title: Eigen: Use SparseMatrix's selfAdjointView
body: <p>According to the Eigen <a href="http://eigen.tuxfamily.org/dox/TutorialSparse.html#TutorialSparse_TriangularSelfadjoint" rel="nofollow">documentation</a>, I would expect the following to work:</p>
  
  <pre><code>#include "Eigen/Dense"
  #include "Eigen/Sparse"
  SparseMatrix&lt;double&gt; mymatrix = SomeFunctionReturningASparseMatrix();
  
  SparseMatrix&lt;double&gt; test = mymatrix.selfadjointView&lt;Lower&gt;();
  </code></pre>
  
  <p>However, I get the compile-time-error</p>
  
  <pre><code>conversion from 'Eigen::SparseSelfAdjointView&lt;Eigen::SparseMatrix&lt;double&gt;, 2u&gt;' to 
  non-scalar type 'Eigen::SparseMatrix&lt;double&gt;' requested
  </code></pre>
  
  <p>What am I doing wrong? Missing include?</p>
  
  <p>Second question: As far as I was able to find, Eigen does not yet support multiplication of SparseSelfadjointViews with SparseMatrices. Am I missing something, or is this in fact not implemented?  </p>