boost_1_45_0/libs/variant/doc/reference/bad_visit.xml

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE header PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
  "http://www.boost.org/tools/boostbook/dtd/boostbook.dtd">
<header name="boost/variant/bad_visit.hpp">
  <namespace name="boost">

    <class name="bad_visit">
      <inherit access="public">
        <classname>std::exception</classname>
      </inherit>

      <purpose>
        <simpara>The exception thrown in the event of a visitor
          unable to handle the visited value.</simpara>
      </purpose>

      <method name="what" specifiers="virtual" cv="const">
        <type>const char *</type>
      </method>
    </class>

  </namespace>
</header>