title: cannot invoke * with an argument list of type ($T12, @lvalue CGFloat)
body: <p>The title is the error message that I receive compiling this line:</p>
  
  <pre><code> let width : Float   = mainView.frame.size.width / 100.0 * value
  </code></pre>
  
  <p>The <code>value</code> variable is of <code>Float</code> type. What's wrong here?</p>