title: C++ convert boost::optional<double> to double
body: <p>In C++ is it possible to convert  boost::optional to double?</p>
  
  <p>I.E.</p>
  
  <pre><code>boost::optional&lt;double&gt; time;
  double realTime;
  
  realTime = time;
  </code></pre>
  
  <p>The last line gives me an error that I </p>
  
  <pre><code>"Assigning to 'double' from incompatible type boost::optional&lt;double&gt;"
  </code></pre>