townforge/bimap
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity
cc
bimap/doc/html/boost_bimap/one_minute_tutorial.html
Steven Watanabe 146671e8d7 Apply patch for documentation typos. Fixes #5955. 
[SVN r82888]
2013-02-14 19:06:34 +00:00

429 lines
46 KiB
HTML
Raw Permalink Blame History

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<title>One minute tutorial</title>
<link rel="stylesheet" href="../boostbook.css" type="text/css">
<meta name="generator" content="DocBook XSL Stylesheets V1.77.1">
<link rel="home" href="../index.html" title="Chapter&#160;1.&#160;Boost.Bimap">
<link rel="up" href="../index.html" title="Chapter&#160;1.&#160;Boost.Bimap">
<link rel="prev" href="introduction.html" title="Introduction">
<link rel="next" href="the_tutorial.html" title="The tutorial">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<table cellpadding="2" width="100%"><tr>
<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../boost.png"></td>
<td align="center"><a href="../../../../../index.html">Home</a></td>
<td align="center"><a href="../../../../../libs/libraries.htm">Libraries</a></td>
<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
<td align="center"><a href="../../../../../more/index.htm">More</a></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="introduction.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="the_tutorial.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
</div>
<div class="section boost_bimap_one_minute_tutorial">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="boost_bimap.one_minute_tutorial"></a><a class="link" href="one_minute_tutorial.html" title="One minute tutorial">One minute tutorial</a>
</h2></div></div></div>
<h4>
<a name="boost_bimap.one_minute_tutorial.h0"></a>
<span class="phrase"><a name="boost_bimap.one_minute_tutorial.what_is_a_bimap_"></a></span><a class="link" href="one_minute_tutorial.html#boost_bimap.one_minute_tutorial.what_is_a_bimap_">What
is a bimap?</a>
</h4>
<p>
A Bimap is a data structure that represents bidirectional relations between
elements of two collections. The container is designed to work as two opposed
STL maps. A bimap between a collection <code class="computeroutput"><span class="identifier">X</span></code>
and a collection <code class="computeroutput"><span class="identifier">Y</span></code> can be viewed
as a map from <code class="computeroutput"><span class="identifier">X</span></code> to <code class="computeroutput"><span class="identifier">Y</span></code> (this view will be called the <span class="emphasis"><em>left
map view</em></span>) or as a map from <code class="computeroutput"><span class="identifier">Y</span></code>
to <code class="computeroutput"><span class="identifier">X</span></code> (known as the <span class="emphasis"><em>right
map view</em></span>). Additionally, the bimap can also be viewed as a set of
relations between <code class="computeroutput"><span class="identifier">X</span></code> and <code class="computeroutput"><span class="identifier">Y</span></code> (named the <span class="emphasis"><em>collection of relations
view</em></span>).
</p>
<p>
The following code creates an empty bimap container:
</p>
<pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">bimap</span><span class="special">&lt;</span><span class="identifier">X</span><span class="special">,</span><span class="identifier">Y</span><span class="special">&gt;</span> <span class="identifier">bm_type</span><span class="special">;</span>
<span class="identifier">bm_type</span> <span class="identifier">bm</span><span class="special">;</span>
</pre>
<p>
Given this code, the following is the complete description of the resulting
bimap. <a href="#ftn.boost_bimap.one_minute_tutorial.f0" class="footnote"><sup class="footnote"><a name="boost_bimap.one_minute_tutorial.f0"></a>[1]</sup></a>
</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<code class="computeroutput"><span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span></code> is signature-compatible with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">map</span><span class="special">&lt;</span><span class="identifier">X</span><span class="special">,</span><span class="identifier">Y</span><span class="special">&gt;</span></code>
</li>
<li class="listitem">
<code class="computeroutput"><span class="identifier">bm</span><span class="special">.</span><span class="identifier">right</span></code> is signature-compatible with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">map</span><span class="special">&lt;</span><span class="identifier">Y</span><span class="special">,</span><span class="identifier">X</span><span class="special">&gt;</span></code>
</li>
<li class="listitem">
<code class="computeroutput"><span class="identifier">bm</span></code> is signature-compatible
with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">set</span><span class="special">&lt;</span> <span class="identifier">relation</span><span class="special">&lt;</span><span class="identifier">X</span><span class="special">,</span><span class="identifier">Y</span><span class="special">&gt;</span> <span class="special">&gt;</span></code>
</li>
</ul></div>
<p>
<span class="inlinemediaobject"><img src="../images/bimap/simple.bimap.png" alt="simple.bimap"></span>
</p>
<p>
You can see how a bimap container offers three views over the same collection
of bidirectional relations.
</p>
<p>
If we have any generic function that work with maps
</p>
<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">class</span> <span class="identifier">MapType</span> <span class="special">&gt;</span>
<span class="keyword">void</span> <span class="identifier">print_map</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">MapType</span> <span class="special">&amp;</span> <span class="identifier">m</span><span class="special">)</span>
<span class="special">{</span>
<span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">MapType</span><span class="special">::</span><span class="identifier">const_iterator</span> <span class="identifier">const_iterator</span><span class="special">;</span>
<span class="keyword">for</span><span class="special">(</span> <span class="identifier">const_iterator</span> <span class="identifier">iter</span> <span class="special">=</span> <span class="identifier">m</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">iend</span> <span class="special">=</span> <span class="identifier">m</span><span class="special">.</span><span class="identifier">end</span><span class="special">();</span> <span class="identifier">iter</span> <span class="special">!=</span> <span class="identifier">iend</span><span class="special">;</span> <span class="special">++</span><span class="identifier">iter</span> <span class="special">)</span>
<span class="special">{</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">iter</span><span class="special">-&gt;</span><span class="identifier">first</span> <span class="special">&lt;&lt;</span> <span class="string">"--&gt;"</span> <span class="special">&lt;&lt;</span> <span class="identifier">iter</span><span class="special">-&gt;</span><span class="identifier">second</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="special">}</span>
<span class="special">}</span>
</pre>
<p>
We can use the <span class="emphasis"><em>left map view</em></span> and the <span class="emphasis"><em>right map
view</em></span> with it
</p>
<pre class="programlisting"><span class="identifier">bimap</span><span class="special">&lt;</span> <span class="keyword">int</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">&gt;</span> <span class="identifier">bm</span><span class="special">;</span>
<span class="special">...</span>
<span class="identifier">print_map</span><span class="special">(</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span> <span class="special">);</span>
<span class="identifier">print_map</span><span class="special">(</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">right</span> <span class="special">);</span>
</pre>
<p>
And the output will be
</p>
<pre class="programlisting"><code class="literal">1 --&gt; one</code>
<code class="literal">2 --&gt; two</code>
...
<code class="literal">one --&gt; 1</code>
<code class="literal">two --&gt; 2</code>
...
</pre>
<h4>
<a name="boost_bimap.one_minute_tutorial.h1"></a>
<span class="phrase"><a name="boost_bimap.one_minute_tutorial.layout_of_the_relation_and_the_pairs_of_a_bimap"></a></span><a class="link" href="one_minute_tutorial.html#boost_bimap.one_minute_tutorial.layout_of_the_relation_and_the_pairs_of_a_bimap">Layout
of the relation and the pairs of a bimap</a>
</h4>
<p>
The <code class="computeroutput"><span class="identifier">relation</span></code> class represents
two related elements. The two values are named left and right to express the
symmetry of this type. The bimap pair classes are signature-compatible with
<code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pairs</span></code>.
</p>
<p>
<span class="inlinemediaobject"><img src="../images/bimap/relation.and.pair.png" alt="relation.and.pair"></span>
</p>
<h4>
<a name="boost_bimap.one_minute_tutorial.h2"></a>
<span class="phrase"><a name="boost_bimap.one_minute_tutorial.step_by_step"></a></span><a class="link" href="one_minute_tutorial.html#boost_bimap.one_minute_tutorial.step_by_step">Step
by step</a>
</h4>
<p>
A convenience header is available in the boost directory:
</p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">bimap</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
</pre>
<p>
Lets define a bidirectional map between integers and strings:
</p>
<p>
</p>
<pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">bimap</span><span class="special">&lt;</span> <span class="keyword">int</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">&gt;</span> <span class="identifier">bm_type</span><span class="special">;</span>
<span class="identifier">bm_type</span> <span class="identifier">bm</span><span class="special">;</span>
</pre>
<p>
</p>
<h4>
<a name="boost_bimap.one_minute_tutorial.h3"></a>
<span class="phrase"><a name="boost_bimap.one_minute_tutorial.the_collection_of_relations_view"></a></span><a class="link" href="one_minute_tutorial.html#boost_bimap.one_minute_tutorial.the_collection_of_relations_view">The
collection of relations view</a>
</h4>
<p>
Remember that <code class="computeroutput"><span class="identifier">bm</span></code> alone can
be used as a set of relations. We can insert elements or iterate over them
using this view.
</p>
<p>
</p>
<pre class="programlisting"><span class="identifier">bm</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span> <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">value_type</span><span class="special">(</span><span class="number">1</span><span class="special">,</span> <span class="string">"one"</span> <span class="special">)</span> <span class="special">);</span>
<span class="identifier">bm</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span> <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">value_type</span><span class="special">(</span><span class="number">2</span><span class="special">,</span> <span class="string">"two"</span> <span class="special">)</span> <span class="special">);</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"There are "</span> <span class="special">&lt;&lt;</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">size</span><span class="special">()</span> <span class="special">&lt;&lt;</span> <span class="string">"relations"</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="keyword">for</span><span class="special">(</span> <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">const_iterator</span> <span class="identifier">iter</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">iend</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">end</span><span class="special">();</span>
<span class="identifier">iter</span> <span class="special">!=</span> <span class="identifier">iend</span><span class="special">;</span> <span class="special">++</span><span class="identifier">iter</span> <span class="special">)</span>
<span class="special">{</span>
<span class="comment">// iter-&gt;left : data : int</span>
<span class="comment">// iter-&gt;right : data : std::string</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">iter</span><span class="special">-&gt;</span><span class="identifier">left</span> <span class="special">&lt;&lt;</span> <span class="string">" &lt;--&gt; "</span> <span class="special">&lt;&lt;</span> <span class="identifier">iter</span><span class="special">-&gt;</span><span class="identifier">right</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
</p>
<h4>
<a name="boost_bimap.one_minute_tutorial.h4"></a>
<span class="phrase"><a name="boost_bimap.one_minute_tutorial.the_left_map_view"></a></span><a class="link" href="one_minute_tutorial.html#boost_bimap.one_minute_tutorial.the_left_map_view">The
left map view</a>
</h4>
<p>
<code class="computeroutput"><span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span></code> works like a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">map</span><span class="special">&lt;</span>
<span class="keyword">int</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span>
<span class="special">&gt;</span></code>. We use it in the same way we will
use a standard map.
</p>
<p>
</p>
<pre class="programlisting"><a class="co" name="boost_bimap.one_minute_tutorial.c0" href="one_minute_tutorial.html#boost_bimap.one_minute_tutorial.c1"><img src="../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a><span class="keyword">typedef</span> <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">left_map</span><span class="special">::</span><span class="identifier">const_iterator</span> <span class="identifier">left_const_iterator</span><span class="special">;</span>
<span class="keyword">for</span><span class="special">(</span> <span class="identifier">left_const_iterator</span> <span class="identifier">left_iter</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">iend</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span><span class="special">.</span><span class="identifier">end</span><span class="special">();</span>
<span class="identifier">left_iter</span> <span class="special">!=</span> <span class="identifier">iend</span><span class="special">;</span> <span class="special">++</span><span class="identifier">left_iter</span> <span class="special">)</span>
<span class="special">{</span>
<span class="comment">// left_iter-&gt;first : key : int</span>
<span class="comment">// left_iter-&gt;second : data : std::string</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">left_iter</span><span class="special">-&gt;</span><span class="identifier">first</span> <span class="special">&lt;&lt;</span> <span class="string">" --&gt; "</span> <span class="special">&lt;&lt;</span> <span class="identifier">left_iter</span><span class="special">-&gt;</span><span class="identifier">second</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="special">}</span>
<a class="co" name="boost_bimap.one_minute_tutorial.c2" href="one_minute_tutorial.html#boost_bimap.one_minute_tutorial.c3"><img src="../../../../../doc/src/images/callouts/2.png" alt="2" border="0"></a><span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">left_const_iterator</span> <span class="identifier">left_iter</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span><span class="special">.</span><span class="identifier">find</span><span class="special">(</span><span class="number">2</span><span class="special">);</span>
<span class="identifier">assert</span><span class="special">(</span> <span class="identifier">left_iter</span><span class="special">-&gt;</span><span class="identifier">second</span> <span class="special">==</span> <span class="string">"two"</span> <span class="special">);</span>
<a class="co" name="boost_bimap.one_minute_tutorial.c4" href="one_minute_tutorial.html#boost_bimap.one_minute_tutorial.c5"><img src="../../../../../doc/src/images/callouts/3.png" alt="3" border="0"></a><span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span> <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">left_value_type</span><span class="special">(</span> <span class="number">3</span><span class="special">,</span> <span class="string">"three"</span> <span class="special">)</span> <span class="special">);</span>
</pre>
<p>
</p>
<div class="calloutlist"><table border="0" summary="Callout list">
<tr>
<td width="5%" valign="top" align="left"><p><a name="boost_bimap.one_minute_tutorial.c1"></a><a href="#boost_bimap.one_minute_tutorial.c0"><img src="../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a> </p></td>
<td valign="top" align="left"><p>
The type of <code class="computeroutput"><span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span></code> is <code class="computeroutput"><span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">left_map</span></code>
and the type of <code class="computeroutput"><span class="identifier">bm</span><span class="special">.</span><span class="identifier">right</span></code> is <code class="computeroutput"><span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">right_map</span></code>
</p></td>
</tr>
<tr>
<td width="5%" valign="top" align="left"><p><a name="boost_bimap.one_minute_tutorial.c3"></a><a href="#boost_bimap.one_minute_tutorial.c2"><img src="../../../../../doc/src/images/callouts/2.png" alt="2" border="0"></a> </p></td>
<td valign="top" align="left"><p>
<code class="computeroutput"><span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">left_</span></code>-type- can be used as a shortcut
for the more verbose <code class="computeroutput"><span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">left_map</span><span class="special">::</span></code>-type-
</p></td>
</tr>
<tr>
<td width="5%" valign="top" align="left"><p><a name="boost_bimap.one_minute_tutorial.c5"></a><a href="#boost_bimap.one_minute_tutorial.c4"><img src="../../../../../doc/src/images/callouts/3.png" alt="3" border="0"></a> </p></td>
<td valign="top" align="left"><p>
This line produces the same effect of <code class="computeroutput"><span class="identifier">bm</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span> <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">value_type</span><span class="special">(</span><span class="number">3</span><span class="special">,</span><span class="string">"three"</span><span class="special">)</span>
<span class="special">);</span></code>
</p></td>
</tr>
</table></div>
<h4>
<a name="boost_bimap.one_minute_tutorial.h5"></a>
<span class="phrase"><a name="boost_bimap.one_minute_tutorial.the_right_map_view"></a></span><a class="link" href="one_minute_tutorial.html#boost_bimap.one_minute_tutorial.the_right_map_view">The
right map view</a>
</h4>
<p>
<code class="computeroutput"><span class="identifier">bm</span><span class="special">.</span><span class="identifier">right</span></code> works like a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">map</span><span class="special">&lt;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">,</span> <span class="keyword">int</span> <span class="special">&gt;</span></code>. It
is important to note that the key is the first type and the data is the second
one, exactly as with standard maps.
</p>
<p>
</p>
<pre class="programlisting"><span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">right_const_iterator</span> <span class="identifier">right_iter</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">right</span><span class="special">.</span><span class="identifier">find</span><span class="special">(</span><span class="string">"two"</span><span class="special">);</span>
<span class="comment">// right_iter-&gt;first : key : std::string</span>
<span class="comment">// right_iter-&gt;second : data : int</span>
<span class="identifier">assert</span><span class="special">(</span> <span class="identifier">right_iter</span><span class="special">-&gt;</span><span class="identifier">second</span> <span class="special">==</span> <span class="number">2</span> <span class="special">);</span>
<span class="identifier">assert</span><span class="special">(</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">right</span><span class="special">.</span><span class="identifier">at</span><span class="special">(</span><span class="string">"one"</span><span class="special">)</span> <span class="special">==</span> <span class="number">1</span> <span class="special">);</span>
<span class="identifier">bm</span><span class="special">.</span><span class="identifier">right</span><span class="special">.</span><span class="identifier">erase</span><span class="special">(</span><span class="string">"two"</span><span class="special">);</span>
<a class="co" name="boost_bimap.one_minute_tutorial.c6" href="one_minute_tutorial.html#boost_bimap.one_minute_tutorial.c7"><img src="../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a><span class="identifier">bm</span><span class="special">.</span><span class="identifier">right</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span> <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">right_value_type</span><span class="special">(</span> <span class="string">"four"</span><span class="special">,</span> <span class="number">4</span> <span class="special">)</span> <span class="special">);</span>
</pre>
<p>
</p>
<div class="calloutlist"><table border="0" summary="Callout list"><tr>
<td width="5%" valign="top" align="left"><p><a name="boost_bimap.one_minute_tutorial.c7"></a><a href="#boost_bimap.one_minute_tutorial.c6"><img src="../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a> </p></td>
<td valign="top" align="left"><p>
This line produces the same effect of <code class="computeroutput"><span class="identifier">bm</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span> <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">value_type</span><span class="special">(</span><span class="number">4</span><span class="special">,</span><span class="string">"four"</span><span class="special">)</span>
<span class="special">);</span></code>
</p></td>
</tr></table></div>
<h4>
<a name="boost_bimap.one_minute_tutorial.h6"></a>
<span class="phrase"><a name="boost_bimap.one_minute_tutorial.differences_with_std__map"></a></span><a class="link" href="one_minute_tutorial.html#boost_bimap.one_minute_tutorial.differences_with_std__map">Differences
with std::map</a>
</h4>
<p>
The main difference between bimap views and their standard containers counterparts
is that, because of the bidirectional nature of a bimap, the values stored
in it can not be modified directly using iterators. For example, when a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">map</span><span class="special">&lt;</span><span class="identifier">X</span><span class="special">,</span><span class="identifier">Y</span><span class="special">&gt;</span></code> iterator
is dereferenced the return type is <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special">&lt;</span><span class="keyword">const</span> <span class="identifier">X</span><span class="special">,</span>
<span class="identifier">Y</span><span class="special">&gt;</span></code>,
so the following code is valid: <code class="computeroutput"><span class="identifier">m</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()-&gt;</span><span class="identifier">second</span> <span class="special">=</span> <span class="identifier">new_value</span><span class="special">;</span></code>.
However dereferencing a <code class="computeroutput"><span class="identifier">bimap</span><span class="special">&lt;</span><span class="identifier">X</span><span class="special">,</span><span class="identifier">Y</span><span class="special">&gt;::</span><span class="identifier">left_iterator</span></code>
returns a type that is <span class="emphasis"><em>signature-compatible</em></span> with a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special">&lt;</span><span class="keyword">const</span> <span class="identifier">X</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">Y</span><span class="special">&gt;</span></code>
</p>
<pre class="programlisting"><span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span><span class="special">.</span><span class="identifier">find</span><span class="special">(</span><span class="number">1</span><span class="special">)-&gt;</span><span class="identifier">second</span> <span class="special">=</span> <span class="string">"1"</span><span class="special">;</span> <span class="comment">// Compilation error</span>
</pre>
<p>
If you insert <code class="computeroutput"><span class="special">(</span><span class="number">1</span><span class="special">,</span><span class="string">"one"</span><span class="special">)</span></code> and <code class="computeroutput"><span class="special">(</span><span class="number">1</span><span class="special">,</span><span class="string">"1"</span><span class="special">)</span></code> in a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">map</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&gt;</span></code> the second insertion will have no effect.
In a <code class="computeroutput"><span class="identifier">bimap</span><span class="special">&lt;</span><span class="identifier">X</span><span class="special">,</span><span class="identifier">Y</span><span class="special">&gt;</span></code> both keys have to remain unique. The insertion
may fail in other situations too. Lets see an example
</p>
<pre class="programlisting"><span class="identifier">bm</span><span class="special">.</span><span class="identifier">clear</span><span class="special">();</span>
<span class="identifier">bm</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span> <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">value_type</span><span class="special">(</span> <span class="number">1</span><span class="special">,</span> <span class="string">"one"</span> <span class="special">)</span> <span class="special">);</span>
<span class="identifier">bm</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span> <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">value_type</span><span class="special">(</span> <span class="number">1</span><span class="special">,</span> <span class="string">"1"</span> <span class="special">)</span> <span class="special">);</span> <span class="comment">// No effect!</span>
<span class="identifier">bm</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span> <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">value_type</span><span class="special">(</span> <span class="number">2</span><span class="special">,</span> <span class="string">"one"</span> <span class="special">)</span> <span class="special">);</span> <span class="comment">// No effect!</span>
<span class="identifier">assert</span><span class="special">(</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">size</span><span class="special">()</span> <span class="special">==</span> <span class="number">1</span> <span class="special">);</span>
</pre>
<h4>
<a name="boost_bimap.one_minute_tutorial.h7"></a>
<span class="phrase"><a name="boost_bimap.one_minute_tutorial.a_simple_example"></a></span><a class="link" href="one_minute_tutorial.html#boost_bimap.one_minute_tutorial.a_simple_example">A
simple example</a>
</h4>
<p>
Look how you can reuse code that is intend to be used with std::maps, like
the print_map function in this example.
</p>
<p>
<a href="../../../example/simple_bimap.cpp" target="_top">Go to source code</a>
</p>
<p>
</p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">string</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">iostream</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">bimap</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
<span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">class</span> <span class="identifier">MapType</span> <span class="special">&gt;</span>
<span class="keyword">void</span> <span class="identifier">print_map</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">MapType</span> <span class="special">&amp;</span> <span class="identifier">map</span><span class="special">,</span>
<span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">&amp;</span> <span class="identifier">separator</span><span class="special">,</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span> <span class="special">&amp;</span> <span class="identifier">os</span> <span class="special">)</span>
<span class="special">{</span>
<span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">MapType</span><span class="special">::</span><span class="identifier">const_iterator</span> <span class="identifier">const_iterator</span><span class="special">;</span>
<span class="keyword">for</span><span class="special">(</span> <span class="identifier">const_iterator</span> <span class="identifier">i</span> <span class="special">=</span> <span class="identifier">map</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">iend</span> <span class="special">=</span> <span class="identifier">map</span><span class="special">.</span><span class="identifier">end</span><span class="special">();</span> <span class="identifier">i</span> <span class="special">!=</span> <span class="identifier">iend</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span> <span class="special">)</span>
<span class="special">{</span>
<span class="identifier">os</span> <span class="special">&lt;&lt;</span> <span class="identifier">i</span><span class="special">-&gt;</span><span class="identifier">first</span> <span class="special">&lt;&lt;</span> <span class="identifier">separator</span> <span class="special">&lt;&lt;</span> <span class="identifier">i</span><span class="special">-&gt;</span><span class="identifier">second</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="special">}</span>
<span class="special">}</span>
<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
<span class="special">{</span>
<span class="comment">// Soccer World cup</span>
<span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">bimap</span><span class="special">&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">,</span> <span class="keyword">int</span> <span class="special">&gt;</span> <span class="identifier">results_bimap</span><span class="special">;</span>
<span class="keyword">typedef</span> <span class="identifier">results_bimap</span><span class="special">::</span><span class="identifier">value_type</span> <span class="identifier">position</span><span class="special">;</span>
<span class="identifier">results_bimap</span> <span class="identifier">results</span><span class="special">;</span>
<span class="identifier">results</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span> <span class="identifier">position</span><span class="special">(</span><span class="string">"Argentina"</span> <span class="special">,</span><span class="number">1</span><span class="special">)</span> <span class="special">);</span>
<span class="identifier">results</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span> <span class="identifier">position</span><span class="special">(</span><span class="string">"Spain"</span> <span class="special">,</span><span class="number">2</span><span class="special">)</span> <span class="special">);</span>
<span class="identifier">results</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span> <span class="identifier">position</span><span class="special">(</span><span class="string">"Germany"</span> <span class="special">,</span><span class="number">3</span><span class="special">)</span> <span class="special">);</span>
<span class="identifier">results</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span> <span class="identifier">position</span><span class="special">(</span><span class="string">"France"</span> <span class="special">,</span><span class="number">4</span><span class="special">)</span> <span class="special">);</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"The number of countries is "</span> <span class="special">&lt;&lt;</span> <span class="identifier">results</span><span class="special">.</span><span class="identifier">size</span><span class="special">()</span>
<span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"The winner is "</span> <span class="special">&lt;&lt;</span> <span class="identifier">results</span><span class="special">.</span><span class="identifier">right</span><span class="special">.</span><span class="identifier">at</span><span class="special">(</span><span class="number">1</span><span class="special">)</span>
<span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span>
<span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"Countries names ordered by their final position:"</span>
<span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="comment">// results.right works like a std::map&lt; int, std::string &gt;</span>
<span class="identifier">print_map</span><span class="special">(</span> <span class="identifier">results</span><span class="special">.</span><span class="identifier">right</span><span class="special">,</span> <span class="string">") "</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">);</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span>
<span class="special">&lt;&lt;</span> <span class="string">"Countries names ordered alphabetically along with"</span>
<span class="string">"their final position:"</span>
<span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="comment">// results.left works like a std::map&lt; std::string, int &gt;</span>
<span class="identifier">print_map</span><span class="special">(</span> <span class="identifier">results</span><span class="special">.</span><span class="identifier">left</span><span class="special">,</span> <span class="string">" ends in position "</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">);</span>
<span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
</p>
<p>
The output of this program will be the following:
</p>
<pre class="programlisting"><code class="literal">The number of countries is 4</code>
<code class="literal">The winner is Argentina</code>
<code class="literal">Countries names ordered by their final position:</code>
<code class="literal">1) Argentina</code>
<code class="literal">2) Spain</code>
<code class="literal">3) Germany</code>
<code class="literal">4) France</code>
<code class="literal">Countries names ordered alphabetically along with their final position:</code>
<code class="literal">Argentina ends in position 1</code>
<code class="literal">France ends in position 4</code>
<code class="literal">Germany ends in position 3</code>
<code class="literal">Spain ends in position 2</code>
</pre>
<h4>
<a name="boost_bimap.one_minute_tutorial.h8"></a>
<span class="phrase"><a name="boost_bimap.one_minute_tutorial.continuing_the_journey"></a></span><a class="link" href="one_minute_tutorial.html#boost_bimap.one_minute_tutorial.continuing_the_journey">Continuing
the journey</a>
</h4>
<p>
For information on function signatures, see any standard library documentation
or read the <a class="link" href="reference.html" title="Reference">reference</a> section
of this documentation.
</p>
<div class="caution"><table border="0" summary="Caution">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="../../../../../doc/src/images/caution.png"></td>
<th align="left">Caution</th>
</tr>
<tr><td align="left" valign="top"><p>
Be aware that a bidirectional map is only signature-compatible with standard
containers. Some functions may give different results, such as in the case
of inserting a pair into the left map where the second value conflicts with
a stored relation in the container. The functions may be slower in a bimap
because of the duplicated constraints. It is strongly recommended that you
read <a class="link" href="the_tutorial.html" title="The tutorial">The full tutorial</a> if
you intend to use a bimap in a serious project.
</p></td></tr>
</table></div>
<div class="footnotes">
<br><hr style="width:100; align:left;">
<div id="ftn.boost_bimap.one_minute_tutorial.f0" class="footnote"><p><a href="#boost_bimap.one_minute_tutorial.f0" class="para"><sup class="para">[1] </sup></a>
A type is <span class="emphasis"><em>signature-compatible</em></span> with other type if it
has the same signature for functions and metadata. Preconditions, postconditions
and the order of operations need not be the same.
</p></div>
</div>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright &#169; 2006-2012 Matias Capeletto<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
</p>
</div></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="introduction.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="the_tutorial.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
</div>
</body>
</html>
Reference in New Issue View Git Blame Copy Permalink