boost_1_45_0/libs/proto/doc/reference/proto_typeof.xml

<?xml version="1.0" encoding="utf-8"?>
<header name="boost/proto/proto_typeof.hpp">
  <para>Boost.Typeof registrations for Proto's types, and definition of the
    <computeroutput><macroname>BOOST_PROTO_AUTO</macroname>()</computeroutput> macro.</para>
  <macro name="BOOST_PROTO_AUTO" kind="functionlike">
    <macro-parameter name="Var"/>
    <macro-parameter name="Expr"/>
    <purpose>For defining a local variable that stores a Proto expression template,
      deep-copying the expression so there are no dangling references.</purpose>
    <description>
      <para>
        To define a local variable <computeroutput>ex</computeroutput> that stores the expression
        <computeroutput><functionname alt="boost::proto::lit">proto::lit</functionname>(1) + 2</computeroutput>,
        do the following:<programlisting>BOOST_PROTO_AUTO( ex, <functionname alt="boost::proto::lit">proto::lit</functionname>(1) + 2 );</programlisting>.
        The above is equivalent to the following:
        <programlisting>BOOST_AUTO( ex, <functionname alt="boost::proto::deep_copy">proto::deep_copy</functionname>( <functionname alt="boost::proto::lit">proto::lit</functionname>(1) + 2 ) );</programlisting>
      </para>
    </description>
  </macro>
</header>