boost_1_45_0/libs/concept_check/doc/reference/DefaultConstructible.xml

<?xml version="1.0"?>
<concept name="DefaultConstructible" category="Utility"><!--
Based on concepts from the SGI Standard Template Library documentation:
Copyright (c) 1996-1999
Silicon Graphics Computer Systems, Inc.

Copyright (c) 1994
Hewlett-Packard Company
--><!--
Copyright 2000-2001 University of Notre Dame du Lac.
Copyright 2001-2002 Indiana University.
Some concepts based on versions from the MTL draft manual and Boost Graph
and Property Map documentation:
Copyright (c) Jeremy Siek, Lie-Quan Lee, and Andrew Lumsdaine 2000
-->
  <param name="X" role="default-constructible-type"/>

  <models-sentence>The type <arg num="1"/> must be a model of <self/>.</models-sentence>

  <description><para>DefaultConstructible objects only need to have a default
  constructor.</para></description>

  <valid-expression name="Construction">
    <construct template-parameters="">
      <type name="X"/>
    </construct>
    <return-type><require-same-type testable="yes"><type name="X"/></require-same-type></return-type>
    <semantics>Construct an instance of the type with default parameters.</semantics>
  </valid-expression>

  <example-model>
    <type name="int"/>
  </example-model>

  <example-model>
    <apply-template name="std::vector">
      <type name="double"/>
    </apply-template>
  </example-model>
</concept>