ceph/src/boost/libs/proto/doc/reference/context/default.xml

   1 <?xml version="1.0" encoding="utf-8"?>
   2 <!--
   3   Copyright 2012 Eric Niebler
   4
   5   Distributed under the Boost
   6   Software License, Version 1.0. (See accompanying
   7   file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   8   -->
   9 <header name="boost/proto/context/default.hpp">
  10   <namespace name="boost">
  11     <namespace name="proto">
  12       <namespace name="context">
  13         <struct name="default_eval">
  14           <template>
  15             <template-type-parameter name="Expr"/>
  16             <template-type-parameter name="Context"/>
  17           </template>
  18           <purpose>
  19             A BinaryFunction that accepts a Proto expression and a context, evaluates
  20             each child expression with the context, and combines the result using the
  21             standard C++ meaning for the operator represented by the current expression
  22             node.
  23           </purpose>
  24           <description>
  25             <para>
  26               Let <computeroutput><computeroutput>OP</computeroutput></computeroutput> be the C++ operator
  27               corresponding to <computeroutput>Expr::proto_tag</computeroutput>. (For example, if
  28               <computeroutput>Tag</computeroutput> is <computeroutput>
  29               <classname>proto::tag::plus</classname></computeroutput>, let <computeroutput>
  30               <computeroutput>OP</computeroutput></computeroutput> be <computeroutput>+</computeroutput>.)
  31             </para>
  32             <para>
  33               The behavior of this class is specified in terms of the C++0x <computeroutput>decltype</computeroutput>
  34               keyword. In systems where this keyword is not available, Proto uses the Boost.Typeof library to
  35               approximate the behavior.
  36             </para>
  37           </description>
  38           <typedef name="Tag">
  39             <purpose>For exposition only</purpose>
  40             <type>typename Expr::tag_type</type>
  41           </typedef>
  42           <data-member name="s_expr" specifiers="static">
  43             <purpose>For exposition only</purpose>
  44             <type>Expr &amp;</type>
  45           </data-member>
  46           <data-member name="s_context" specifiers="static">
  47             <purpose>For exposition only</purpose>
  48             <type>Context &amp;</type>
  49           </data-member>
  50           <typedef name="result_type">
  51             <type><emphasis>see-below</emphasis></type>
  52             <description>
  53               <itemizedlist>
  54                 <listitem>
  55                   <para>
  56                     If <computeroutput>Tag</computeroutput> corresponds to a unary prefix operator,
  57                     then the result type is
  58                     <programlisting>decltype(
  59   OP <functionname>proto::eval</functionname>(<functionname>proto::child</functionname>(s_expr), s_context)
  60 )</programlisting>
  61                   </para>
  62                 </listitem>
  63                 <listitem>
  64                   <para>
  65                     If <computeroutput>Tag</computeroutput> corresponds to a unary postfix operator,
  66                     then the result type is
  67                     <programlisting>decltype(
  68   <functionname>proto::eval</functionname>(<functionname>proto::child</functionname>(s_expr), s_context) OP
  69 )</programlisting>
  70                   </para>
  71                 </listitem>
  72                 <listitem>
  73                   <para>
  74                     If <computeroutput>Tag</computeroutput> corresponds to a binary infix operator,
  75                     then the result type is
  76                     <programlisting>decltype(
  77   <functionname>proto::eval</functionname>(<functionname>proto::left</functionname>(s_expr), s_context) OP
  78   <functionname>proto::eval</functionname>(<functionname>proto::right</functionname>(s_expr), s_context)
  79 )</programlisting>
  80                   </para>
  81                 </listitem>
  82                 <listitem>
  83                 <para>
  84                   If <computeroutput>Tag</computeroutput> is <computeroutput>
  85                     <classname>proto::tag::subscript</classname>
  86                   </computeroutput>,
  87                   then the result type is
  88                   <programlisting>decltype(
  89   <functionname>proto::eval</functionname>(<functionname>proto::left</functionname>(s_expr), s_context) [
  90   <functionname>proto::eval</functionname>(<functionname>proto::right</functionname>(s_expr), s_context) ]
  91 )</programlisting>
  92                 </para>
  93                 </listitem>
  94                 <listitem>
  95                   <para>
  96                     If <computeroutput>Tag</computeroutput> is <computeroutput>
  97                       <classname>proto::tag::if_else_</classname>
  98                     </computeroutput>,
  99                     then the result type is
 100                     <programlisting>decltype(
 101   <functionname>proto::eval</functionname>(<functionname>proto::child_c</functionname>&lt;0&gt;(s_expr), s_context) ?
 102   <functionname>proto::eval</functionname>(<functionname>proto::child_c</functionname>&lt;1&gt;(s_expr), s_context) :
 103   <functionname>proto::eval</functionname>(<functionname>proto::child_c</functionname>&lt;2&gt;(s_expr), s_context)
 104 )</programlisting>
 105                   </para>
 106                 </listitem>
 107                 <listitem>
 108                   <para>
 109                     If <computeroutput>Tag</computeroutput> is <computeroutput>
 110                       <classname>proto::tag::function</classname>
 111                     </computeroutput>,
 112                     then the result type is
 113                     <programlisting>decltype(
 114   <functionname>proto::eval</functionname>(<functionname>proto::child_c</functionname>&lt;0&gt;(s_expr), s_context) (
 115   <functionname>proto::eval</functionname>(<functionname>proto::child_c</functionname>&lt;1&gt;(s_expr), s_context),
 116   ...
 117   <functionname>proto::eval</functionname>(<functionname>proto::child_c</functionname>&lt;N&gt;(s_expr), s_context) )
 118 )</programlisting>
 119                   </para>
 120                 </listitem>
 121               </itemizedlist>
 122             </description>
 123           </typedef>
 124           <method-group name="public member functions">
 125             <method name="operator()" cv="const">
 126               <type>result_type</type>
 127               <parameter name="expr">
 128                 <paramtype>Expr &amp;</paramtype>
 129                 <description>
 130                   <para>The current expression </para>
 131                 </description>
 132               </parameter>
 133               <parameter name="context">
 134                 <paramtype>Context &amp;</paramtype>
 135                 <description>
 136                   <para>The evaluation context </para>
 137                 </description>
 138               </parameter>
 139             <description>
 140               <itemizedlist>
 141                 <listitem>
 142                   <para>
 143                     If <computeroutput>Tag</computeroutput> corresponds to a unary prefix operator,
 144                     then return
 145                     <programlisting>OP <functionname>proto::eval</functionname>(<functionname>proto::child</functionname>(expr), context)</programlisting>
 146                   </para>
 147                 </listitem>
 148                 <listitem>
 149                   <para>
 150                     If <computeroutput>Tag</computeroutput> corresponds to a unary postfix operator,
 151                     then return
 152                     <programlisting><functionname>proto::eval</functionname>(<functionname>proto::child</functionname>(expr), context) OP</programlisting>
 153                   </para>
 154                 </listitem>
 155                 <listitem>
 156                   <para>
 157                     If <computeroutput>Tag</computeroutput> corresponds to a binary infix operator,
 158                     then return
 159                     <programlisting><functionname>proto::eval</functionname>(<functionname>proto::left</functionname>(expr), context) OP
 160 <functionname>proto::eval</functionname>(<functionname>proto::right</functionname>(expr), context)</programlisting>
 161                   </para>
 162                 </listitem>
 163                 <listitem>
 164                 <para>
 165                   If <computeroutput>Tag</computeroutput> is <computeroutput>
 166                     <classname>proto::tag::subscript</classname>
 167                   </computeroutput>,
 168                   then return
 169                   <programlisting><functionname>proto::eval</functionname>(<functionname>proto::left</functionname>(expr), context) [
 170 <functionname>proto::eval</functionname>(<functionname>proto::right</functionname>(expr), context) ]</programlisting>
 171                 </para>
 172                 </listitem>
 173                 <listitem>
 174                   <para>
 175                     If <computeroutput>Tag</computeroutput> is <computeroutput>
 176                       <classname>proto::tag::if_else_</classname>
 177                     </computeroutput>,
 178                     then return
 179                     <programlisting><functionname>proto::eval</functionname>(<functionname>proto::child_c</functionname>&lt;0&gt;(expr), context) ?
 180 <functionname>proto::eval</functionname>(<functionname>proto::child_c</functionname>&lt;1&gt;(expr), context) :
 181 <functionname>proto::eval</functionname>(<functionname>proto::child_c</functionname>&lt;2&gt;(expr), context)</programlisting>
 182                   </para>
 183                 </listitem>
 184                 <listitem>
 185                   <para>
 186                     If <computeroutput>Tag</computeroutput> is <computeroutput>
 187                       <classname>proto::tag::function</classname>
 188                     </computeroutput>,
 189                     then return
 190                     <programlisting><functionname>proto::eval</functionname>(<functionname>proto::child_c</functionname>&lt;0&gt;(expr), context) (
 191 <functionname>proto::eval</functionname>(<functionname>proto::child_c</functionname>&lt;1&gt;(expr), context),
 192 ...
 193 <functionname>proto::eval</functionname>(<functionname>proto::child_c</functionname>&lt;N&gt;(expr), context) )</programlisting>
 194                   </para>
 195                 </listitem>
 196               </itemizedlist>
 197             </description>
 198             </method>
 199           </method-group>
 200         </struct>
 201
 202         <struct name="default_context">
 203           <purpose>An evaluation context that gives the operators their normal C++ semantics.</purpose>
 204           <description>
 205             <para>An evaluation context that gives the operators their normal C++ semantics.</para>
 206           </description>
 207           <struct name="eval">
 208             <template>
 209               <template-type-parameter name="Expr"/>
 210               <template-type-parameter name="ThisContext">
 211                 <default>default_context const</default>
 212               </template-type-parameter>
 213             </template>
 214             <inherit><classname>proto::context::default_eval</classname>&lt; Expr, ThisContext &gt;</inherit>
 215           </struct>
 216         </struct>
 217       </namespace>
 218     </namespace>
 219   </namespace>
 220 </header>