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//
// $Id: G4El_EqRhs.hh,v 1.8 2003/11/05 12:54:13 japost Exp $
// GEANT4 tag $Name: geant4-06-00-patch-01 $
//
//
// class G4El_EqRhs
//
// Class description:
//
// The "standard" equation of motion of a particle in a pure electric field.

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

#ifndef G4_EL_EQRHS_DEF
#define G4_EL_EQRHS_DEF

#include "G4Types.hh"
#include "G4EquationOfMotion.hh"

class G4ElectricField;

class G4El_EqRhs : public G4EquationOfMotion
{
public: // with description
  
  G4El_EqRhs( G4ElectricField *elField );
  virtual ~G4El_EqRhs();
  // Constructor and destructor. No actions.
  
  virtual void EvaluateRhsGivenB( const  G4double y[],
				  const  G4double E[3],
				  G4double dydx[] ) const = 0;
  // Given the value of the  field "B", this function 
  // calculates the value of the derivative dydx.
  // This is the _only_ function a subclass must define.
  // The other two functions use Rhs_givenB.
  
  inline G4double FCof() const;
  void RightHandSide( const  G4double y[],  G4double dydx[]   ) const;
  virtual void SetChargeMomentumMass( G4double particleCharge, // in e+ units
				      G4double MomentumXc,
				      G4double mass);
  
private:
  
  G4double fCof_val;
  
  static const G4double fUnitConstant;     // Set in G4El_EqRhs.cc 
  // to 0.299792458
  // Coefficient in the Lorentz motion equation (Lorentz force), if the
  //  electric field B is in Tesla, the particle charge in units of the 
  //  elementary (positron?) charge, the momentum P in MeV/c, and the
  //  space coordinates and path along the trajectory in mm .
};

inline
G4double G4El_EqRhs::FCof() const
{
  return fCof_val;
}


#endif /* G4_EL_EQRHS_DEF */