diff --git a/src/Block.h b/src/Block.h
index a32d72d70..68c4439cd 100644
--- a/src/Block.h
+++ b/src/Block.h
@@ -49,14 +49,14 @@ template<typename MatrixType> class MatrixBlock
     int rows() const { return m_endRow - m_startRow + 1; }
     int cols() const { return m_endCol - m_startCol + 1; }
     
-    Scalar& operator()(int row, int col=0)
+    Scalar& write(int row, int col=0)
     {
-      return m_matrix(row + m_startRow, col + m_startCol);
+      return m_matrix.write(row + m_startRow, col + m_startCol);
     }
     
-    Scalar operator()(int row, int col=0) const
+    Scalar read(int row, int col=0) const
     {
-      return m_matrix(row + m_startRow, col + m_startCol);
+      return m_matrix.read(row + m_startRow, col + m_startCol);
     }
     
   protected:
@@ -65,33 +65,18 @@ template<typename MatrixType> class MatrixBlock
 };
 
 template<typename Derived>
-MatrixConstXpr<
+MatrixXpr<
   MatrixBlock<
-    const MatrixConstRef<
+    MatrixRef<
       MatrixBase<Derived>
     >
   >
 >
-MatrixBase<Derived>::block(int startRow, int endRow, int startCol, int endCol) const
+MatrixBase<Derived>::block(int startRow, int endRow, int startCol, int endCol)
 {
-  typedef MatrixBlock<const ConstRef> ProductType;
-  typedef MatrixConstXpr<ProductType> XprType;
-  return XprType(ProductType(constRef(), startRow, endRow, startCol, endCol));
-}
-
-template<typename Content>
-MatrixConstXpr<
-  MatrixBlock<
-    const MatrixConstXpr<Content>
-  >
->
-MatrixConstXpr<Content>::block(int startRow, int endRow, int startCol, int endCol) const
-{
-  typedef MatrixBlock<
-            const MatrixConstXpr<Content>
-          > ProductType;
-  typedef MatrixConstXpr<ProductType> XprType;
-  return XprType(ProductType(*this, startRow, endRow, startCol, endCol));
+  typedef MatrixBlock<Ref> ProductType;
+  typedef MatrixXpr<ProductType> XprType;
+  return XprType(ProductType(ref(), startRow, endRow, startCol, endCol));
 }
 
 template<typename Content>
diff --git a/src/Matrix.h b/src/Matrix.h
index f18624573..8ff819902 100644
--- a/src/Matrix.h
+++ b/src/Matrix.h
@@ -84,11 +84,11 @@ class Matrix: public MatrixBase< Matrix<T, Rows, Cols> >
     { Base::operator=(other); }
 
     template<typename XprContent>
-    void operator=(const MatrixConstXpr<XprContent> &xpr)
+    void operator=(const MatrixXpr<XprContent> &xpr)
     { Base::operator=(xpr); }
 
     template<typename XprContent>
-    explicit Matrix(const MatrixConstXpr<XprContent>& xpr)
+    explicit Matrix(const MatrixXpr<XprContent>& xpr)
     {
       *this = xpr;
     }
@@ -125,11 +125,11 @@ class MatrixX : public MatrixBase< MatrixX<T> >
     { Base::operator=(other); }
 
     template<typename XprContent>
-    void operator=(const MatrixConstXpr<XprContent> &xpr)
+    void operator=(const MatrixXpr<XprContent> &xpr)
     { Base::operator=(xpr); }
 
     template<typename XprContent>
-    explicit MatrixX(const MatrixConstXpr<XprContent>& xpr)
+    explicit MatrixX(const MatrixXpr<XprContent>& xpr)
     {
       _init(xpr.rows(), xpr.cols());
       *this = xpr;
diff --git a/src/MatrixBase.h b/src/MatrixBase.h
index e21887df6..d49ce8c21 100644
--- a/src/MatrixBase.h
+++ b/src/MatrixBase.h
@@ -32,37 +32,6 @@
 namespace Eigen
 {
 
-template<typename MatrixType> class MatrixConstRef
-{
-  public:
-    typedef typename ForwardDecl<MatrixType>::Scalar Scalar;
-    
-    MatrixConstRef(const MatrixType& matrix) : m_matrix(matrix) {}
-    MatrixConstRef(const MatrixConstRef& other) : m_matrix(other.m_matrix) {}
-    ~MatrixConstRef() {}
-
-    static bool hasDynamicNumRows()
-    {
-      return MatrixType::hasDynamicNumRows();
-    }
-
-    static bool hasDynamicNumCols()
-    {
-      return MatrixType::hasDynamicNumCols();
-    }
-    
-    int rows() const { return m_matrix.rows(); }
-    int cols() const { return m_matrix.cols(); }
-
-    const Scalar& operator()(int row, int col) const
-    {
-      return m_matrix(row, col);
-    }
-
-  protected:
-    const MatrixType& m_matrix;
-};
-
 template<typename MatrixType> class MatrixRef
 {
   public:
@@ -86,12 +55,15 @@ template<typename MatrixType> class MatrixRef
     int rows() const { return m_matrix.rows(); }
     int cols() const { return m_matrix.cols(); }
 
-    Scalar& operator()(int row, int col)
+    const Scalar& read(int row, int col) const
     {
-      return m_matrix(row, col);
+      return m_matrix.read(row, col);
     }
     
-    MatrixType& matrix() { return m_matrix; }
+    Scalar& write(int row, int col)
+    {
+      return m_matrix.write(row, col);
+    }
 
     Xpr xpr()
     {
@@ -108,9 +80,7 @@ class MatrixBase
   public:
 
     typedef typename ForwardDecl<Derived>::Scalar Scalar;
-    typedef MatrixConstRef<MatrixBase<Derived> > ConstRef;
     typedef MatrixRef<MatrixBase<Derived> > Ref;
-    typedef MatrixConstXpr<ConstRef> ConstXpr;
     typedef MatrixXpr<Ref> Xpr;
     typedef MatrixAlias<Derived> Alias;
 
@@ -118,22 +88,12 @@ class MatrixBase
     {
       return Ref(*this);
     }
-    
-    ConstRef constRef() const
-    {
-      return ConstRef(*this);
-    }
-    
+   
     Xpr xpr()
     {
       return Xpr(ref());
     }
     
-    ConstXpr constXpr() const
-    {
-      return ConstXpr(constRef());
-    }
-    
     Alias alias();
     
     static bool hasDynamicNumRows()
@@ -171,20 +131,30 @@ class MatrixBase
       return static_cast<Derived*>(this)->m_array;
     }
 
-    const Scalar& operator()(int row, int col = 0) const
+    const Scalar& read(int row, int col = 0) const
     {
       EIGEN_CHECK_RANGES(*this, row, col);
       return array()[row + col * rows()];
     }
 
-    Scalar& operator()(int row, int col = 0)
+    const Scalar& operator()(int row, int col = 0) const
+    {
+      return read(row, col);
+    }
+
+    Scalar& write(int row, int col = 0)
     {
       EIGEN_CHECK_RANGES(*this, row, col);
       return array()[row + col * rows()];
     }
     
+    Scalar& operator()(int row, int col = 0)
+    {
+      return write(row, col);
+    }
+    
     template<typename XprContent> 
-    MatrixBase& operator=(const MatrixConstXpr<XprContent> &otherXpr)
+    MatrixBase& operator=(const MatrixXpr<XprContent> &otherXpr)
     {
       resize(otherXpr.rows(), otherXpr.cols());
       xpr() = otherXpr;
@@ -193,23 +163,27 @@ class MatrixBase
     
     MatrixBase& operator=(const MatrixBase &other)
     {
-      return *this = other.constXpr();
+      resize(other.rows(), other.cols());
+      for(int i = 0; i < rows(); i++)
+        for(int j = 0; j < cols(); j++)
+          this->operator()(i, j) = other(i, j);
+      return *this;
     }
     
-    MatrixConstXpr<MatrixRow<const ConstRef> > row(int i) const;
-    MatrixConstXpr<MatrixCol<const ConstRef> > col(int i) const;
-    MatrixConstXpr<MatrixMinor<const ConstRef> > minor(int row, int col) const;
-    MatrixConstXpr<MatrixBlock<const ConstRef> >
-      block(int startRow, int endRow, int startCol = 0, int endCol = 0) const;
+    MatrixXpr<MatrixRow<Ref> > row(int i);
+    MatrixXpr<MatrixCol<Ref> > col(int i);
+    MatrixXpr<MatrixMinor<Ref> > minor(int row, int col);
+    MatrixXpr<MatrixBlock<Ref> >
+      block(int startRow, int endRow, int startCol = 0, int endCol = 0);
     
     template<typename Content>
-    MatrixBase& operator+=(const MatrixConstXpr<Content> &xpr);
+    MatrixBase& operator+=(const MatrixXpr<Content> &xpr);
     template<typename Content>
-    MatrixBase& operator-=(const MatrixConstXpr<Content> &xpr);
+    MatrixBase& operator-=(const MatrixXpr<Content> &xpr);
     template<typename Derived2>
-    MatrixBase& operator+=(const MatrixBase<Derived2> &other);
+    MatrixBase& operator+=(MatrixBase<Derived2> &other);
     template<typename Derived2>
-    MatrixBase& operator-=(const MatrixBase<Derived2> &other);
+    MatrixBase& operator-=(MatrixBase<Derived2> &other);
     
   protected:
   
@@ -223,7 +197,7 @@ MatrixXpr<Content>& MatrixXpr<Content>::operator=(const MatrixBase<Derived>& mat
   assert(rows() == matrix.rows() && cols() == matrix.cols());
   for(int i = 0; i < rows(); i++)
     for(int j = 0; j < cols(); j++)
-      this->operator()(i, j) = matrix(i, j);
+      write(i, j) = matrix(i, j);
   return *this;
 }
 
@@ -245,14 +219,14 @@ std::ostream & operator <<
 
 template<typename Content>
 std::ostream & operator << (std::ostream & s,
-                            const MatrixConstXpr<Content>& m)
+                            const MatrixXpr<Content>& xpr)
 {
-  for( int i = 0; i < m.rows(); i++ )
+  for( int i = 0; i < xpr.rows(); i++ )
   {
-    s << m( i, 0 );
-    for (int j = 1; j < m.cols(); j++ )
-      s << " " << m( i, j );
-    if( i < m.rows() - 1)
+    s << xpr.read(i, 0);
+    for (int j = 1; j < xpr.cols(); j++ )
+      s << " " << xpr.read(i, j);
+    if( i < xpr.rows() - 1)
       s << std::endl;
   }
   return s;
@@ -291,9 +265,9 @@ template<typename Derived> class MatrixAlias
     int rows() const { return m_tmp.rows(); }
     int cols() const { return m_tmp.cols(); }
     
-    Scalar& operator()(int row, int col)
+    Scalar& write(int row, int col)
     {
-      return m_tmp(row, col);
+      return m_tmp.write(row, col);
     }
     
     Ref ref()
@@ -301,20 +275,29 @@ template<typename Derived> class MatrixAlias
       return Ref(*this);
     }
     
+    MatrixXpr<MatrixRow<Xpr> > row(int i) { return xpr().row(i); };
+    MatrixXpr<MatrixCol<Xpr> > col(int i) { return xpr().col(i); };
+    MatrixXpr<MatrixMinor<Xpr> > minor(int row, int col) { return xpr().minor(row, col); };
+    MatrixXpr<MatrixBlock<Xpr> >
+    block(int startRow, int endRow, int startCol = 0, int endCol = 0)
+    {
+      return xpr().block(startRow, endRow, startCol, endCol);
+    }
+    
     template<typename XprContent> 
-    void operator=(const MatrixConstXpr<XprContent> &xpr)
+    void operator=(const MatrixXpr<XprContent> &xpr)
     {
       ref().xpr() = xpr;
     }
     
     template<typename XprContent> 
-    void operator+=(const MatrixConstXpr<XprContent> &xpr)
+    void operator+=(const MatrixXpr<XprContent> &xpr)
     {
       ref().xpr() += xpr;
     }
     
     template<typename XprContent> 
-    void operator-=(const MatrixConstXpr<XprContent> &xpr)
+    void operator-=(const MatrixXpr<XprContent> &xpr)
     {
       ref().xpr() -= xpr;
     }
diff --git a/src/MatrixOps.h b/src/MatrixOps.h
index 67e10d9d7..e76e64c85 100644
--- a/src/MatrixOps.h
+++ b/src/MatrixOps.h
@@ -46,9 +46,9 @@ template<typename Lhs, typename Rhs> class Matrix##NAME \
     int rows() const { return m_lhs.rows(); } \
     int cols() const { return m_lhs.cols(); } \
 \
-    Scalar operator()(int row, int col) const \
+    Scalar read(int row, int col) const \
     { \
-      return m_lhs(row, col) SYMBOL m_rhs(row, col); \
+      return m_lhs.read(row, col) SYMBOL m_rhs.read(row, col); \
     } \
 \
   protected: \
@@ -78,11 +78,11 @@ template<typename Lhs, typename Rhs> class MatrixProduct
     int rows() const { return m_lhs.rows(); }
     int cols() const { return m_rhs.cols(); }
     
-    Scalar operator()(int row, int col) const
+    Scalar read(int row, int col) const
     {
       Scalar x = static_cast<Scalar>(0);
       for(int i = 0; i < m_lhs.cols(); i++)
-        x += m_lhs(row, i) * m_rhs(i, col);
+        x += m_lhs.read(row, i) * m_rhs.read(i, col);
       return x;
     }
 
@@ -93,72 +93,72 @@ template<typename Lhs, typename Rhs> class MatrixProduct
 
 #define EIGEN_MAKE_MATRIX_OP(NAME, SYMBOL) \
 template<typename Content1, typename Content2> \
-const MatrixConstXpr< \
-  const Matrix##NAME< \
-    MatrixConstXpr<Content1>, \
-    MatrixConstXpr<Content2> \
+MatrixXpr< \
+  Matrix##NAME< \
+    MatrixXpr<Content1>, \
+    MatrixXpr<Content2> \
   > \
 > \
-operator SYMBOL(const MatrixConstXpr<Content1> &xpr1, const MatrixConstXpr<Content2> &xpr2) \
+operator SYMBOL(const MatrixXpr<Content1> &xpr1, const MatrixXpr<Content2> &xpr2) \
 { \
-  typedef const Matrix##NAME< \
-              MatrixConstXpr<Content1>, \
-              MatrixConstXpr<Content2> \
-            > ProductType; \
-  typedef const MatrixConstXpr<ProductType> XprType; \
+  typedef Matrix##NAME< \
+            MatrixXpr<Content1>, \
+            MatrixXpr<Content2> \
+          > ProductType; \
+  typedef MatrixXpr<ProductType> XprType; \
   return XprType(ProductType(xpr1, xpr2)); \
 } \
 \
 template<typename Derived, typename Content> \
-const MatrixConstXpr< \
-  const Matrix##NAME< \
-    MatrixConstRef<MatrixBase<Derived> >, \
-    MatrixConstXpr<Content> \
+MatrixXpr< \
+  Matrix##NAME< \
+    MatrixRef<MatrixBase<Derived> >, \
+    MatrixXpr<Content> \
   > \
 > \
-operator SYMBOL(const MatrixBase<Derived> &mat, const MatrixConstXpr<Content> &xpr) \
+operator SYMBOL(MatrixBase<Derived> &mat, const MatrixXpr<Content> &xpr) \
 { \
-  typedef const Matrix##NAME< \
-              MatrixConstRef<MatrixBase<Derived> >, \
-              MatrixConstXpr<Content> \
-            > ProductType; \
-  typedef const MatrixConstXpr<ProductType> XprType; \
-  return XprType(ProductType(mat.constRef(), xpr)); \
+  typedef Matrix##NAME< \
+            MatrixRef<MatrixBase<Derived> >, \
+            MatrixXpr<Content> \
+          > ProductType; \
+  typedef MatrixXpr<ProductType> XprType; \
+  return XprType(ProductType(mat.ref(), xpr)); \
 } \
 \
 template<typename Content, typename Derived> \
-const MatrixConstXpr< \
-  const Matrix##NAME< \
-    MatrixConstXpr<Content>, \
-    MatrixConstRef<MatrixBase<Derived> > \
+MatrixXpr< \
+  Matrix##NAME< \
+    MatrixXpr<Content>, \
+    MatrixRef<MatrixBase<Derived> > \
   > \
 > \
-operator SYMBOL(const MatrixConstXpr<Content> &xpr, const MatrixBase<Derived> &mat) \
+operator SYMBOL(const MatrixXpr<Content> &xpr, MatrixBase<Derived> &mat) \
 { \
-  typedef const Matrix##NAME< \
-              MatrixConstXpr<Content>, \
-              MatrixConstRef<MatrixBase<Derived> > \
-            > ProductType; \
-  typedef const MatrixConstXpr<ProductType> XprType; \
-  return XprType(ProductType(xpr, mat.constRef())); \
+  typedef Matrix##NAME< \
+            MatrixXpr<Content>, \
+            MatrixRef<MatrixBase<Derived> > \
+          > ProductType; \
+  typedef MatrixXpr<ProductType> XprType; \
+  return XprType(ProductType(xpr, mat.ref())); \
 } \
 \
 template<typename Derived1, typename Derived2> \
-const MatrixConstXpr< \
-  const Matrix##NAME< \
-    MatrixConstRef<MatrixBase<Derived1> >, \
-    MatrixConstRef<MatrixBase<Derived2> > \
+MatrixXpr< \
+  Matrix##NAME< \
+    MatrixRef<MatrixBase<Derived1> >, \
+    MatrixRef<MatrixBase<Derived2> > \
   > \
 > \
-operator SYMBOL(const MatrixBase<Derived1> &mat1, const MatrixBase<Derived2> &mat2) \
+operator SYMBOL(MatrixBase<Derived1> &mat1, MatrixBase<Derived2> &mat2) \
 { \
-  typedef const Matrix##NAME< \
-            MatrixConstRef<MatrixBase<Derived1> >, \
-            MatrixConstRef<MatrixBase<Derived2> > \
+  typedef Matrix##NAME< \
+            MatrixRef<MatrixBase<Derived1> >, \
+            MatrixRef<MatrixBase<Derived2> > \
           > ProductType; \
-  typedef const MatrixConstXpr<ProductType> XprType; \
-  return XprType(ProductType(MatrixConstRef<MatrixBase<Derived1> >(mat1), \
-                             MatrixConstRef<MatrixBase<Derived2> >(mat2))); \
+  typedef MatrixXpr<ProductType> XprType; \
+  return XprType(ProductType(mat1.ref(), \
+                             mat2.ref())); \
 }
 
 EIGEN_MAKE_MATRIX_OP(Sum,        +)
@@ -171,7 +171,7 @@ EIGEN_MAKE_MATRIX_OP(Product,    *)
 template<typename Derived1> \
 template<typename Derived2> \
 MatrixBase<Derived1> & \
-MatrixBase<Derived1>::operator SYMBOL##=(const MatrixBase<Derived2> &mat2) \
+MatrixBase<Derived1>::operator SYMBOL##=(MatrixBase<Derived2> &mat2) \
 { \
   return *this = *this SYMBOL mat2; \
 } \
@@ -179,7 +179,7 @@ MatrixBase<Derived1>::operator SYMBOL##=(const MatrixBase<Derived2> &mat2) \
 template<typename Derived> \
 template<typename Content> \
 MatrixBase<Derived> & \
-MatrixBase<Derived>::operator SYMBOL##=(const MatrixConstXpr<Content> &xpr) \
+MatrixBase<Derived>::operator SYMBOL##=(const MatrixXpr<Content> &xpr) \
 { \
   return *this = *this SYMBOL xpr; \
 } \
@@ -187,24 +187,24 @@ MatrixBase<Derived>::operator SYMBOL##=(const MatrixConstXpr<Content> &xpr) \
 template<typename Content> \
 template<typename Derived> \
 MatrixXpr<Content> & \
-MatrixXpr<Content>::operator SYMBOL##=(const MatrixBase<Derived> &mat) \
+MatrixXpr<Content>::operator SYMBOL##=(MatrixBase<Derived> &mat) \
 { \
   assert(rows() == mat.rows() && cols() == mat.cols()); \
   for(int i = 0; i < rows(); i++) \
     for(int j = 0; j < cols(); j++) \
-      this->operator()(i, j) SYMBOL##= mat(i, j); \
+      write(i, j) SYMBOL##= mat.read(i, j); \
   return *this; \
 } \
 \
 template<typename Content1> \
 template<typename Content2> \
 MatrixXpr<Content1> & \
-MatrixXpr<Content1>::operator SYMBOL##=(const MatrixConstXpr<Content2> &other) \
+MatrixXpr<Content1>::operator SYMBOL##=(const MatrixXpr<Content2> &other) \
 { \
   assert(rows() == other.rows() && cols() == other.cols()); \
   for(int i = 0; i < rows(); i++) \
     for(int j = 0; j < cols(); j++) \
-      this->operator()(i, j) SYMBOL##= other(i, j); \
+      write(i, j) SYMBOL##= other.read(i, j); \
   return *this; \
 }
 
diff --git a/src/MatrixXpr.h b/src/MatrixXpr.h
index 5caf365ed..a42f84af6 100644
--- a/src/MatrixXpr.h
+++ b/src/MatrixXpr.h
@@ -34,42 +34,6 @@ template<typename MatrixType> class MatrixCol;
 template<typename MatrixType> class MatrixMinor;
 template<typename MatrixType> class MatrixBlock;
 
-template<typename Content> class MatrixConstXpr
-{
-  public:
-    typedef typename Content::Scalar Scalar;
-  
-    MatrixConstXpr(const Content& content)
-      : m_content(content) {}
-    
-    MatrixConstXpr(const MatrixConstXpr& other)
-      : m_content(other.m_content) {}
-    
-    ~MatrixConstXpr() {}
-    
-    static bool hasDynamicSize()
-    {
-      return Content::hasDynamicSize();
-    }
-    
-    int rows() const { return m_content.rows(); }
-    int cols() const { return m_content.cols(); }
-    
-    Scalar operator()(int row, int col) const
-    {
-      return m_content(row, col);
-    }
-    
-    MatrixConstXpr<MatrixRow<const MatrixConstXpr<Content> > > row(int i) const;
-    MatrixConstXpr<MatrixCol<const MatrixConstXpr<Content> > > col(int i) const;
-    MatrixConstXpr<MatrixMinor<const MatrixConstXpr<Content> > > minor(int row, int col) const;
-    MatrixConstXpr<MatrixBlock<const MatrixConstXpr<Content> > >
-      block(int startRow, int endRow, int startCol= 0, int endCol = 0) const;
-    
-  protected:
-    const Content m_content;
-};
-
 template<typename Content> class MatrixXpr
 {
   public:
@@ -83,26 +47,35 @@ template<typename Content> class MatrixXpr
     
     ~MatrixXpr() {}
     
-    static bool hasDynamicSize()
-    {
-      return Content::hasDynamicSize();
-    }
-    
     int rows() const { return m_content.rows(); }
     int cols() const { return m_content.cols(); }
     
-    Scalar& operator()(int row, int col)
+    Scalar& write(int row, int col)
     {
-      return m_content(row, col);
+      return m_content.write(row, col);
+    }
+    
+    Scalar read(int row, int col) const
+    {
+      return m_content.read(row, col);
     }
     
     template<typename OtherContent>
-    MatrixXpr& operator=(const MatrixConstXpr<OtherContent> &other)
+    MatrixXpr& operator=(const MatrixXpr<OtherContent>& other)
     {
       assert(rows() == other.rows() && cols() == other.cols());
       for(int i = 0; i < rows(); i++)
         for(int j = 0; j < cols(); j++)
-          this->operator()(i, j) = other(i, j);
+          write(i, j) = other.read(i, j);
+      return *this;
+    }
+    
+    MatrixXpr& operator=(const MatrixXpr& other)
+    {
+      assert(rows() == other.rows() && cols() == other.cols());
+      for(int i = 0; i < rows(); i++)
+        for(int j = 0; j < cols(); j++)
+          write(i, j) = other.read(i, j);
       return *this;
     }
     
@@ -116,17 +89,13 @@ template<typename Content> class MatrixXpr
       block(int startRow, int endRow, int startCol= 0, int endCol = 0);
     
     template<typename Content2>
-    MatrixXpr& operator+=(const MatrixConstXpr<Content2> &other);
+    MatrixXpr& operator+=(const MatrixXpr<Content2> &other);
     template<typename Content2>
-    MatrixXpr& operator-=(const MatrixConstXpr<Content2> &other);
+    MatrixXpr& operator-=(const MatrixXpr<Content2> &other);
     template<typename Derived>
-    MatrixXpr& operator+=(const MatrixBase<Derived> &matrix);
+    MatrixXpr& operator+=(MatrixBase<Derived> &matrix);
     template<typename Derived>
-    MatrixXpr& operator-=(const MatrixBase<Derived> &matrix);
-  
-  private:
-    void operator=(const MatrixXpr &other)
-    {}
+    MatrixXpr& operator-=(MatrixBase<Derived> &matrix);
     
   protected:
     Content m_content;
diff --git a/src/Minor.h b/src/Minor.h
index 0617361b2..da0d759de 100644
--- a/src/Minor.h
+++ b/src/Minor.h
@@ -45,14 +45,14 @@ template<typename MatrixType> class MatrixMinor
     int rows() const { return m_matrix.rows() - 1; }
     int cols() const { return m_matrix.cols() - 1; }
     
-    Scalar& operator()(int row, int col=0)
+    Scalar& write(int row, int col=0)
     {
-      return m_matrix(row + (row >= m_row), col + (col >= m_col));
+      return m_matrix.write(row + (row >= m_row), col + (col >= m_col));
     }
     
-    Scalar operator()(int row, int col=0) const
+    Scalar read(int row, int col=0) const
     {
-      return m_matrix(row + (row >= m_row), col + (col >= m_col));
+      return m_matrix.read(row + (row >= m_row), col + (col >= m_col));
     }
     
   protected:
@@ -61,33 +61,18 @@ template<typename MatrixType> class MatrixMinor
 };
 
 template<typename Derived>
-MatrixConstXpr<
+MatrixXpr<
   MatrixMinor<
-    const MatrixConstRef<
+    MatrixRef<
       MatrixBase<Derived>
     >
   >
 >
-MatrixBase<Derived>::minor(int row, int col) const
+MatrixBase<Derived>::minor(int row, int col)
 {
-  typedef MatrixMinor<const ConstRef> ProductType;
-  typedef MatrixConstXpr<ProductType> XprType;
-  return XprType(ProductType(constRef(), row, col));
-}
-
-template<typename Content>
-MatrixConstXpr<
-  MatrixMinor<
-    const MatrixConstXpr<Content>
-  >
->
-MatrixConstXpr<Content>::minor(int row, int col) const
-{
-  typedef MatrixMinor<
-            const MatrixConstXpr<Content>
-          > ProductType;
-  typedef MatrixConstXpr<ProductType> XprType;
-  return XprType(ProductType(*this, row, col));
+  typedef MatrixMinor<Ref> ProductType;
+  typedef MatrixXpr<ProductType> XprType;
+  return XprType(ProductType(ref(), row, col));
 }
 
 template<typename Content>
diff --git a/src/RowAndCol.h b/src/RowAndCol.h
index 5e348781d..5da3cfa23 100644
--- a/src/RowAndCol.h
+++ b/src/RowAndCol.h
@@ -45,18 +45,18 @@ template<typename MatrixType> class MatrixRow
     int rows() const { return m_matrix.cols(); }
     int cols() const { return 1; }
     
-    Scalar& operator()(int row, int col=0)
+    Scalar& write(int row, int col=0)
     {
       EIGEN_UNUSED(col);
       EIGEN_CHECK_ROW_RANGE(*this, row);
-      return m_matrix(m_row, row);
+      return m_matrix.write(m_row, row);
     }
     
-    Scalar operator()(int row, int col=0) const
+    Scalar read(int row, int col=0) const
     {
       EIGEN_UNUSED(col);
       EIGEN_CHECK_ROW_RANGE(*this, row);
-      return m_matrix(m_row, row);
+      return m_matrix.read(m_row, row);
     }
     
   protected:
@@ -81,18 +81,18 @@ template<typename MatrixType> class MatrixCol
     int rows() const { return m_matrix.rows(); }
     int cols() const { return 1; }
     
-    Scalar& operator()(int row, int col=0)
+    Scalar& write(int row, int col=0)
     {
       EIGEN_UNUSED(col);
       EIGEN_CHECK_ROW_RANGE(*this, row);
-      return m_matrix(row, m_col);
+      return m_matrix.write(row, m_col);
     }
     
-    Scalar operator()(int row, int col=0) const
+    Scalar read(int row, int col=0) const
     {
       EIGEN_UNUSED(col);
       EIGEN_CHECK_ROW_RANGE(*this, row);
-      return m_matrix(row, m_col);
+      return m_matrix.read(row, m_col);
     }
     
   protected:
@@ -102,33 +102,18 @@ template<typename MatrixType> class MatrixCol
 
 #define EIGEN_MAKE_ROW_COL_FUNCTIONS(func, Func) \
 template<typename Derived> \
-MatrixConstXpr< \
+MatrixXpr< \
   Matrix##Func< \
-    const MatrixConstRef< \
+    MatrixRef< \
       MatrixBase<Derived> \
     > \
   > \
 > \
-MatrixBase<Derived>::func(int i) const\
+MatrixBase<Derived>::func(int i)\
 { \
-  typedef Matrix##Func<const ConstRef> ProductType; \
-  typedef MatrixConstXpr<ProductType> XprType; \
-  return XprType(ProductType(constRef(), i)); \
-} \
-\
-template<typename Content> \
-MatrixConstXpr< \
-  Matrix##Func< \
-    const MatrixConstXpr<Content> \
-  > \
-> \
-MatrixConstXpr<Content>::func(int i) const\
-{ \
-  typedef Matrix##Func< \
-            const MatrixConstXpr<Content> \
-          > ProductType; \
-  typedef MatrixConstXpr<ProductType> XprType; \
-  return XprType(ProductType(*this, i)); \
+  typedef Matrix##Func<Ref> ProductType; \
+  typedef MatrixXpr<ProductType> XprType; \
+  return XprType(ProductType(ref(), i)); \
 } \
 \
 template<typename Content> \
@@ -137,7 +122,7 @@ MatrixXpr< \
     MatrixXpr<Content> \
   > \
 > \
-MatrixXpr<Content>::func(int i) \
+MatrixXpr<Content>::func(int i)\
 { \
   typedef Matrix##Func< \
             MatrixXpr<Content> \
diff --git a/src/ScalarOps.h b/src/ScalarOps.h
index 5d0a16ec9..01772569a 100644
--- a/src/ScalarOps.h
+++ b/src/ScalarOps.h
@@ -42,9 +42,9 @@ template<typename MatrixType> class ScalarProduct
     int rows() const { return m_matrix.rows(); }
     int cols() const { return m_matrix.cols(); }
 
-    Scalar operator()(int row, int col) const
+    Scalar read(int row, int col) const
     {
-      return m_matrix(row, col) * m_scalar;
+      return m_matrix.read(row, col) * m_scalar;
     }
 
   protected:
@@ -53,89 +53,89 @@ template<typename MatrixType> class ScalarProduct
 };
 
 template<typename Content>
-const MatrixConstXpr<
-  const ScalarProduct<
-    MatrixConstXpr<Content>
+MatrixXpr<
+  ScalarProduct<
+    MatrixXpr<Content>
   >
 >
-operator *(const MatrixConstXpr<Content>& xpr,
-                typename Content::Scalar scalar)
+operator *(const MatrixXpr<Content>& xpr,
+           typename Content::Scalar scalar)
 {
-  typedef const ScalarProduct<
-              MatrixConstXpr<Content>
-            > ProductType;
-  typedef const MatrixConstXpr<ProductType> XprType;
+  typedef ScalarProduct<
+            MatrixXpr<Content>
+          > ProductType;
+  typedef MatrixXpr<ProductType> XprType;
   return XprType(ProductType(xpr, scalar));
 }
 
 template<typename Content>
-const MatrixConstXpr<
-  const ScalarProduct<
-    MatrixConstXpr<Content>
+MatrixXpr<
+  ScalarProduct<
+    MatrixXpr<Content>
   >
 >
 operator *(typename Content::Scalar scalar,
-                const MatrixConstXpr<Content>& xpr)
+           const MatrixXpr<Content>& xpr)
 {
-  typedef const ScalarProduct<
-              MatrixConstXpr<Content>
-            > ProductType;
-  typedef const MatrixConstXpr<ProductType> XprType;
+  typedef ScalarProduct<
+            MatrixXpr<Content>
+          > ProductType;
+  typedef MatrixXpr<ProductType> XprType;
   return XprType(ProductType(xpr, scalar));
 }
 
 template<typename Derived>
-const MatrixConstXpr<
-  const ScalarProduct<
-    MatrixConstRef<MatrixBase<Derived> >
+MatrixXpr<
+  ScalarProduct<
+    MatrixRef<MatrixBase<Derived> >
   >
 >
-operator *(const MatrixBase<Derived>& matrix,
-                typename Derived::Scalar scalar)
+operator *(MatrixBase<Derived>& matrix,
+           typename Derived::Scalar scalar)
 {
-  typedef const ScalarProduct<
-              MatrixConstRef<MatrixBase<Derived> >
+  typedef ScalarProduct<
+              MatrixRef<MatrixBase<Derived> >
             > ProductType;
-  typedef const MatrixConstXpr<ProductType> XprType;
-  return XprType(ProductType(matrix.constRef(), scalar));
+  typedef MatrixXpr<ProductType> XprType;
+  return XprType(ProductType(matrix.ref(), scalar));
 }
 
 template<typename Derived>
-const MatrixConstXpr<
-  const ScalarProduct<
-    MatrixConstRef<MatrixBase<Derived> >
+MatrixXpr<
+  ScalarProduct<
+    MatrixRef<MatrixBase<Derived> >
   >
 >
 operator *(typename Derived::Scalar scalar,
-                const MatrixBase<Derived>& matrix)
+           MatrixBase<Derived>& matrix)
 {
-  typedef const ScalarProduct<
-              MatrixConstRef<MatrixBase<Derived> >
-            > ProductType;
-  typedef const MatrixConstXpr<ProductType> XprType;
-  return XprType(ProductType(matrix.constRef(), scalar));
+  typedef ScalarProduct<
+            MatrixRef<MatrixBase<Derived> >
+          > ProductType;
+  typedef MatrixXpr<ProductType> XprType;
+  return XprType(ProductType(matrix.ref(), scalar));
 }
 
 template<typename Content>
-const MatrixConstXpr<
-  const ScalarProduct<
-    MatrixConstXpr<Content>
+MatrixXpr<
+  ScalarProduct<
+    MatrixXpr<Content>
   >
 >
-operator /(const MatrixConstXpr<Content>& xpr,
-                typename Content::Scalar scalar)
+operator /(MatrixXpr<Content>& xpr,
+           typename Content::Scalar scalar)
 {
   return xpr * (static_cast<typename Content::Scalar>(1) / scalar);
 }
 
 template<typename Derived>
-const MatrixConstXpr<
-  const ScalarProduct<
-    MatrixConstRef<MatrixBase<Derived> >
+MatrixXpr<
+  ScalarProduct<
+    MatrixRef<MatrixBase<Derived> >
   >
 >
-operator /(const MatrixBase<Derived>& matrix,
-                typename Derived::Scalar scalar)
+operator /(MatrixBase<Derived>& matrix,
+           typename Derived::Scalar scalar)
 {
   return matrix * (static_cast<typename Derived::Scalar>(1) / scalar);
 }
diff --git a/src/Vector.h b/src/Vector.h
index f36364d4b..ae43a50c7 100644
--- a/src/Vector.h
+++ b/src/Vector.h
@@ -84,13 +84,13 @@ class Vector: public MatrixBase<Vector<T, Size> >
     { Base::operator=(other); }
     
     template<typename XprContent>
-    void operator=(const MatrixConstXpr<XprContent> &xpr)
+    void operator=(const MatrixXpr<XprContent> &xpr)
     {
       Base::operator=(xpr);
     }
 
     template<typename XprContent>
-    explicit Vector(const MatrixConstXpr<XprContent>& xpr)
+    explicit Vector(const MatrixXpr<XprContent>& xpr)
     {
       *this = xpr;
     }
@@ -131,13 +131,13 @@ class VectorX : public MatrixBase<VectorX<T> >
     }
     
     template<typename XprContent>
-    void operator=(const MatrixConstXpr<XprContent> &xpr)
+    void operator=(const MatrixXpr<XprContent> &xpr)
     {
       Base::operator=(xpr);
     }
 
     template<typename XprContent>
-    explicit VectorX(const MatrixConstXpr<XprContent>& xpr)
+    explicit VectorX(const MatrixXpr<XprContent>& xpr)
     {
       _init(xpr.rows());
       *this = xpr;
diff --git a/test/matrixmanip.cpp b/test/matrixmanip.cpp
index aa55d02cf..b3413212a 100644
--- a/test/matrixmanip.cpp
+++ b/test/matrixmanip.cpp
@@ -35,10 +35,10 @@ template<typename MatrixType> void matrixManip(const MatrixType& m)
   a.col(j);
   a.minor(i, j);
   a.block(1, rows-1, 1, cols-1);
-  a.xpr().row(i) = b.row(i);
-  a.xpr().row(i) += b.row(i);
-  a.xpr().minor(i, j) = b.block(1, rows-1, 1, cols-1);
-  a.alias().xpr().minor(i, j) -= a.block(1, rows-1, 1, cols-1);
+  a.row(i) = b.row(i);
+  a.row(i) += b.row(i);
+  a.minor(i, j) = b.block(1, rows-1, 1, cols-1);
+  a.alias().minor(i, j) -= a.block(1, rows-1, 1, cols-1);
 }
 
 void EigenTest::testMatrixManip()