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// $Id: G4HelixSimpleRunge.cc,v 1.7 2006/06/29 18:24:08 gunter Exp $
// GEANT4 tag $Name: geant4-09-02-cand-01 $
//
//
//  Simple Runge:
//        x_1 = x_0 + h * ( dx( t_0+h/2, x_0 + h/2 * dx( t_0, x_0) ) )
//
//  Second order solver.
//  Take the derivative at a position to be assumed at the middle of the
//  Step and add it to the current position.
//
//  W.Wander <wwc@mit.edu> 12/09/97 
// -------------------------------------------------------------------------

#include "G4HelixSimpleRunge.hh"
#include "G4ThreeVector.hh"

void
G4HelixSimpleRunge::DumbStepper( const G4double  yIn[],
				 G4ThreeVector   Bfld,
				 G4double        h,
				 G4double        yOut[])
{
  const G4int nvar = 6 ;
  G4double yTemp[nvar];   // , yAdd[nvar];
  G4ThreeVector Bfld_midpoint;

  AdvanceHelix( yIn, Bfld, 0.5 * h, yTemp);
  
  // now obtain the new field value at the new point
  MagFieldEvaluate(yTemp, Bfld_midpoint);      

  AdvanceHelix( yIn, Bfld_midpoint, h, yOut);
  
  // NormaliseTangentVector( yOut );           
}