140 lines
5.8 KiB
HTML
140 lines
5.8 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0.1 Transitional//EN">
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<html>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>Boost.MultiIndex Documentation - Tutorial</title>
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<link rel="stylesheet" href="../style.css" type="text/css">
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<link rel="start" href="../index.html">
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</head>
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<body>
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<h1><img src="../../../../boost.png" alt="boost.png (6897 bytes)" align=
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"middle" width="277" height="86">Boost.MultiIndex Tutorial</h1>
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<div class="prev_link"><a href="../index.html"><img src="../prev.gif" alt="index" border="0"><br>
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Index
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</a></div>
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Index
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</a></div>
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<div class="next_link"><a href="basics.html"><img src="../next.gif" alt="basics" border="0"><br>
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Basics
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</a></div><br clear="all" style="clear: all;">
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<hr>
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<h2>Contents</h2>
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<ul>
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<li><a href="#rationale">Rationale</a></li>
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<li><a href="#namespace">Namespace</a></li>
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<li><a href="basics.html">Basics</a></li>
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<li><a href="indices.html">Index types</a></li>
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<li><a href="key_extraction.html">Key extraction</a></li>
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<li><a href="creation.html">Container creation</a></li>
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<li><a href="debug.html">Debugging support</a></li>
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<li><a href="techniques.html">Techniques</a></li>
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</ul>
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<h2><a name="rationale">Rationale</a></h2>
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<p>
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STL containers are designed around the concept that each container controls its
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own collection of elements, giving access to them in a manner specified by the
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container's type: so, an <code>std::set</code> maintains the elements ordered
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by a specified sorting criterion, <code>std::list</code> allows for free
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positioning of elements along a linear sequence, and so on.
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</p>
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<p>
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Sometimes, the necessity arises of having different access interfaces
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to the same underlying collection: for instance, some data might need to be
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sorted according to more than one comparison predicate, or a bidirectional list
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might benefit from a supplemental logarithmic lookup interface. In these
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situations, programmers typically resort to manual compositions of different
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containers, a solution that generally involves a fair amount of code
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devoted to preserve the synchronization of the different parts of
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the composition. Boost.MultiIndex allows for the specification of
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<code>multi_index_container</code>s comprised of one or more <i>indices</i> with
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different interfaces to the same collection of elements. The resulting constructs
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are conceptually cleaner than manual compositions, and often perform much better.
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An important design decision has been taken that the indices of a given
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<code>multi_index_container</code> instantiation be specified at compile time: this
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gives ample room for static type checking and code optimization.
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</p>
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<p>
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Boost.MultiIndex takes inspiration from basic concepts of indexing arising in the
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theory of relational databases, though it is not intended to provide a full-fledged
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relational database framework. <code>multi_index_container</code> integrates seamlessly
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into the STL container/algorithm design, and features some extra capabilities regarding
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lookup operations and element updating which are useful extensions even for
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single-indexed containers.
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</p>
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<p align="center">
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<img src="multi_index_cont_example.png"
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alt="diagram of a multi_index_container with three indices"
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width="600" height="304"><br>
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<b>Fig. 1: Diagram of a <code>multi_index_container</code> with three indices.</b>
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</p>
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<p>
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The figure above depicts a <code>multi_index_container</code> composed of three indices:
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the first two present a set-like interface to the elements sorted by
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shape and id, respectively, while the latter index provides the functionality
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of a bidirectional list in the spirit of <code>std::list</code>. These
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indices act as "views" to the internal collection of elements, but they do not only
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provide read access to the set: insertion/deletion methods are also implemented much
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as those of <code>std::set</code>s or <code>std::list</code>s. Insertion of an
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element through one given index will only succeed if the uniqueness constraints of all
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indices are met.
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</p>
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<h2>
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<a name="namespace">Namespace</a>
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</h2>
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<p>
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All the public types of Boost.MultiIndex reside in namespace <code>::boost::multi_index</code>.
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Additionaly, the main class template <code>multi_index_container</code> and global functions
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<code>get</code> and <code>project</code> are lifted to namespace <code>::boost</code>
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by means of <code>using</code> declarations. For brevity of exposition, the fragments
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of code in the documentation are written as if the following declarations were in effect:
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</p>
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<blockquote><pre>
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<span class=keyword>using</span> <span class=keyword>namespace</span> <span class=special>::</span><span class=identifier>boost</span><span class=special>;</span>
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<span class=keyword>using</span> <span class=keyword>namespace</span> <span class=special>::</span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>;</span>
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</pre></blockquote>
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<hr>
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<div class="prev_link"><a href="../index.html"><img src="../prev.gif" alt="index" border="0"><br>
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Index
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Index
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<div class="next_link"><a href="basics.html"><img src="../next.gif" alt="basics" border="0"><br>
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Basics
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</a></div><br clear="all" style="clear: all;">
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<br>
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<p>Revised February 21st 2006</p>
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<p>© Copyright 2003-2006 Joaquín M López Muñoz.
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Distributed under the Boost Software
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License, Version 1.0. (See accompanying file <a href="../../../../LICENSE_1_0.txt">
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LICENSE_1_0.txt</a> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt">
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http://www.boost.org/LICENSE_1_0.txt</a>)
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</p>
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</body>
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