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| <a name="boost.proto.context.default_eval"></a><div class="titlepage"></div> |
| <div class="refnamediv"> |
| <h2><span class="refentrytitle">Struct template default_eval</span></h2> |
| <p>boost::proto::context::default_eval — |
| A BinaryFunction that accepts a Proto expression and a context, evaluates |
| each child expression with the context, and combines the result using the |
| standard C++ meaning for the operator represented by the current expression |
| node. |
| </p> |
| </div> |
| <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> |
| <div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: <<a class="link" href="../../../proto/reference.html#header.boost.proto.context.default_hpp" title="Header <boost/proto/context/default.hpp>">boost/proto/context/default.hpp</a>> |
| |
| </span><span class="keyword">template</span><span class="special"><</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">></span> |
| <span class="keyword">struct</span> <a class="link" href="default_eval.html" title="Struct template default_eval">default_eval</a> <span class="special">{</span> |
| <span class="comment">// <a class="link" href="default_eval.html#boost.proto.context.default_evaltypes">types</a></span> |
| <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> |
| <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> |
| |
| <span class="comment">// <a class="link" href="default_eval.html#id1298448-bb">public member functions</a></span> |
| <span class="identifier">result_type</span> <a class="link" href="default_eval.html#id1298453-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">&</span><span class="special">,</span> <span class="identifier">Context</span> <span class="special">&</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> |
| <span class="keyword">static</span> <span class="identifier">Expr</span> <span class="special">&</span> s_expr<span class="special">;</span> <span class="comment">// For exposition only</span> |
| <span class="keyword">static</span> <span class="identifier">Context</span> <span class="special">&</span> s_context<span class="special">;</span> <span class="comment">// For exposition only</span> |
| <span class="special">}</span><span class="special">;</span></pre></div> |
| <div class="refsect1"> |
| <a name="id2453181"></a><h2>Description</h2> |
| <p> |
| Let <code class="computeroutput"><code class="computeroutput">OP</code></code> be the C++ operator |
| corresponding to <code class="computeroutput">Expr::proto_tag</code>. (For example, if |
| <code class="computeroutput">Tag</code> is <code class="computeroutput"> |
| <a class="link" href="../tag/plus.html" title="Struct plus">proto::tag::plus</a></code>, let <code class="computeroutput"> |
| <code class="computeroutput">OP</code></code> be <code class="computeroutput">+</code>.) |
| </p> |
| <p> |
| The behavior of this class is specified in terms of the C++0x <code class="computeroutput">decltype</code> |
| keyword. In systems where this keyword is not available, Proto uses the Boost.Typeof library to |
| approximate the behavior. |
| </p> |
| <div class="refsect2"> |
| <a name="id2453252"></a><h3> |
| <a name="boost.proto.context.default_evaltypes"></a><code class="computeroutput">default_eval</code> |
| public |
| types</h3> |
| <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"> |
| <p> |
| <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> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| <p> |
| If <code class="computeroutput">Tag</code> corresponds to a unary prefix operator, |
| then the result type is |
| </p> |
| <pre class="programlisting"><span class="identifier">decltype</span><span class="special">(</span> |
| <span class="identifier">OP</span> <a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../child_id1289346.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="special">)</span></pre> |
| <p> |
| </p> |
| </li> |
| <li class="listitem"> |
| <p> |
| If <code class="computeroutput">Tag</code> corresponds to a unary postfix operator, |
| then the result type is |
| </p> |
| <pre class="programlisting"><span class="identifier">decltype</span><span class="special">(</span> |
| <a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../child_id1289346.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> |
| <span class="special">)</span></pre> |
| <p> |
| </p> |
| </li> |
| <li class="listitem"> |
| <p> |
| If <code class="computeroutput">Tag</code> corresponds to a binary infix operator, |
| then the result type is |
| </p> |
| <pre class="programlisting"><span class="identifier">decltype</span><span class="special">(</span> |
| <a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../left_id1289856.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> |
| <a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../right_id1289979.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></pre> |
| <p> |
| </p> |
| </li> |
| <li class="listitem"> |
| <p> |
| If <code class="computeroutput">Tag</code> is <code class="computeroutput"> |
| <a class="link" href="../tag/subscript.html" title="Struct subscript">proto::tag::subscript</a> |
| </code>, |
| then the result type is |
| </p> |
| <pre class="programlisting"><span class="identifier">decltype</span><span class="special">(</span> |
| <a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../left_id1289856.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> |
| <a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../right_id1289979.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> |
| <span class="special">)</span></pre> |
| <p> |
| </p> |
| </li> |
| <li class="listitem"> |
| <p> |
| If <code class="computeroutput">Tag</code> is <code class="computeroutput"> |
| <a class="link" href="../tag/if_else_.html" title="Struct if_else_">proto::tag::if_else_</a> |
| </code>, |
| then the result type is |
| </p> |
| <pre class="programlisting"><span class="identifier">decltype</span><span class="special">(</span> |
| <a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../child_c_id1289588.html" title="Function child_c">proto::child_c</a><span class="special"><</span><span class="number">0</span><span class="special">></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> |
| <a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../child_c_id1289588.html" title="Function child_c">proto::child_c</a><span class="special"><</span><span class="number">1</span><span class="special">></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> |
| <a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../child_c_id1289588.html" title="Function child_c">proto::child_c</a><span class="special"><</span><span class="number">2</span><span class="special">></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></pre> |
| <p> |
| </p> |
| </li> |
| <li class="listitem"> |
| <p> |
| If <code class="computeroutput">Tag</code> is <code class="computeroutput"> |
| <a class="link" href="../tag/function.html" title="Struct function">proto::tag::function</a> |
| </code>, |
| then the result type is |
| </p> |
| <pre class="programlisting"><span class="identifier">decltype</span><span class="special">(</span> |
| <a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../child_c_id1289588.html" title="Function child_c">proto::child_c</a><span class="special"><</span><span class="number">0</span><span class="special">></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> |
| <a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../child_c_id1289588.html" title="Function child_c">proto::child_c</a><span class="special"><</span><span class="number">1</span><span class="special">></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> |
| <span class="special">...</span> |
| <a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a><span class="special">(</span><a class="link" href="../child_c_id1289588.html" title="Function child_c">proto::child_c</a><span class="special"><</span><span class="identifier">N</span><span class="special">></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> |
| <span class="special">)</span></pre> |
| <p> |
| </p> |
| </li> |
| </ul></div> |
| </li></ol></div> |
| </div> |
| <div class="refsect2"> |
| <a name="id2454221"></a><h3> |
| <a name="id1298448-bb"></a><code class="computeroutput">default_eval</code> public member functions</h3> |
| <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"> |
| <pre class="literallayout"><span class="identifier">result_type</span> <a name="id1298453-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">&</span> expr<span class="special">,</span> <span class="identifier">Context</span> <span class="special">&</span> context<span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| <p> |
| If <code class="computeroutput">Tag</code> corresponds to a unary prefix operator, |
| then return |
| </p> |
| <pre class="programlisting">OP <code class="computeroutput"><a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../child_id1289346.html" title="Function child">proto::child</a></code>(expr), context)</pre> |
| <p> |
| </p> |
| </li> |
| <li class="listitem"> |
| <p> |
| If <code class="computeroutput">Tag</code> corresponds to a unary postfix operator, |
| then return |
| </p> |
| <pre class="programlisting"><code class="computeroutput"><a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../child_id1289346.html" title="Function child">proto::child</a></code>(expr), context) OP</pre> |
| <p> |
| </p> |
| </li> |
| <li class="listitem"> |
| <p> |
| If <code class="computeroutput">Tag</code> corresponds to a binary infix operator, |
| then return |
| </p> |
| <pre class="programlisting"><code class="computeroutput"><a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../left_id1289856.html" title="Function left">proto::left</a></code>(expr), context) OP |
| <code class="computeroutput"><a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../right_id1289979.html" title="Function right">proto::right</a></code>(expr), context)</pre> |
| <p> |
| </p> |
| </li> |
| <li class="listitem"> |
| <p> |
| If <code class="computeroutput">Tag</code> is <code class="computeroutput"> |
| <code class="computeroutput"><a class="link" href="../tag/subscript.html" title="Struct subscript">proto::tag::subscript</a></code> |
| </code>, |
| then return |
| </p> |
| <pre class="programlisting"><code class="computeroutput"><a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../left_id1289856.html" title="Function left">proto::left</a></code>(expr), context) [ |
| <code class="computeroutput"><a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../right_id1289979.html" title="Function right">proto::right</a></code>(expr), context) ]</pre> |
| <p> |
| </p> |
| </li> |
| <li class="listitem"> |
| <p> |
| If <code class="computeroutput">Tag</code> is <code class="computeroutput"> |
| <code class="computeroutput"><a class="link" href="../tag/if_else_.html" title="Struct if_else_">proto::tag::if_else_</a></code> |
| </code>, |
| then return |
| </p> |
| <pre class="programlisting"><code class="computeroutput"><a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../child_c_id1289588.html" title="Function child_c">proto::child_c</a></code><0>(expr), context) ? |
| <code class="computeroutput"><a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../child_c_id1289588.html" title="Function child_c">proto::child_c</a></code><1>(expr), context) : |
| <code class="computeroutput"><a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../child_c_id1289588.html" title="Function child_c">proto::child_c</a></code><2>(expr), context)</pre> |
| <p> |
| </p> |
| </li> |
| <li class="listitem"> |
| <p> |
| If <code class="computeroutput">Tag</code> is <code class="computeroutput"> |
| <code class="computeroutput"><a class="link" href="../tag/function.html" title="Struct function">proto::tag::function</a></code> |
| </code>, |
| then return |
| </p> |
| <pre class="programlisting"><code class="computeroutput"><a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../child_c_id1289588.html" title="Function child_c">proto::child_c</a></code><0>(expr), context) ( |
| <code class="computeroutput"><a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../child_c_id1289588.html" title="Function child_c">proto::child_c</a></code><1>(expr), context), |
| ... |
| <code class="computeroutput"><a class="link" href="../eval_id1259332.html" title="Function eval">proto::eval</a></code>(<code class="computeroutput"><a class="link" href="../child_c_id1289588.html" title="Function child_c">proto::child_c</a></code><N>(expr), context) )</pre> |
| <p> |
| </p> |
| </li> |
| </ul></div> |
| <div class="variablelist"><table border="0"> |
| <col align="left" valign="top"> |
| <tbody><tr> |
| <td><p><span class="term">Parameters:</span></p></td> |
| <td><div class="variablelist"><table border="0"> |
| <col align="left" valign="top"> |
| <tbody> |
| <tr> |
| <td><p><span class="term"><code class="computeroutput">context</code></span></p></td> |
| <td><p>The evaluation context </p></td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><code class="computeroutput">expr</code></span></p></td> |
| <td><p>The current expression </p></td> |
| </tr> |
| </tbody> |
| </table></div></td> |
| </tr></tbody> |
| </table></div> |
| </li></ol></div> |
| </div> |
| </div> |
| </div> |
| <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> |
| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 2008 Eric Niebler<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| 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>) |
| </p> |
| </div></td> |
| </tr></table> |
| <hr> |
| <div class="spirit-nav"> |
| <a accesskey="p" href="callable_context/eval.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../proto/reference.html#header.boost.proto.context.default_hpp"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="default_context.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> |
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