title: Getting the index of boost::fusion::vector from a boost::mpl::vector
body: <p>I started to play around with the boost fusion and mpl library and got stuck with a quite simple problem.</p>
  
  <p>I declared the following types:</p>
  
  <pre><code>typedef boost::mpl::vector&lt;char, int, long&gt;   TypeVector;
  typedef boost::fusion::vector&lt;char, int, long&gt; FusionVector_t;
  </code></pre>
  
  <p>Now I wanted to write a function that gets me the value from the FusionVector.</p>
  
  <pre><code>template&lt;size_t N typename T&gt;
  T getValue(FusionVector_t fvec)
  {
      return boost::fusion::at_c&lt;N&gt;(fvec);
  }
  </code></pre>
  
  <p>The function works as expected but I would like to get the index from the boost::mpl vector and use it in this function and not pass it to the function as a template parameter.
  But I did not figure out so far how to do this.</p>
  
  <p>Could someone give me a hint?</p>