https://svn.boost.org/trac10/ticket/5273 <p> I'm having a problem distinguishing the difference between metafunctions at_key and value_at_key. The documentation for value_at_key shows the following example: </p> <pre class="wiki">typedef map&lt;pair&lt;int, char&gt;, pair&lt;char, char&gt;, pair&lt;double, char&gt; &gt; mymap; BOOST_MPL_ASSERT((boost::is_same&lt;result_of::at_key&lt;mymap, int&gt;::type, char&gt;)); </pre><p> note the absence of value_at_key in the example! while the example in at_key shows </p> <pre class="wiki">typedef map&lt;pair&lt;int, char&gt;, pair&lt;char, char&gt;, pair&lt;double, char&gt; &gt; mymap; BOOST_MPL_ASSERT((boost::is_same&lt;result_of::at_key&lt;mymap, int&gt;::type, char&amp;&gt;)); </pre><p> I see the &amp; indicating a reference, but I can't see how this would be any different than using add_reference to the result of at_value_key. </p> <p> Any little bit of light you might want shed here would be helpful. At the very least, I think the documention should be clarified. </p> <p> Robert Ramey </p> en-us /htdocs/site/boost.png https://svn.boost.org/trac10/ticket/5273 Trac 1.4.3 Steven Watanabe Sun, 13 Mar 2011 19:25:42 GMT https://svn.boost.org/trac10/ticket/5273#comment:2 https://svn.boost.org/trac10/ticket/5273#comment:2 <ul> <li><strong>status</strong> <span class="trac-field-old">new</span> → <span class="trac-field-new">closed</span> </li> <li><strong>resolution</strong> → <span class="trac-field-new">fixed</span> </li> </ul> Ticket