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<html xmlns="http://www.w3.org/1999/xhtml"><head><title>Chapter 23. HP/SGI Extensions</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="policy_data_structures_biblio.html" title="Acknowledgments"/><link rel="next" href="bk01pt03ch23s02.html" title="Deprecated"/></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 23. HP/SGI Extensions</th></tr><tr><td align="left"><a accesskey="p" href="policy_data_structures_biblio.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="bk01pt03ch23s02.html">Next</a></td></tr></table><hr/></div><div class="chapter" title="Chapter 23. HP/SGI Extensions"><div class="titlepage"><div><div><h2 class="title"><a id="manual.ext.containers"/>Chapter 23. HP/SGI Extensions</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl><dt><span class="section"><a href="ext_containers.html#manual.ext.containers.sgi">Backwards Compatibility</a></span></dt><dt><span class="section"><a href="bk01pt03ch23s02.html">Deprecated</a></span></dt></dl></div><div class="section" title="Backwards Compatibility"><div class="titlepage"><div><div><h2 class="title"><a id="manual.ext.containers.sgi"/>Backwards Compatibility</h2></div></div></div><p>A few extensions and nods to backwards-compatibility have
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been made with containers. Those dealing with older SGI-style
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allocators are dealt with elsewhere. The remaining ones all deal
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with bits:
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</p><p>The old pre-standard <code class="code">bit_vector</code> class is
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present for backwards compatibility. It is simply a typedef for
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the <code class="code">vector<bool></code> specialization.
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</p><p>The <code class="code">bitset</code> class has a number of extensions, described in the
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rest of this item. First, we'll mention that this implementation of
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<code class="code">bitset<N></code> is specialized for cases where N number of
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bits will fit into a single word of storage. If your choice of N is
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within that range (<=32 on i686-pc-linux-gnu, for example), then all
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of the operations will be faster.
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</p><p>There are
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versions of single-bit test, set, reset, and flip member functions which
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do no range-checking. If we call them member functions of an instantiation
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of <code class="code">bitset<N></code>, then their names and signatures are:
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</p><pre class="programlisting">
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bitset<N>& _Unchecked_set (size_t pos);
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bitset<N>& _Unchecked_set (size_t pos, int val);
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bitset<N>& _Unchecked_reset (size_t pos);
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bitset<N>& _Unchecked_flip (size_t pos);
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bool _Unchecked_test (size_t pos);
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</pre><p>Note that these may in fact be removed in the future, although we have
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no present plans to do so (and there doesn't seem to be any immediate
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reason to).
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</p><p>The member function <code class="code">operator[]</code> on a const bitset returns
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a bool, and for a non-const bitset returns a <code class="code">reference</code> (a
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nested type). No range-checking is done on the index argument, in keeping
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with other containers' <code class="code">operator[]</code> requirements.
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</p><p>Finally, two additional searching functions have been added. They return
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the index of the first "on" bit, and the index of the first
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"on" bit that is after <code class="code">prev</code>, respectively:
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</p><pre class="programlisting">
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size_t _Find_first() const;
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size_t _Find_next (size_t prev) const;</pre><p>The same caveat given for the _Unchecked_* functions applies here also.
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</p></div></div><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td align="left"><a accesskey="p" href="policy_data_structures_biblio.html">Prev</a> </td><td align="center"><a accesskey="u" href="extensions.html">Up</a></td><td align="right"> <a accesskey="n" href="bk01pt03ch23s02.html">Next</a></td></tr><tr><td align="left" valign="top">Acknowledgments </td><td align="center"><a accesskey="h" href="../index.html">Home</a></td><td align="right" valign="top"> Deprecated</td></tr></table></div></body></html>
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