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// $Id: G4MagHelicalStepper.icc,v 1.7 2002/05/31 16:22:54 japost Exp $
// GEANT4 tag $Name: geant4-05-01 $
//

// linear Step in regions of no field

inline void
G4MagHelicalStepper::LinearStep( const G4double  yIn[],
			               G4double  h,
			               G4double  yLinear[])
{
  G4double  momentum_val = sqrt(yIn[3]*yIn[3] + yIn[4]*yIn[4] + yIn[5]*yIn[5]) ;
  G4double  inv_momentum = 1.0 / momentum_val ;
  G4double  yDir[3];
  // G4double  h_div_momentum = 1.0 / momentum_val ;

  for( G4int i = 0; i < 3; i++ ) {
    yDir[i]   = inv_momentum * yIn[i+3];
    yLinear[i]   = yIn[i] + h * yDir[i];
    // yLinear[i]   = yIn[i] + h_div_momentum * yIn[i+3];
    yLinear[i+3] = yIn[i+3];
  }
}

inline void
G4MagHelicalStepper::MagFieldEvaluate(const G4double y[],
                                      G4ThreeVector& Bfield )   
{
  G4double B[3];
  GetEquationOfMotion()->  GetFieldValue(y, B);
  Bfield= G4ThreeVector( B[0], B[1], B[2] );
}