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| <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> |
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