<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en"
lang="en" dir="ltr">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>
namespace [C++ Reference]
</title>
<meta name="generator" content="DokuWiki Release 2009-12-25c "Lemming"" />
<meta name="robots" content="index,follow" />
<meta name="date" content="2009-12-26T05:10:04-0800" />
<meta name="keywords" content="keywords,namespace" />
<link rel="search" type="application/opensearchdescription+xml" href="/wiki/lib/exe/opensearch.php" title="C++ Reference" />
<link rel="start" href="/wiki/" />
<link rel="contents" href="/wiki/keywords/namespace?do=index" title="Index" />
<link rel="alternate" type="application/rss+xml" title="Recent Changes" href="/wiki/feed.php" />
<link rel="alternate" type="application/rss+xml" title="Current Namespace" href="/wiki/feed.php?mode=list&ns=keywords" />
<link rel="edit" title="Edit this page" href="/wiki/keywords/namespace?do=edit" />
<link rel="alternate" type="text/html" title="Plain HTML" href="/wiki/_export/xhtml/keywords/namespace" />
<link rel="alternate" type="text/plain" title="Wiki Markup" href="/wiki/_export/raw/keywords/namespace" />
<link rel="canonical" href="http://www.cppreference.com/wiki/keywords/namespace" />
<link rel="stylesheet" media="all" type="text/css" href="/wiki/lib/exe/css.php?s=all&t=custom1&tseed=1272971091" />
<link rel="stylesheet" media="screen" type="text/css" href="/wiki/lib/exe/css.php?t=custom1&tseed=1272971091" />
<link rel="stylesheet" media="print" type="text/css" href="/wiki/lib/exe/css.php?s=print&t=custom1&tseed=1272971091" />
<script type="text/javascript" charset="utf-8" ><!--//--><![CDATA[//><!--
var NS='keywords';var JSINFO = {"id":"keywords:namespace","namespace":"keywords"};
//--><!]]></script>
<script type="text/javascript" charset="utf-8" src="/wiki/lib/exe/js.php?tseed=1272971091" ></script>
<link rel="shortcut icon" href="/wiki/lib/tpl/custom1/images/favicon.png" />
</head>
<body>
<div class="dokuwiki">
<div class="stylehead">
<div class="header">
<div class="pagename">
[[<a href="../keywords/namespace.html" title="Backlinks">namespace</a>]]
</div>
<div class="logo">
<a href="http://www.cppreference.com" name="dokuwiki__top" id="dokuwiki__top" accesskey="h" title="[ALT+H]">C++ Reference</a> </div>
<div class="clearer"></div>
</div>
<div class="breadcrumbs">
<span class="bchead">You are here: </span><a href="../start.html" title="start">C++ Reference</a> » <a href="../keywords/start.html" title="keywords:start">C++ Keywords</a> » <a href="../keywords/namespace.html" title="keywords:namespace">namespace</a> </div>
</div>
<div class="plugin_translation"><span>Translations of this page<sup><a href="../localization.html" class="wikilink1" title="localization">?</a></sup>:</span> <ul> <li><div class="li"><span class="curid"><a href="../keywords/namespace.html" class="wikilink1" title="keywords:namespace">en</a></span></div></li> <li><div class="li"><a href="../br-pt/keywords/namespace.html" class="wikilink2" title="br-pt:keywords:namespace" rel="nofollow">br-pt</a></div></li> <li><div class="li"><a href="../cn/keywords/namespace.html" class="wikilink2" title="cn:keywords:namespace" rel="nofollow">cn</a></div></li> <li><div class="li"><a href="../cz/keywords/namespace.html" class="wikilink2" title="cz:keywords:namespace" rel="nofollow">cz</a></div></li> <li><div class="li"><a href="../de/keywords/namespace.html" class="wikilink2" title="de:keywords:namespace" rel="nofollow">de</a></div></li> <li><div class="li"><a href="../es/keywords/namespace.html" class="wikilink2" title="es:keywords:namespace" rel="nofollow">es</a></div></li> <li><div class="li"><a href="../fr/keywords/namespace.html" class="wikilink2" title="fr:keywords:namespace" rel="nofollow">fr</a></div></li> <li><div class="li"><a href="../it/keywords/namespace.html" class="wikilink2" title="it:keywords:namespace" rel="nofollow">it</a></div></li> <li><div class="li"><a href="../jp/keywords/namespace.html" class="wikilink1" title="jp:keywords:namespace">jp</a></div></li> <li><div class="li"><a href="../nl/keywords/namespace.html" class="wikilink2" title="nl:keywords:namespace" rel="nofollow">nl</a></div></li> <li><div class="li"><a href="../pl/keywords/namespace.html" class="wikilink2" title="pl:keywords:namespace" rel="nofollow">pl</a></div></li> <li><div class="li"><a href="../ro/keywords/namespace.html" class="wikilink2" title="ro:keywords:namespace" rel="nofollow">ro</a></div></li> <li><div class="li"><a href="../ru/keywords/namespace.html" class="wikilink2" title="ru:keywords:namespace" rel="nofollow">ru</a></div></li> <li><div class="li"><a href="../sk/keywords/namespace.html" class="wikilink2" title="sk:keywords:namespace" rel="nofollow">sk</a></div></li> <li><div class="li"><a href="../tr/keywords/namespace.html" class="wikilink2" title="tr:keywords:namespace" rel="nofollow">tr</a></div></li> <li><div class="li"><a href="../tw/keywords/namespace.html" class="wikilink2" title="tw:keywords:namespace" rel="nofollow">tw</a></div></li></ul></div>
<div class="page">
<script src="http://www.google-analytics.com/urchin.js" type="text/javascript">
</script>
<script type="text/javascript">
_uacct = "UA-2828341-1";
urchinTracker();
</script>
<!-- wikipage start -->
<!-- TOC START -->
<div class="toc">
<div class="tocheader toctoggle" id="toc__header">Table of Contents</div>
<div id="toc__inside">
<ul class="toc">
<li class="clear">
<ul class="toc">
<li class="level2"><div class="li"><span class="li"><a href="#namespace" class="toc">namespace</a></span></div>
<ul class="toc">
<li class="level3"><div class="li"><span class="li"><a href="#anonymous_namespace" class="toc">anonymous namespace</a></span></div></li>
<li class="level3"><div class="li"><span class="li"><a href="#namespace_alias" class="toc">namespace alias</a></span></div></li></ul>
</li></ul>
</li></ul>
</div>
</div>
<!-- TOC END -->
<h2><a name="namespace" id="namespace">namespace</a></h2>
<div class="level2">
<p>
Syntax:
</p>
<pre class="c code c++" style="font-family:monospace;"> namespace name <span class="br0">{</span>
declaration<span class="sy0">-</span>list<span class="sy0">;</span>
<span class="br0">}</span></pre>
<p>
The namespace keyword allows you to create a new scope. The name is optional,
and can be omitted to create an unnamed namespace. Once you create a namespace,
you'll have to refer to it explicitly or use the using keyword.
Example code:
</p>
<pre class="c code c++" style="font-family:monospace;"> namespace CartoonNameSpace <span class="br0">{</span>
<span class="kw4">int</span> HomersAge<span class="sy0">;</span>
<span class="kw4">void</span> incrementHomersAge<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span>
HomersAge<span class="sy0">++;</span>
<span class="br0">}</span>
<span class="br0">}</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span>
...
<span class="me1">CartoonNameSpace</span><span class="sy0">::</span><span class="me2">HomersAge</span> <span class="sy0">=</span> <span class="nu0">39</span><span class="sy0">;</span>
CartoonNameSpace<span class="sy0">::</span><span class="me2">incrementHomersAge</span><span class="br0">(</span><span class="br0">)</span><span class="sy0">;</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/cout.html"><span class="kw3">cout</span></a> <span class="sy0"><<</span> CartoonNameSpace<span class="sy0">::</span><span class="me2">HomersAge</span> <span class="sy0"><<</span> endl<span class="sy0">;</span>
...
<span class="br0">}</span></pre>
</div>
<div class="secedit"><form class="button btn_secedit" method="post" action="/wiki/keywords/namespace"><div class="no"><input type="hidden" name="do" value="edit" /><input type="hidden" name="lines" value="3-664" /><input type="hidden" name="rev" value="1261833004" /><input type="submit" value="Edit" class="button" title="namespace" /></div></form></div>
<h3><a name="anonymous_namespace" id="anonymous_namespace">anonymous namespace</a></h3>
<div class="level3">
<p>
A namespace without a name called anonymous namespace. For such a namespace, a unique name will be generated for each translation unit. It is not possible to apply the <a href="../keywords/using.html" class="wikilink1" title="keywords:using">using</a> keyword to anonymous namespaces, so an anonymous namespace works as if the using keyword has been applied to it.
</p>
<pre class="c code c++" style="font-family:monospace;"> namespace <span class="br0">{</span>
declaration<span class="sy0">-</span>list<span class="sy0">;</span>
<span class="br0">}</span></pre>
</div>
<div class="secedit"><form class="button btn_secedit" method="post" action="/wiki/keywords/namespace"><div class="no"><input type="hidden" name="do" value="edit" /><input type="hidden" name="lines" value="665-1045" /><input type="hidden" name="rev" value="1261833004" /><input type="submit" value="Edit" class="button" title="anonymous namespace" /></div></form></div>
<h3><a name="namespace_alias" id="namespace_alias">namespace alias</a></h3>
<div class="level3">
<p>
You can create new names (aliases) for namespaces, including nested namespaces.
</p>
<pre class="c code c++" style="font-family:monospace;"> namespace identifier <span class="sy0">=</span> namespace<span class="sy0">-</span>specifier<span class="sy0">;</span></pre>
<p>
Related Topics: <a href="../keywords/using.html" class="wikilink1" title="keywords:using">using</a>
</p>
</div>
<div class="secedit"><form class="button btn_secedit" method="post" action="/wiki/keywords/namespace"><div class="no"><input type="hidden" name="do" value="edit" /><input type="hidden" name="lines" value="1046-" /><input type="hidden" name="rev" value="1261833004" /><input type="submit" value="Edit" class="button" title="namespace alias" /></div></form></div>
<!-- wikipage stop -->
</div>
<div class="clearer"> </div>
<div class="stylefoot">
<div class="meta">
<div class="user">
</div>
<!--
<div class="doc">
keywords/namespace.txt · Last modified: 12/26/2009 05:10 by 75.66.105.111 </div>
-->
</div>
<div class="bar" id="bar__bottom">
<div class="bar-left" id="bar__bottomleft">
<a href="../keywords/namespace.html" class="action edit" accesskey="e" rel="nofollow">Edit this page</a> •
<a href="../keywords/namespace.html" class="action revisions" accesskey="o" rel="nofollow">Old revisions</a> </div>
<div class="bar-right" id="bar__bottomright">
•
•
•
<a href="../keywords/namespace.html" class="action login" rel="nofollow">Login</a> •
<a href="../keywords/namespace.html" class="action index" accesskey="x" rel="nofollow">Index</a> •
<a href="../keywords/namespace.html" class="action recent" accesskey="r" rel="nofollow">Recent changes</a> •
<a href="../feed.php.html" title="Recent changes RSS feed">RSS</a> •
<a href='http://creativecommons.org/licenses/by/3.0/us/' title='Creative Commons license'>cc</a> •
<form action="/wiki/" accept-charset="utf-8" class="search" id="dw__search"><div class="no"><input type="hidden" name="do" value="search" /><input type="text" id="qsearch__in" accesskey="f" name="id" class="edit" title="[ALT+F]" /><input type="submit" value="Search" class="button" title="Search" /><div id="qsearch__out" class="ajax_qsearch JSpopup"></div></div></form>
</div>
<div class="clearer"></div>
</div>
</div>
</div>
<div class="no"><img src="/wiki/lib/exe/indexer.php?id=keywords%3Anamespace&1273193132" width="1" height="1" alt="" /></div>
</body>
</html>