s="keyword">auto</span> <span class="identifier">pos</span> <span class="special">=</span> <span class="identifier">positions</span><span class="special">.</span><span class="identifier">position_of</span><span class="special">(</span><span class="identifier">ast</span><span class="special">[</span><span class="number">1</span><span class="special">]);</span> <span class="comment">// zero based of course!</span>
</pre>
<p>
        <code class="computeroutput"><span class="identifier">pos</span></code> is an