51 lines
4.7 KiB
HTML
51 lines
4.7 KiB
HTML
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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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>Deprecated HP/SGI</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content=" ISO C++ , library " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="ext_containers.html" title="Chapter 21. Containers" /><link rel="prev" href="bk01pt03ch21s02.html" title="HP/SGI" /><link rel="next" href="ext_utilities.html" title="Chapter 22. Utilities" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Deprecated HP/SGI</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk01pt03ch21s02.html">Prev</a> </td><th width="60%" align="center">Chapter 21. Containers</th><td width="20%" align="right"> <a accesskey="n" href="ext_utilities.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="Deprecated HP/SGI"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.containers.deprecated_sgi"></a>Deprecated HP/SGI</h2></div></div></div><p>
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The SGI hashing classes <code class="classname">hash_set</code> and
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<code class="classname">hash_set</code> have been deprecated by the
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unordered_set, unordered_multiset, unordered_map,
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unordered_multimap containers in TR1 and the upcoming C++0x, and
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may be removed in future releases.
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</p><p>The SGI headers</p><pre class="programlisting">
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<hash_map>
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<hash_set>
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<rope>
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<slist>
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<rb_tree>
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</pre><p>are all here;
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<code class="code"><hash_map></code> and <code class="code"><hash_set></code>
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are deprecated but available as backwards-compatible extensions,
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as discussed further below. <code class="code"><rope></code> is the
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SGI specialization for large strings ("rope,"
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"large strings," get it? Love that geeky humor.)
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<code class="code"><slist></code> is a singly-linked list, for when the
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doubly-linked <code class="code">list<></code> is too much space
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overhead, and <code class="code"><rb_tree></code> exposes the red-black
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tree classes used in the implementation of the standard maps and
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sets.
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</p><p>Each of the associative containers map, multimap, set, and multiset
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have a counterpart which uses a
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<a class="ulink" href="http://www.sgi.com/tech/stl/HashFunction.html" target="_top">hashing
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function</a> to do the arranging, instead of a strict weak ordering
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function. The classes take as one of their template parameters a
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function object that will return the hash value; by default, an
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instantiation of
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<a class="ulink" href="http://www.sgi.com/tech/stl/hash.html" target="_top">hash</a>.
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You should specialize this functor for your class, or define your own,
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before trying to use one of the hashing classes.
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</p><p>The hashing classes support all the usual associative container
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functions, as well as some extra constructors specifying the number
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of buckets, etc.
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</p><p>Why would you want to use a hashing class instead of the
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<span class="quote">“<span class="quote">normal</span>”</span>implementations? Matt Austern writes:
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</p><div class="blockquote"><blockquote class="blockquote"><p>
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<span class="emphasis"><em>[W]ith a well chosen hash function, hash tables
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generally provide much better average-case performance than
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binary search trees, and much worse worst-case performance. So
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if your implementation has hash_map, if you don't mind using
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nonstandard components, and if you aren't scared about the
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possibility of pathological cases, you'll probably get better
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performance from hash_map.
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</em></span>
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</p></blockquote></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt03ch21s02.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ext_containers.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ext_utilities.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">HP/SGI </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 22. Utilities</td></tr></table></div></body></html>
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