title: Boost: typedef for rpm
body: <p>I'm trying to use boost::units in my code to define a type RoundsPerMinute. However I am not really understanding how to do that.</p>
  
  <p>I've defined a minute via</p>
  
  <pre><code>using boost::units::si::seconds;
  
  typedef boost::units::make_scaled_unit &lt; boost::units::si::time, boost::units::scale&lt;60, boost::units::static_rational&lt;1&gt; &gt; &gt;::type minute;
  BOOST_UNITS_STATIC_CONSTANT(minutes, minute);
  
  typedef boost::units::quantity&lt;minute, float&gt; Minute;
  </code></pre>
  
  <p>and can now do e.g.</p>
  
  <pre><code>Minute m = 5*minutes;
  </code></pre>
  
  <p>What I now would like to do is something along the lines of</p>
  
  <pre><code>RoundsPerMinute rpm1 = 50 * rpm;
  RoundsPerMinute rpm2 = 100 / (2*minutes);
  Minute m = 1/rpm2; // how many minutes does it take for one round?
  </code></pre>
  
  <p>but I am not sure how to define these types - frankly the whole boost documentation is way too technical for me to understand :-( If anybody could help me out with the definitions, this would be great.</p>