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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0.1 Transitional//EN">
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<html>
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<head>
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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 - Techniques</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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<link rel="prev" href="debug.html">
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<link rel="up" href="index.html">
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<link rel="next" href="../reference/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: Techniques</h1>
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||||
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||||
<div class="prev_link"><a href="debug.html"><img src="../prev.gif" alt="debugging support" border="0"><br>
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||||
Debugging support
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||||
</a></div>
|
||||
<div class="up_link"><a href="index.html"><img src="../up.gif" alt="Boost.MultiIndex tutorial" border="0"><br>
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||||
Boost.MultiIndex tutorial
|
||||
</a></div>
|
||||
<div class="next_link"><a href="../reference/index.html"><img src="../next.gif" alt="Boost.MultiIndex reference" border="0"><br>
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||||
Boost.MultiIndex reference
|
||||
</a></div><br clear="all" style="clear: all;">
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||||
|
||||
<hr>
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||||
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||||
<h2>Contents</h2>
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||||
<ul>
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||||
<li><a href="#emulate_std_containers">Emulating standard containers with
|
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<code>multi_index_container</code></a>
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||||
<ul>
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||||
<li><a href="#emulate_assoc_containers">Emulation of associative
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||||
containers</a></li>
|
||||
<li><a href="#emulate_std_list">Emulation of <code>std::list</code></a></li>
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||||
</ul>
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||||
</li>
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||||
<li><a href="#metaprogrammming">Metaprogramming and <code>multi_index_container</code></a>
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||||
<ul>
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||||
<li><a href="#mpl_analysis">MPL analysis</a></li>
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||||
<li><a href="#mpl_synthesis">MPL synthesis</a></li>
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||||
</ul>
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||||
</li>
|
||||
</ul>
|
||||
|
||||
<h2><a name="emulate_std_containers">Emulating standard containers with
|
||||
<code>multi_index_container</code></a></h2>
|
||||
|
||||
<h3><a name="emulate_assoc_containers">Emulation of associative
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||||
containers</a></h3>
|
||||
|
||||
<p>
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||||
Academic movitations aside, there is a practical interest in emulating standard
|
||||
associative containers by means of <code>multi_index_container</code>, namely to take
|
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advantage of extended functionalities provided by <code>multi_index_container</code> for
|
||||
lookup, range querying and updating.
|
||||
</p>
|
||||
|
||||
<p>
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In order to emulate a <code>std::set</code> one can follow the substitution
|
||||
rule:
|
||||
</p>
|
||||
|
||||
<blockquote><pre>
|
||||
<span class=identifier>std</span><span class=special>::</span><span class=identifier>set</span><span class=special><</span><span class=identifier>Key</span><span class=special>,</span><span class=identifier>Compare</span><span class=special>,</span><span class=identifier>Allocator</span><span class=special>></span> <span class=special>-></span>
|
||||
<span class=identifier>multi_index_container</span><span class=special><</span>
|
||||
<span class=identifier>Key</span><span class=special>,</span>
|
||||
<span class=identifier>indexed_by</span><span class=special><</span><span class=identifier>ordered_unique</span><span class=special><</span><span class=identifier>identity</span><span class=special><</span><span class=identifier>Key</span><span class=special>>,</span><span class=identifier>Compare</span><span class=special>></span> <span class=special>>,</span>
|
||||
<span class=identifier>Allocator</span>
|
||||
<span class=special>></span>
|
||||
</pre></blockquote>
|
||||
|
||||
<p>
|
||||
In the default case where <code>Compare=std::less<Key></code> and
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||||
<code>Allocator=std::allocator<Key></code>, the substitution rule is
|
||||
simplified as
|
||||
</p>
|
||||
|
||||
<blockquote><pre>
|
||||
<span class=identifier>std</span><span class=special>::</span><span class=identifier>set</span><span class=special><</span><span class=identifier>Key</span><span class=special>></span> <span class=special>-></span> <span class=identifier>multi_index_container</span><span class=special><</span><span class=identifier>Key</span><span class=special>></span>
|
||||
</pre></blockquote>
|
||||
|
||||
<p>
|
||||
The substitution of <code>multi_index_container</code> for <code>std::set</code> keeps
|
||||
the whole set of functionality provided by <code>std::set</code>, so in
|
||||
principle it is a drop-in replacement needing no further adjustments.
|
||||
</p>
|
||||
|
||||
<p>
|
||||
<code>std::multiset</code> can be emulated in a similar manner, according to the
|
||||
following rule:
|
||||
</p>
|
||||
|
||||
<blockquote><pre>
|
||||
<span class=identifier>std</span><span class=special>::</span><span class=identifier>multiset</span><span class=special><</span><span class=identifier>Key</span><span class=special>,</span><span class=identifier>Compare</span><span class=special>,</span><span class=identifier>Allocator</span><span class=special>></span> <span class=special>-></span>
|
||||
<span class=identifier>multi_index_container</span><span class=special><</span>
|
||||
<span class=identifier>Key</span><span class=special>,</span>
|
||||
<span class=identifier>indexed_by</span><span class=special><</span><span class=identifier>ordered_non_unique</span><span class=special><</span><span class=identifier>identity</span><span class=special><</span><span class=identifier>Key</span><span class=special>>,</span><span class=identifier>Compare</span><span class=special>></span> <span class=special>>,</span>
|
||||
<span class=identifier>Allocator</span>
|
||||
<span class=special>></span>
|
||||
</pre></blockquote>
|
||||
|
||||
<p>
|
||||
When default values are taken into consideration, the rule takes the form
|
||||
</p>
|
||||
|
||||
<blockquote><pre>
|
||||
<span class=identifier>std</span><span class=special>::</span><span class=identifier>multiset</span><span class=special><</span><span class=identifier>Key</span><span class=special>></span> <span class=special>-></span>
|
||||
<span class=identifier>multi_index_container</span><span class=special><</span>
|
||||
<span class=identifier>Key</span><span class=special>,</span>
|
||||
<span class=identifier>indexed_by</span><span class=special><</span><span class=identifier>ordered_non_unique</span><span class=special><</span><span class=identifier>identity</span><span class=special><</span><span class=identifier>Key</span><span class=special>></span> <span class=special>></span> <span class=special>></span>
|
||||
<span class=special>></span>
|
||||
</pre></blockquote>
|
||||
|
||||
<p>
|
||||
The emulation of <code>std::multiset</code>s with <code>multi_index_container</code>
|
||||
results in a slight difference with respect to the interface offered: the member
|
||||
function <code>insert(const value_type&)</code> does not return an
|
||||
<code>iterator</code> as in <code>std::multiset</code>s, but rather a
|
||||
<code>std::pair<iterator,bool></code> in the spirit of <code>std::set</code>s.
|
||||
In this particular case, however, the <code>bool</code> member of the returned
|
||||
pair is always <code>true</code>.
|
||||
</p>
|
||||
|
||||
<p>
|
||||
The case of <code>std::map</code>s and <code>std::multimap</code>s does not lend
|
||||
itself to such a direct emulation by means of <code>multi_index_container</code>. The main
|
||||
problem lies in the fact that elements of a <code>multi_index_container</code> are treated
|
||||
as constant, while the <code>std::map</code> and <code>std::multimap</code> handle
|
||||
objects of type <code>std::pair<const Key,T></code>, thus allowing for free
|
||||
modification of the value part. To overcome this difficulty we need to create an ad
|
||||
hoc pair class:
|
||||
</p>
|
||||
|
||||
<blockquote><pre>
|
||||
<span class=keyword>template</span> <span class=special><</span><span class=keyword>typename</span> <span class=identifier>T1</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>T2</span><span class=special>></span>
|
||||
<span class=keyword>struct</span> <span class=identifier>mutable_pair</span>
|
||||
<span class=special>{</span>
|
||||
<span class=keyword>typedef</span> <span class=identifier>T1</span> <span class=identifier>first_type</span><span class=special>;</span>
|
||||
<span class=keyword>typedef</span> <span class=identifier>T2</span> <span class=identifier>second_type</span><span class=special>;</span>
|
||||
|
||||
<span class=identifier>mutable_pair</span><span class=special>():</span><span class=identifier>first</span><span class=special>(</span><span class=identifier>T1</span><span class=special>()),</span><span class=identifier>second</span><span class=special>(</span><span class=identifier>T2</span><span class=special>()){}</span>
|
||||
<span class=identifier>mutable_pair</span><span class=special>(</span><span class=keyword>const</span> <span class=identifier>T1</span><span class=special>&</span> <span class=identifier>f</span><span class=special>,</span><span class=keyword>const</span> <span class=identifier>T2</span><span class=special>&</span> <span class=identifier>s</span><span class=special>):</span><span class=identifier>first</span><span class=special>(</span><span class=identifier>f</span><span class=special>),</span><span class=identifier>second</span><span class=special>(</span><span class=identifier>s</span><span class=special>){}</span>
|
||||
<span class=identifier>mutable_pair</span><span class=special>(</span><span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>pair</span><span class=special><</span><span class=identifier>T1</span><span class=special>,</span><span class=identifier>T2</span><span class=special>>&</span> <span class=identifier>p</span><span class=special>):</span><span class=identifier>first</span><span class=special>(</span><span class=identifier>p</span><span class=special>.</span><span class=identifier>first</span><span class=special>),</span><span class=identifier>second</span><span class=special>(</span><span class=identifier>p</span><span class=special>.</span><span class=identifier>second</span><span class=special>){}</span>
|
||||
|
||||
<span class=identifier>T1</span> <span class=identifier>first</span><span class=special>;</span>
|
||||
<span class=keyword>mutable</span> <span class=identifier>T2</span> <span class=identifier>second</span><span class=special>;</span>
|
||||
<span class=special>};</span>
|
||||
</pre></blockquote>
|
||||
|
||||
<p>
|
||||
and so the substitution rules are:
|
||||
</p>
|
||||
|
||||
<blockquote><pre>
|
||||
<span class=identifier>std</span><span class=special>::</span><span class=identifier>map</span><span class=special><</span><span class=identifier>Key</span><span class=special>,</span><span class=identifier>T</span><span class=special>,</span><span class=identifier>Compare</span><span class=special>,</span><span class=identifier>Allocator</span><span class=special>></span> <span class=special>-></span>
|
||||
<span class=identifier>multi_index_container</span><span class=special><</span>
|
||||
<span class=identifier>Element</span><span class=special>,</span>
|
||||
<span class=identifier>indexed_by</span><span class=special><</span>
|
||||
<span class=identifier>ordered_unique</span><span class=special><</span><span class=identifier>member</span><span class=special><</span><span class=identifier>Element</span><span class=special>,</span><span class=identifier>Key</span><span class=special>,&</span><span class=identifier>Element</span><span class=special>::</span><span class=identifier>first</span><span class=special>>,</span><span class=identifier>Compare</span><span class=special>></span>
|
||||
<span class=special>>,</span>
|
||||
<span class=keyword>typename</span> <span class=identifier>Allocator</span><span class=special>::</span><span class=keyword>template</span> <span class=identifier>rebind</span><span class=special><</span><span class=identifier>Element</span><span class=special>>::</span><span class=identifier>other</span>
|
||||
<span class=special>></span>
|
||||
|
||||
<span class=identifier>std</span><span class=special>::</span><span class=identifier>multimap</span><span class=special><</span><span class=identifier>Key</span><span class=special>,</span><span class=identifier>T</span><span class=special>,</span><span class=identifier>Compare</span><span class=special>,</span><span class=identifier>Allocator</span><span class=special>></span> <span class=special>-></span>
|
||||
<span class=identifier>multi_index_container</span><span class=special><</span>
|
||||
<span class=identifier>Element</span><span class=special>,</span>
|
||||
<span class=identifier>indexed_by</span><span class=special><</span>
|
||||
<span class=identifier>ordered_non_unique</span><span class=special><</span><span class=identifier>member</span><span class=special><</span><span class=identifier>Element</span><span class=special>,</span><span class=identifier>Key</span><span class=special>,&</span><span class=identifier>Element</span><span class=special>::</span><span class=identifier>first</span><span class=special>>,</span><span class=identifier>Compare</span><span class=special>></span>
|
||||
<span class=special>>,</span>
|
||||
<span class=keyword>typename</span> <span class=identifier>Allocator</span><span class=special>::</span><span class=keyword>template</span> <span class=identifier>rebind</span><span class=special><</span><span class=identifier>Element</span><span class=special>>::</span><span class=identifier>other</span>
|
||||
<span class=special>></span>
|
||||
|
||||
(<span class=identifier>with</span> <span class=identifier>Element</span><span class=special>=</span><span class=identifier>mutable_pair</span><span class=special><</span><span class=identifier>Key</span><span class=special>,</span><span class=identifier>T</span><span class=special>></span>)
|
||||
</pre></blockquote>
|
||||
|
||||
<p>
|
||||
If default values are considered, the rules take the form:
|
||||
</p>
|
||||
|
||||
<blockquote><pre>
|
||||
<span class=identifier>std</span><span class=special>::</span><span class=identifier>map</span><span class=special><</span><span class=identifier>Key</span><span class=special>,</span><span class=identifier>T</span><span class=special>></span> <span class=special>-></span>
|
||||
<span class=identifier>multi_index_container</span><span class=special><</span>
|
||||
<span class=identifier>Element</span><span class=special>,
|
||||
</span><span class=identifier>indexed_by</span><span class=special><</span><span class=identifier>ordered_unique</span><span class=special><</span><span class=identifier>member</span><span class=special><</span><span class=identifier>Element</span><span class=special>,</span><span class=identifier>Key</span><span class=special>,&</span><span class=identifier>Element</span><span class=special>::</span><span class=identifier>first</span><span class=special>></span> <span class=special>></span> <span class=special>></span>
|
||||
<span class=special>></span>
|
||||
|
||||
<span class=identifier>std</span><span class=special>::</span><span class=identifier>multimap</span><span class=special><</span><span class=identifier>Key</span><span class=special>,</span><span class=identifier>T</span><span class=special>></span> <span class=special>-></span>
|
||||
<span class=identifier>multi_index_container</span><span class=special><</span>
|
||||
<span class=identifier>Element</span><span class=special>,
|
||||
</span><span class=identifier>indexed_by</span><span class=special><</span><span class=identifier>ordered_non_unique</span><span class=special><</span><span class=identifier>member</span><span class=special><</span><span class=identifier>Element</span><span class=special>,</span><span class=identifier>Key</span><span class=special>,&</span><span class=identifier>Element</span><span class=special>::</span><span class=identifier>first</span><span class=special>></span> <span class=special>></span> <span class=special>></span>
|
||||
<span class=special>></span>
|
||||
|
||||
(<span class=identifier>with</span> <span class=identifier>Element</span><span class=special>=</span><span class=identifier>mutable_pair</span><span class=special><</span><span class=identifier>Key</span><span class=special>,</span><span class=identifier>T</span><span class=special>></span>)
|
||||
</pre></blockquote>
|
||||
|
||||
<p>
|
||||
Unlike as with standard sets, the interface of these <code>multi_index_container</code>-emulated
|
||||
maps does not exactly conform to that of <code>std::map</code>s and
|
||||
<code>std::multimap</code>s. The most obvious difference is the lack of
|
||||
<code>operator []</code>, either in read or write mode; this, however, can be
|
||||
emulated with appropriate use of <code>find</code> and <code>insert</code>.
|
||||
</p>
|
||||
|
||||
<p>
|
||||
These emulations of standard associative containers with <code>multi_index_container</code>
|
||||
are comparable to the original constructs in terms of space and time efficiency.
|
||||
See the <a href="../performance.html">performance section</a> for further details.
|
||||
</p>
|
||||
|
||||
<h3><a name="emulate_std_list">Emulation of <code>std::list</code></a></h3>
|
||||
|
||||
<p>
|
||||
Unlike the case of associative containers, emulating <code>std::list</code>
|
||||
in Boost.MultiIndex does not add any significant functionality, so the following
|
||||
is presented merely for completeness sake.
|
||||
</p>
|
||||
|
||||
<p>
|
||||
Much as with standard maps, the main difficulty to overcome when emulating
|
||||
<code>std::list</code> derives from the constant nature of elements of a
|
||||
<code>multi_index_container</code>. Again, some sort of adaption class is needed, like
|
||||
for instance the following:
|
||||
</p>
|
||||
|
||||
<blockquote><pre>
|
||||
<span class=keyword>template</span> <span class=special><</span><span class=keyword>typename</span> <span class=identifier>T</span><span class=special>></span>
|
||||
<span class=keyword>struct</span> <span class=identifier>mutable_value</span>
|
||||
<span class=special>{</span>
|
||||
<span class=identifier>mutable_value</span><span class=special>(</span><span class=keyword>const</span> <span class=identifier>T</span><span class=special>&</span> <span class=identifier>t</span><span class=special>):</span><span class=identifier>t</span><span class=special>(</span><span class=identifier>t</span><span class=special>){}</span>
|
||||
<span class=keyword>operator</span> <span class=identifier>T</span><span class=special>&()</span><span class=keyword>const</span><span class=special>{</span><span class=keyword>return</span> <span class=identifier>t</span><span class=special>;}</span>
|
||||
|
||||
<span class=keyword>private</span><span class=special>:</span>
|
||||
<span class=keyword>mutable</span> <span class=identifier>T</span> <span class=identifier>t</span><span class=special>;</span>
|
||||
<span class=special>};</span>
|
||||
</pre></blockquote>
|
||||
|
||||
<p>
|
||||
which allows us to use the substitution rule:
|
||||
</p>
|
||||
|
||||
<blockquote><pre>
|
||||
<span class=identifier>std</span><span class=special>::</span><span class=identifier>list</span><span class=special><</span><span class=identifier>T</span><span class=special>,</span><span class=identifier>Allocator</span><span class=special>></span> <span class=special>-></span>
|
||||
<span class=identifier>multi_index_container</span><span class=special><</span>
|
||||
<span class=identifier>Element</span><span class=special>,</span>
|
||||
<span class=identifier>indexed_by</span><span class=special><</span><span class=identifier>sequenced</span><span class=special><></span> <span class=special>>,</span>
|
||||
<span class=keyword>typename</span> <span class=identifier>Allocator</span><span class=special>::</span><span class=keyword>template</span> <span class=identifier>rebind</span><span class=special><</span><span class=identifier>Element</span><span class=special>>::</span><span class=identifier>other</span>
|
||||
<span class=special>></span>
|
||||
|
||||
(<span class=identifier>with</span> <span class=identifier>Element</span><span class=special>=</span><span class=identifier>mutable_value</span><span class=special><</span><span class=identifier>T</span><span class=special>></span>)
|
||||
</pre></blockquote>
|
||||
|
||||
<p>
|
||||
or, if the default value <code>Allocator=std::allocator<T></code> is used:
|
||||
</p>
|
||||
|
||||
<blockquote><pre>
|
||||
<span class=identifier>std</span><span class=special>::</span><span class=identifier>list</span><span class=special><</span><span class=identifier>T</span><span class=special>></span> <span class=special>-></span>
|
||||
<span class=identifier>multi_index_container</span><span class=special><</span><span class=identifier>mutable_value</span><span class=special><</span><span class=identifier>T</span><span class=special>>,</span><span class=identifier>indexed_by</span><span class=special><</span><span class=identifier>sequenced</span><span class=special><></span> <span class=special>></span> <span class=special>></span>
|
||||
</pre></blockquote>
|
||||
|
||||
<h2><a name="metaprogrammming">Metaprogramming and <code>multi_index_container</code></a></h2>
|
||||
|
||||
<p>
|
||||
Boost.MultiIndex provides a number of facilities intended to allow the analysis and
|
||||
synthesis of <code>multi_index_container</code> instantiations by
|
||||
<a href="../../../../libs/mpl/doc/index.html">MPL</a> metaprograms.
|
||||
</p>
|
||||
|
||||
<h3><a name="mpl_analysis">MPL analysis</a></h3>
|
||||
|
||||
<p>
|
||||
Given a <code>multi_index_container</code> instantiation, the following nested types are
|
||||
provided for compile-time inspection of the various types occurring in the
|
||||
definition of the <code>multi_index_container</code>:
|
||||
<ul>
|
||||
<li><code>index_specifier_type_list</code>,</li>
|
||||
<li><code>index_type_list</code>,</li>
|
||||
<li><code>iterator_type_list</code>,</li>
|
||||
<li><code>const_iterator_type_list</code>.</li>
|
||||
</ul>
|
||||
Each of these types is an MPL sequence with as many elements as indices
|
||||
comprise the <code>multi_index_container</code>: for instance, the <code>n</code>-th
|
||||
element of <code>iterator_type_list</code> is the same as
|
||||
<code>nth_index<n>::type::iterator</code>.
|
||||
</p>
|
||||
|
||||
<p>
|
||||
A subtle but important distinction exists between
|
||||
<code>index_specifier_type_list</code> and <code>index_type_list</code>:
|
||||
the former typelist holds the index <i>specifiers</i>
|
||||
with which the <code>multi_index_container</code> instantiation was defined,
|
||||
while the latter gives access to the actual implementation classes
|
||||
corresponding to each specifier. An example will help to clarify
|
||||
this distinction. Given the instantiation:
|
||||
</p>
|
||||
|
||||
<blockquote><pre>
|
||||
<span class=keyword>typedef</span> <span class=identifier>multi_index_container</span><span class=special><</span>
|
||||
<span class=keyword>int</span><span class=special>,</span>
|
||||
<span class=identifier>indexed_by</span><span class=special><</span>
|
||||
<span class=identifier>ordered_unique</span><span class=special><</span><span class=identifier>identity</span><span class=special><</span><span class=keyword>int</span><span class=special>></span> <span class=special>>,</span>
|
||||
<span class=identifier>sequenced</span><span class=special><></span>
|
||||
<span class=special>></span>
|
||||
<span class=special>></span> <span class=identifier>indexed_t</span><span class=special>;</span>
|
||||
</pre></blockquote>
|
||||
|
||||
<p>
|
||||
<code>indexed_t::index_specifier_type_list</code> is a type list with
|
||||
elements
|
||||
</p>
|
||||
|
||||
<blockquote><pre>
|
||||
<span class=identifier>ordered_unique</span><span class=special><</span><span class=identifier>identity</span><span class=special><</span><span class=keyword>int</span><span class=special>></span> <span class=special>></span>
|
||||
<span class=identifier>sequenced</span><span class=special><></span>
|
||||
</pre></blockquote>
|
||||
|
||||
<p>
|
||||
while <code>indexed_t::index_type_list</code> holds the types
|
||||
</p>
|
||||
|
||||
<blockquote><pre>
|
||||
<span class=identifier>multi_index_container</span><span class=special>::</span><span class=identifier>nth_type</span><span class=special><</span><span class=number>0</span><span class=special>>::</span><span class=identifier>type</span>
|
||||
<span class=identifier>multi_index_container</span><span class=special>::</span><span class=identifier>nth_type</span><span class=special><</span><span class=number>1</span><span class=special>>::</span><span class=identifier>type</span>
|
||||
</pre></blockquote>
|
||||
|
||||
<p>
|
||||
so the typelists are radically different. Check the
|
||||
<a href="../reference/multi_index_container.html#types">reference</a>
|
||||
for the exact MPL sequence concepts modeled by these type lists.
|
||||
</p>
|
||||
|
||||
<h3><a name="mpl_synthesis">MPL synthesis</a></h3>
|
||||
|
||||
<p>
|
||||
Although typically indices are specified by means of the
|
||||
<code>indexed_by</code> construct, actually any MPL sequence of
|
||||
index specifiers can be provided instead:
|
||||
</p>
|
||||
|
||||
<blockquote><pre>
|
||||
<span class=keyword>typedef</span> <span class=identifier>mpl</span><span class=special>::</span><span class=identifier>vector</span><span class=special><</span><span class=identifier>ordered_unique</span><span class=special><</span><span class=identifier>identity</span><span class=special><</span><span class=keyword>int</span><span class=special>></span> <span class=special>>,</span><span class=identifier>sequenced</span><span class=special><></span> <span class=special>></span> <span class=identifier>index_list_t</span><span class=special>;</span>
|
||||
|
||||
<span class=keyword>typedef</span> <span class=identifier>multi_index_container</span><span class=special><</span>
|
||||
<span class=keyword>int</span><span class=special>,</span>
|
||||
<span class=identifier>index_list_t</span>
|
||||
<span class=special>></span> <span class=identifier>indexed_t</span><span class=special>;</span>
|
||||
</pre></blockquote>
|
||||
|
||||
<p>
|
||||
This possibility enables the synthesis of instantiations of
|
||||
<code>multi_index_container</code> through MPL metaprograms, as the following
|
||||
example shows:
|
||||
</p>
|
||||
|
||||
<blockquote><pre>
|
||||
<span class=comment>// original multi_index_container instantiation</span>
|
||||
<span class=keyword>typedef</span> <span class=identifier>multi_index_container</span><span class=special><</span>
|
||||
<span class=keyword>int</span><span class=special>,</span>
|
||||
<span class=identifier>indexed_by</span><span class=special><</span>
|
||||
<span class=identifier>ordered_unique</span><span class=special><</span><span class=identifier>identity</span><span class=special><</span><span class=keyword>int</span><span class=special>></span> <span class=special>></span>
|
||||
<span class=special>></span>
|
||||
<span class=special>></span> <span class=identifier>indexed_t1</span><span class=special>;</span>
|
||||
|
||||
<span class=comment>// we take its index list and add an index</span>
|
||||
<span class=keyword>typedef</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>mpl</span><span class=special>::</span><span class=identifier>push_front</span><span class=special><</span>
|
||||
<span class=identifier>indexed_t1</span><span class=special>::</span><span class=identifier>index_specifier_type_list</span><span class=special>,</span>
|
||||
<span class=identifier>sequenced</span><span class=special><></span>
|
||||
<span class=special>>::</span><span class=identifier>type</span> <span class=identifier>index_list_t</span><span class=special>;</span>
|
||||
|
||||
<span class=comment>// augmented multi_index_container</span>
|
||||
<span class=keyword>typedef</span> <span class=identifier>multi_index_container</span><span class=special><</span>
|
||||
<span class=keyword>int</span><span class=special>,</span>
|
||||
<span class=identifier>index_list_t</span>
|
||||
<span class=special>></span> <span class=identifier>indexed_t2</span><span class=special>;</span>
|
||||
</pre></blockquote>
|
||||
|
||||
<hr>
|
||||
|
||||
<div class="prev_link"><a href="debug.html"><img src="../prev.gif" alt="debugging support" border="0"><br>
|
||||
Debugging support
|
||||
</a></div>
|
||||
<div class="up_link"><a href="index.html"><img src="../up.gif" alt="Boost.MultiIndex tutorial" border="0"><br>
|
||||
Boost.MultiIndex tutorial
|
||||
</a></div>
|
||||
<div class="next_link"><a href="../reference/index.html"><img src="../next.gif" alt="Boost.MultiIndex reference" border="0"><br>
|
||||
Boost.MultiIndex reference
|
||||
</a></div><br clear="all" style="clear: all;">
|
||||
|
||||
<br>
|
||||
|
||||
<p>Revised November 7th 2008</p>
|
||||
|
||||
<p>© Copyright 2003-2008 Joaquín M López Muñoz.
|
||||
Distributed under the Boost Software
|
||||
License, Version 1.0. (See accompanying file <a href="../../../../LICENSE_1_0.txt">
|
||||
LICENSE_1_0.txt</a> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt">
|
||||
http://www.boost.org/LICENSE_1_0.txt</a>)
|
||||
</p>
|
||||
|
||||
</body>
|
||||
</html>
|
||||
Reference in New Issue
Block a user