1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
|
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<title>Party's height average</title>
<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
<meta name="generator" content="DocBook XSL Stylesheets V1.74.0">
<link rel="home" href="../../index.html" title="Chapter 1. Boost.Icl">
<link rel="up" href="../examples.html" title="Examples">
<link rel="prev" href="overlap_counter.html" title="Overlap counter">
<link rel="next" href="partys_tallest_guests.html" title="Party's tallest guests">
</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="../../../../../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="overlap_counter.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../examples.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="partys_tallest_guests.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
</div>
<div class="section" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_icl.examples.partys_height_average"></a><a class="link" href="partys_height_average.html" title="Party's height average"> Party's height
average</a>
</h3></div></div></div>
<p>
In the example <code class="computeroutput"><span class="identifier">partys_height_average</span><span class="special">.</span><span class="identifier">cpp</span></code> we
compute yet another aggregation: The average height of guests. This is done
by defining a <code class="computeroutput"><span class="keyword">class</span> <span class="identifier">counted_sum</span></code>
that sums up heights and counts the number of guests via an <code class="computeroutput"><span class="keyword">operator</span> <span class="special">+=</span></code>.
</p>
<p>
Based on the <code class="computeroutput"><span class="keyword">operator</span> <span class="special">+=</span></code>
we can aggregate counted sums on addition of interval value pairs into an
interval_map.
</p>
<p>
</p>
<p>
</p>
<pre class="programlisting"><span class="comment">// The next line includes <boost/date_time/posix_time/posix_time.hpp>
</span><span class="comment">// and a few lines of adapter code.
</span><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">icl</span><span class="special">/</span><span class="identifier">ptime</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span>
<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">icl</span><span class="special">/</span><span class="identifier">interval_map</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">icl</span><span class="special">/</span><span class="identifier">split_interval_map</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
<span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">std</span><span class="special">;</span>
<span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">posix_time</span><span class="special">;</span>
<span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">icl</span><span class="special">;</span>
<span class="keyword">class</span> <span class="identifier">counted_sum</span>
<span class="special">{</span>
<span class="keyword">public</span><span class="special">:</span>
<span class="identifier">counted_sum</span><span class="special">():</span><span class="identifier">_sum</span><span class="special">(</span><span class="number">0</span><span class="special">),</span><span class="identifier">_count</span><span class="special">(</span><span class="number">0</span><span class="special">){}</span>
<span class="identifier">counted_sum</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">sum</span><span class="special">):</span><span class="identifier">_sum</span><span class="special">(</span><span class="identifier">sum</span><span class="special">),</span><span class="identifier">_count</span><span class="special">(</span><span class="number">1</span><span class="special">){}</span>
<span class="keyword">int</span> <span class="identifier">sum</span><span class="special">()</span><span class="keyword">const</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">_sum</span><span class="special">;}</span>
<span class="keyword">int</span> <span class="identifier">count</span><span class="special">()</span><span class="keyword">const</span><span class="special">{</span><span class="keyword">return</span> <span class="identifier">_count</span><span class="special">;}</span>
<span class="keyword">double</span> <span class="identifier">average</span><span class="special">()</span><span class="keyword">const</span><span class="special">{</span> <span class="keyword">return</span> <span class="identifier">_count</span><span class="special">==</span><span class="number">0</span> <span class="special">?</span> <span class="number">0.0</span> <span class="special">:</span> <span class="identifier">_sum</span><span class="special">/</span><span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">double</span><span class="special">>(</span><span class="identifier">_count</span><span class="special">);</span> <span class="special">}</span>
<span class="identifier">counted_sum</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">+=</span> <span class="special">(</span><span class="keyword">const</span> <span class="identifier">counted_sum</span><span class="special">&</span> <span class="identifier">right</span><span class="special">)</span>
<span class="special">{</span> <span class="identifier">_sum</span> <span class="special">+=</span> <span class="identifier">right</span><span class="special">.</span><span class="identifier">sum</span><span class="special">();</span> <span class="identifier">_count</span> <span class="special">+=</span> <span class="identifier">right</span><span class="special">.</span><span class="identifier">count</span><span class="special">();</span> <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;</span> <span class="special">}</span>
<span class="keyword">private</span><span class="special">:</span>
<span class="keyword">int</span> <span class="identifier">_sum</span><span class="special">;</span>
<span class="keyword">int</span> <span class="identifier">_count</span><span class="special">;</span>
<span class="special">};</span>
<span class="keyword">bool</span> <span class="keyword">operator</span> <span class="special">==</span> <span class="special">(</span><span class="keyword">const</span> <span class="identifier">counted_sum</span><span class="special">&</span> <span class="identifier">left</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">counted_sum</span><span class="special">&</span> <span class="identifier">right</span><span class="special">)</span>
<span class="special">{</span> <span class="keyword">return</span> <span class="identifier">left</span><span class="special">.</span><span class="identifier">sum</span><span class="special">()==</span><span class="identifier">right</span><span class="special">.</span><span class="identifier">sum</span><span class="special">()</span> <span class="special">&&</span> <span class="identifier">left</span><span class="special">.</span><span class="identifier">count</span><span class="special">()==</span><span class="identifier">right</span><span class="special">.</span><span class="identifier">count</span><span class="special">();</span> <span class="special">}</span>
<span class="keyword">void</span> <span class="identifier">partys_height_average</span><span class="special">()</span>
<span class="special">{</span>
<span class="identifier">interval_map</span><span class="special"><</span><span class="identifier">ptime</span><span class="special">,</span> <span class="identifier">counted_sum</span><span class="special">></span> <span class="identifier">height_sums</span><span class="special">;</span>
<span class="identifier">height_sums</span> <span class="special">+=</span>
<span class="identifier">make_pair</span><span class="special">(</span>
<span class="identifier">discrete_interval</span><span class="special"><</span><span class="identifier">ptime</span><span class="special">>::</span><span class="identifier">right_open</span><span class="special">(</span>
<span class="identifier">time_from_string</span><span class="special">(</span><span class="string">"2008-05-20 19:30"</span><span class="special">),</span>
<span class="identifier">time_from_string</span><span class="special">(</span><span class="string">"2008-05-20 23:00"</span><span class="special">)),</span>
<span class="identifier">counted_sum</span><span class="special">(</span><span class="number">165</span><span class="special">));</span> <span class="comment">// Mary is 1,65 m tall.
</span>
<span class="identifier">height_sums</span> <span class="special">+=</span>
<span class="identifier">make_pair</span><span class="special">(</span>
<span class="identifier">discrete_interval</span><span class="special"><</span><span class="identifier">ptime</span><span class="special">>::</span><span class="identifier">right_open</span><span class="special">(</span>
<span class="identifier">time_from_string</span><span class="special">(</span><span class="string">"2008-05-20 19:30"</span><span class="special">),</span>
<span class="identifier">time_from_string</span><span class="special">(</span><span class="string">"2008-05-20 23:00"</span><span class="special">)),</span>
<span class="identifier">counted_sum</span><span class="special">(</span><span class="number">180</span><span class="special">));</span> <span class="comment">// Harry is 1,80 m tall.
</span>
<span class="identifier">height_sums</span> <span class="special">+=</span>
<span class="identifier">make_pair</span><span class="special">(</span>
<span class="identifier">discrete_interval</span><span class="special"><</span><span class="identifier">ptime</span><span class="special">>::</span><span class="identifier">right_open</span><span class="special">(</span>
<span class="identifier">time_from_string</span><span class="special">(</span><span class="string">"2008-05-20 20:10"</span><span class="special">),</span>
<span class="identifier">time_from_string</span><span class="special">(</span><span class="string">"2008-05-21 00:00"</span><span class="special">)),</span>
<span class="identifier">counted_sum</span><span class="special">(</span><span class="number">170</span><span class="special">));</span> <span class="comment">// Diana is 1,70 m tall.
</span>
<span class="identifier">height_sums</span> <span class="special">+=</span>
<span class="identifier">make_pair</span><span class="special">(</span>
<span class="identifier">discrete_interval</span><span class="special"><</span><span class="identifier">ptime</span><span class="special">>::</span><span class="identifier">right_open</span><span class="special">(</span>
<span class="identifier">time_from_string</span><span class="special">(</span><span class="string">"2008-05-20 20:10"</span><span class="special">),</span>
<span class="identifier">time_from_string</span><span class="special">(</span><span class="string">"2008-05-21 00:00"</span><span class="special">)),</span>
<span class="identifier">counted_sum</span><span class="special">(</span><span class="number">165</span><span class="special">));</span> <span class="comment">// Susan is 1,65 m tall.
</span>
<span class="identifier">height_sums</span> <span class="special">+=</span>
<span class="identifier">make_pair</span><span class="special">(</span>
<span class="identifier">discrete_interval</span><span class="special"><</span><span class="identifier">ptime</span><span class="special">>::</span><span class="identifier">right_open</span><span class="special">(</span>
<span class="identifier">time_from_string</span><span class="special">(</span><span class="string">"2008-05-20 22:15"</span><span class="special">),</span>
<span class="identifier">time_from_string</span><span class="special">(</span><span class="string">"2008-05-21 00:30"</span><span class="special">)),</span>
<span class="identifier">counted_sum</span><span class="special">(</span><span class="number">200</span><span class="special">));</span> <span class="comment">// Peters height is 2,00 m
</span>
<span class="identifier">interval_map</span><span class="special"><</span><span class="identifier">ptime</span><span class="special">,</span> <span class="identifier">counted_sum</span><span class="special">>::</span><span class="identifier">iterator</span> <span class="identifier">height_sum_</span> <span class="special">=</span> <span class="identifier">height_sums</span><span class="special">.</span><span class="identifier">begin</span><span class="special">();</span>
<span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"-------------- History of average guest height -------------------\n"</span><span class="special">;</span>
<span class="keyword">while</span><span class="special">(</span><span class="identifier">height_sum_</span> <span class="special">!=</span> <span class="identifier">height_sums</span><span class="special">.</span><span class="identifier">end</span><span class="special">())</span>
<span class="special">{</span>
<span class="identifier">discrete_interval</span><span class="special"><</span><span class="identifier">ptime</span><span class="special">></span> <span class="identifier">when</span> <span class="special">=</span> <span class="identifier">height_sum_</span><span class="special">-></span><span class="identifier">first</span><span class="special">;</span>
<span class="keyword">double</span> <span class="identifier">height_average</span> <span class="special">=</span> <span class="special">(*</span><span class="identifier">height_sum_</span><span class="special">++).</span><span class="identifier">second</span><span class="special">.</span><span class="identifier">average</span><span class="special">();</span>
<span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">setprecision</span><span class="special">(</span><span class="number">3</span><span class="special">)</span>
<span class="special"><<</span> <span class="string">"["</span> <span class="special"><<</span> <span class="identifier">first</span><span class="special">(</span><span class="identifier">when</span><span class="special">)</span> <span class="special"><<</span> <span class="string">" - "</span> <span class="special"><<</span> <span class="identifier">upper</span><span class="special">(</span><span class="identifier">when</span><span class="special">)</span> <span class="special"><<</span> <span class="string">")"</span>
<span class="special"><<</span> <span class="string">": "</span> <span class="special"><<</span> <span class="identifier">height_average</span> <span class="special"><<</span><span class="string">" cm = "</span> <span class="special"><<</span> <span class="identifier">height_average</span><span class="special">/</span><span class="number">30.48</span> <span class="special"><<</span> <span class="string">" ft"</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="identifier">cout</span> <span class="special"><<</span> <span class="string">">>Interval Container Library: Sample partys_height_average.cpp <<\n"</span><span class="special">;</span>
<span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"------------------------------------------------------------------\n"</span><span class="special">;</span>
<span class="identifier">partys_height_average</span><span class="special">();</span>
<span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
<span class="special">}</span>
<span class="comment">// Program output:
</span><span class="comment">/*-----------------------------------------------------------------------------
>>Interval Container Library: Sample partys_height_average.cpp <<
------------------------------------------------------------------
-------------- History of average guest height -------------------
[2008-May-20 19:30:00 - 2008-May-20 20:10:00): 173 cm = 5.66 ft
[2008-May-20 20:10:00 - 2008-May-20 22:15:00): 170 cm = 5.58 ft
[2008-May-20 22:15:00 - 2008-May-20 23:00:00): 176 cm = 5.77 ft
[2008-May-20 23:00:00 - 2008-May-21 00:00:00): 178 cm = 5.85 ft
[2008-May-21 00:00:00 - 2008-May-21 00:30:00): 200 cm = 6.56 ft
-----------------------------------------------------------------------------*/</span>
</pre>
<p>
</p>
<p>
</p>
<p>
Required for <code class="computeroutput"><span class="keyword">class</span> <span class="identifier">counted_sum</span></code>
is a default constructor <code class="computeroutput"><span class="identifier">counted_sum</span><span class="special">()</span></code>and an <code class="computeroutput"><span class="keyword">operator</span>
<span class="special">==</span></code> to test equality. To enable additive
aggregation on overlap also an <code class="computeroutput"><span class="keyword">operator</span>
<span class="special">+=</span></code> is needed.
</p>
<p>
Note that no <code class="computeroutput"><span class="keyword">operator</span> <span class="special">-=</span></code>
for a subtraction of <code class="computeroutput"><span class="identifier">counted_sum</span></code>
values is defined. So you can only add to the <code class="computeroutput"><span class="identifier">interval_map</span><span class="special"><</span><span class="identifier">ptime</span><span class="special">,</span> <span class="identifier">counted_sum</span><span class="special">></span></code> but not subtract from it.
</p>
<p>
In many real world applications only addition is needed and user defined
classes will work fine, if they only implement <code class="computeroutput"><span class="keyword">operator</span>
<span class="special">+=</span></code>. Only if any of the <code class="computeroutput"><span class="keyword">operator</span></code>s <code class="computeroutput"><span class="special">-=</span></code>
or <code class="computeroutput"><span class="special">-</span></code> is called on the interval_map,
the user defined class has to implement it's own <code class="computeroutput"><span class="keyword">operator</span>
<span class="special">-=</span></code> to provide the subtractive aggregation
on overlap.
</p>
</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 © 2007 -2010 Joachim Faulhaber<br>Copyright © 1999 -2006 Cortex Software GmbH<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="overlap_counter.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../examples.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="partys_tallest_guests.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
</div>
</body>
</html>
|
