unter' is used as a functor counting the
          characters, words and lines in the analyzed input sequence by identifying
          the matched tokens as passed from the <span class="emphasis"><em>Spirit.Lex</em></span> library.
        </p>
<p>
</p>
<pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">counter</span>
<span class="special">{</span>
    <span class="comment">// the function operator gets called for each of the matched tokens</span>
    <span class="comme