<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<title>Struct template otherwise</title>
<link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css">
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
<link rel="home" href="../../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset">
<link rel="up" href="../../proto/reference.html#header.boost.proto.transform.when_hpp" title="Header <boost/proto/transform/when.hpp>">
<link rel="prev" href="when_Gra_idm45506983606192/impl.html" title="Struct template impl">
<link rel="next" href="external_transform.html" title="Struct external_transform">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<table cellpadding="2" width="100%"><tr>
<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../boost.png"></td>
<td align="center"><a href="../../../../index.html">Home</a></td>
<td align="center"><a href="../../../../libs/libraries.htm">Libraries</a></td>
<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
<td align="center"><a href="../../../../more/index.htm">More</a></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="when_Gra_idm45506983606192/impl.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../proto/reference.html#header.boost.proto.transform.when_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="external_transform.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a>
</div>
<div class="refentry">
<a name="boost.proto.otherwise"></a><div class="titlepage"></div>
<div class="refnamediv">
<h2><span class="refentrytitle">Struct template otherwise</span></h2>
<p>boost::proto::otherwise —
Syntactic sugar for <code class="computeroutput"><a class="link" href="when.html" title="Struct template when">proto::when</a>< <a class="link" href="_.html" title="Struct _">proto::_</a>, Fun ></code>,
for use in grammars to handle all the cases not yet handled.
</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.transform.when_hpp" title="Header <boost/proto/transform/when.hpp>">boost/proto/transform/when.hpp</a>>
</span><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Fun<span class="special">></span>
<span class="keyword">struct</span> <a class="link" href="otherwise.html" title="Struct template otherwise">otherwise</a> <span class="special">:</span> <span class="keyword"></span> <a class="link" href="when.html" title="Struct template when">proto::when</a>< <a class="link" href="_.html" title="Struct _">proto::_</a>, Fun > <span class="special">{</span>
<span class="special">}</span><span class="special">;</span></pre></div>
<div class="refsect1">
<a name="idm45555168969600"></a><h2>Description</h2>
<p>
Use <code class="computeroutput">proto::otherwise<T></code> in your grammars as a synonym for
<code class="computeroutput"><a class="link" href="when.html" title="Struct template when">proto::when</a>< <a class="link" href="_.html" title="Struct _">proto::_</a>, Fun ></code>
as in the following transform which counts the number of terminals in an expression.
</p>
<p>
</p>
<pre class="programlisting"><span class="comment">// Count the terminals in an expression tree.</span>
<span class="comment">// Must be invoked with initial state == mpl::int_<0>().</span>
<span class="keyword">struct</span> <span class="identifier">CountLeaves</span> <span class="special">:</span>
<a class="link" href="or_.html" title="Struct template or_">proto::or_</a><span class="special"><</span>
<span class="identifier">proto</span><span class="special">::</span><span class="identifier">when</span><span class="special"><</span><a class="link" href="terminal.html" title="Struct template terminal">proto::terminal</a><span class="special"><</span><a class="link" href="_.html" title="Struct _">proto::_</a><span class="special">></span><span class="special">,</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">next</span><span class="special"><</span><a class="link" href="_state.html" title="Struct _state">proto::_state</a><span class="special">></span><span class="special">(</span><span class="special">)</span><span class="special">></span><span class="special">,</span>
<span class="identifier">proto</span><span class="special">::</span><span class="identifier">otherwise</span><span class="special"><</span><a class="link" href="fold.html" title="Struct template fold">proto::fold</a><span class="special"><</span><a class="link" href="_.html" title="Struct _">proto::_</a><span class="special">,</span> <a class="link" href="_state.html" title="Struct _state">proto::_state</a><span class="special">,</span> <span class="identifier">CountLeaves</span><span class="special">></span> <span class="special">></span>
<span class="special">></span>
<span class="special">{</span><span class="special">}</span><span class="special">;</span></pre>
<p>
</p>
</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="when_Gra_idm45506983606192/impl.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../proto/reference.html#header.boost.proto.transform.when_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="external_transform.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a>
</div>
</body>
</html>
