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diff --git a/src/Core/DynBlock.h b/src/Core/DynBlock.h
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+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra. Eigen itself is part of the KDE project.
+//
+// Copyright (C) 2006-2007 Benoit Jacob <jacob@math.jussieu.fr>
+//
+// Eigen 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.
+//
+// Eigen 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 Eigen; if not, write to the Free Software Foundation, Inc., 51
+// Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+//
+// As a special exception, if other files instantiate templates or use macros
+// or functions from this file, or you compile this file and link it
+// with other works to produce a work based on this file, this file does not
+// by itself cause the resulting work to be covered by the GNU General Public
+// License. This exception does not invalidate any other reasons why a work
+// based on this file might be covered by the GNU General Public License.
+
+#ifndef EIGEN_BLOCK_H
+#define EIGEN_BLOCK_H
+
+template<typename MatrixType> class DynBlock
+  : public MatrixBase<typename MatrixType::Scalar, DynBlock<MatrixType> >
+{
+  public:
+    typedef typename MatrixType::Scalar Scalar;
+    typedef typename MatrixType::Ref MatRef;
+    friend class MatrixBase<Scalar, DynBlock<MatrixType> >;
+    
+    static const int RowsAtCompileTime = Dynamic,
+                     ColsAtCompileTime = Dynamic;
+
+    DynBlock(const MatRef& matrix,
+          int startRow, int startCol,
+          int blockRows, int blockCols)
+      : m_matrix(matrix), m_startRow(startRow), m_startCol(startCol),
+                          m_blockRows(blockRows), m_blockCols(blockCols)
+    {
+      assert(startRow >= 0 && blockRows >= 1 && startRow + blockRows <= matrix.rows()
+          && startCol >= 0 && blockCols >= 1 && startCol + blockCols <= matrix.rows());
+    }
+    
+    DynBlock(const DynBlock& other)
+      : m_matrix(other.m_matrix),
+        m_startRow(other.m_startRow), m_startCol(other.m_startCol),
+        m_blockRows(other.m_blockRows), m_blockCols(other.m_blockCols) {}
+    
+    EIGEN_INHERIT_ASSIGNMENT_OPERATORS(DynBlock)
+    
+  private:
+    const DynBlock& _ref() const { return *this; }
+    int _rows() const { return m_blockRows; }
+    int _cols() const { return m_blockCols; }
+    
+    Scalar& _write(int row, int col=0)
+    {
+      return m_matrix.write(row + m_startRow, col + m_startCol);
+    }
+    
+    Scalar _read(int row, int col=0) const
+    {
+      return m_matrix.read(row + m_startRow, col + m_startCol);
+    }
+    
+  protected:
+    MatRef m_matrix;
+    const int m_startRow, m_startCol, m_blockRows, m_blockCols;
+};
+
+template<typename Scalar, typename Derived>
+DynBlock<Derived> MatrixBase<Scalar, Derived>
+  ::dynBlock(int startRow, int startCol, int blockRows, int blockCols) const
+{
+  return DynBlock<Derived>(static_cast<Derived*>(const_cast<MatrixBase*>(this))->ref(),
+                        startRow, startCol, blockRows, blockCols);
+}
+
+#endif // EIGEN_BLOCK_H