during the calculation, so then a temporary variable is
      created in this case.
    </p>
<p>
      Given the comments above, you might be forgiven for thinking that expression-templates
      are some kind of universal-panacea: sadly though, all tricks like this have
      their downsides. For one thing, expression template libraries like this one,
      tend to be slower to compile than their simpler cousins, they're also harder
      to debug (should you actually want to step through our code!), and r