2012-08-29 06:44:10 +02:00
|
|
|
|
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
|
2013-04-02 02:09:44 +02:00
|
|
|
|
<!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>Deprecated</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.78.1" /><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="ext_containers.html" title="Chapter 23. HP/SGI Extensions" /><link rel="prev" href="ext_containers.html" title="Chapter 23. HP/SGI Extensions" /><link rel="next" href="ext_utilities.html" title="Chapter 24. Utilities" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Deprecated</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ext_containers.html">Prev</a> </td><th width="60%" align="center">Chapter 23. HP/SGI Extensions</th><td width="20%" align="right"> <a accesskey="n" href="ext_utilities.html">Next</a></td></tr></table><hr /></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.containers.deprecated_sgi"></a>Deprecated</h2></div></div></div><p>
|
2011-09-28 03:37:10 +02:00
|
|
|
|
The SGI hashing classes <code class="classname">hash_set</code> and
|
|
|
|
|
|
<code class="classname">hash_set</code> have been deprecated by the
|
|
|
|
|
|
unordered_set, unordered_multiset, unordered_map,
|
2011-11-06 21:15:53 +01:00
|
|
|
|
unordered_multimap containers in TR1 and C++11, and
|
2011-09-28 03:37:10 +02:00
|
|
|
|
may be removed in future releases.
|
|
|
|
|
|
</p><p>The SGI headers</p><pre class="programlisting">
|
|
|
|
|
|
<hash_map>
|
|
|
|
|
|
<hash_set>
|
|
|
|
|
|
<rope>
|
|
|
|
|
|
<slist>
|
|
|
|
|
|
<rb_tree>
|
|
|
|
|
|
</pre><p>are all here;
|
2012-01-18 00:50:28 +01:00
|
|
|
|
<code class="filename"><backwards/hash_map></code> and
|
|
|
|
|
|
<code class="filename"><backwards/hash_set></code>
|
2011-09-28 03:37:10 +02:00
|
|
|
|
are deprecated but available as backwards-compatible extensions,
|
2012-01-18 00:50:28 +01:00
|
|
|
|
as discussed further below.
|
|
|
|
|
|
<code class="filename"><ext/rope></code> is the SGI
|
|
|
|
|
|
specialization for large strings ("rope," "large strings," get it? Love
|
|
|
|
|
|
that geeky humor.)
|
|
|
|
|
|
<code class="filename"><ext/slist></code> (superseded in
|
|
|
|
|
|
C++11 by <code class="filename"><forward_list></code>)
|
|
|
|
|
|
is a singly-linked list, for when the doubly-linked <code class="code">list<></code>
|
|
|
|
|
|
is too much space overhead, and
|
|
|
|
|
|
<code class="filename"><ext/rb_tree></code> exposes the
|
|
|
|
|
|
red-black tree classes used in the implementation of the standard maps
|
|
|
|
|
|
and sets.
|
2011-09-28 03:37:10 +02:00
|
|
|
|
</p><p>Each of the associative containers map, multimap, set, and multiset
|
|
|
|
|
|
have a counterpart which uses a
|
2012-08-29 04:09:55 +02:00
|
|
|
|
<a class="link" href="http://www.sgi.com/tech/stl/HashFunction.html" target="_top">hashing
|
2011-09-28 03:37:10 +02:00
|
|
|
|
function</a> to do the arranging, instead of a strict weak ordering
|
|
|
|
|
|
function. The classes take as one of their template parameters a
|
|
|
|
|
|
function object that will return the hash value; by default, an
|
|
|
|
|
|
instantiation of
|
2012-08-29 04:09:55 +02:00
|
|
|
|
<a class="link" href="http://www.sgi.com/tech/stl/hash.html" target="_top">hash</a>.
|
2011-09-28 03:37:10 +02:00
|
|
|
|
You should specialize this functor for your class, or define your own,
|
|
|
|
|
|
before trying to use one of the hashing classes.
|
|
|
|
|
|
</p><p>The hashing classes support all the usual associative container
|
|
|
|
|
|
functions, as well as some extra constructors specifying the number
|
|
|
|
|
|
of buckets, etc.
|
|
|
|
|
|
</p><p>Why would you want to use a hashing class instead of the
|
|
|
|
|
|
<span class="quote">“<span class="quote">normal</span>”</span>implementations? Matt Austern writes:
|
|
|
|
|
|
</p><div class="blockquote"><blockquote class="blockquote"><p>
|
|
|
|
|
|
<span class="emphasis"><em>[W]ith a well chosen hash function, hash tables
|
|
|
|
|
|
generally provide much better average-case performance than
|
|
|
|
|
|
binary search trees, and much worse worst-case performance. So
|
|
|
|
|
|
if your implementation has hash_map, if you don't mind using
|
|
|
|
|
|
nonstandard components, and if you aren't scared about the
|
|
|
|
|
|
possibility of pathological cases, you'll probably get better
|
|
|
|
|
|
performance from hash_map.
|
|
|
|
|
|
</em></span>
|
2012-01-18 00:50:28 +01:00
|
|
|
|
</p></blockquote></div><p>
|
|
|
|
|
|
The deprecated hash tables are superseded by the standard unordered
|
|
|
|
|
|
associative containers defined in the ISO C++ 2011 standard in the
|
|
|
|
|
|
headers <code class="filename"><unordered_map></code>
|
|
|
|
|
|
and <code class="filename"><unordered_set></code>.
|
2013-02-12 00:24:26 +01:00
|
|
|
|
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ext_containers.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">Chapter 23. HP/SGI Extensions </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 24. Utilities</td></tr></table></div></body></html>
|
