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// $Id: G4MagErrorStepper.hh,v 1.11 2006/06/29 18:22:50 gunter Exp $
// GEANT4 tag $Name: geant4-09-02-cand-01 $
//
//
// class G4MagErrorStepper
//
// Class description:
//
// Abstract base class for integrator of particle's equation of motion,
// used in tracking in space dependent magnetic field.

// History:
// 09.12.97  W.Wander <wwc@mit.edu>  Created G4MagErrorStepper
// --------------------------------------------------------------------

#ifndef G4MAGERRORSTEPPER_HH
#define G4MAGERRORSTEPPER_HH

#include "G4Types.hh"
#include "G4MagIntegratorStepper.hh"
#include "G4Mag_EqRhs.hh"
#include "G4ThreeVector.hh"

class G4MagErrorStepper : public G4MagIntegratorStepper
{
  public:  // with description

    // G4MagErrorStepper(G4Mag_EqRhs *EqRhs, G4int numberOfVariables);
    G4MagErrorStepper(G4EquationOfMotion *EqRhs, G4int numberOfVariables);
    virtual ~G4MagErrorStepper();
  
    void Stepper( const G4double y[],
                  const G4double dydx[],
                        G4double h,
                        G4double yout[],
                        G4double yerr[]  );
      // The stepper for the Runge Kutta integration. The stepsize 
      // is fixed, with the Step size given by h.
      // Integrates ODE starting values y[0 to 6].
      // Outputs yout[] and its estimated error yerr[].

    virtual  void DumbStepper( const G4double y[],
                               const G4double dydx[],
                                     G4double h,
                                     G4double yout[] ) = 0;
      // Performs a 'dump' Step without error calculation.

    G4double DistChord() const;

  private:

    G4MagErrorStepper(const G4MagErrorStepper&);
    G4MagErrorStepper& operator=(const G4MagErrorStepper&);
      // Private copy constructor and assignment operator.

  private:

    G4ThreeVector fInitialPoint, fMidPoint, fFinalPoint;
      // Data stored in order to find the chord
 
    // G4int theNumberOfVariables ; 

    G4double *yInitial, *yMiddle, *dydxMid, *yOneStep;
      // The following arrays are used only for temporary storage
      // they are allocated at the class level only for efficiency -
      // so that calls to new and delete are not made in Stepper().
};

#include  "G4MagErrorStepper.icc"

#endif  /* G4MAGERRORSTEPPER_HH */
