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diff --git a/Eigen/Core/Identity.h b/Eigen/Core/Identity.h
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+++ b/Eigen/Core/Identity.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_IDENTITY_H
+#define EIGEN_IDENTITY_H
+
+template<typename MatrixType> class Identity : NoOperatorEquals,
+  public MatrixBase<typename MatrixType::Scalar, Identity<MatrixType> >
+{
+  public:
+    typedef typename MatrixType::Scalar Scalar;
+    friend class MatrixBase<Scalar, Identity<MatrixType> >;
+    
+    Identity(int rows) : m_rows(rows)
+    {
+      assert(rows > 0 && _RowsAtCompileTime == _ColsAtCompileTime);
+    }
+    
+  private:
+    static const int _RowsAtCompileTime = MatrixType::RowsAtCompileTime,
+                     _ColsAtCompileTime = MatrixType::ColsAtCompileTime;
+
+    const Identity& _ref() const { return *this; }
+    int _rows() const { return m_rows; }
+    int _cols() const { return m_rows; }
+    
+    Scalar _coeff(int row, int col) const
+    {
+      return row == col ? static_cast<Scalar>(1) : static_cast<Scalar>(0);
+    }
+    
+  protected:
+    int m_rows;
+};
+
+template<typename Scalar, typename Derived>
+const Identity<Derived> MatrixBase<Scalar, Derived>::identity(int rows)
+{
+  return Identity<Derived>(rows);
+}
+
+#endif // EIGEN_IDENTITY_H