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=UTF-8"> 5<title>Struct template nullary_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.traits_hpp" title="Header <boost/proto/traits.hpp>"> 10<link rel="prev" href="function/impl.html" title="Struct template impl"> 11<link rel="next" href="nullary_expr/impl.html" title="Struct template impl"> 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" 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name="boost.proto.nullary_expr"></a><div class="titlepage"></div> 28<div class="refnamediv"> 29<h2><span class="refentrytitle">Struct template nullary_expr</span></h2> 30<p>boost::proto::nullary_expr — A metafunction for generating nullary expression types, a grammar element for matching 31 nullary expressions, and 32 a <a class="link" href="../../PrimitiveTransform.html" title="Concept PrimitiveTransform">PrimitiveTransform</a> that returns the current expression unchanged. </p> 33</div> 34<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> 35<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.traits_hpp" title="Header <boost/proto/traits.hpp>">boost/proto/traits.hpp</a>> 36 37</span><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Tag<span class="special">,</span> <span class="keyword">typename</span> T<span class="special">></span> 38<span class="keyword">struct</span> <a class="link" href="nullary_expr.html" title="Struct template nullary_expr">nullary_expr</a> <span class="special">:</span> <span class="keyword"></span> <a class="link" href="transform.html" title="Struct template transform">proto::transform</a><span class="special"><</span> <span class="identifier">nullary_expr</span><span class="special"><</span><span class="identifier">Tag</span><span class="special">,</span> <span class="identifier">T</span><span class="special">></span> <span class="special">></span> <span class="special">{</span> 39 <span class="comment">// types</span> 40 <span class="keyword">typedef</span> <a class="link" href="expr.html" title="Struct template expr">proto::expr</a><span class="special"><</span> <span class="identifier">Tag</span><span class="special">,</span> <a class="link" href="term.html" title="Struct template term">proto::term</a><span class="special"><</span> <span class="identifier">T</span> <span class="special">></span> <span class="special">></span> <a name="boost.proto.nullary_expr.type"></a><span class="identifier">type</span><span class="special">;</span> 41 <span class="keyword">typedef</span> <a class="link" href="basic_expr.html" title="Struct template basic_expr">proto::basic_expr</a><span class="special"><</span> <span class="identifier">Tag</span><span class="special">,</span> <a class="link" href="term.html" title="Struct template term">proto::term</a><span class="special"><</span> <span class="identifier">T</span> <span class="special">></span> <span class="special">></span> <a name="boost.proto.nullary_expr.proto_grammar"></a><span class="identifier">proto_grammar</span><span class="special">;</span> 42 43 <span class="comment">// member classes/structs/unions</span> 44 <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> State<span class="special">,</span> <span class="keyword">typename</span> Data<span class="special">></span> 45 <span class="keyword">struct</span> <a class="link" href="nullary_expr/impl.html" title="Struct template impl">impl</a> <span class="special">:</span> <span class="keyword"></span> <a class="link" href="transform_impl.html" title="Struct template transform_impl">proto::transform_impl</a><span class="special"><</span> <span class="identifier">Expr</span><span class="special">,</span> <span class="identifier">State</span><span class="special">,</span> <span class="identifier">Data</span> <span class="special">></span> <span class="special">{</span> 46 <span class="comment">// types</span> 47 <span class="keyword">typedef</span> <span class="identifier">Expr</span> <a class="link" href="nullary_expr/impl.html#boost.proto.nullary_expr.impl.result_type"><span class="identifier">result_type</span></a><span class="special">;</span> 48 49 <span class="comment">// <a class="link" href="nullary_expr/impl.html#id-1_3_33_5_39_2_1_50_5_4-bb">public member functions</a></span> 50 <span class="identifier">Expr</span> <a class="link" href="nullary_expr/impl.html#id-1_3_33_5_39_2_1_50_5_4_1-bb"><span class="keyword">operator</span><span class="special">(</span><span class="special">)</span></a><span class="special">(</span><span class="keyword">typename</span> <span class="identifier">impl</span><span class="special">::</span><span class="identifier">expr_param</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">impl</span><span class="special">::</span><span class="identifier">state_param</span><span class="special">,</span> 51 <span class="keyword">typename</span> <span class="identifier">impl</span><span class="special">::</span><span class="identifier">data_param</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> 52 <span class="special">}</span><span class="special">;</span> 53<span class="special">}</span><span class="special">;</span></pre></div> 54<div class="refsect1"> 55<a name="id-1.3.33.5.41.66.4"></a><h2>Description</h2> 56<p> 57 Use <code class="computeroutput">proto::nullary_expr<<a class="link" href="_.html" title="Struct _">proto::_</a>, <a class="link" href="_.html" title="Struct _">proto::_</a>></code> 58 as a grammar element to match any nullary expression. 59 </p> 60</div> 61</div> 62<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 63<td align="left"></td> 64<td align="right"><div class="copyright-footer">Copyright © 2008 Eric Niebler<p> 65 Distributed under the Boost Software License, Version 1.0. (See accompanying 66 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>) 67 </p> 68</div></td> 69</tr></table> 70<hr> 71<div class="spirit-nav"> 72<a accesskey="p" href="function/impl.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../proto/reference.html#header.boost.proto.traits_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="nullary_expr/impl.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 73</div> 74</body> 75</html> 76
