A better question: &quot;What impressive programs are written in Lisp?&quot;.  Or &quot;Why isn&#x27;t there a Squeak-like Lisp machine environment, where &#x27;compatibility&#x27; doesn&#x27;t have to matter?&quot;.  If a language is incredibly productive and programmable, why don&#x27;t we already have a VPRI-like STEPS environment in 20,000 lines?<p><a href="http:&#x2F;&#x2F;www.vpri.org&#x2F;pdf&#x2F;tr2011004_steps11.pdf" rel="nofollow">http:&#x2F;&#x2F;www.vpri.org&#x2F;pdf&#x2F;tr2011004_steps11.pdf</a>