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| <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 22. HP/SGI Extensions</title><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><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="policy_data_structures_ack.html" title="Acknowledgments" /><link rel="next" href="ext_sgi.html" title="Deprecated" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 22. HP/SGI Extensions</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="policy_data_structures_ack.html">Prev</a> </td><th width="60%" align="center">Part III. |
| Extensions |
| |
| </th><td width="20%" align="right"> <a accesskey="n" href="ext_sgi.html">Next</a></td></tr></table><hr /></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="manual.ext.containers"></a>Chapter 22. HP/SGI Extensions</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl class="toc"><dt><span class="section"><a href="ext_containers.html#manual.ext.containers.sgi">Backwards Compatibility</a></span></dt><dt><span class="section"><a href="ext_sgi.html">Deprecated</a></span></dt></dl></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.containers.sgi"></a>Backwards Compatibility</h2></div></div></div><p>A few extensions and nods to backwards-compatibility have |
| been made with containers. Those dealing with older SGI-style |
| allocators are dealt with elsewhere. The remaining ones all deal |
| with bits: |
| </p><p>The old pre-standard <code class="code">bit_vector</code> class is |
| present for backwards compatibility. It is simply a typedef for |
| the <code class="code">vector<bool></code> specialization. |
| </p><p>The <code class="code">bitset</code> class has a number of extensions, described in the |
| rest of this item. First, we'll mention that this implementation of |
| <code class="code">bitset<N></code> is specialized for cases where N number of |
| bits will fit into a single word of storage. If your choice of N is |
| within that range (<=32 on i686-pc-linux-gnu, for example), then all |
| of the operations will be faster. |
| </p><p>There are |
| versions of single-bit test, set, reset, and flip member functions which |
| do no range-checking. If we call them member functions of an instantiation |
| of <code class="code">bitset<N></code>, then their names and signatures are: |
| </p><pre class="programlisting"> |
| bitset<N>& _Unchecked_set (size_t pos); |
| bitset<N>& _Unchecked_set (size_t pos, int val); |
| bitset<N>& _Unchecked_reset (size_t pos); |
| bitset<N>& _Unchecked_flip (size_t pos); |
| bool _Unchecked_test (size_t pos); |
| </pre><p>Note that these may in fact be removed in the future, although we have |
| no present plans to do so (and there doesn't seem to be any immediate |
| reason to). |
| </p><p>The member function <code class="code">operator[]</code> on a const bitset returns |
| a bool, and for a non-const bitset returns a <code class="code">reference</code> (a |
| nested type). No range-checking is done on the index argument, in keeping |
| with other containers' <code class="code">operator[]</code> requirements. |
| </p><p>Finally, two additional searching functions have been added. They return |
| the index of the first "on" bit, and the index of the first |
| "on" bit that is after <code class="code">prev</code>, respectively: |
| </p><pre class="programlisting"> |
| size_t _Find_first() const; |
| size_t _Find_next (size_t prev) const;</pre><p>The same caveat given for the _Unchecked_* functions applies here also. |
| </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="policy_data_structures_ack.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="extensions.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ext_sgi.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Acknowledgments </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> Deprecated</td></tr></table></div></body></html> |
