Import Geant4 0.0.0 source tree

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+// This code implementation is the intellectual property of
+// the RD44 GEANT4 collaboration.
+//
+// By copying, distributing or modifying the Program (or any work
+// based on the Program) you indicate your acceptance of this statement,
+// and all its terms.
+//
+// $Id: G4HelixImplicitEuler.cc,v 2.2 1998/11/10 18:17:14 japost Exp $
+// GEANT4 tag $Name: geant4-00 $
+//
+#include "G4HelixImplicitEuler.hh"
+#include "G4ThreeVector.hh"
+
+//
+//  Helix Implicit Euler:
+//        x_1 = x_0 + 1/2 * ( helix(h,t_0,x_0)
+//                          + helix(h,t_0+h,x_0+helix(h,t0,x0) ) )
+//  W.Wander <wwc@mit.edu> 12/09/97 
+//
+
+// -------------------------------------------------------------------------
+
+// second order solver
+// Take the current derivative and add it to the current position.
+// Take the output and its derivative. Add the mean of both derivatives
+// to form the final output
+//
+
+void
+G4HelixImplicitEuler::DumbStepper( const G4double  yIn[],
+				   const G4double  dydx[],
+				   const G4double  h,
+				   G4double  yOut[])
+{
+  const G4int nvar = 6 ;
+  G4double dydxTemp[6];
+  G4double yTemp[6], yTemp2[6];
+
+  G4int i;
+
+  // Step forward like in the explicit euler case
+  AdvanceHelix( yIn, dydx, h, yTemp);
+
+  // now obtain the new field value at the new point
+  RightHandSide(yTemp,dydxTemp);
+
+  // and also advance along a helix for this field value
+  AdvanceHelix( yIn, dydxTemp, h, yTemp2);
+
+  // we take the average 
+  for( i = 0; i < nvar; i++ ) 
+    yOut[i] = 0.5 * ( yTemp[i] + yTemp2[i] );
+
+  // NormaliseTangentVector( yOut );           
+  
+  return ;
+}