ecide.</li>
	<li>In addition to <code>sequence(sym)</code>, there is also
  <code>simple(sym)</code> and <code>subtree(sym)</code>. Those match simple
  strings and entire subtrees respectively. Caution with the latter.</li>
</ul>
<p>Here&#8217;s how you would write a somewhat classical interpreter for our little 
language by using a transformation. Note that from this point on, there is
not one way to go about this, but thousands; you are really free (and on
your own):</p>
<pre class="sh_ruby"><code title=