Improved I13_FunctionsTakingEigenTypes.dox.

Removed the r-value reference part and focused on EIGEN_REF_TO_TEMPORARY only.

1 files changed, 2 insertions, 21 deletions

diff --git a/doc/I13_FunctionsTakingEigenTypes.dox b/doc/I13_FunctionsTakingEigenTypes.dox
index 6da09491b..fea6b940f 100644
--- a/doc/I13_FunctionsTakingEigenTypes.dox
+++ b/doc/I13_FunctionsTakingEigenTypes.dox
@@ -104,10 +104,9 @@ When trying to execute the following code
 MatrixXf C = MatrixXf::Zero(3,6);
 cov(x,y, C.block(0,0,3,3));
 \endcode
-the compiler will fail, because it is not possible to convert the expression returned by \c MatrixXf::block() in a non-const \c MatrixXf&. This is the case because the compiler wants to protect you from writing your result to a temporary object. In this special case this protection is not intended -- we want to write to a temporary object. So how can we overcome this problem? There are two possible solutions depending on the type of compiler you are using. 
+the compiler will fail, because it is not possible to convert the expression returned by \c MatrixXf::block() into a non-const \c MatrixXf&. This is the case because the compiler wants to protect you from writing your result to a temporary object. In this special case this protection is not intended -- we want to write to a temporary object. So how can we overcome this problem? 
 
-<b>Solution A)</b>
-Assuming you are using a compiler following the C98 standard, the only thing you can do is to use a little \em hack. You need to pass a const reference and internally the constness needs to be cast away. The correct implementation for C98 compliant compilers would be
+The solution which is preferred at the moment is based on a little \em hack. One needs to pass a const reference to the matrix and internally the constness needs to be cast away. The correct implementation for C98 compliant compilers would be
 \code
 template <typename Derived, typename OtherDerived>
 void cov(const MatrixBase<Derived>& x, const MatrixBase<Derived>& y, MatrixBase<OtherDerived> EIGEN_REF_TO_TEMPORARY C)
@@ -128,24 +127,6 @@ The implementation above does now not only work with temporary expressions but i
 
 \b Note: The const cast hack will only work with templated functions. It will not work with the MatrixXf implementation because it is not possible to cast a Block expression to a Matrix reference!
 
-<b>Solution B)</b>
-In the next solution we are going to utilize a new feature introduced with C++0x compliant compilers -- so called rvalue references. Rvalue references allow to explicitly tell the compiler that the object we are going to pass to a function is a temporary object that is writeable. The C++0x compliant implementation of the covariance function will be
-\code
-template <typename Derived, typename OtherDerived>
-void cov(const MatrixBase<Derived>& x, const MatrixBase<Derived>& y, MatrixBase<OtherDerived>&& C)
-{
-  typedef typename ei_traits<Derived>::Scalar Scalar;
-  typedef typename ei_plain_row_type<Derived>::type RowVectorType;
-
-  const Scalar num_observations = static_cast<Scalar>(x.rows());
-
-  const RowVectorType x_mean = x.colwise().sum() / num_observations;
-  const RowVectorType y_mean = y.colwise().sum() / num_observations;
-
-  C = (x.rowwise() - x_mean).transpose() * (y.rowwise() - y_mean) / num_observations;
-}
-\endcode
-
 \section TopicResizingInGenericImplementations How to resize matrices in generic implementations?
 
 One might think we are done now, right? This is not completely true because in order for our covariance function to be generically applicable, we want the follwing code to work