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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 34. Utilities</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /><meta name="keywords" content=" ISO C++ , library " /><link rel="start" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="extensions.html" title="Part XII. Extensions" /><link rel="prev" href="bk01pt12ch33s03.html" title="Deprecated HP/SGI" /><link rel="next" href="bk01pt12ch35.html" title="Chapter 35. Algorithms" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 34. Utilities</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk01pt12ch33s03.html">Prev</a> </td><th width="60%" align="center">Part XII. Extensions</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt12ch35.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.ext.util"></a>Chapter 34. Utilities</h2></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 type="disc"><li><p><code class="code">identity_element</code> for addition and multiplication. * |
| </p></li><li><p>The functor <code class="code">identity</code>, whose <code class="code">operator()</code> |
| returns the argument unchanged. * |
| </p></li><li><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><p><code class="code">select1st</code> and <code class="code">select2nd</code>, to strip pairs. * |
| </p></li><li><p><code class="code">project1st</code> and <code class="code">project2nd</code>. * </p></li><li><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><p>The class <code class="code">subtractive_rng</code>. * </p></li><li><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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