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| <html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 22. Generalized Operations</title><meta name="generator" content="DocBook XSL Stylesheets V1.74.0" /><meta name="keywords" content=" ISO C++ , library " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="numerics.html" title="Part X. Numerics" /><link rel="prev" href="complex.html" title="Chapter 21. Complex" /><link rel="next" href="numerics_and_c.html" title="Chapter 23. Interacting with C" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 22. Generalized Operations</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="complex.html">Prev</a> </td><th width="60%" align="center">Part X. |
| Numerics |
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| </th><td width="20%" align="right"> <a accesskey="n" href="numerics_and_c.html">Next</a></td></tr></table><hr /></div><div class="chapter" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title"><a id="manual.numerics.generalized_ops"></a>Chapter 22. Generalized Operations</h2></div></div></div><p> |
| </p><p>There are four generalized functions in the <numeric> header |
| that follow the same conventions as those in <algorithm>. Each |
| of them is overloaded: one signature for common default operations, |
| and a second for fully general operations. Their names are |
| self-explanatory to anyone who works with numerics on a regular basis: |
| </p><div class="itemizedlist"><ul type="disc"><li><p><code class="code">accumulate</code></p></li><li><p><code class="code">inner_product</code></p></li><li><p><code class="code">partial_sum</code></p></li><li><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>. |
| </p><pre class="programlisting"> |
| int ar[50]; |
| int someval = somefunction(); |
| |
| // ...initialize members of ar to something... |
| |
| int sum = std::accumulate(ar,ar+50,0); |
| int sum_stuff = std::accumulate(ar,ar+50,someval); |
| int product = std::accumulate(ar,ar+50,1,std::multiplies<int>()); |
| </pre><p>The first call adds all the members of the array, using zero as an |
| initial value for <code class="code">sum</code>. The second does the same, but uses |
| <code class="code">someval</code> as the starting value (thus, <code class="code">sum_stuff == sum + |
| someval</code>). The final call uses the second of the two signatures, |
| and multiplies all the members of the array; here we must obviously |
| use 1 as a starting value instead of 0. |
| </p><p>The other three functions have similar dual-signature forms. |
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