doc/html/boost/proto/is_proto_expr.html

   1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
   2 <html>
   3 <head>
   4 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
   5 <title>Struct is_proto_expr</title>
   6 <link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css">
   7 <meta name="generator" content="DocBook XSL Stylesheets V1.79.1">
   8 <link rel="home" href="../../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset">
   9 <link rel="up" href="../../proto/reference.html#header.boost.proto.extends_hpp" title="Header &lt;boost/proto/extends.hpp&gt;">
  10 <link rel="prev" href="unexpr.html" title="Struct template unexpr">
  11 <link rel="next" href="extends.html" title="Struct template extends">
  12 </head>
  13 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
  14 <table cellpadding="2" width="100%"><tr>
  15 <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../boost.png"></td>
  16 <td align="center"><a href="../../../../index.html">Home</a></td>
  17 <td align="center"><a href="../../../../libs/libraries.htm">Libraries</a></td>
  18 <td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
  19 <td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
  20 <td align="center"><a href="../../../../more/index.htm">More</a></td>
  21 </tr></table>
  22 <hr>
  23 <div class="spirit-nav">
  24 <a accesskey="p" href="unexpr.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../proto/reference.html#header.boost.proto.extends_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="extends.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a>
  25 </div>
  26 <div class="refentry">
  27 <a name="boost.proto.is_proto_expr"></a><div class="titlepage"></div>
  28 <div class="refnamediv">
  29 <h2><span class="refentrytitle">Struct is_proto_expr</span></h2>
  30 <p>boost::proto::is_proto_expr &#8212; Empty type to be used as a dummy template parameter of POD expression wrappers. It allows
  31           argument-dependent lookup to find Proto's operator overloads.</p>
  32 </div>
  33 <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
  34 <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.extends_hpp" title="Header &lt;boost/proto/extends.hpp&gt;">boost/proto/extends.hpp</a>&gt;
  35
  36 </span>
  37 <span class="keyword">struct</span> <a class="link" href="is_proto_expr.html" title="Struct is_proto_expr">is_proto_expr</a> <span class="special">{</span>
  38 <span class="special">}</span><span class="special">;</span></pre></div>
  39 <div class="refsect1">
  40 <a name="idp463028672"></a><h2>Description</h2>
  41 <p>
  42             <code class="computeroutput">proto::is_proto_expr</code> allows argument-dependent lookup to find Proto's operator overloads. For example:
  43           </p>
  44 <p>
  45             </p>
  46 <pre class="programlisting"> <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Dummy</span> <span class="special">=</span> <a class="link" href="is_proto_expr.html" title="Struct is_proto_expr">proto::is_proto_expr</a><span class="special">&gt;</span>
  47  <span class="keyword">struct</span> <span class="identifier">my_terminal</span>
  48  <span class="special">{</span>
  49      <a class="link" href="../../BOOST_PROTO_BASIC_EXTENDS.html" title="Macro BOOST_PROTO_BASIC_EXTENDS">BOOST_PROTO_BASIC_EXTENDS</a><span class="special">(</span>
  50          <span class="keyword">typename</span> <a class="link" href="terminal.html" title="Struct template terminal">proto::terminal</a><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span><span class="special">::</span><span class="identifier">type</span>
  51        <span class="special">,</span> <span class="identifier">my_terminal</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span>
  52        <span class="special">,</span> <a class="link" href="default_domain.html" title="Struct default_domain">proto::default_domain</a>
  53      <span class="special">)</span>
  54  <span class="special">}</span><span class="special">;</span>
  55
  56  <span class="comment">// ...</span>
  57  <span class="identifier">my_terminal</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">_1</span><span class="special">,</span> <span class="identifier">_2</span><span class="special">;</span>
  58  <span class="identifier">_1</span> <span class="special">+</span> <span class="identifier">_2</span><span class="special">;</span> <span class="comment">// OK, uses proto::operator+</span></pre>
  59 <p>
  60           </p>
  61 <p>
  62             Without the second <code class="computeroutput">Dummy</code> template parameter, Proto's operator overloads
  63             would not be considered by name lookup.
  64           </p>
  65 </div>
  66 </div>
  67 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
  68 <td align="left"></td>
  69 <td align="right"><div class="copyright-footer">Copyright &#169; 2008 Eric Niebler<p>
  70         Distributed under the Boost Software License, Version 1.0. (See accompanying
  71         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>)
  72       </p>
  73 </div></td>
  74 </tr></table>
  75 <hr>
  76 <div class="spirit-nav">
  77 <a accesskey="p" href="unexpr.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../proto/reference.html#header.boost.proto.extends_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="extends.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a>
  78 </div>
  79 </body>
  80 </html>