n><span class="n">stack</span><span class="p">%</span><span class="n">top_index</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
<span class="k">      print</span><span class="o">*</span><span class="p">,</span><span class="s2">&quot;Attempt to pop from empty token stack&quot;</span><span class="w"></span>
<span class="w">    </span><span class="k">else</span>
<span class="k"