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// $Id: G4ExplicitEuler.cc,v 1.8 2006/06/29 18:23:53 gunter Exp $
// GEANT4 tag $Name: geant4-09-02-cand-01 $
//
//
//  Explicit Euler: x_1 = x_0 + h * dx_0
//
//  most simple approach for solving linear differential equations.
//  Take the current derivative and add it to the current position.
//
//  W.Wander <wwc@mit.edu> 12/09/97 
// -------------------------------------------------------------------

#include "G4ExplicitEuler.hh"
#include "G4ThreeVector.hh"

//////////////////////////////////////////////////////////////////////////
//
// Constructor

G4ExplicitEuler::G4ExplicitEuler(G4EquationOfMotion* EqRhs, 
                                 G4int numberOfVariables)
 : G4MagErrorStepper(EqRhs, numberOfVariables)
{
}


///////////////////////////////////////////////////////////////////////
//
// Destructor

G4ExplicitEuler::~G4ExplicitEuler()
{
}


///////////////////////////////////////////////////////////////////////
//
//

void
G4ExplicitEuler::DumbStepper( const G4double  yIn[],
			      const G4double  dydx[],
			            G4double  h,
			 	    G4double  yOut[]        )
{
  const G4int numberOfVariables= GetNumberOfVariables();

  // Initialise time to t0, needed when it is not updated by the integration.
  // yOut[7] = yIn[7];   //  Better to set it to NaN;  // TODO

  G4int i;

  for(i=0;i< numberOfVariables;i++)
  {
    yOut[i] = yIn[i] + h*dydx[i] ;             // 1st and only Step 
  }
  
  return ;
}  
