title: adding interpretations
body: <p>excuse me if this is a dumb question, but I just want to know what exactly do they mean by this?</p>
  
  <pre><code> (define-struct squar (x y size outline c))
  </code></pre>
  
  <p>"Add interpretations for the Square  class"</p>
  
  <p>I've tried looking this up online, but nothing.</p>