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33 lines
3.5 KiB
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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml"><head><title>Generalized Operations</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.76.1"/><meta name="keywords" content=" ISO C++ , library "/><meta name="keywords" content=" ISO C++ , runtime , library "/><link rel="home" href="../index.html" title="The GNU C++ Library"/><link rel="up" href="numerics.html" title="Chapter 12. Numerics"/><link rel="prev" href="numerics.html" title="Chapter 12. Numerics"/><link rel="next" href="numerics_and_c.html" title="Interacting with C"/></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Generalized Operations</th></tr><tr><td align="left"><a accesskey="p" href="numerics.html">Prev</a> </td><th width="60%" align="center">Chapter 12.
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Numerics
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</th><td align="right"> <a accesskey="n" href="numerics_and_c.html">Next</a></td></tr></table><hr/></div><div class="section" title="Generalized Operations"><div class="titlepage"><div><div><h2 class="title"><a id="std.numerics.generalized_ops"/>Generalized Operations</h2></div></div></div><p>
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</p><p>There are four generalized functions in the <numeric> header
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that follow the same conventions as those in <algorithm>. Each
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of them is overloaded: one signature for common default operations,
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and a second for fully general operations. Their names are
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self-explanatory to anyone who works with numerics on a regular basis:
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</p><div class="itemizedlist"><ul class="itemizedlist"><li class="listitem"><p><code class="code">accumulate</code></p></li><li class="listitem"><p><code class="code">inner_product</code></p></li><li class="listitem"><p><code class="code">chapterial_sum</code></p></li><li class="listitem"><p><code class="code">adjacent_difference</code></p></li></ul></div><p>Here is a simple example of the two forms of <code class="code">accumulate</code>.
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</p><pre class="programlisting">
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int ar[50];
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int someval = somefunction();
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// ...initialize members of ar to something...
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int sum = std::accumulate(ar,ar+50,0);
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int sum_stuff = std::accumulate(ar,ar+50,someval);
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int product = std::accumulate(ar,ar+50,1,std::multiplies<int>());
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</pre><p>The first call adds all the members of the array, using zero as an
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initial value for <code class="code">sum</code>. The second does the same, but uses
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<code class="code">someval</code> as the starting value (thus, <code class="code">sum_stuff == sum +
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someval</code>). The final call uses the second of the two signatures,
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and multiplies all the members of the array; here we must obviously
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use 1 as a starting value instead of 0.
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</p><p>The other three functions have similar dual-signature forms.
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</p></div><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td align="left"><a accesskey="p" href="numerics.html">Prev</a> </td><td align="center"><a accesskey="u" href="numerics.html">Up</a></td><td align="right"> <a accesskey="n" href="numerics_and_c.html">Next</a></td></tr><tr><td align="left" valign="top">Chapter 12.
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Numerics
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</td><td align="center"><a accesskey="h" href="../index.html">Home</a></td><td align="right" valign="top"> Interacting with C</td></tr></table></div></body></html>
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