| <?xml version="1.0" encoding="UTF-8" standalone="no"?> |
| <!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 HP/SGI</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="bk01pt12ch33.html" title="Chapter 33. Containers" /><link rel="prev" href="bk01pt12ch33s02.html" title="HP/SGI" /><link rel="next" href="bk01pt12ch34.html" title="Chapter 34. 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="bk01pt12ch33s02.html">Prev</a> </td><th width="60%" align="center">Chapter 33. Containers</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt12ch34.html">Next</a></td></tr></table><hr /></div><div class="sect1" lang="en" xml:lang="en"><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> |
| 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, |
| unordered_multimap containers in TR1 and the upcoming C++0x, and |
| 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; |
| <code class="code"><hash_map></code> and <code class="code"><hash_set></code> |
| are deprecated but available as backwards-compatible extensions, |
| as discussed further below. <code class="code"><rope></code> is the |
| SGI specialization for large strings ("rope," |
| "large strings," get it? Love that geeky humor.) |
| <code class="code"><slist></code> is a singly-linked list, for when the |
| doubly-linked <code class="code">list<></code> is too much space |
| overhead, and <code class="code"><rb_tree></code> exposes the red-black |
| tree classes used in the implementation of the standard maps and |
| sets. |
| </p><p>Each of the associative containers map, multimap, set, and multiset |
| have a counterpart which uses a |
| <a class="ulink" href="http://www.sgi.com/tech/stl/HashFunction.html" target="_top">hashing |
| 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 |
| <a class="ulink" href="http://www.sgi.com/tech/stl/hash.html" target="_top">hash</a>. |
| 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">normal</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> |
| </p></blockquote></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt12ch33s02.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="bk01pt12ch33.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt12ch34.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 34. Utilities</td></tr></table></div></body></html> |
