<!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>
inner_product [C++ Reference]
</title>
<meta name="generator" content="DokuWiki Release 2009-12-25c "Lemming"" />
<meta name="robots" content="index,follow" />
<meta name="date" content="2009-10-09T00:38:18-0700" />
<meta name="keywords" content="stl,algorithm,inner_product" />
<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/inner_product?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/inner_product?do=edit" />
<link rel="alternate" type="text/html" title="Plain HTML" href="/wiki/_export/xhtml/stl/algorithm/inner_product" />
<link rel="alternate" type="text/plain" title="Wiki Markup" href="/wiki/_export/raw/stl/algorithm/inner_product" />
<link rel="canonical" href="http://www.cppreference.com/wiki/stl/algorithm/inner_product" />
<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:inner_product","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="header">
<div class="pagename">
[[<a href="../../stl/algorithm/inner_product.html" title="Backlinks">inner_product</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="../../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/inner_product.html" title="stl:algorithm:inner_product">inner_product</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="../../stl/algorithm/inner_product.html" class="wikilink1" title="stl:algorithm:inner_product">en</a></span></div></li> <li><div class="li"><a href="../../br-pt/stl/algorithm/inner_product.html" class="wikilink2" title="br-pt:stl:algorithm:inner_product" rel="nofollow">br-pt</a></div></li> <li><div class="li"><a href="../../cn/stl/algorithm/inner_product.html" class="wikilink2" title="cn:stl:algorithm:inner_product" rel="nofollow">cn</a></div></li> <li><div class="li"><a href="../../cz/stl/algorithm/inner_product.html" class="wikilink2" title="cz:stl:algorithm:inner_product" rel="nofollow">cz</a></div></li> <li><div class="li"><a href="../../de/stl/algorithm/inner_product.html" class="wikilink2" title="de:stl:algorithm:inner_product" rel="nofollow">de</a></div></li> <li><div class="li"><a href="../../es/stl/algorithm/inner_product.html" class="wikilink2" title="es:stl:algorithm:inner_product" rel="nofollow">es</a></div></li> <li><div class="li"><a href="../../fr/stl/algorithm/inner_product.html" class="wikilink2" title="fr:stl:algorithm:inner_product" rel="nofollow">fr</a></div></li> <li><div class="li"><a href="../../it/stl/algorithm/inner_product.html" class="wikilink2" title="it:stl:algorithm:inner_product" rel="nofollow">it</a></div></li> <li><div class="li"><a href="../../jp/stl/algorithm/inner_product.html" class="wikilink2" title="jp:stl:algorithm:inner_product" rel="nofollow">jp</a></div></li> <li><div class="li"><a href="../../nl/stl/algorithm/inner_product.html" class="wikilink2" title="nl:stl:algorithm:inner_product" rel="nofollow">nl</a></div></li> <li><div class="li"><a href="../../pl/stl/algorithm/inner_product.html" class="wikilink2" title="pl:stl:algorithm:inner_product" rel="nofollow">pl</a></div></li> <li><div class="li"><a href="../../ro/stl/algorithm/inner_product.html" class="wikilink2" title="ro:stl:algorithm:inner_product" rel="nofollow">ro</a></div></li> <li><div class="li"><a href="../../ru/stl/algorithm/inner_product.html" class="wikilink2" title="ru:stl:algorithm:inner_product" rel="nofollow">ru</a></div></li> <li><div class="li"><a href="../../sk/stl/algorithm/inner_product.html" class="wikilink2" title="sk:stl:algorithm:inner_product" rel="nofollow">sk</a></div></li> <li><div class="li"><a href="../../tr/stl/algorithm/inner_product.html" class="wikilink2" title="tr:stl:algorithm:inner_product" rel="nofollow">tr</a></div></li> <li><div class="li"><a href="../../tw/stl/algorithm/inner_product.html" class="wikilink2" title="tw:stl:algorithm:inner_product" 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 -->
<h2><a name="inner_product" id="inner_product">inner_product</a></h2>
<div class="level2">
<p>
Syntax:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="co2">#include <numeric></span>
TYPE inner_product<span class="br0">(</span> input_iterator start1<span class="sy0">,</span> input_iterator end1<span class="sy0">,</span> input_iterator2 start2<span class="sy0">,</span> TYPE val <span class="br0">)</span><span class="sy0">;</span>
TYPE inner_product<span class="br0">(</span> input_iterator start1<span class="sy0">,</span> input_iterator end1<span class="sy0">,</span> input_iterator2 start2<span class="sy0">,</span> TYPE val<span class="sy0">,</span> BinaryFunction f1<span class="sy0">,</span> BinaryFunction2 f2 <span class="br0">)</span><span class="sy0">;</span></pre>
<p>
The inner_product function computes the inner product of <code>[start1,end1)</code> and a
range of the same size starting at <code>start2</code>.
</p>
<p>
inner_product() runs in <a href="../../complexity.html" class="wikilink1" title="complexity">linear time</a>.
</p>
<p>
For example, the following code shows how inner_product (or, alternatively, <a href="../../stl/algorithm/accumulate.html" class="wikilink1" title="stl:algorithm:accumulate">accumulate</a>) can be used to compute the sums of squares of some data:
</p>
<pre class="c code c++" style="font-family:monospace;"><span class="co1">// Examples of std::accumulate and std::inner_product from wordaligned.org</span>
<span class="co2">#include <functional></span>
<span class="co2">#include <iostream></span>
<span class="co2">#include <numeric></span>
<span class="co2">#include <string></span>
<span class="co2">#include <valarray></span>
<span class="co2">#include <vector></span>
<span class="kw4">typedef</span> std<span class="sy0">::</span><span class="me2">valarray</span><span class="sy0"><</span>double<span class="sy0">></span> xyz<span class="sy0">;</span>
<span class="co1">// Xyz output operator</span>
std<span class="sy0">::</span><span class="me2">ostream</span> <span class="sy0">&</span> operator<span class="sy0"><<</span><span class="br0">(</span>std<span class="sy0">::</span><span class="me2">ostream</span> <span class="sy0">&</span> os<span class="sy0">,</span> xyz <span class="kw4">const</span> <span class="sy0">&</span> pt<span class="br0">)</span> <span class="br0">{</span>
os <span class="sy0"><<</span> <span class="st0">'('</span><span class="sy0">;</span>
<span class="kw4">char</span> <span class="kw4">const</span> <span class="sy0">*</span> sep <span class="sy0">=</span> <span class="st0">""</span><span class="sy0">;</span>
<span class="kw1">for</span><span class="br0">(</span> size_t i <span class="sy0">=</span> <span class="nu0">0</span><span class="sy0">;</span> i <span class="sy0">!=</span> pt.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="sy0">;</span> sep <span class="sy0">=</span> <span class="st0">", "</span><span class="sy0">,</span> <span class="sy0">++</span>i <span class="br0">)</span> <span class="br0">{</span>
os <span class="sy0"><<</span> sep <span class="sy0"><<</span> pt<span class="br0">[</span>i<span class="br0">]</span><span class="sy0">;</span>
<span class="br0">}</span>
os <span class="sy0"><<</span> <span class="st0">')'</span><span class="sy0">;</span>
<span class="kw1">return</span> os<span class="sy0">;</span>
<span class="br0">}</span>
<span class="co1">// Bitwise or function, for use in reductions</span>
<span class="kw4">unsigned</span> bit_or<span class="br0">(</span><span class="kw4">unsigned</span> u<span class="sy0">,</span> <span class="kw4">unsigned</span> v<span class="br0">)</span> <span class="br0">{</span>
<span class="kw1">return</span> u <span class="sy0">|</span> v<span class="sy0">;</span>
<span class="br0">}</span>
<span class="co1">// Create and return a triangle</span>
std<span class="sy0">::</span><span class="me2">vector</span><span class="sy0"><</span>xyz<span class="sy0">></span> create_triangle<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span>
std<span class="sy0">::</span><span class="me2">vector</span><span class="sy0"><</span>xyz<span class="sy0">></span> pts<span class="sy0">;</span>
<span class="kw4">double</span> <span class="kw4">const</span> p<span class="br0">[</span>9<span class="br0">]</span> <span class="sy0">=</span> <span class="br0">{</span>1.<span class="sy0">,</span>1.<span class="sy0">,</span>0.<span class="sy0">,</span>1.<span class="sy0">,</span>0.<span class="sy0">,</span>1.<span class="sy0">,</span>0.<span class="sy0">,</span>1.<span class="sy0">,</span>1.<span class="br0">}</span><span class="sy0">;</span>
pts.<span class="me1">push_back</span><span class="br0">(</span>xyz<span class="br0">(</span>p <span class="sy0">+</span> 0<span class="sy0">,</span> 3<span class="br0">)</span><span class="br0">)</span><span class="sy0">;</span>
pts.<span class="me1">push_back</span><span class="br0">(</span>xyz<span class="br0">(</span>p <span class="sy0">+</span> 3<span class="sy0">,</span> 3<span class="br0">)</span><span class="br0">)</span><span class="sy0">;</span>
pts.<span class="me1">push_back</span><span class="br0">(</span>xyz<span class="br0">(</span>p <span class="sy0">+</span> 6<span class="sy0">,</span> 3<span class="br0">)</span><span class="br0">)</span><span class="sy0">;</span>
<span class="kw1">return</span> pts<span class="sy0">;</span>
<span class="br0">}</span>
<span class="co1">// Set up some test arrays, accumulate them and print the results to stdout.</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span>
<span class="kw4">int</span> <span class="kw4">const</span> a<span class="br0">[</span>3<span class="br0">]</span> <span class="sy0">=</span> <span class="br0">{</span> 1<span class="sy0">,</span> 2<span class="sy0">,</span> 3 <span class="br0">}</span><span class="sy0">;</span>
<span class="kw4">int</span> <span class="kw4">const</span> b<span class="br0">[</span>3<span class="br0">]</span> <span class="sy0">=</span> <span class="br0">{</span> 3<span class="sy0">,</span> 2<span class="sy0">,</span> 1 <span class="br0">}</span><span class="sy0">;</span>
std<span class="sy0">::</span><span class="kw4">string</span> <span class="kw4">const</span> s<span class="br0">[</span><span class="nu0">3</span><span class="br0">]</span> <span class="sy0">=</span> <span class="br0">{</span> <span class="st0">"http://"</span><span class="sy0">,</span> <span class="st0">"wordaligned"</span><span class="sy0">,</span> <span class="st0">".org"</span> <span class="br0">}</span><span class="sy0">;</span>
bool <span class="kw4">const</span> t<span class="br0">[</span>3<span class="br0">]</span> <span class="sy0">=</span> <span class="br0">{</span> <span class="kw2">false</span><span class="sy0">,</span> <span class="kw2">true</span><span class="sy0">,</span> <span class="kw2">false</span> <span class="br0">}</span><span class="sy0">;</span>
std<span class="sy0">::</span><span class="me2">vector</span><span class="sy0"><</span>xyz<span class="sy0">></span> tri <span class="sy0">=</span> create_triangle<span class="br0">(</span><span class="br0">)</span><span class="sy0">;</span>
<span class="kw4">unsigned</span> m<span class="br0">[</span>3<span class="br0">]</span> <span class="sy0">=</span> <span class="br0">{</span> 1<span class="sy0"><<</span>1<span class="sy0">,</span> 1<span class="sy0"><<</span>3<span class="sy0">,</span> 1<span class="sy0"><<</span>5 <span class="br0">}</span><span class="sy0">;</span>
std<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> <span class="st0">"sum(a) "</span>
<span class="sy0"><<</span> std<span class="sy0">::</span><span class="me2">accumulate</span><span class="br0">(</span>a<span class="sy0">,</span> a <span class="sy0">+</span> <span class="nu0">3</span><span class="sy0">,</span> <span class="nu0">0</span><span class="br0">)</span>
<span class="sy0"><<</span> <span class="st0">"<span class="es1">\n</span>prod(a) "</span>
<span class="sy0"><<</span> std<span class="sy0">::</span><span class="me2">accumulate</span><span class="br0">(</span>a<span class="sy0">,</span> a <span class="sy0">+</span> <span class="nu0">3</span><span class="sy0">,</span> <span class="nu0">1</span><span class="sy0">,</span> std<span class="sy0">::</span><span class="me2">multiplies</span><span class="sy0"><</span>int<span class="sy0">></span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span>
<span class="sy0"><<</span> <span class="st0">"<span class="es1">\n</span>sum_sqs(a) "</span>
<span class="sy0"><<</span> std<span class="sy0">::</span><span class="me2">inner_product</span><span class="br0">(</span>a<span class="sy0">,</span> a <span class="sy0">+</span> <span class="nu0">3</span><span class="sy0">,</span> a<span class="sy0">,</span> <span class="nu0">0</span><span class="br0">)</span>
<span class="sy0"><<</span> <span class="st0">"<span class="es1">\n</span>dot(a, b) "</span>
<span class="sy0"><<</span> std<span class="sy0">::</span><span class="me2">inner_product</span><span class="br0">(</span>a<span class="sy0">,</span> a <span class="sy0">+</span> <span class="nu0">3</span><span class="sy0">,</span> b<span class="sy0">,</span> <span class="nu0">0</span><span class="br0">)</span>
<span class="sy0"><<</span> <span class="st0">"<span class="es1">\n</span>concat(s) "</span>
<span class="sy0"><<</span> std<span class="sy0">::</span><span class="me2">accumulate</span><span class="br0">(</span>s<span class="sy0">,</span> s <span class="sy0">+</span> 3<span class="sy0">,</span> std<span class="sy0">::</span><span class="kw4">string</span><span class="br0">(</span><span class="st0">""</span><span class="br0">)</span><span class="br0">)</span>
<span class="sy0"><<</span> <span class="st0">"<span class="es1">\n</span>any(t) "</span> <span class="sy0"><<</span> std<span class="sy0">::</span><span class="me2">boolalpha</span>
<span class="sy0"><<</span> std<span class="sy0">::</span><span class="me2">accumulate</span><span class="br0">(</span>t<span class="sy0">,</span> t <span class="sy0">+</span> 3<span class="sy0">,</span> <span class="kw2">false</span><span class="sy0">,</span> std<span class="sy0">::</span><span class="me2">logical_or</span><span class="sy0"><</span>bool<span class="sy0">></span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span>
<span class="sy0"><<</span> <span class="st0">"<span class="es1">\n</span>centroid(tri) "</span>
<span class="sy0"><<</span> std<span class="sy0">::</span><span class="me2">accumulate</span><span class="br0">(</span>tri.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span><span class="sy0">,</span> tri.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span><span class="sy0">,</span> xyz<span class="br0">(</span>0.<span class="sy0">,</span> <span class="nu0">3</span><span class="br0">)</span><span class="br0">)</span> <span class="sy0">/</span> <span class="nu0">3</span>.
<span class="sy0"><<</span> <span class="st0">"<span class="es1">\n</span>bitor(m) "</span> <span class="sy0"><<</span> std<span class="sy0">::</span><span class="me2">hex</span> <span class="sy0"><<</span> <span class="st0">"0x"</span>
<span class="sy0"><<</span> std<span class="sy0">::</span><span class="me2">accumulate</span><span class="br0">(</span>m<span class="sy0">,</span> m <span class="sy0">+</span> <span class="nu0">3</span><span class="sy0">,</span> <span class="nu0">0</span><span class="sy0">,</span> bit_or<span class="br0">)</span>
<span class="sy0"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy0">;</span>
<span class="kw1">return</span> <span class="nu0">0</span><span class="sy0">;</span>
<span class="br0">}</span></pre>
<p>
When run, this code generates the following output:
</p>
<pre class="code">
sum(a) 6
prod(a) 6
sum_sqs(a) 14
dot(a, b) 10
concat(s) http://wordaligned.org
any(t) true
centroid(tri) (0.666667, 0.666667, 0.666667)
bitor(m) 0x2a</pre>
<p>
Related Topics: <a href="../../stl/algorithm/accumulate.html" class="wikilink1" title="stl:algorithm:accumulate">accumulate</a>, <a href="../../stl/algorithm/adjacent_difference.html" class="wikilink1" title="stl:algorithm:adjacent_difference">adjacent_difference</a>, <a href="../../stl/algorithm/count.html" class="wikilink1" title="stl:algorithm:count">count</a>, <a href="../../stl/algorithm/partial_sum.html" class="wikilink1" title="stl:algorithm:partial_sum">partial_sum</a>
</p>
</div>
<div class="secedit"><form class="button btn_secedit" method="post" action="/wiki/stl/algorithm/inner_product"><div class="no"><input type="hidden" name="do" value="edit" /><input type="hidden" name="lines" value="3-" /><input type="hidden" name="rev" value="1255073898" /><input type="submit" value="Edit" class="button" title="inner_product" /></div></form></div>
<!-- wikipage stop -->
</div>
<div class="clearer"> </div>
<div class="stylefoot">
<div class="meta">
<div class="user">
</div>
<!--
<div class="doc">
stl/algorithm/inner_product.txt · Last modified: 10/09/2009 00:38 by 124.255.102.233 </div>
-->
</div>
<div class="bar" id="bar__bottom">
<div class="bar-left" id="bar__bottomleft">
<a href="../../stl/algorithm/inner_product.html" class="action edit" accesskey="e" rel="nofollow">Edit this page</a> •
<a href="../../stl/algorithm/inner_product.html" class="action revisions" accesskey="o" rel="nofollow">Old revisions</a> </div>
<div class="bar-right" id="bar__bottomright">
•
•
•
<a href="../../stl/algorithm/inner_product.html" class="action login" rel="nofollow">Login</a> •
<a href="../../stl/algorithm/inner_product.html" class="action index" accesskey="x" rel="nofollow">Index</a> •
<a href="../../stl/algorithm/inner_product.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=stl%3Aalgorithm%3Ainner_product&1273196403" width="1" height="1" alt="" /></div>
</body>
</html>