<?xml version="1.0" encoding="utf-8"?>
<header name="boost/proto/traits.hpp">
  <para>Contains definitions for child&lt;&gt;, child_c&lt;&gt;, left&lt;&gt;, right&lt;&gt;, tag_of&lt;&gt;, and the helper functions child(), child_c(), value(), left() and right(). </para>
  <namespace name="boost">
    <namespace name="proto">
      <struct name="is_callable">
        <template>
          <template-type-parameter name="T"/>
        </template>
        <purpose>Boolean metafunction which tells whether a type is a callable
          <conceptname>PolymorphicFunctionObject</conceptname> or not.</purpose>
        <description>
          <para>
            <computeroutput>proto::is_callable&lt;&gt;</computeroutput> is used by the
            <computeroutput><classname alt="proto::when">proto::when&lt;&gt;</classname></computeroutput>
            transform to determine whether a function type <computeroutput>R(A<subscript>1</subscript>,...<subscript>n</subscript>)</computeroutput>
            is a <conceptname>CallableTransform</conceptname> or an <conceptname>ObjectTransform</conceptname>.
            The former are evaluated using <computeroutput><classname>proto::call&lt;&gt;</classname></computeroutput>
            and the later with <computeroutput><classname>proto::make&lt;&gt;</classname></computeroutput>.
            If <computeroutput>proto::is_callable&lt;R&gt;::value</computeroutput> is <computeroutput>true</computeroutput>,
            the function type is a <conceptname>CallableTransform</conceptname>; otherwise, it is an <conceptname>ObjectTransform</conceptname>.
          </para>
          <para>
            Unless specialized for a type
            <computeroutput>T</computeroutput>, <computeroutput>proto::is_callable&lt;T&gt;::value</computeroutput>
            is computed as follows:
            <itemizedlist>
              <listitem>
                <para>
                  If <computeroutput>T</computeroutput> is a template type
                  <computeroutput>X&lt;Y<subscript>0</subscript>,...Y<subscript>n</subscript>&gt;</computeroutput>,
                  where all <computeroutput>Y<subscript>x</subscript></computeroutput> are types for
                  <computeroutput>x</computeroutput> in <computeroutput>[0,n]</computeroutput>,
                  <computeroutput>proto::is_callable&lt;T&gt;::value</computeroutput> is
                  <computeroutput>boost::is_same&lt;Y<subscript>n</subscript>, <classname>proto::callable</classname>&gt;::value</computeroutput>.
                </para>
              </listitem>
              <listitem>
                <para>
                  If <computeroutput>T</computeroutput> is derived from <computeroutput><classname>proto::callable</classname></computeroutput>,
                  <computeroutput>proto::is_callable&lt;T&gt;::value</computeroutput> is <computeroutput>true</computeroutput>.
                </para>
              </listitem>
              <listitem>
                <para>
                  Otherwise, <computeroutput>proto::is_callable&lt;T&gt;::value</computeroutput>
                  is <computeroutput>false</computeroutput>.
                </para>
              </listitem>
            </itemizedlist>
          </para>
        </description>
      </struct>

      <struct name="is_aggregate">
        <template>
          <template-type-parameter name="T"/>
        </template>
        <purpose>A Boolean metafunction that indicates whether a type requires aggregate initialization. </purpose>
        <description>
          <para>
            <computeroutput>proto::is_aggregate&lt;&gt;</computeroutput> is used by the
            <computeroutput><classname>proto::make&lt;&gt;</classname></computeroutput> transform to determine how
            to construct an object of some type <computeroutput>T</computeroutput>, given some initialization arguments
            <computeroutput>a<subscript>0</subscript>,...a<subscript>n</subscript></computeroutput>.
            If <computeroutput>proto::is_aggregate&lt;T&gt;::value</computeroutput> is <computeroutput>true</computeroutput>,
            then an object of type <computeroutput>T</computeroutput> will be initialized as
            <computeroutput>T t = {a<subscript>0</subscript>,...a<subscript>n</subscript>};</computeroutput>.
            Otherwise, it will be initialized as <computeroutput>T t(a<subscript>0</subscript>,...a<subscript>n</subscript>)</computeroutput>.
          </para>
          <para>
            Note: <computeroutput><classname>proto::expr&lt;&gt;</classname> is an aggregate.</computeroutput>
          </para>
        </description>
      </struct>
      <namespace name="functional">
        <struct name="as_expr">
          <template>
            <template-type-parameter name="Domain">
              <default><classname>proto::default_domain</classname></default>
            </template-type-parameter>
          </template>
          <purpose>A callable <conceptname>PolymorphicFunctionObject</conceptname> that is equivalent to the
            <computeroutput><functionname alt="proto::as_expr">proto::as_expr()</functionname></computeroutput> function.
          </purpose>
          <inherit><type><classname>proto::callable</classname></type></inherit>
          <struct-specialization name="result">
            <template>
              <template-type-parameter name="This"/>
              <template-type-parameter name="T"/>
            </template>
            <specialization>
              <template-arg>This(T)</template-arg>
            </specialization>
            <inherit><type><classname>proto::result_of::as_expr</classname>&lt; T, Domain &gt;</type></inherit>
          </struct-specialization>
          <method-group name="public member functions">
            <method name="operator()" cv="const">
              <type>typename <classname>proto::result_of::as_expr</classname>&lt; T, Domain &gt;::type</type>
              <template>
                <template-type-parameter name="T"/>
              </template>
              <parameter name="t">
                <paramtype>T &amp;</paramtype>
                <description>
                  <para>The object to wrap. </para>
                </description>
              </parameter>
              <description>
                <para>
                  Wrap an object in a Proto terminal if it isn't a Proto expression already.
                </para>
              </description>
              <returns>
                <para>
                  <computeroutput>proto::as_expr&lt;Domain&gt;(t)</computeroutput>
                </para>
              </returns>
            </method>
            <method name="operator()" cv="const">
              <type>typename <classname>proto::result_of::as_expr</classname>&lt; T const, Domain &gt;::type</type>
              <template>
                <template-type-parameter name="T"/>
              </template>
              <parameter name="t">
                <paramtype>T const &amp;</paramtype>
              </parameter>
              <description>
                <para>This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. </para>
              </description>
            </method>
          </method-group>
        </struct>
        
        <struct name="as_child">
          <template>
            <template-type-parameter name="Domain">
              <default><classname>proto::default_domain</classname></default>
            </template-type-parameter>
          </template>
          <purpose>
            A callable <conceptname>PolymorphicFunctionObject</conceptname> that is equivalent to the
            <computeroutput><functionname alt="proto::as_child">proto::as_child()</functionname></computeroutput> function.
          </purpose>
          <inherit><type><classname>proto::callable</classname></type></inherit>
          <struct-specialization name="result">
            <template>
              <template-type-parameter name="This"/>
              <template-type-parameter name="T"/>
            </template>
            <specialization>
              <template-arg>This(T)</template-arg>
            </specialization>
            <inherit><type><classname>proto::result_of::as_child</classname>&lt; T, Domain &gt;</type></inherit>
          </struct-specialization>
          <method-group name="public member functions">
            <method name="operator()" cv="const">
              <type>typename <classname>proto::result_of::as_child</classname>&lt; T, Domain &gt;::type</type>
              <template>
                <template-type-parameter name="T"/>
              </template>
              <parameter name="t">
                <paramtype>T &amp;</paramtype>
                <description>
                  <para>The object to wrap. </para>
                </description>
              </parameter>
              <description>
                <para>
                  Wrap an object in a Proto terminal if it isn't a Proto expression already.
                </para>
              </description>
              <returns>
                <para>
                  <computeroutput>proto::as_child&lt;Domain&gt;(t)</computeroutput>
                </para>
              </returns>
            </method>
            <method name="operator()" cv="const">
              <type>typename <classname>proto::result_of::as_child</classname>&lt; T const, Domain &gt;::type</type>
              <template>
                <template-type-parameter name="T"/>
              </template>
              <parameter name="t">
                <paramtype>T const &amp;</paramtype>
              </parameter>
              <description>
                <para>This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. </para>
              </description>
            </method>
          </method-group>
        </struct>
        
        <struct name="child_c">
          <template>
            <template-nontype-parameter name="N">
              <type>long</type>
            </template-nontype-parameter>
          </template>
          <purpose>
            A callable <conceptname>PolymorphicFunctionObject</conceptname> that is equivalent to the
            <computeroutput><functionname alt="proto::child_c">proto::child_c()</functionname></computeroutput> function.
          </purpose>
          <inherit><type><classname>proto::callable</classname></type></inherit>
          <struct-specialization name="result">
            <template>
              <template-type-parameter name="This"/>
              <template-type-parameter name="Expr"/>
            </template>
            <specialization>
              <template-arg>This(Expr)</template-arg>
            </specialization>
            <inherit><type><classname>proto::result_of::child_c</classname>&lt; Expr, N &gt;</type></inherit>
          </struct-specialization>
          <method-group name="public member functions">
            <method name="operator()" cv="const">
              <type>typename <classname>proto::result_of::child_c</classname>&lt; Expr &amp;, N &gt;::type</type>
              <template>
                <template-type-parameter name="Expr"/>
              </template>
              <parameter name="expr">
                <paramtype>Expr &amp;</paramtype>
                <description>
                  <para>The expression node. </para>
                </description>
              </parameter>
              <description>
                <para>
                  Return the <replaceable>N</replaceable><superscript>th</superscript> child of the given expression.
                </para>
              </description>
              <requires>
                <para>
                  <computeroutput><classname>proto::is_expr</classname>&lt;Expr&gt;::value</computeroutput> is
                  <computeroutput>true</computeroutput>
                </para>
                <para>
                  <computeroutput>N &lt; Expr::proto_arity::value</computeroutput>
                </para>
              </requires>
              <returns>
                <para>
                  <computeroutput><functionname>proto::child_c</functionname>&lt;N&gt;(expr)</computeroutput>
                </para>
              </returns>
              <throws>
                <simpara>Will not throw.</simpara>
              </throws>
            </method>
            <method name="operator()" cv="const">
              <type>typename <classname>proto::result_of::child_c</classname>&lt; Expr const &amp;, N &gt;::type</type>
              <template>
                <template-type-parameter name="Expr"/>
              </template>
              <parameter name="expr">
                <paramtype>Expr const &amp;</paramtype>
              </parameter>
              <description>
                <para>This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. </para>
              </description>
            </method>
          </method-group>
        </struct>

        <struct name="child">
          <template>
            <template-type-parameter name="N">
              <default>mpl::long_&lt;0&gt;</default>
            </template-type-parameter>
          </template>
          <purpose>A callable <conceptname>PolymorphicFunctionObject</conceptname> that is equivalent to the
            <computeroutput><functionname alt="proto::child">proto::child()</functionname></computeroutput> function.</purpose>
          <description>
            <para>
              A callable <conceptname>PolymorphicFunctionObject</conceptname> that is equivalent to the
              <computeroutput><functionname alt="proto::child">proto::child()</functionname></computeroutput>
              function. <computeroutput>N</computeroutput> is required to be an MPL Integral Constant.
            </para>
          </description>
          <inherit><type><classname>proto::callable</classname></type></inherit>
          <struct-specialization name="result">
            <template>
              <template-type-parameter name="This"/>
              <template-type-parameter name="Expr"/>
            </template>
            <specialization>
              <template-arg>This(Expr)</template-arg>
            </specialization>
            <inherit>
              <type><classname>proto::result_of::child</classname>&lt; Expr, N &gt;</type>
            </inherit>
          </struct-specialization>
          <method-group name="public member functions">
            <method name="operator()" cv="const">
              <type>typename <classname>proto::result_of::child</classname>&lt; Expr &amp;, N &gt;::type</type>
              <template>
                <template-type-parameter name="Expr"/>
              </template>
              <parameter name="expr">
                <paramtype>Expr &amp;</paramtype>
                <description>
                  <para>The expression node. </para>
                </description>
              </parameter>
              <description>
                <para>
                  Return the <replaceable>N</replaceable><superscript>th</superscript> child of the given expression.
                </para>
              </description>
              <requires>
                <para>
                  <computeroutput><classname>proto::is_expr</classname>&lt;Expr&gt;::value</computeroutput> is
                  <computeroutput>true</computeroutput>
                </para>
                <para>
                  <computeroutput>N::value &lt; Expr::proto_arity::value</computeroutput>
                </para>
              </requires>
              <returns>
                <para>
                  <computeroutput><functionname>proto::child</functionname>&lt;N&gt;(expr)</computeroutput>
                </para>
              </returns>
              <throws>
                <simpara>Will not throw.</simpara>
              </throws>
            </method>
            <method name="operator()" cv="const">
              <type>typename <classname>proto::result_of::child</classname>&lt; Expr const &amp;, N &gt;::type</type>
              <template>
                <template-type-parameter name="Expr"/>
              </template>
              <parameter name="expr">
                <paramtype>Expr const &amp;</paramtype>
              </parameter>
              <description>
                <para>This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. </para>
              </description>
            </method>
          </method-group>
        </struct>

        <struct name="value">
          <purpose>
            A callable <conceptname>PolymorphicFunctionObject</conceptname> that is equivalent to the
            <computeroutput><functionname alt="proto::value">proto::value()</functionname></computeroutput> function.
          </purpose>
          <inherit><type><classname>proto::callable</classname></type></inherit>
          <struct-specialization name="result">
            <template>
              <template-type-parameter name="This"/>
              <template-type-parameter name="Expr"/>
            </template>
            <specialization>
              <template-arg>This(Expr)</template-arg>
            </specialization>
            <inherit>
              <type><classname>proto::result_of::value</classname>&lt; Expr &gt;</type>
            </inherit>
          </struct-specialization>
          <method-group name="public member functions">
            <method name="operator()" cv="const">
              <type>typename <classname>proto::result_of::value</classname>&lt; Expr &amp; &gt;::type</type>
              <template>
                <template-type-parameter name="Expr"/>
              </template>
              <parameter name="expr">
                <paramtype>Expr &amp;</paramtype>
                <description>
                  <para>The terminal expression node. </para>
                </description>
              </parameter>
              <description>
                <para>
                  Return the value of the given terminal expression.
                </para>
              </description>
              <requires>
                <para>
                  <computeroutput><classname>proto::is_expr</classname>&lt;Expr&gt;::value</computeroutput> is
                  <computeroutput>true</computeroutput>
                </para>
                <para>
                  <computeroutput>0 == Expr::proto_arity::value</computeroutput>
                </para>
                <para>
                  <computeroutput>Expr::proto_tag</computeroutput> is
                  <computeroutput><classname>proto::tag::terminal</classname></computeroutput>
                </para>
              </requires>
              <returns>
                <para>
                  <computeroutput><functionname>proto::value</functionname>(expr)</computeroutput>
                </para>
              </returns>
              <throws>
                <simpara>Will not throw.</simpara>
              </throws>
            </method>
            <method name="operator()" cv="const">
              <type>typename <classname>proto::result_of::value</classname>&lt; Expr const &amp; &gt;::type</type>
              <template>
                <template-type-parameter name="Expr"/>
              </template>
              <parameter name="expr">
                <paramtype>Expr const &amp;</paramtype>
              </parameter>
              <description>
                <para>This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. </para>
              </description>
            </method>
          </method-group>
        </struct>
        
        <struct name="left">
          <purpose>A callable <conceptname>PolymorphicFunctionObject</conceptname> that is equivalent to the
            <computeroutput><functionname alt="proto::left">proto::left()</functionname></computeroutput> function.</purpose>
          <struct-specialization name="result">
            <template>
              <template-type-parameter name="This"/>
              <template-type-parameter name="Expr"/>
            </template>
            <specialization>
              <template-arg>This(Expr)</template-arg>
            </specialization>
            <inherit>
              <type><classname>proto::result_of::left</classname>&lt; Expr &gt;</type>
            </inherit>
          </struct-specialization>
          <inherit>
            <type><classname>proto::callable</classname></type>
          </inherit>
          <method-group name="public member functions">
            <method name="operator()" cv="const">
              <type>typename <classname>proto::result_of::left</classname>&lt; Expr &amp; &gt;::type</type>
              <template>
                <template-type-parameter name="Expr"/>
              </template>
              <parameter name="expr">
                <paramtype>Expr &amp;</paramtype>
                <description>
                  <para>The expression node. </para>
                </description>
              </parameter>
              <description>
                <para>
                  Return the left child of the given binary expression.
                </para>
              </description>
              <requires>
                <para>
                  <computeroutput><classname>proto::is_expr</classname>&lt;Expr&gt;::value</computeroutput> is
                  <computeroutput>true</computeroutput>
                </para>
                <para>
                  <computeroutput>2 == Expr::proto_arity::value</computeroutput>
                </para>
              </requires>
              <returns>
                <para>
                  <computeroutput><functionname>proto::left</functionname>(expr)</computeroutput>
                </para>
              </returns>
              <throws>
                <simpara>Will not throw.</simpara>
              </throws>
            </method>
            <method name="operator()" cv="const">
              <type>typename <classname>proto::result_of::left</classname>&lt; Expr const &amp; &gt;::type</type>
              <template>
                <template-type-parameter name="Expr"/>
              </template>
              <parameter name="expr">
                <paramtype>Expr const &amp;</paramtype>
              </parameter>
              <description>
                <para>This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. </para>
              </description>
            </method>
          </method-group>
        </struct>

        <struct name="right">
          <purpose>A callable <conceptname>PolymorphicFunctionObject</conceptname> that is equivalent to the
            <computeroutput><functionname alt="proto::right">proto::right()</functionname></computeroutput> function.</purpose>
          <struct-specialization name="result">
            <template>
              <template-type-parameter name="This"/>
              <template-type-parameter name="Expr"/>
            </template>
            <specialization>
              <template-arg>This(Expr)</template-arg>
            </specialization>
            <inherit>
              <type><classname>proto::result_of::right</classname>&lt; Expr &gt;</type>
            </inherit>
          </struct-specialization>
          <inherit>
            <type><classname>proto::callable</classname></type>
          </inherit>
          <method-group name="public member functions">
            <method name="operator()" cv="const">
              <type>typename <classname>proto::result_of::right</classname>&lt; Expr &amp; &gt;::type</type>
              <template>
                <template-type-parameter name="Expr"/>
              </template>
              <parameter name="expr">
                <paramtype>Expr &amp;</paramtype>
                <description>
                  <para>The expression node. </para>
                </description>
              </parameter>
              <description>
                <para>Return the right child of the given binary expression.</para>
              </description>
              <requires>
                <para>
                  <computeroutput><classname>proto::is_expr</classname>&lt;Expr&gt;::value</computeroutput> is <computeroutput>true</computeroutput>
                </para>
                <para>
                  <computeroutput>2 == Expr::proto_arity::value</computeroutput>
                </para>
              </requires>
              <returns>
                <para>
                  <computeroutput><functionname>proto::right</functionname>(expr)</computeroutput>
                </para>
              </returns>
              <throws>
                <simpara>Will not throw.</simpara>
              </throws>
            </method>
            <method name="operator()" cv="const">
              <type>typename <classname>proto::result_of::right</classname>&lt; Expr const &amp; &gt;::type</type>
              <template>
                <template-type-parameter name="Expr"/>
              </template>
              <parameter name="expr">
                <paramtype>Expr const &amp;</paramtype>
              </parameter>
            </method>
          </method-group>
        </struct>
      </namespace>

      <struct name="terminal">
        <template>
          <template-type-parameter name="T"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; terminal&lt;T&gt; &gt;</inherit>
        <purpose>A metafunction for generating terminal expression types, a grammar element for matching
          terminal expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that returns the current expression unchanged. </purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit><classname>proto::transform_impl</classname>&lt; Expr, State, Data &gt;</inherit>
          <typedef name="result_type">
            <type>Expr</type>
          </typedef>
          <method-group name="public member functions">
            <method name="operator()" cv="const">
              <type>impl::expr_param</type>
              <parameter name="expr">
                <paramtype>typename impl::expr_param</paramtype>
                <description>
                  <para>The current expression </para>
                </description>
              </parameter>
              <parameter name="">
                <paramtype>typename impl::state_param</paramtype>
              </parameter>
              <parameter name="">
                <paramtype>typename impl::data_param</paramtype>
              </parameter>
              <requires>
                <para>
                  <computeroutput><classname>proto::matches</classname>&lt;Expr, proto::terminal&lt;T&gt; &gt;::value</computeroutput> is <computeroutput>true</computeroutput>.
                </para>
              </requires>
              <returns>
                <para>
                  <computeroutput>expr</computeroutput>
                </para>
              </returns>
              <throws>
                <simpara>Will not throw.</simpara>
              </throws>
            </method>
          </method-group>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::terminal</classname>, <classname>proto::term</classname>&lt; T &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="if_else_">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
          <template-type-parameter name="V"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; if_else_&lt;T, U, V&gt; &gt;</inherit>
        <purpose>A metafunction for generating ternary conditional expression types, a grammar element for
          matching ternary conditional expressions, and
          a <conceptname>PrimitiveTransform</conceptname>
          that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;if_else_&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::if_else_</classname>, <classname alt="proto::listN">proto::list3</classname>&lt; T, U, V &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="unary_plus">
        <template>
          <template-type-parameter name="T"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; unary_plus&lt;T&gt; &gt;</inherit>
        <purpose>A metafunction for generating unary plus expression types,
          a grammar element for matching unary plus expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;unary_plus&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::unary_plus</classname>, <classname alt="proto::listN">proto::list1</classname>&lt; T &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>
      
      <struct name="negate">
        <template>
          <template-type-parameter name="T"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; negate&lt;T&gt; &gt;</inherit>
        <purpose>A metafunction for generating unary minus expression types, 
          a grammar element for matching unary minus expressions, and 
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the 
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput> 
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;negate&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::negate</classname>, <classname alt="proto::listN">proto::list1</classname>&lt; T &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>
      
      <struct name="dereference">
        <template>
          <template-type-parameter name="T"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; dereference&lt;T&gt; &gt;</inherit>
        <purpose>A metafunction for generating defereference expression types, 
          a grammar element for matching dereference expressions, and 
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the 
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;dereference&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::dereference</classname>, <classname alt="proto::listN">proto::list1</classname>&lt; T &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>
      
      <struct name="complement">
        <template>
          <template-type-parameter name="T"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; complement&lt;T&gt; &gt;</inherit>
        <purpose>A metafunction for generating complement expression types, 
          a grammar element for matching complement expressions, and 
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the 
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;complement&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::complement</classname>, <classname alt="proto::listN">proto::list1</classname>&lt; T &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>
      
      <struct name="address_of">
        <template>
          <template-type-parameter name="T"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; address_of&lt;T&gt; &gt;</inherit>
        <purpose>A metafunction for generating address_of expression types, 
          a grammar element for matching address_of expressions, and 
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the 
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;address_of&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::address_of</classname>, <classname alt="proto::listN">proto::list1</classname>&lt; T &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>
      
      <struct name="logical_not">
        <template>
          <template-type-parameter name="T"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; logical_not&lt;T&gt; &gt;</inherit>
        <purpose>A metafunction for generating logical_not expression types, 
          a grammar element for matching logical_not expressions, and 
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the 
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;logical_not&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::logical_not</classname>, <classname alt="proto::listN">proto::list1</classname>&lt; T &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="pre_inc">
        <template>
          <template-type-parameter name="T"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; pre_inc&lt;T&gt; &gt;</inherit>
        <purpose>A metafunction for generating pre-increment expression types,
          a grammar element for matching pre-increment expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;pre_inc&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::pre_inc</classname>, <classname alt="proto::listN">proto::list1</classname>&lt; T &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="pre_dec">
        <template>
          <template-type-parameter name="T"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; pre_dec&lt;T&gt; &gt;</inherit>
        <purpose>A metafunction for generating pre-decrement expression types,
          a grammar element for matching pre-decrement expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;pre_dec&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::pre_dec</classname>, <classname alt="proto::listN">proto::list1</classname>&lt; T &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>
      
      <struct name="post_inc">
        <template>
          <template-type-parameter name="T"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; post_inc&lt;T&gt; &gt;</inherit>
        <purpose>A metafunction for generating post-increment expression types,
          a grammar element for matching post-increment expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;post_inc&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::post_inc</classname>, <classname alt="proto::listN">proto::list1</classname>&lt; T &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>
      
      <struct name="post_dec">
        <template>
          <template-type-parameter name="T"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; post_dec&lt;T&gt; &gt;</inherit>
        <purpose>A metafunction for generating post-decrement expression types,
          a grammar element for matching post-decrement expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;post_dec&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::post_dec</classname>, <classname alt="proto::listN">proto::list1</classname>&lt; T &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="shift_left">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; shift_left&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating left-shift expression types,
          a grammar element for matching left-shift expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;shift_left&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::shift_left</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="shift_right">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; shift_right&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating right-shift expression types,
          a grammar element for matching right-shift expressions, and a
          <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;shift_right&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::shift_right</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="multiplies">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; multiplies&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating multiplies expression types,
          a grammar element for matching multiplies expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;multiplies&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::multiplies</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>
      
      <struct name="divides">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; divides&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating divides expression types,
          a grammar element for matching divides expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the 
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;divides&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::divides</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="modulus">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; modulus&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating modulus expression types,
          a grammar element for matching modulus expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;modulus&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::modulus</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="plus">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; plus&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating binary plus expression types,
          a grammar element for matching binary plus expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;plus&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::plus</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="minus">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; minus&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating binary minus expression types,
          a grammar element for matching binary minus expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;minus&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::minus</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="less">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; less&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating less expression types,
          a grammar element for matching less expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;less&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::less</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="greater">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; greater&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating greater expression types,
          a grammar element for matching greater expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;greater&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::greater</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="less_equal">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; less_equal&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating less-or-equal expression types,
          a grammar element for matching less-or-equal expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;less_equal&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::less_equal</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="greater_equal">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; greater_equal&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating greater-or-equal expression types,
          a grammar element for matching greater-or-equal expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;greater_equal&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::greater_equal</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="equal_to">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; equal_to&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating equal-to expression types,
          a grammar element for matching equal-to expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;equal_to&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::equal_to</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="not_equal_to">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; not_equal_to&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating not-equal-to expression types,
          a grammar element for matching not-equal-to expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;mot_equal_to&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::not_equal_to</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="logical_or">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; logical_or&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating logical-or expression types,
          a grammar element for matching logical-or expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;logical_or&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::logical_or</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="logical_and">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; logical_and&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating logical-and expression types,
          a grammar element for matching logical-and expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;logical_and&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::logical_and</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="bitwise_and">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; bitwise_and&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating bitwise-and expression types,
          a grammar element for matching bitwise-and expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;bitwise_and&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::bitwise_and</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="bitwise_or">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; bitwise_or&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating bitwise-or expression types,
          a grammar element for matching bitwise-or expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;bitwise_or&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::bitwise_or</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="bitwise_xor">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; bitwise_xor&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating bitwise-xor expression types,
          a grammar element for matching bitwise-xor expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;bitwise_xor&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::bitwise_xor</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="comma">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; comma&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating comma expression types,
          a grammar element for matching comma expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;comma&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::comma</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="mem_ptr">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; mem_ptr&lt;T, U&gt; &gt;</inherit>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;mem_ptr&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::mem_ptr</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="assign">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; assign&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating assignment expression types,
          a grammar element for matching assignment expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;assign&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::assign</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="shift_left_assign">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; shift_left_assign&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating left-shift-assign expression types,
          a grammar element for matching left-shift-assign expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;shift_left_assign&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::shift_left_assign</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="shift_right_assign">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; shift_right_assign&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating right-shift-assign expression types,
          a grammar element for matching right-shift-assign expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;shift_right_assign&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::shift_right_assign</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="multiplies_assign">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; multiplies_assign&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating multiplies-assign expression types,
          a grammar element for matching multiplies-assign expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;multiplies_assign&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::multiplies_assign</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="divides_assign">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; divides_assign&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating divides-assign expression types,
          a grammar element for matching divides-assign expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;divides_assign&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::divides_assign</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="modulus_assign">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; modulus_assign&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating modulus-assign expression types,
          a grammar element for matching modulus-assign expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;modulus_assign&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::modulus_assign</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="plus_assign">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; plus_assign&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating plus-assign expression types,
          a grammar element for matching plus-assign expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;plus_assign&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::plus_assign</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="minus_assign">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; minus_assign&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating minus-assign expression types,
          a grammar element for matching minus-assign expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;minus_assign&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::minus_assign</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="bitwise_and_assign">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; bitwise_and_assign&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating bitwise-and-assign expression types,
          a grammar element for matching bitwise-and-assign expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;bitwise_and_assign&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::bitwise_and_assign</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="bitwise_or_assign">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; bitwise_or_assign&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating bitwise-or-assign expression types,
          a grammar element for matching bitwise-or-assign expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;bitwise_or_assign&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::bitwise_or_assign</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="bitwise_xor_assign">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; bitwise_xor_assign&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating bitwise-xor-assign expression types,
          a grammar element for matching bitwise-xor-assign expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;bitwise_xor_assign&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::bitwise_xor_assign</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="subscript">
        <template>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; subscript&lt;T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating subscript expression types,
          a grammar element for matching subscript expressions, and
          a <conceptname>PrimitiveTransform</conceptname> that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;subscript&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::subscript</classname>, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>
      
      <struct name="function">
        <template>
          <template-type-parameter name="A" pack="1"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; function&lt;A...&gt; &gt;</inherit>
        <purpose>A metafunction for generating function-call expression types, a grammar element for
          matching function-call expressions, and
          a <conceptname>PrimitiveTransform</conceptname>
          that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;function&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; <classname>proto::tag::function</classname>, <classname alt="proto::listN">proto::list<replaceable>N</replaceable></classname>&lt; A... &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>
      
      <struct name="unary_expr">
        <template>
          <template-type-parameter name="Tag"/>
          <template-type-parameter name="T"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; unary_expr&lt;Tag, T&gt; &gt;</inherit>
        <purpose>A metafunction for generating unary expression types with a specified tag type,
          a grammar element for matching unary expressions, and
          a <conceptname>PrimitiveTransform</conceptname>
          that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <description>
          <para>
            Use <computeroutput>proto::unary_expr&lt;<classname>proto::_</classname>, <classname>proto::_</classname>&gt;</computeroutput>
            as a grammar element to match any unary expression.
          </para>
        </description>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;unary_expr&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; Tag, <classname alt="proto::listN">proto::list1</classname>&lt; T &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>
      
      <struct name="binary_expr">
        <template>
          <template-type-parameter name="Tag"/>
          <template-type-parameter name="T"/>
          <template-type-parameter name="U"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; binary_expr&lt;Tag, T, U&gt; &gt;</inherit>
        <purpose>A metafunction for generating binary expression types with a specified tag type,
          a grammar element for matching binary expressions, and
          a <conceptname>PrimitiveTransform</conceptname>
          that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <description>
          <para>
            Use <computeroutput>proto::binary_expr&lt;<classname>proto::_</classname>, <classname>proto::_</classname>, <classname>proto::_</classname>&gt;</computeroutput> as a grammar element to match any binary expression.
          </para>
        </description>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;binary_expr&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; Tag, <classname alt="proto::listN">proto::list2</classname>&lt; T, U &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="nary_expr">
        <template>
          <template-type-parameter name="Tag"/>
          <template-type-parameter name="A" pack="1"/>
        </template>
        <inherit><classname>proto::transform</classname>&lt; nary_expr&lt;Tag, A...&gt; &gt;</inherit>
        <purpose>A metafunction for generating n-ary expression types with a specified tag type,
          a grammar element for matching n-ary expressions, and
          a <conceptname>PrimitiveTransform</conceptname>
          that dispatches to the
          <computeroutput><classname alt="proto::pass_through">proto::pass_through&lt;&gt;</classname></computeroutput>
          transform.</purpose>
        <description>
          <para>
            Use <computeroutput>proto::nary_expr&lt;<classname>proto::_</classname>, <classname>proto::vararg</classname>&lt;<classname>proto::_</classname>&gt; &gt;</computeroutput>
            as a grammar element to match any n-ary expression; that is, any non-terminal.
          </para>
        </description>
        <struct name="impl">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="State"/>
            <template-type-parameter name="Data"/>
          </template>
          <inherit>
            <type><classname>proto::pass_through</classname>&lt;nary_expr&gt;::template impl&lt;Expr, State, Data&gt;</type>
          </inherit>
        </struct>
        <typedef name="type">
          <type><classname>proto::expr</classname>&lt; Tag, <classname alt="proto::listN">proto::list<replaceable>N</replaceable></classname>&lt; A0 &gt; &gt;</type>
        </typedef>
        <typedef name="proto_base_expr">
          <type>type</type>
        </typedef>
      </struct>

      <struct name="is_expr">
        <template>
          <template-type-parameter name="T"/>
        </template>
        <inherit><type>mpl::bool_&lt;<replaceable>true-or-false</replaceable>&gt;</type></inherit>
        <purpose>A Boolean metafunction that indicates whether a given type <computeroutput>T</computeroutput>
          is a Proto expression type.</purpose>
        <description>
          <para>
            If <computeroutput>T</computeroutput> is an instantiation of <computeroutput>
            <classname alt="proto::expr">proto::expr&lt;&gt;</classname></computeroutput> or is an extension
            (via <classname alt="proto::extends">proto::extends&lt;&gt;</classname> or
            <macroname>BOOST_PROTO_EXTENDS</macroname>()) of such an instantiation, 
            <computeroutput><classname>proto::is_expr</classname>&lt;T&gt;::value</computeroutput>
            is <computeroutput>true</computeroutput>. 
            Otherwise, <computeroutput><classname>proto::is_expr</classname>&lt;T&gt;::value</computeroutput>
            is <computeroutput>false</computeroutput>.
          </para>
        </description>
      </struct>

      <struct name="tag_of">
        <template>
          <template-type-parameter name="Expr"/>
        </template>
        <purpose>A metafunction that returns the tag type of a Proto expression. </purpose>
        <typedef name="type">
          <type>typename Expr::proto_tag</type>
        </typedef>
      </struct>

      <struct name="arity_of">
        <template>
          <template-type-parameter name="Expr"/>
        </template>
        <purpose>A metafunction that returns the arity of a Proto expression. </purpose>
        <inherit><type>Expr::proto_arity</type></inherit>
      </struct>

      <namespace name="result_of">
        <struct name="as_expr">
          <template>
            <template-type-parameter name="T"/>
            <template-type-parameter name="Domain">
              <default><classname>proto::default_domain</classname></default>
            </template-type-parameter>
          </template>
          <purpose>A metafunction that computes the return type of the
            <computeroutput><functionname alt="proto::as_expr">proto::as_expr()</functionname></computeroutput> function.</purpose>
          <description>
            <para>
              The <computeroutput>proto::result_of::as_expr&lt;&gt;</computeroutput> metafunction turns types into Proto types if they are
              not already, by making them Proto terminals held by value if possible. Types which are already Proto types are
              left alone.
            </para>
            <para>
              If <computeroutput>T</computeroutput> is not yet a Proto type, the resulting terminal type is calculated
              as follows:
            </para>
            <para>
              If <computeroutput>T</computeroutput> is a function type, let
              <computeroutput>A</computeroutput> be <computeroutput>T &amp;</computeroutput>. Otherwise, let
              <computeroutput>A</computeroutput> be the type <computeroutput>T</computeroutput> stripped of
              cv-qualifiers. Then, the result type <computeroutput>proto::result_of::as_expr&lt;T, Domain&gt;::type</computeroutput>
              is <computeroutput>boost::result_of&lt;Domain(<classname>proto::expr</classname>&lt; <classname>proto::tag::terminal</classname>, <classname>proto::term</classname>&lt;A&gt; &gt;)&gt;::type</computeroutput>.
            </para>
          </description>
          <typedef name="type">
            <type><replaceable>see-below</replaceable></type>
          </typedef>
        </struct>

        <struct name="as_child">
          <template>
            <template-type-parameter name="T"/>
            <template-type-parameter name="Domain">
              <default><classname>proto::default_domain</classname></default>
            </template-type-parameter>
          </template>
          <purpose>A metafunction that computes the return type of the
            <computeroutput><functionname alt="proto::as_child">proto::as_child()</functionname></computeroutput> function.</purpose>
          <description>
            <para>
              The <computeroutput>proto::result_of::as_child&lt;&gt;</computeroutput> metafunction turns types into Proto types
              if they are not already by making them Proto terminals held by reference. Types which are already Proto
              types are left alone.
            </para>
            <para>
              When <computeroutput>T</computeroutput> is not yet a Proto type,
              the result type <computeroutput>proto::result_of::as_child&lt;T, Domain&gt;::type</computeroutput> is
              <computeroutput>boost::result_of&lt;Domain(<classname>proto::expr</classname>&lt; <classname>proto::tag::terminal</classname>, <classname>proto::term</classname>&lt;T &amp;&gt; &gt;)&gt;::type</computeroutput>.
            </para>
            <para>
              When <computeroutput>T</computeroutput> is already a Proto type
              The result type <computeroutput>proto::result_of::as_child&lt;T, Domain&gt;::type</computeroutput> is
              <computeroutput>T &amp;</computeroutput>.
            </para>
          </description>
          <typedef name="type">
            <type><replaceable>see-below</replaceable></type>
          </typedef>
        </struct>

        <struct name="child">
          <template>
            <template-type-parameter name="Expr"/>
            <template-type-parameter name="N">
              <default>mpl::long_&lt;0&gt;</default>
            </template-type-parameter>
          </template>
          <inherit><type><classname>proto::result_of::child_c</classname>&lt;Expr, N::value&gt;</type></inherit>
          <purpose>A metafunction that returns the type of the <replaceable>N</replaceable><superscript>th</superscript>
            child of a Proto expression, where N is an MPL Integral Constant. </purpose>
          <description>
            <para>
              <computeroutput>proto::result_of::child&lt;Expr, N&gt;</computeroutput> is equivalent to
              <computeroutput><classname>proto::result_of::child_c</classname>&lt;Expr, N::value&gt;</computeroutput>.
            </para>
          </description>
        </struct>

        <struct name="value">
          <template>
            <template-type-parameter name="Expr"/>
          </template>
          <purpose>A metafunction that returns the type of the value of a terminal Proto expression. </purpose>
          <typedef name="value_type">
            <description>
              <para>
                The raw type of the <replaceable>N</replaceable><superscript>th</superscript> child as it is
                stored within <computeroutput>Expr</computeroutput>. This may be a value or a reference.
              </para>
            </description>
            <type>typename Expr::proto_child0</type>
          </typedef>
          <typedef name="type">
            <description>
              <para>
                If <computeroutput>Expr</computeroutput> is not a reference type, <computeroutput>type</computeroutput>
                is computed as follows:
                <itemizedlist>
                  <listitem>
                    <para>
                      <computeroutput>T const(&amp;)[N]</computeroutput> becomes <computeroutput>T const(&amp;)[N]</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>T[N]</computeroutput> becomes <computeroutput>T(&amp;)[N]</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>T(&amp;)[N]</computeroutput> becomes <computeroutput>T(&amp;)[N]</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>R(&amp;)(A0,...)</computeroutput> becomes <computeroutput>R(&amp;)(A0,...)</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>T const &amp;</computeroutput> becomes <computeroutput>T</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>T &amp;</computeroutput> becomes <computeroutput>T</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>T</computeroutput> becomes <computeroutput>T</computeroutput>
                    </para>
                  </listitem>
                </itemizedlist>
              </para>
              <para>
                If <computeroutput>Expr</computeroutput> is a non-const reference type, <computeroutput>type</computeroutput>
                is computed as follows:
                <itemizedlist>
                  <listitem>
                    <para>
                      <computeroutput>T const(&amp;)[N]</computeroutput> becomes <computeroutput>T const(&amp;)[N]</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>T[N]</computeroutput> becomes <computeroutput>T(&amp;)[N]</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>T(&amp;)[N]</computeroutput> becomes <computeroutput>T(&amp;)[N]</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>R(&amp;)(A0,...)</computeroutput> becomes <computeroutput>R(&amp;)(A0,...)</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>T const &amp;</computeroutput> becomes <computeroutput>T const &amp;</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>T &amp;</computeroutput> becomes <computeroutput>T &amp;</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>T</computeroutput> becomes <computeroutput>T &amp;</computeroutput>
                    </para>
                  </listitem>
                </itemizedlist>
              </para>
              <para>
                If <computeroutput>Expr</computeroutput> is a const reference type, <computeroutput>type</computeroutput>
                is computed as follows:
                <itemizedlist>
                  <listitem>
                    <para>
                      <computeroutput>T const(&amp;)[N]</computeroutput> becomes <computeroutput>T const(&amp;)[N]</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>T[N]</computeroutput> becomes <computeroutput>T const(&amp;)[N]</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>T(&amp;)[N]</computeroutput> becomes <computeroutput>T(&amp;)[N]</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>R(&amp;)(A0,...)</computeroutput> becomes <computeroutput>R(&amp;)(A0,...)</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>T const &amp;</computeroutput> becomes <computeroutput>T const &amp;</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>T &amp;</computeroutput> becomes <computeroutput>T &amp;</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>T</computeroutput> becomes <computeroutput>T const &amp;</computeroutput>
                    </para>
                  </listitem>
                </itemizedlist>
              </para>
            </description>
            <type><replaceable>see-below</replaceable></type>
          </typedef>
        </struct>

        <struct name="left">
          <template>
            <template-type-parameter name="Expr"/>
          </template>
          <inherit>proto::result_of::child_c&lt; Expr, 0 &gt;</inherit>
          <purpose>A metafunction that returns the type of the left child of a binary Proto expression. </purpose>
          <description>
            <para>
              <computeroutput>proto::result_of::left&lt;Expr&gt;</computeroutput> is equivalent to
              <computeroutput><classname>proto::result_of::child_c</classname>&lt;Expr, 0&gt;</computeroutput>.
            </para>
          </description>
        </struct>

        <struct name="right">
          <template>
            <template-type-parameter name="Expr"/>
          </template>
          <inherit>proto::result_of::child_c&lt; Expr, 1 &gt;</inherit>
          <purpose>A metafunction that returns the type of the right child of a binary Proto expression. </purpose>
          <description>
            <para>
              <computeroutput>proto::result_of::right&lt;Expr&gt;</computeroutput> is equivalent to
              <computeroutput><classname>proto::result_of::child_c</classname>&lt;Expr, 1&gt;</computeroutput>.
            </para>
          </description>
        </struct>

        <struct name="child_c">
          <template>
            <template-type-parameter name="Expr"/>
            <template-nontype-parameter name="N">
              <type>long</type>
            </template-nontype-parameter>
          </template>
          <purpose>A metafunction that returns the type of the <replaceable>N</replaceable><superscript>th</superscript>
            child of a Proto expression. </purpose>
          <description>
            <para>
              A metafunction that returns the type of the <replaceable>N</replaceable><superscript>th</superscript>
              child of a Proto expression. <computeroutput>N</computeroutput> must be 0 or less than
              <computeroutput>Expr::proto_arity::value</computeroutput>.
            </para>
          </description>
          <typedef name="value_type">
            <description>
              <para>
                The raw type of the <replaceable>N</replaceable><superscript>th</superscript> child as it is stored
                within <computeroutput>Expr</computeroutput>. This may be a value or a reference.
              </para>
            </description>
            <type>typename Expr::proto_child0</type>
          </typedef>
          <typedef name="type">
            <description>
              <para>
                If <computeroutput>Expr</computeroutput> is not a reference type, <computeroutput>type</computeroutput>
                is computed as follows:
                <itemizedlist>
                  <listitem>
                    <para>
                      <computeroutput>T const &amp;</computeroutput> becomes <computeroutput>T</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>T &amp;</computeroutput> becomes <computeroutput>T</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>T</computeroutput> becomes <computeroutput>T</computeroutput>
                    </para>
                  </listitem>
                </itemizedlist>
              </para>
              <para>
                If <computeroutput>Expr</computeroutput> is a non-const reference type, <computeroutput>type</computeroutput>
                is computed as follows:
                <itemizedlist>
                  <listitem>
                    <para>
                      <computeroutput>T const &amp;</computeroutput> becomes <computeroutput>T const &amp;</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>T &amp;</computeroutput> becomes <computeroutput>T &amp;</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>T</computeroutput> becomes <computeroutput>T &amp;</computeroutput>
                    </para>
                  </listitem>
                </itemizedlist>
              </para>
              <para>
                If <computeroutput>Expr</computeroutput> is a const reference type, <computeroutput>type</computeroutput>
                is computed as follows:
                <itemizedlist>
                  <listitem>
                    <para>
                      <computeroutput>T const &amp;</computeroutput> becomes <computeroutput>T const &amp;</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>T &amp;</computeroutput> becomes <computeroutput>T &amp;</computeroutput>
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      <computeroutput>T</computeroutput> becomes <computeroutput>T const &amp;</computeroutput>
                    </para>
                  </listitem>
                </itemizedlist>
              </para>
            </description>
            <type><replaceable>see-below</replaceable></type>
          </typedef>
        </struct>

      </namespace>

      <overloaded-function name="as_expr">
        <signature>
          <type>typename <classname>proto::result_of::as_expr</classname>&lt; T &gt;::type</type>
          <template>
            <template-type-parameter name="T"/>
          </template>
          <parameter name="t">
            <paramtype>T &amp;</paramtype>
          </parameter>
        </signature>
        <signature>
          <type>typename <classname>proto::result_of::as_expr</classname>&lt; T const &gt;::type</type>
          <template>
            <template-type-parameter name="T"/>
          </template>
          <parameter name="t">
            <paramtype>T const &amp;</paramtype>
          </parameter>
        </signature>
        <signature>
          <type>typename <classname>proto::result_of::as_expr</classname>&lt; T, Domain &gt;::type</type>
          <template>
            <template-type-parameter name="Domain"/>
            <template-type-parameter name="T"/>
          </template>
          <parameter name="t">
            <paramtype>T &amp;</paramtype>
          </parameter>
        </signature>
        <signature>
          <type>typename <classname>proto::result_of::as_expr</classname>&lt; T const, Domain &gt;::type</type>
          <template>
            <template-type-parameter name="Domain"/>
            <template-type-parameter name="T"/>
          </template>
          <parameter name="t">
            <paramtype>T const &amp;</paramtype>
          </parameter>
        </signature>
        <purpose>A function that wraps non-Proto expression types in Proto terminals and leaves Proto
          expression types alone.</purpose>
        <description>
          <para>
            The <computeroutput>proto::as_expr()</computeroutput> function turns objects into Proto terminals if they
            are not Proto expression types already. Non-Proto types are held by value, if possible. Types which are
            already Proto types are left alone.
          </para>
          <para>
            This function can be called either with an explicitly specified
            <computeroutput>Domain</computeroutput> parameter
            (i.e., <computeroutput>proto::as_expr&lt;Domain&gt;(t)</computeroutput>), or without
            (i.e., <computeroutput>proto::as_expr(t)</computeroutput>). If no domain is specified,
            <computeroutput><classname>proto::default_domain</classname></computeroutput> is assumed.
          </para>
          <para>
            If <computeroutput><classname>proto::is_expr</classname>&lt;T&gt;::value</computeroutput> is
            <computeroutput>true</computeroutput>, then the argument is returned unmodified. Otherwise,
            the argument is wrapped in a Proto terminal expression node according to the following rules.
            If <computeroutput>T</computeroutput> is a function type, let
            <computeroutput>A</computeroutput> be <computeroutput>T &amp;</computeroutput>. Otherwise, let
            <computeroutput>A</computeroutput> be the type <computeroutput>T</computeroutput> stripped of
            cv-qualifiers. Then, <computeroutput>proto::as_expr()</computeroutput> returns
            <computeroutput>Domain()(<classname>proto::terminal</classname>&lt;A&gt;::type::make(t))</computeroutput>.
          </para>
        </description>
      </overloaded-function>
      
      <overloaded-function name="as_child">
        <signature>
          <type>typename <classname>proto::result_of::as_child</classname>&lt; T &gt;::type</type>
          <template>
            <template-type-parameter name="T"/>
          </template>
          <parameter name="t">
            <paramtype>T &amp;</paramtype>
          </parameter>
        </signature>
        <signature>
          <type>typename <classname>proto::result_of::as_child</classname>&lt; T const &gt;::type</type>
          <template>
            <template-type-parameter name="T"/>
          </template>
          <parameter name="t">
            <paramtype>T const &amp;</paramtype>
          </parameter>
        </signature>
        <signature>
          <type>typename <classname>proto::result_of::as_child</classname>&lt; T, Domain &gt;::type</type>
          <template>
            <template-type-parameter name="Domain"/>
            <template-type-parameter name="T"/>
          </template>
          <parameter name="t">
            <paramtype>T &amp;</paramtype>
          </parameter>
        </signature>
        <signature>
          <type>typename <classname>proto::result_of::as_child</classname>&lt; T const, Domain &gt;::type</type>
          <template>
            <template-type-parameter name="Domain"/>
            <template-type-parameter name="T"/>
          </template>
          <parameter name="t">
            <paramtype>T const &amp;</paramtype>
          </parameter>
        </signature>
        <purpose>A function that wraps non-Proto expression types in Proto terminals (by reference) and leaves
          Proto expression types alone.</purpose>
        <description>
          <para>
            The <computeroutput>proto::as_child()</computeroutput> function turns objects into Proto terminals
            if they are not Proto expression types already. Non-Proto types are held by reference. Types which
            are already Proto types are simply returned as-is.
          </para>
          <para>
            This function can be called either with an explicitly specified
            <computeroutput>Domain</computeroutput> parameter
            (i.e., <computeroutput>proto::as_child&lt;Domain&gt;(t)</computeroutput>), or without
            (i.e., <computeroutput>proto::as_child(t)</computeroutput>). If no domain is specified,
            <computeroutput><classname>proto::default_domain</classname></computeroutput> is assumed.
          </para>
          <para>
            If <computeroutput><classname>proto::is_expr</classname>&lt;T&gt;::value</computeroutput> is
            <computeroutput>true</computeroutput>, then the argument is returned as-is. Otherwise,
            <computeroutput>proto::as_child()</computeroutput> returns
            <computeroutput>Domain()(<classname>proto::terminal</classname>&lt;T &amp;&gt;::type::make(t))</computeroutput>.
          </para>
        </description>
      </overloaded-function>

      <overloaded-function name="child">
        <signature>
          <type>typename <classname>proto::result_of::child</classname>&lt; Expr &amp;, N &gt;::type</type>
          <template>
            <template-type-parameter name="N"/>
            <template-type-parameter name="Expr"/>
          </template>
          <parameter name="expr">
            <paramtype>Expr &amp;</paramtype>
            <description>
              <para>The Proto expression. </para>
            </description>
          </parameter>
        </signature>
        <signature>
          <type>typename <classname>proto::result_of::child</classname>&lt; Expr const &amp;, N &gt;::type</type>
          <template>
            <template-type-parameter name="N"/>
            <template-type-parameter name="Expr"/>
          </template>
          <parameter name="expr">
            <paramtype>Expr const &amp;</paramtype>
          </parameter>
        </signature>
        <signature>
          <type>typename <classname>proto::result_of::child</classname>&lt; Expr &amp; &gt;::type</type>
          <template>
            <template-type-parameter name="Expr"/>
          </template>
          <parameter name="expr">
            <paramtype>Expr &amp;</paramtype>
          </parameter>
        </signature>
        <signature>
          <type>typename <classname>proto::result_of::child</classname>&lt; Expr const &amp; &gt;::type</type>
          <template>
            <template-type-parameter name="Expr"/>
          </template>
          <parameter name="expr">
            <paramtype>Expr const &amp;</paramtype>
          </parameter>
        </signature>
        <purpose>Return the <replaceable>N</replaceable><superscript>th</superscript> child of the specified Proto expression. </purpose>
        <description>
          <para>
            Return the <replaceable>N</replaceable><superscript>th</superscript> child of the specified Proto expression.
            If <computeroutput>N</computeroutput> is not specified, as in <computeroutput>proto::child(expr)</computeroutput>,
            then <computeroutput>N</computeroutput> is assumed to be <computeroutput>mpl::long_&lt;0&gt;</computeroutput>.
            The child is returned by reference.
          </para>
        </description>
        <requires>
          <para>
            <computeroutput><classname>proto::is_expr</classname>&lt;Expr&gt;::value</computeroutput> is
            <computeroutput>true</computeroutput>.
          </para>
          <para>
            <computeroutput>N</computeroutput> is an MPL Integral Constant.
          </para>
          <para>
            <computeroutput>N::value &lt; Expr::proto_arity::value</computeroutput>
          </para>
        </requires>
        <returns>
          <para>A reference to the <replaceable>N</replaceable><superscript>th</superscript> child
          of <computeroutput>expr</computeroutput>.</para>
        </returns>
        <throws>
          <simpara>Will not throw.</simpara>
        </throws>
      </overloaded-function>

      <overloaded-function name="child_c">
        <signature>
          <type>typename <classname>proto::result_of::child_c</classname>&lt; Expr &amp;, N &gt;::type</type>
          <template>
            <template-nontype-parameter name="N">
              <type>long</type>
            </template-nontype-parameter>
            <template-type-parameter name="Expr"/>
          </template>
          <parameter name="expr">
            <paramtype>Expr &amp;</paramtype>
          </parameter>
        </signature>
        <signature>
          <type>typename <classname>proto::result_of::child_c</classname>&lt; Expr const &amp;, N &gt;::type</type>
          <template>
            <template-nontype-parameter name="N">
              <type>long</type>
            </template-nontype-parameter>
            <template-type-parameter name="Expr"/>
          </template>
          <parameter name="expr">
            <paramtype>Expr const &amp;</paramtype>
          </parameter>
        </signature>
        <purpose>Return the <replaceable>N</replaceable><superscript>th</superscript> child of the specified
          Proto expression. </purpose>
        <description>
          <para>
            Return the <replaceable>N</replaceable><superscript>th</superscript> child of the specified Proto
            expression. The child is returned by reference.
          </para>
        </description>
        <requires>
          <para>
            <computeroutput><classname>proto::is_expr</classname>&lt;Expr&gt;::value</computeroutput> is
            <computeroutput>true</computeroutput>.
          </para>
          <para>
            <computeroutput>N &lt; Expr::proto_arity::value</computeroutput>
          </para>
        </requires>
        <returns>
          <para>A reference to the <replaceable>N</replaceable><superscript>th</superscript> child
            of <computeroutput>expr</computeroutput>.</para>
        </returns>
        <throws>
          <simpara>Will not throw.</simpara>
        </throws>
      </overloaded-function>

      <overloaded-function name="value">
        <signature>
          <type>typename <classname>proto::result_of::value</classname>&lt; Expr &amp; &gt;::type</type>
          <template>
            <template-type-parameter name="Expr"/>
          </template>
          <parameter name="expr">
            <paramtype>Expr &amp;</paramtype>
          </parameter>
        </signature>
        <signature>
          <type>typename <classname>proto::result_of::value</classname>&lt; Expr const &amp; &gt;::type</type>
          <template>
            <template-type-parameter name="Expr"/>
          </template>
          <parameter name="expr">
            <paramtype>Expr const &amp;</paramtype>
          </parameter>
        </signature>
        <purpose>Return the value stored within the specified Proto terminal expression. </purpose>
        <description>
          <para>
            Return the the value stored within the specified Proto terminal expression. The value is
            returned by reference.
          </para>
        </description>
        <requires>
          <para>
            <computeroutput>0 == Expr::proto_arity::value</computeroutput>
          </para>
        </requires>
        <returns>
          <para>A reference to the terminal's value </para>
        </returns>
        <throws>
          <simpara>Will not throw.</simpara>
        </throws>
      </overloaded-function>

      <overloaded-function name="left">
        <signature>
          <type>typename <classname>proto::result_of::left</classname>&lt; Expr &amp; &gt;::type</type>
          <template>
            <template-type-parameter name="Expr"/>
          </template>
          <parameter name="expr">
            <paramtype>Expr &amp;</paramtype>
          </parameter>
        </signature>
        <signature>
          <type>typename <classname>proto::result_of::left</classname>&lt; Expr const &amp; &gt;::type</type>
          <template>
            <template-type-parameter name="Expr"/>
          </template>
          <parameter name="expr">
            <paramtype>Expr const &amp;</paramtype>
          </parameter>
        </signature>
        <purpose>Return the left child of the specified binary Proto expression. </purpose>
        <description>
          <para>Return the left child of the specified binary Proto expression. The child is returned by reference.</para>
        </description>
        <requires>
          <para>
            <computeroutput><classname>proto::is_expr</classname>&lt;Expr&gt;::value</computeroutput> is
            <computeroutput>true</computeroutput>.
          </para>
          <para>
            <computeroutput>2 == Expr::proto_arity::value</computeroutput>
          </para>
        </requires>
        <returns>
          <para>A reference to the left child of <computeroutput>expr</computeroutput>.
        </para>
        </returns>
        <throws>
          <simpara>Will not throw.</simpara>
        </throws>
      </overloaded-function>

      <overloaded-function name="right">
        <signature>
          <type>typename <classname>proto::result_of::right</classname>&lt; Expr &amp; &gt;::type</type>
          <template>
            <template-type-parameter name="Expr"/>
          </template>
          <parameter name="expr">
            <paramtype>Expr &amp;</paramtype>
            <description>
              <para>The Proto expression. </para>
            </description>
          </parameter>
        </signature>
        <signature>
          <type>typename <classname>proto::result_of::right</classname>&lt; Expr const &amp; &gt;::type</type>
          <template>
            <template-type-parameter name="Expr"/>
          </template>
          <parameter name="expr">
            <paramtype>Expr const &amp;</paramtype>
          </parameter>
        </signature>
        <purpose>Return the right child of the specified binary Proto expression. </purpose>
        <description>
          <para>Return the right child of the specified binary Proto expression. The child is returned by reference.</para>
        </description>
        <requires>
          <para>
            <computeroutput><classname>proto::is_expr</classname>&lt;Expr&gt;::value</computeroutput> is
            <computeroutput>true</computeroutput>.
          </para>
          <para>
            <computeroutput>2 == Expr::proto_arity::value</computeroutput>
          </para>
        </requires>
        <returns>
          <para>
            A reference to the right child of <computeroutput>expr</computeroutput>.
          </para>
        </returns>
        <throws>
          <simpara>Will not throw.</simpara>
        </throws>
      </overloaded-function>
    </namespace>
  </namespace>
</header>
