https://svn.boost.org/trac10/ticket/797 <pre class="wiki">he 3 expression requirements on: http://www.boost.org/libs/mpl/doc/refmanual/placeholder-expression.html make no mention that X should have a nested type typedef. IOW, X must be a metafunction as defined here: http://www.boost.org/libs/mpl/doc/refmanual/metafunction.html However, I believe it should since I'm getting compile-time error messages without the nested typedef. </pre> en-us /htdocs/site/boost.png https://svn.boost.org/trac10/ticket/797 Trac 1.4.3 david_abrahams Sat, 16 Dec 2006 22:22:49 GMT https://svn.boost.org/trac10/ticket/797#comment:1 https://svn.boost.org/trac10/ticket/797#comment:1 <ul> <li><strong>status</strong> <span class="trac-field-old">assigned</span> → <span class="trac-field-new">closed</span> </li> </ul> <pre class="wiki">Logged In: YES user_id=52572 Originator: NO The documentation is correct as is. std::vector&lt;_1&gt; is a placeholder expression even though std::vector has no nested ::type. Whatever compiler errors you're seeing are not caused by a bug in the documentation. </pre> Ticket