
  parser.parse(
    'puts(1,2,3, 4+5)'))
        
ast.eval # =&gt; [1, 2, 3, 9]
</code></pre>
<p>That&#8217;s a bunch of code for printing <code>[1, 2, 3, 9]</code>. Welcome to the
fantastic world of compiler and interpreter writing!</p>
<p><sup class="footnote" id="fnr1"><a href="#fn1">1</a></sup> As far as parsing goes. There is a subtle difference between
<code>#repeat(0,1)</code> and <code>#maybe</code>. Can you figure it out?</p>
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