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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>Chapter 24. Utilities</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="extensions.html" title="Part III. Extensions"/><link rel="prev" href="bk01pt03ch23s02.html" title="Deprecated"/><link rel="next" href="ext_algorithms.html" title="Chapter 25. Algorithms"/></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 24. Utilities</th></tr><tr><td align="left"><a accesskey="p" href="bk01pt03ch23s02.html">Prev</a> </td><th width="60%" align="center">Part III.
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Extensions
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</th><td align="right"> <a accesskey="n" href="ext_algorithms.html">Next</a></td></tr></table><hr/></div><div class="chapter" title="Chapter 24. Utilities"><div class="titlepage"><div><div><h2 class="title"><a id="manual.ext.util"/>Chapter 24. Utilities</h2></div></div></div><p>
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The <code class="filename"><functional></code> header
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contains many additional functors
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and helper functions, extending section 20.3. They are
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implemented in the file stl_function.h:
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</p><div class="itemizedlist"><ul class="itemizedlist"><li class="listitem"><p><code class="code">identity_element</code> for addition and multiplication.
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</p></li><li class="listitem"><p>The functor <code class="code">identity</code>, whose <code class="code">operator()</code>
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returns the argument unchanged.
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</p></li><li class="listitem"><p>Composition functors <code class="code">unary_function</code> and
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<code class="code">binary_function</code>, and their helpers <code class="code">compose1</code>
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and <code class="code">compose2</code>.
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</p></li><li class="listitem"><p><code class="code">select1st</code> and <code class="code">select2nd</code>, to strip pairs.
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</p></li><li class="listitem"><p><code class="code">project1st</code> and <code class="code">project2nd</code>. </p></li><li class="listitem"><p>A set of functors/functions which always return the same result. They
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are <code class="code">constant_void_fun</code>, <code class="code">constant_binary_fun</code>,
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<code class="code">constant_unary_fun</code>, <code class="code">constant0</code>,
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<code class="code">constant1</code>, and <code class="code">constant2</code>. </p></li><li class="listitem"><p>The class <code class="code">subtractive_rng</code>. </p></li><li class="listitem"><p>mem_fun adaptor helpers <code class="code">mem_fun1</code> and
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<code class="code">mem_fun1_ref</code> are provided for backwards compatibility. </p></li></ul></div><p>
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20.4.1 can use several different allocators; they are described on the
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main extensions page.
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</p><p>
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20.4.3 is extended with a special version of
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<code class="code">get_temporary_buffer</code> taking a second argument. The
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argument is a pointer, which is ignored, but can be used to specify
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the template type (instead of using explicit function template
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arguments like the standard version does). That is, in addition to
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</p><pre class="programlisting">
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get_temporary_buffer<int>(5);
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</pre><p>
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you can also use
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</p><pre class="programlisting">
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get_temporary_buffer(5, (int*)0);
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</pre><p>
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A class <code class="code">temporary_buffer</code> is given in stl_tempbuf.h.
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</p><p>
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The specialized algorithms of section 20.4.4 are extended with
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<code class="code">uninitialized_copy_n</code>.
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</p></div><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td align="left"><a accesskey="p" href="bk01pt03ch23s02.html">Prev</a> </td><td align="center"><a accesskey="u" href="extensions.html">Up</a></td><td align="right"> <a accesskey="n" href="ext_algorithms.html">Next</a></td></tr><tr><td align="left" valign="top">Deprecated </td><td align="center"><a accesskey="h" href="../index.html">Home</a></td><td align="right" valign="top"> Chapter 25. Algorithms</td></tr></table></div></body></html>
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