 allowing
          to stop the tokenization process. The default token type used in this example
          carries a token value of the type <a href="../../../../../../../libs/range/doc/html/range/reference/utilities/iterator_range.html" target="_top"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">iterator_range</span></code></a><code class="computeroutput"><span class="special">&lt;</span><span class="identifier">BaseIterator</span