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<html xmlns="http://www.w3.org/1999/xhtml"><head><title>Chapter 22. Utilities</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.75.2"/><meta name="keywords" content=" ISO C++ , library "/><link rel="home" href="../spine.html" title="The GNU C++ Library"/><link rel="up" href="extensions.html" title="Part III. Extensions"/><link rel="prev" href="bk01pt03ch21s03.html" title="Deprecated HP/SGI"/><link rel="next" href="ext_algorithms.html" title="Chapter 23. Algorithms"/></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 22. Utilities</th></tr><tr><td align="left"><a accesskey="p" href="bk01pt03ch21s03.html">Prev</a> </td><th width="60%" align="center">Part III.
Extensions
</th><td align="right"> <a accesskey="n" href="ext_algorithms.html">Next</a></td></tr></table><hr/></div><div class="chapter" title="Chapter 22. Utilities"><div class="titlepage"><div><div><h1 class="title"><a id="manual.ext.util"/>Utilities</h1></div></div></div><p>
The <functional> header contains many additional functors
and helper functions, extending section 20.3. They are
implemented in the file stl_function.h:
</p><div class="itemizedlist"><ul class="itemizedlist"><li class="listitem"><p><code class="code">identity_element</code> for addition and multiplication. *
</p></li><li class="listitem"><p>The functor <code class="code">identity</code>, whose <code class="code">operator()</code>
returns the argument unchanged. *
</p></li><li class="listitem"><p>Composition functors <code class="code">unary_function</code> and
<code class="code">binary_function</code>, and their helpers <code class="code">compose1</code>
and <code class="code">compose2</code>. *
</p></li><li class="listitem"><p><code class="code">select1st</code> and <code class="code">select2nd</code>, to strip pairs. *
</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
are <code class="code">constant_void_fun</code>, <code class="code">constant_binary_fun</code>,
<code class="code">constant_unary_fun</code>, <code class="code">constant0</code>,
<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
<code class="code">mem_fun1_ref</code> are provided for backwards compatibility. </p></li></ul></div><p>
20.4.1 can use several different allocators; they are described on the
main extensions page.
</p><p>
20.4.3 is extended with a special version of
<code class="code">get_temporary_buffer</code> taking a second argument. The
argument is a pointer, which is ignored, but can be used to specify
the template type (instead of using explicit function template
arguments like the standard version does). That is, in addition to
</p><pre class="programlisting">
get_temporary_buffer<int>(5);
</pre><p>
you can also use
</p><pre class="programlisting">
get_temporary_buffer(5, (int*)0);
</pre><p>
A class <code class="code">temporary_buffer</code> is given in stl_tempbuf.h. *
</p><p>
The specialized algorithms of section 20.4.4 are extended with
<code class="code">uninitialized_copy_n</code>. *
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