diff --git a/src/rungekutta.h b/src/rungekutta.h
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--- /dev/null
+++ b/src/rungekutta.h
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+/*
+ *
+ *  $Id$
+ *
+ *  This file is part of the Virtual Leaf.
+ *
+ *  The Virtual Leaf is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  The Virtual Leaf is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with the Virtual Leaf.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *  Copyright 2010 Roeland Merks.
+ *
+ */
+
+
+#ifndef _RUNGEKUTTA_H_
+#define _RUNGEKUTTA_H_
+
+class RungeKutta  {
+
+ public:
+  RungeKutta(void) {
+    kmax=kount=0;
+    dxsav=0.;
+    xp=0;
+    yp=0;
+  }
+  virtual ~RungeKutta() {}
+  
+  void odeint(double ystart[], int nvar, double x1, double x2, double eps, double h1,
+	      double hmin, int *nok, int *nbad);
+  
+
+ protected:
+  // implement "derivs" in a derived class
+  virtual void derivs(double x, double *y, double *dxdy) = 0;
+  int kmax,kount;
+  double *xp,**yp,dxsav;
+  
+ private:
+  void rkqs(double *y, double *dydx, int n, double *x, double htry, double eps,
+       double *yscal, double *hdid, double *hnext);
+  
+  void rkck(double *y, double *dydx, int n, double x, double h, double yout[],
+	    double *yerr);
+
+  static const double Safety;
+  static const double PGrow;
+  static const double Pshrnk;
+  static const double Errcon;
+  static const double Maxstp;
+  static const double Tiny;
+  
+
+};
+#endif