumXc;   // This extra state enables us 
                                    // to save a square root in a
                                    // critical method.
};

#endif /* G4MAG_USUAL_EQRHS */
