<!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>
remove_if [C++ Reference]
</title>
<meta name="generator" content="DokuWiki Release 2009-12-25c "Lemming"" />
<meta name="robots" content="index,follow" />
<meta name="date" content="2009-10-09T01:22:10-0700" />
<meta name="keywords" content="stl,algorithm,remove_if" />
<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/stl/algorithm/remove_if?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=stl:algorithm" />
<link rel="edit" title="Edit this page" href="/wiki/stl/algorithm/remove_if?do=edit" />
<link rel="alternate" type="text/html" title="Plain HTML" href="/wiki/_export/xhtml/stl/algorithm/remove_if" />
<link rel="alternate" type="text/plain" title="Wiki Markup" href="/wiki/_export/raw/stl/algorithm/remove_if" />
<link rel="canonical" href="http://www.cppreference.com/wiki/stl/algorithm/remove_if" />
<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='stl:algorithm';var JSINFO = {"id":"stl:algorithm:remove_if","namespace":"stl:algorithm"};
//--><!]]></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="breadcrumbs">
<span class="bchead">You are here: </span><a href="../../start.html" title="start">C++ Reference</a> » <a href="../../stl/start.html" title="stl:start">C++ Standard Template Library</a> » <a href="../../stl/algorithm/start.html" title="stl:algorithm:start">C++ Algorithms</a> » <a href="../../stl/algorithm/remove_if.html" title="stl:algorithm:remove_if">remove_if</a> </div>
</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 -->
<h2><a name="remove_if" id="remove_if">remove_if</a></h2>
<div class="level2">
<p>
Syntax:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="co2">#include <algorithm></span>
forward_iterator remove_if<span class="br0">(</span> forward_iterator start<span class="sy0">,</span> forward_iterator end<span class="sy0">,</span> Predicate p <span class="br0">)</span><span class="sy0">;</span></pre>
<p>
The remove_if() function removes all elements in the range [start,end) for
which the predicate p returns true.
</p>
<p>
The return value of this function is an iterator to the last element of the
pruned range.
</p>
<p>
Note that remove_if() doesn't actually “remove” things from the range [start, end); if
remove_if() is called on a container, the length of the container will remain the same
afterwards (remove_if() couldn't possibly affect that through the iterators alone), and
all the elements will still be in the container. Instead, remove_if() puts all the “removed”
elements to the end of the container, and returns the iterator that separates the not-removed
and removed elements. To actually remove items from a container, you would have to call the
erase() method of the container, to erase elements starting at the returned iterator.
This is usually combined in what is called the <a href="http://en.wikipedia.org/wiki/Erase-remove_idiom" class="urlextern" title="http://en.wikipedia.org/wiki/Erase-remove_idiom" rel="nofollow">erase-remove idiom</a>:
</p>
<pre class="code">container.erase(remove_if(container.begin(), container.end(), pred), container.end());</pre>
<p>
remove_if() is similar to <a href="../../stl/algorithm/partition.html" class="wikilink1" title="stl:algorithm:partition">partition</a>() except that the predicate is reversed.
</p>
<p>
remove_if() runs in <a href="../../complexity.html" class="wikilink1" title="complexity">linear time</a>.
</p>
<p>
remove_if() cannot be used with associative containers like set<> or map<>.
</p>
<p>
Related Topics: <a href="../../stl/algorithm/remove.html" class="wikilink1" title="stl:algorithm:remove">remove</a>, <a href="../../stl/algorithm/remove_copy.html" class="wikilink1" title="stl:algorithm:remove_copy">remove_copy</a>, <a href="../../stl/algorithm/remove_copy_if.html" class="wikilink1" title="stl:algorithm:remove_copy_if">remove_copy_if</a>
</p>
</div>
<!-- wikipage stop -->
</div>
<div class="clearer"> </div>
<div class="stylefoot">
<div class="meta">
<div class="user">
</div>
<!--
<div class="doc">
stl/algorithm/remove_if.txt · Last modified: 10/09/2009 01:22 by 124.255.102.233 </div>
-->
</div>
</div></div></body>
</html>