key types, the information will be mutable using iterators.
      </p>
<p>
</p>
<pre class="programlisting"><span class="identifier">i</span><span class="special">-&gt;</span><span class="identifier">info</span> <span class="special">+=</span> <span class="string">"More details about this book"</span><span class="special">;</span>
</pre>
<p>
      </p>
<p>
        A new function is included in <span class="emphasis"><em>unique</em></span> map views: <code class="computeroutput"><span class="identifier">info