new file mode 100644
--- /dev/null
+++ b/liboctave/base-dae.h
@@ -0,0 +1,86 @@
+/*
+
+Copyright (C) 2002 John W. Eaton
+
+This file is part of Octave.
+
+Octave 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 2, or (at your option) any
+later version.
+
+Octave 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 Octave; see the file COPYING.  If not, write to the Free
+Software Foundation, 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+
+*/
+
+#if !defined (octave_base_dae_h)
+#define octave_base_dae_h 1
+
+#include "base-de.h"
+
+class
+base_diff_alg_eqn : public base_diff_eqn
+{
+public:
+
+  base_diff_alg_eqn (void)
+    : base_diff_eqn (), xdot () { }
+
+  base_diff_alg_eqn (const ColumnVector& xx, double tt)
+    : base_diff_eqn (xx, tt), xdot (xx.length (), 0.0) { }
+
+  base_diff_alg_eqn (const ColumnVector& xx, const ColumnVector& xxdot,
+		     double tt)
+    : base_diff_eqn (xx, tt), xdot (xxdot) { }
+
+  base_diff_alg_eqn (const base_diff_alg_eqn& a)
+    : base_diff_eqn (a), xdot (a.xdot) { }
+
+  virtual ~base_diff_alg_eqn (void) { }
+
+  base_diff_alg_eqn& operator = (const base_diff_alg_eqn& a)
+    {
+      if (this != &a)
+	{
+	  base_diff_eqn::operator = (a);
+	  xdot = a.xdot;
+	}
+      return *this;
+    }
+
+  void initialize (const ColumnVector& x0, double t0)
+    {
+      base_diff_eqn::initialize (x0, t0);
+      xdot.resize (x0.length (), 0.0);
+      force_restart ();
+    }
+
+  void initialize (const ColumnVector& x0, const ColumnVector& xdot0,
+		   double t0)
+    {
+      base_diff_eqn::initialize (x0, t0);
+      xdot = xdot0;
+      force_restart ();
+    }
+
+  ColumnVector state_derivative (void) { return xdot; }
+
+protected:
+
+  ColumnVector xdot;
+};
+
+#endif
+
+/*
+;;; Local Variables: ***
+;;; mode: C++ ***
+;;; End: ***
+*/