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25<div class="section boost_icl_examples_partys_height_average" lang="en">
26<div class="titlepage"><div><div><h3 class="title">
27<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
28 average</a>
29</h3></div></div></div>
30<p>
31 In the example <code class="computeroutput"><span class="identifier">partys_height_average</span><span class="special">.</span><span class="identifier">cpp</span></code> we
32 compute yet another aggregation: The average height of guests. This is done
33 by defining a <code class="computeroutput"><span class="keyword">class</span> <span class="identifier">counted_sum</span></code>
34 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>.
35 </p>
36<p>
37 Based on the <code class="computeroutput"><span class="keyword">operator</span> <span class="special">+=</span></code>
38 we can aggregate counted sums on addition of interval value pairs into an
39 interval_map.
40 </p>
41<p>
42 </p>
43<p>
44
45</p>
46<pre class="programlisting"><span class="comment">// The next line includes &lt;boost/date_time/posix_time/posix_time.hpp&gt;
47</span><span class="comment">// and a few lines of adapter code.
48</span><span class="preprocessor">#include</span> <span class="special">&lt;</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">&gt;</span>
49<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">iostream</span><span class="special">&gt;</span>
50<span class="preprocessor">#include</span> <span class="special">&lt;</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">&gt;</span>
51<span class="preprocessor">#include</span> <span class="special">&lt;</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">&gt;</span>
52
53<span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">std</span><span class="special">;</span>
54<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>
55<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>
56
57
58<span class="keyword">class</span> <span class="identifier">counted_sum</span>
59<span class="special">{</span>
60<span class="keyword">public</span><span class="special">:</span>
61 <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>
62 <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>
63
64 <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>
65 <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>
66 <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">&lt;</span><span class="keyword">double</span><span class="special">&gt;(</span><span class="identifier">_count</span><span class="special">);</span> <span class="special">}</span>
67
68 <span class="identifier">counted_sum</span><span class="special">&amp;</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">&amp;</span> <span class="identifier">right</span><span class="special">)</span>
69 <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>
70
71<span class="keyword">private</span><span class="special">:</span>
72 <span class="keyword">int</span> <span class="identifier">_sum</span><span class="special">;</span>
73 <span class="keyword">int</span> <span class="identifier">_count</span><span class="special">;</span>
74<span class="special">};</span>
75
76<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">&amp;</span> <span class="identifier">left</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">counted_sum</span><span class="special">&amp;</span> <span class="identifier">right</span><span class="special">)</span>
77<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">&amp;&amp;</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>
78
79
80<span class="keyword">void</span> <span class="identifier">partys_height_average</span><span class="special">()</span>
81<span class="special">{</span>
82 <span class="identifier">interval_map</span><span class="special">&lt;</span><span class="identifier">ptime</span><span class="special">,</span> <span class="identifier">counted_sum</span><span class="special">&gt;</span> <span class="identifier">height_sums</span><span class="special">;</span>
83
84 <span class="identifier">height_sums</span> <span class="special">+=</span>
85 <span class="identifier">make_pair</span><span class="special">(</span>
86 <span class="identifier">discrete_interval</span><span class="special">&lt;</span><span class="identifier">ptime</span><span class="special">&gt;::</span><span class="identifier">right_open</span><span class="special">(</span>
87 <span class="identifier">time_from_string</span><span class="special">(</span><span class="string">"2008-05-20 19:30"</span><span class="special">),</span>
88 <span class="identifier">time_from_string</span><span class="special">(</span><span class="string">"2008-05-20 23:00"</span><span class="special">)),</span>
89 <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.
90</span>
91 <span class="identifier">height_sums</span> <span class="special">+=</span>
92 <span class="identifier">make_pair</span><span class="special">(</span>
93 <span class="identifier">discrete_interval</span><span class="special">&lt;</span><span class="identifier">ptime</span><span class="special">&gt;::</span><span class="identifier">right_open</span><span class="special">(</span>
94 <span class="identifier">time_from_string</span><span class="special">(</span><span class="string">"2008-05-20 19:30"</span><span class="special">),</span>
95 <span class="identifier">time_from_string</span><span class="special">(</span><span class="string">"2008-05-20 23:00"</span><span class="special">)),</span>
96 <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.
97</span>
98 <span class="identifier">height_sums</span> <span class="special">+=</span>
99 <span class="identifier">make_pair</span><span class="special">(</span>
100 <span class="identifier">discrete_interval</span><span class="special">&lt;</span><span class="identifier">ptime</span><span class="special">&gt;::</span><span class="identifier">right_open</span><span class="special">(</span>
101 <span class="identifier">time_from_string</span><span class="special">(</span><span class="string">"2008-05-20 20:10"</span><span class="special">),</span>
102 <span class="identifier">time_from_string</span><span class="special">(</span><span class="string">"2008-05-21 00:00"</span><span class="special">)),</span>
103 <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.
104</span>
105 <span class="identifier">height_sums</span> <span class="special">+=</span>
106 <span class="identifier">make_pair</span><span class="special">(</span>
107 <span class="identifier">discrete_interval</span><span class="special">&lt;</span><span class="identifier">ptime</span><span class="special">&gt;::</span><span class="identifier">right_open</span><span class="special">(</span>
108 <span class="identifier">time_from_string</span><span class="special">(</span><span class="string">"2008-05-20 20:10"</span><span class="special">),</span>
109 <span class="identifier">time_from_string</span><span class="special">(</span><span class="string">"2008-05-21 00:00"</span><span class="special">)),</span>
110 <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.
111</span>
112 <span class="identifier">height_sums</span> <span class="special">+=</span>
113 <span class="identifier">make_pair</span><span class="special">(</span>
114 <span class="identifier">discrete_interval</span><span class="special">&lt;</span><span class="identifier">ptime</span><span class="special">&gt;::</span><span class="identifier">right_open</span><span class="special">(</span>
115 <span class="identifier">time_from_string</span><span class="special">(</span><span class="string">"2008-05-20 22:15"</span><span class="special">),</span>
116 <span class="identifier">time_from_string</span><span class="special">(</span><span class="string">"2008-05-21 00:30"</span><span class="special">)),</span>
117 <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
118</span>
119 <span class="identifier">interval_map</span><span class="special">&lt;</span><span class="identifier">ptime</span><span class="special">,</span> <span class="identifier">counted_sum</span><span class="special">&gt;::</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>
120 <span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"-------------- History of average guest height -------------------\n"</span><span class="special">;</span>
121 <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>
122 <span class="special">{</span>
123 <span class="identifier">discrete_interval</span><span class="special">&lt;</span><span class="identifier">ptime</span><span class="special">&gt;</span> <span class="identifier">when</span> <span class="special">=</span> <span class="identifier">height_sum_</span><span class="special">-&gt;</span><span class="identifier">first</span><span class="special">;</span>
124
125 <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>
126 <span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">setprecision</span><span class="special">(</span><span class="number">3</span><span class="special">)</span>
127 <span class="special">&lt;&lt;</span> <span class="string">"["</span> <span class="special">&lt;&lt;</span> <span class="identifier">first</span><span class="special">(</span><span class="identifier">when</span><span class="special">)</span> <span class="special">&lt;&lt;</span> <span class="string">" - "</span> <span class="special">&lt;&lt;</span> <span class="identifier">upper</span><span class="special">(</span><span class="identifier">when</span><span class="special">)</span> <span class="special">&lt;&lt;</span> <span class="string">")"</span>
128 <span class="special">&lt;&lt;</span> <span class="string">": "</span> <span class="special">&lt;&lt;</span> <span class="identifier">height_average</span> <span class="special">&lt;&lt;</span><span class="string">" cm = "</span> <span class="special">&lt;&lt;</span> <span class="identifier">height_average</span><span class="special">/</span><span class="number">30.48</span> <span class="special">&lt;&lt;</span> <span class="string">" ft"</span> <span class="special">&lt;&lt;</span> <span class="identifier">endl</span><span class="special">;</span>
129 <span class="special">}</span>
130<span class="special">}</span>
131
132
133<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
134<span class="special">{</span>
135 <span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"&gt;&gt;Interval Container Library: Sample partys_height_average.cpp &lt;&lt;\n"</span><span class="special">;</span>
136 <span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"------------------------------------------------------------------\n"</span><span class="special">;</span>
137 <span class="identifier">partys_height_average</span><span class="special">();</span>
138 <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
139<span class="special">}</span>
140
141<span class="comment">// Program output:
142</span><span class="comment">/*-----------------------------------------------------------------------------
143&gt;&gt;Interval Container Library: Sample partys_height_average.cpp &lt;&lt;
144------------------------------------------------------------------
145-------------- History of average guest height -------------------
146[2008-May-20 19:30:00 - 2008-May-20 20:10:00): 173 cm = 5.66 ft
147[2008-May-20 20:10:00 - 2008-May-20 22:15:00): 170 cm = 5.58 ft
148[2008-May-20 22:15:00 - 2008-May-20 23:00:00): 176 cm = 5.77 ft
149[2008-May-20 23:00:00 - 2008-May-21 00:00:00): 178 cm = 5.85 ft
150[2008-May-21 00:00:00 - 2008-May-21 00:30:00): 200 cm = 6.56 ft
151-----------------------------------------------------------------------------*/</span>
152</pre>
153<p>
154 </p>
155<p>
156 </p>
157<p>
158 Required for <code class="computeroutput"><span class="keyword">class</span> <span class="identifier">counted_sum</span></code>
159 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>
160 <span class="special">==</span></code> to test equality. To enable additive
161 aggregation on overlap also an <code class="computeroutput"><span class="keyword">operator</span>
162 <span class="special">+=</span></code> is needed.
163 </p>
164<p>
165 Note that no <code class="computeroutput"><span class="keyword">operator</span> <span class="special">-=</span></code>
166 for a subtraction of <code class="computeroutput"><span class="identifier">counted_sum</span></code>
167 values is defined. So you can only add to the <code class="computeroutput"><span class="identifier">interval_map</span><span class="special">&lt;</span><span class="identifier">ptime</span><span class="special">,</span> <span class="identifier">counted_sum</span><span class="special">&gt;</span></code> but not subtract from it.
168 </p>
169<p>
170 In many real world applications only addition is needed and user defined
171 classes will work fine, if they only implement <code class="computeroutput"><span class="keyword">operator</span>
172 <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>
173 or <code class="computeroutput"><span class="special">-</span></code> is called on the interval_map,
174 the user defined class has to implement it's own <code class="computeroutput"><span class="keyword">operator</span>
175 <span class="special">-=</span></code> to provide the subtractive aggregation
176 on overlap.
177 </p>
178</div>
179<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
180<td align="left"></td>
181<td align="right"><div class="copyright-footer">Copyright &#169; 2007 -2010 Joachim Faulhaber<br>Copyright &#169; 1999 -2006 Cortex Software GmbH<p>
182 Distributed under the Boost Software License, Version 1.0. (See accompanying
183 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>)
184 </p>
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