Chez Scheme is now free
Dybvig&#x27;s compiler course was exemplary. Say what you may about Scheme, you learned so much more in those classes. His Scheme Programming Language book is highly recommended. Especially check out his extended examples chapter:  <a href="http:&#x2F;&#x2F;www.scheme.com&#x2F;tspl4&#x2F;examples.html#.&#x2F;examples:h0" rel="nofollow">http:&#x2F;&#x2F;www.scheme.com&#x2F;tspl4&#x2F;examples.html#.&#x2F;examples:h0</a>