add unary operator-(), computing the opposite.

src/Core.h

@@ -17,6 +17,7 @@ namespace Eigen {
 #include "Core/Sum.h"
 #include "Core/Difference.h"
 #include "Core/Product.h"
+#include "Core/Opposite.h"
 #include "Core/Row.h"
 #include "Core/Column.h"
 #include "Core/Block.h"

src/Core/Object.h

@@ -119,6 +119,8 @@ template<typename Scalar, typename Derived> class Object
     Product<Derived, OtherDerived>
     lazyProduct(const Object<Scalar, OtherDerived>& other) const EI_ALWAYS_INLINE;
     
+    Opposite<Derived> operator-() const;
+    
     template<typename OtherDerived>
     Derived& operator+=(const Object<Scalar, OtherDerived>& other);
     template<typename OtherDerived>

src/Core/Opposite.h

@@ -0,0 +1,69 @@
+// 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 EI_OPPOSITE_H
+#define EI_OPPOSITE_H
+
+template<typename MatrixType> class Opposite
+  : public Object<typename MatrixType::Scalar, Opposite<MatrixType> >
+{
+  public:
+    typedef typename MatrixType::Scalar Scalar;
+    typedef typename MatrixType::ConstRef MatRef;
+    friend class Object<Scalar, Opposite<MatrixType> >;
+    
+    static const int RowsAtCompileTime = MatrixType::RowsAtCompileTime,
+                     ColsAtCompileTime = MatrixType::ColsAtCompileTime;
+
+    Opposite(const MatRef& matrix) : m_matrix(matrix) {}
+    
+    Opposite(const Opposite& other)
+      : m_matrix(other.m_matrix) {}
+    
+    EI_INHERIT_ASSIGNMENT_OPERATORS(Opposite)
+    
+  private:
+    Opposite& _ref() { return *this; }
+    const Opposite& _constRef() const { return *this; }
+    int _rows() const { return m_matrix.rows(); }
+    int _cols() const { return m_matrix.cols(); }
+    
+    Scalar _read(int row, int col) const
+    {
+      return -(m_matrix.read(row, col));
+    }
+    
+  protected:
+    MatRef m_matrix;
+};
+
+template<typename Scalar, typename Derived>
+Opposite<Derived>
+Object<Scalar, Derived>::operator-() const
+{
+  return Opposite<Derived>(static_cast<const Derived*>(this)->constRef());
+}
+
+#endif // EI_OPPOSITE_H

src/Core/Util.h

@@ -50,6 +50,7 @@ template<typename MatrixType> class Minor;
 template<typename MatrixType> class Block;
 template<typename MatrixType> class Transpose;
 template<typename MatrixType> class Conjugate;
+template<typename MatrixType> class Opposite;
 template<typename Lhs, typename Rhs> class Sum;
 template<typename Lhs, typename Rhs> class Difference;
 template<typename Lhs, typename Rhs> class Product;