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>Macro BOOST_VARIANT_ENUM_PARAMS</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="variant/reference.html#header.boost.variant.variant_fwd_hpp" title="Header <boost/variant/variant_fwd.hpp>"> 10<link rel="prev" href="BOOST_VARIANT_1_3_46_5_3_4.html" title="Macro BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES"> 11<link rel="next" href="BOOST_VARIANT_1_3_46_5_3_6.html" title="Macro BOOST_VARIANT_ENUM_SHIFTED_PARAMS"> 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 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name="BOOST_VARIANT_ENUM_PARAMS"></a><div class="titlepage"></div> 28<div class="refnamediv"> 29<h2><span class="refentrytitle">Macro BOOST_VARIANT_ENUM_PARAMS</span></h2> 30<p>BOOST_VARIANT_ENUM_PARAMS — Enumerate parameters for use with 31 <code class="computeroutput"><a class="link" href="boost/variant.html" title="Class template variant">variant</a></code>.</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: <<a class="link" href="variant/reference.html#header.boost.variant.variant_fwd_hpp" title="Header <boost/variant/variant_fwd.hpp>">boost/variant/variant_fwd.hpp</a>> 35 36</span>BOOST_VARIANT_ENUM_PARAMS(param)</pre></div> 37<div class="refsect1"> 38<a name="id-1.3.46.5.4.6.4"></a><h2>Description</h2> 39<p> When variadic templates are available and 40 <code class="computeroutput"><a class="link" href="BOOST_VARIANT_1_3_46_5_3_4.html" title="Macro BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES">BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES</a></code> 41 is not defined, expands to variadic template list in the following manner: 42 <code class="computeroutput"><pre class="programlisting"> 43 <span class="identifier">BOOST_VARIANT_ENUM_PARAMS</span><span class="special">(</span><span class="identifier">T</span><span class="special">)</span> <span class="special">=</span><span class="special">></span> <span class="identifier">T0</span><span class="special">,</span> <span class="identifier">TN</span><span class="special">...</span> 44 <span class="identifier">BOOST_VARIANT_ENUM_PARAMS</span><span class="special">(</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">)</span> <span class="special">=</span><span class="special">></span> <span class="keyword">class</span> <span class="identifier">T0</span><span class="special">,</span> <span class="keyword">class</span><span class="special">...</span> <span class="identifier">TN</span> 45 <span class="identifier">BOOST_VARIANT_ENUM_PARAMS</span><span class="special">(</span><span class="keyword">class</span> <span class="identifier">Something</span><span class="special">)</span> <span class="special">=</span><span class="special">></span> <span class="keyword">class</span> <span class="identifier">Something0</span><span class="special">,</span> <span class="keyword">class</span><span class="special">...</span> <span class="identifier">SomethingN</span> 46 <span class="identifier">BOOST_VARIANT_ENUM_PARAMS</span><span class="special">(</span><span class="keyword">typename</span> <span class="identifier">Something</span><span class="special">)</span> <span class="special">=</span><span class="special">></span> <span class="keyword">typename</span> <span class="identifier">Something0</span><span class="special">,</span> <span class="keyword">typename</span><span class="special">...</span> <span class="identifier">SomethingN</span> 47 <span class="identifier">BOOST_VARIANT_ENUM_PARAMS</span><span class="special">(</span><span class="identifier">Something</span><span class="special">)</span> <span class="special">=</span><span class="special">></span> <span class="identifier">Something0</span><span class="special">,</span> <span class="identifier">SomethingN</span><span class="special">...</span> 48 <span class="identifier">BOOST_VARIANT_ENUM_PARAMS</span><span class="special">(</span><span class="identifier">Something</span><span class="special">)</span> <span class="special">=</span><span class="special">></span> <span class="identifier">Something0</span><span class="special">,</span> <span class="identifier">SomethingN</span><span class="special">...</span> 49 </pre></code> 50 </p> 51<p> 52 Otherwise expands to a comma-separated sequence of length 53 <code class="computeroutput"><a class="link" href="BOOST_VARIANT_LIMIT_TYPES.html" title="Macro BOOST_VARIANT_LIMIT_TYPES">BOOST_VARIANT_LIMIT_TYPES</a></code>, where 54 each element in the sequence consists of the concatenation of 55 <span class="emphasis"><em>param</em></span> with its zero-based index into the 56 sequence. That is, 57 <code class="computeroutput">param ## 0, param ## 1, ..., param ## BOOST_VARIANT_LIMIT_TYPES - 1</code>.</p> 58<p><span class="bold"><strong>Rationale</strong></span>: This macro greatly 59 simplifies for the user the process of declaring 60 <code class="computeroutput"><a class="link" href="boost/variant.html" title="Class template variant">variant</a></code> types 61 in function templates or explicit partial specializations of class 62 templates, as shown in the 63 <a class="link" href="variant/tutorial.html#variant.tutorial.preprocessor" title="Preprocessor macros">tutorial</a>.</p> 64</div> 65</div> 66<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 67<td align="left"></td> 68<td align="right"><div class="copyright-footer">Copyright © 2002, 2003 Eric Friedman, Itay Maman<br>Copyright © 2014-2020 Antony Polukhin<p>Distributed under the Boost Software License, Version 1.0. 69 (See accompanying file <code class="filename">LICENSE_1_0.txt</code> or copy at 70 <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) 71 </p> 72</div></td> 73</tr></table> 74<hr> 75<div class="spirit-nav"> 76<a accesskey="p" href="BOOST_VARIANT_1_3_46_5_3_4.html"><img src="../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="variant/reference.html#header.boost.variant.variant_fwd_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="BOOST_VARIANT_1_3_46_5_3_6.html"><img src="../../doc/src/images/next.png" alt="Next"></a> 77</div> 78</body> 79</html> 80
