doc/html/boost/proto/context/default_eval.html

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   5 <title>Struct template default_eval</title>
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  25 </div>
  26 <div class="refentry">
  27 <a name="boost.proto.context.default_eval"></a><div class="titlepage"></div>
  28 <div class="refnamediv">
  29 <h2><span class="refentrytitle">Struct template default_eval</span></h2>
  30 <p>boost::proto::context::default_eval &#8212;
  31             A BinaryFunction that accepts a Proto expression and a context, evaluates
  32             each child expression with the context, and combines the result using the
  33             standard C++ meaning for the operator represented by the current expression
  34             node.
  35           </p>
  36 </div>
  37 <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
  38 <div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: &lt;<a class="link" href="../../../proto/reference.html#header.boost.proto.context.default_hpp" title="Header &lt;boost/proto/context/default.hpp&gt;">boost/proto/context/default.hpp</a>&gt;
  39
  40 </span><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <a class="link" href="../../../Expr.html" title="Concept Expr">Expr</a><span class="special">,</span> <span class="keyword">typename</span> Context<span class="special">&gt;</span>
  41 <span class="keyword">struct</span> <a class="link" href="default_eval.html" title="Struct template default_eval">default_eval</a> <span class="special">{</span>
  42   <span class="comment">// <a class="link" href="default_eval.html#boost.proto.context.default_evaltypes">types</a></span>
  43   <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">Expr</span><span class="special">::</span><span class="identifier">tag_type</span> <a name="boost.proto.context.default_eval.Tag"></a><span class="identifier">Tag</span><span class="special">;</span>          <span class="comment">// For exposition only</span>
  44   <span class="keyword">typedef</span> <span class="emphasis"><em><span class="identifier">see</span><span class="special">-</span><span class="identifier">below</span></em></span>               <a class="link" href="default_eval.html#boost.proto.context.default_eval.result_type"><span class="identifier">result_type</span></a><span class="special">;</span>
  45
  46   <span class="comment">// <a class="link" href="default_eval.html#idp706003024-bb">public member functions</a></span>
  47   <span class="identifier">result_type</span> <a class="link" href="default_eval.html#idp706003584-bb"><span class="keyword">operator</span><span class="special">(</span><span class="special">)</span></a><span class="special">(</span><span class="identifier">Expr</span> <span class="special">&amp;</span><span class="special">,</span> <span class="identifier">Context</span> <span class="special">&amp;</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
  48
  49   <span class="comment">// public data members</span>
  50   <span class="keyword">static</span> <span class="identifier">Expr</span> <span class="special">&amp;</span> <span class="identifier">s_expr</span><span class="special">;</span>  <span class="comment">// For exposition only</span>
  51   <span class="keyword">static</span> <span class="identifier">Context</span> <span class="special">&amp;</span> <span class="identifier">s_context</span><span class="special">;</span>  <span class="comment">// For exposition only</span>
  52 <span class="special">}</span><span class="special">;</span></pre></div>
  53 <div class="refsect1">
  54 <a name="idp485827856"></a><h2>Description</h2>
  55 <p>
  56               Let <code class="computeroutput"><code class="computeroutput">OP</code></code> be the C++ operator
  57               corresponding to <code class="computeroutput">Expr::proto_tag</code>. (For example, if
  58               <code class="computeroutput">Tag</code> is <code class="computeroutput">
  59               <a class="link" href="../tag/plus.html" title="Struct plus">proto::tag::plus</a></code>, let <code class="computeroutput">
  60               <code class="computeroutput">OP</code></code> be <code class="computeroutput">+</code>.)
  61             </p>
  62 <p>
  63               The behavior of this class is specified in terms of the C++0x <code class="computeroutput">decltype</code>
  64               keyword. In systems where this keyword is not available, Proto uses the Boost.Typeof library to
  65               approximate the behavior.
  66             </p>
  67 <div class="refsect2">
  68 <a name="idp485835968"></a><h3>
  69 <a name="boost.proto.context.default_evaltypes"></a><code class="computeroutput">default_eval</code>
  70         public
  71        types</h3>
  72 <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
  73 <p>
  74 <span class="keyword">typedef</span> <span class="emphasis"><em><span class="identifier">see</span><span class="special">-</span><span class="identifier">below</span></em></span> <a name="boost.proto.context.default_eval.result_type"></a><span class="identifier">result_type</span><span class="special">;</span></p>
  75 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  76 <li class="listitem">
  77 <p>
  78                     If <code class="computeroutput">Tag</code> corresponds to a unary prefix operator,
  79                     then the result type is
  80                     </p>
  81 <pre class="programlisting"><span class="keyword">decltype</span><span class="special">(</span>
  82   <span class="identifier">OP</span> <a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../child_idp704469456.html" title="Function child">proto::child</a><span class="special">(</span><span class="identifier">s_expr</span><span class="special">)</span><span class="special">,</span> <span class="identifier">s_context</span><span class="special">)</span>
  83 <span class="special">)</span></pre>
  84 <p>
  85                   </p>
  86 </li>
  87 <li class="listitem">
  88 <p>
  89                     If <code class="computeroutput">Tag</code> corresponds to a unary postfix operator,
  90                     then the result type is
  91                     </p>
  92 <pre class="programlisting"><span class="keyword">decltype</span><span class="special">(</span>
  93   <a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../child_idp704469456.html" title="Function child">proto::child</a><span class="special">(</span><span class="identifier">s_expr</span><span class="special">)</span><span class="special">,</span> <span class="identifier">s_context</span><span class="special">)</span> <span class="identifier">OP</span>
  94 <span class="special">)</span></pre>
  95 <p>
  96                   </p>
  97 </li>
  98 <li class="listitem">
  99 <p>
 100                     If <code class="computeroutput">Tag</code> corresponds to a binary infix operator,
 101                     then the result type is
 102                     </p>
 103 <pre class="programlisting"><span class="keyword">decltype</span><span class="special">(</span>
 104   <a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../left_idp704529472.html" title="Function left">proto::left</a><span class="special">(</span><span class="identifier">s_expr</span><span class="special">)</span><span class="special">,</span> <span class="identifier">s_context</span><span class="special">)</span> <span class="identifier">OP</span>
 105   <a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../right_idp704543952.html" title="Function right">proto::right</a><span class="special">(</span><span class="identifier">s_expr</span><span class="special">)</span><span class="special">,</span> <span class="identifier">s_context</span><span class="special">)</span>
 106 <span class="special">)</span></pre>
 107 <p>
 108                   </p>
 109 </li>
 110 <li class="listitem">
 111 <p>
 112                   If <code class="computeroutput">Tag</code> is <code class="computeroutput">
 113                     <a class="link" href="../tag/subscript.html" title="Struct subscript">proto::tag::subscript</a>
 114                   </code>,
 115                   then the result type is
 116                   </p>
 117 <pre class="programlisting"><span class="keyword">decltype</span><span class="special">(</span>
 118   <a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../left_idp704529472.html" title="Function left">proto::left</a><span class="special">(</span><span class="identifier">s_expr</span><span class="special">)</span><span class="special">,</span> <span class="identifier">s_context</span><span class="special">)</span> <span class="special">[</span>
 119   <a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../right_idp704543952.html" title="Function right">proto::right</a><span class="special">(</span><span class="identifier">s_expr</span><span class="special">)</span><span class="special">,</span> <span class="identifier">s_context</span><span class="special">)</span> <span class="special">]</span>
 120 <span class="special">)</span></pre>
 121 <p>
 122                 </p>
 123 </li>
 124 <li class="listitem">
 125 <p>
 126                     If <code class="computeroutput">Tag</code> is <code class="computeroutput">
 127                       <a class="link" href="../tag/if_else_.html" title="Struct if_else_">proto::tag::if_else_</a>
 128                     </code>,
 129                     then the result type is
 130                     </p>
 131 <pre class="programlisting"><span class="keyword">decltype</span><span class="special">(</span>
 132   <a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../child_c_idp704497952.html" title="Function child_c">proto::child_c</a><span class="special">&lt;</span><span class="number">0</span><span class="special">&gt;</span><span class="special">(</span><span class="identifier">s_expr</span><span class="special">)</span><span class="special">,</span> <span class="identifier">s_context</span><span class="special">)</span> <span class="special">?</span>
 133   <a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../child_c_idp704497952.html" title="Function child_c">proto::child_c</a><span class="special">&lt;</span><span class="number">1</span><span class="special">&gt;</span><span class="special">(</span><span class="identifier">s_expr</span><span class="special">)</span><span class="special">,</span> <span class="identifier">s_context</span><span class="special">)</span> <span class="special">:</span>
 134   <a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../child_c_idp704497952.html" title="Function child_c">proto::child_c</a><span class="special">&lt;</span><span class="number">2</span><span class="special">&gt;</span><span class="special">(</span><span class="identifier">s_expr</span><span class="special">)</span><span class="special">,</span> <span class="identifier">s_context</span><span class="special">)</span>
 135 <span class="special">)</span></pre>
 136 <p>
 137                   </p>
 138 </li>
 139 <li class="listitem">
 140 <p>
 141                     If <code class="computeroutput">Tag</code> is <code class="computeroutput">
 142                       <a class="link" href="../tag/function.html" title="Struct function">proto::tag::function</a>
 143                     </code>,
 144                     then the result type is
 145                     </p>
 146 <pre class="programlisting"><span class="keyword">decltype</span><span class="special">(</span>
 147   <a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../child_c_idp704497952.html" title="Function child_c">proto::child_c</a><span class="special">&lt;</span><span class="number">0</span><span class="special">&gt;</span><span class="special">(</span><span class="identifier">s_expr</span><span class="special">)</span><span class="special">,</span> <span class="identifier">s_context</span><span class="special">)</span> <span class="special">(</span>
 148   <a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../child_c_idp704497952.html" title="Function child_c">proto::child_c</a><span class="special">&lt;</span><span class="number">1</span><span class="special">&gt;</span><span class="special">(</span><span class="identifier">s_expr</span><span class="special">)</span><span class="special">,</span> <span class="identifier">s_context</span><span class="special">)</span><span class="special">,</span>
 149   <span class="special">...</span>
 150   <a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../child_c_idp704497952.html" title="Function child_c">proto::child_c</a><span class="special">&lt;</span><span class="identifier">N</span><span class="special">&gt;</span><span class="special">(</span><span class="identifier">s_expr</span><span class="special">)</span><span class="special">,</span> <span class="identifier">s_context</span><span class="special">)</span> <span class="special">)</span>
 151 <span class="special">)</span></pre>
 152 <p>
 153                   </p>
 154 </li>
 155 </ul></div>
 156 </li></ol></div>
 157 </div>
 158 <div class="refsect2">
 159 <a name="idp485953168"></a><h3>
 160 <a name="idp706003024-bb"></a><code class="computeroutput">default_eval</code> public member functions</h3>
 161 <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
 162 <pre class="literallayout"><span class="identifier">result_type</span> <a name="idp706003584-bb"></a><span class="keyword">operator</span><span class="special">(</span><span class="special">)</span><span class="special">(</span><span class="identifier">Expr</span> <span class="special">&amp;</span> expr<span class="special">,</span> <span class="identifier">Context</span> <span class="special">&amp;</span> context<span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>
 163 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
 164 <li class="listitem">
 165 <p>
 166                     If <code class="computeroutput">Tag</code> corresponds to a unary prefix operator,
 167                     then return
 168                     </p>
 169 <pre class="programlisting">OP <code class="computeroutput"><a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../child_idp704469456.html" title="Function child">proto::child</a></code>(expr), context)</pre>
 170 <p>
 171                   </p>
 172 </li>
 173 <li class="listitem">
 174 <p>
 175                     If <code class="computeroutput">Tag</code> corresponds to a unary postfix operator,
 176                     then return
 177                     </p>
 178 <pre class="programlisting"><code class="computeroutput"><a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../child_idp704469456.html" title="Function child">proto::child</a></code>(expr), context) OP</pre>
 179 <p>
 180                   </p>
 181 </li>
 182 <li class="listitem">
 183 <p>
 184                     If <code class="computeroutput">Tag</code> corresponds to a binary infix operator,
 185                     then return
 186                     </p>
 187 <pre class="programlisting"><code class="computeroutput"><a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../left_idp704529472.html" title="Function left">proto::left</a></code>(expr), context) OP
 188 <code class="computeroutput"><a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../right_idp704543952.html" title="Function right">proto::right</a></code>(expr), context)</pre>
 189 <p>
 190                   </p>
 191 </li>
 192 <li class="listitem">
 193 <p>
 194                   If <code class="computeroutput">Tag</code> is <code class="computeroutput">
 195                     <code class="computeroutput"><a class="link" href="../tag/subscript.html" title="Struct subscript">proto::tag::subscript</a></code>
 196                   </code>,
 197                   then return
 198                   </p>
 199 <pre class="programlisting"><code class="computeroutput"><a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../left_idp704529472.html" title="Function left">proto::left</a></code>(expr), context) [
 200 <code class="computeroutput"><a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../right_idp704543952.html" title="Function right">proto::right</a></code>(expr), context) ]</pre>
 201 <p>
 202                 </p>
 203 </li>
 204 <li class="listitem">
 205 <p>
 206                     If <code class="computeroutput">Tag</code> is <code class="computeroutput">
 207                       <code class="computeroutput"><a class="link" href="../tag/if_else_.html" title="Struct if_else_">proto::tag::if_else_</a></code>
 208                     </code>,
 209                     then return
 210                     </p>
 211 <pre class="programlisting"><code class="computeroutput"><a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../child_c_idp704497952.html" title="Function child_c">proto::child_c</a></code>&lt;0&gt;(expr), context) ?
 212 <code class="computeroutput"><a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../child_c_idp704497952.html" title="Function child_c">proto::child_c</a></code>&lt;1&gt;(expr), context) :
 213 <code class="computeroutput"><a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../child_c_idp704497952.html" title="Function child_c">proto::child_c</a></code>&lt;2&gt;(expr), context)</pre>
 214 <p>
 215                   </p>
 216 </li>
 217 <li class="listitem">
 218 <p>
 219                     If <code class="computeroutput">Tag</code> is <code class="computeroutput">
 220                       <code class="computeroutput"><a class="link" href="../tag/function.html" title="Struct function">proto::tag::function</a></code>
 221                     </code>,
 222                     then return
 223                     </p>
 224 <pre class="programlisting"><code class="computeroutput"><a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../child_c_idp704497952.html" title="Function child_c">proto::child_c</a></code>&lt;0&gt;(expr), context) (
 225 <code class="computeroutput"><a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../child_c_idp704497952.html" title="Function child_c">proto::child_c</a></code>&lt;1&gt;(expr), context),
 226 ...
 227 <code class="computeroutput"><a class="link" href="../eval_idp700521824.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../child_c_idp704497952.html" title="Function child_c">proto::child_c</a></code>&lt;N&gt;(expr), context) )</pre>
 228 <p>
 229                   </p>
 230 </li>
 231 </ul></div>
 232 <div class="variablelist"><table border="0" class="variablelist compact">
 233 <colgroup>
 234 <col align="left" valign="top">
 235 <col>
 236 </colgroup>
 237 <tbody><tr>
 238 <td><p><span class="term">Parameters:</span></p></td>
 239 <td><div class="variablelist"><table border="0" class="variablelist compact">
 240 <colgroup>
 241 <col align="left" valign="top">
 242 <col>
 243 </colgroup>
 244 <tbody>
 245 <tr>
 246 <td><p><span class="term"><code class="computeroutput">context</code></span></p></td>
 247 <td><p>The evaluation context </p></td>
 248 </tr>
 249 <tr>
 250 <td><p><span class="term"><code class="computeroutput">expr</code></span></p></td>
 251 <td><p>The current expression </p></td>
 252 </tr>
 253 </tbody>
 254 </table></div></td>
 255 </tr></tbody>
 256 </table></div>
 257 </li></ol></div>
 258 </div>
 259 </div>
 260 </div>
 261 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 262 <td align="left"></td>
 263 <td align="right"><div class="copyright-footer">Copyright &#169; 2008 Eric Niebler<p>
 264         Distributed under the Boost Software License, Version 1.0. (See accompanying
 265         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
 266       </p>
 267 </div></td>
 268 </tr></table>
 269 <hr>
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