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<div class="titlepage"><div><div><h3 class="title">
<a name="boost_icl.examples.std_transform"></a><a class="link" href="std_transform.html" title="Std transform">Std transform</a>
</h3></div></div></div>
<p>
Instead of writing loops, the standard algorithm <a href="http://www.cplusplus.com/reference/algorithm/transform/" target="_top"><code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">transform</span></code></a>
can be used to fill interval containers from std containers of user defined
objects. We need a function, that maps the <span class="emphasis"><em>user defined object</em></span>
into the <span class="emphasis"><em>segement type</em></span> of an interval map or the <span class="emphasis"><em>interval
type</em></span> of an interval set. Based on that we can use <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">transform</span></code>
with an <code class="computeroutput"><span class="identifier">icl</span><span class="special">::</span><span class="identifier">inserter</span></code> or <code class="computeroutput"><span class="identifier">icl</span><span class="special">::</span><span class="identifier">adder</span></code>
to transform the user objects into interval containers.
</p>
<p>
</p>
<p>
</p>
<pre class="programlisting"><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">vector</span><span class="special">></span>
<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">algorithm</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="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">separate_interval_set</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="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="comment">// Suppose we are working with a class called MyObject, containing some
</span><span class="comment">// information about interval bounds e.g. _from, _to and some data members
</span><span class="comment">// that carry associated information like e.g. _value.
</span><span class="keyword">class</span> <span class="identifier">MyObject</span>
<span class="special">{</span>
<span class="keyword">public</span><span class="special">:</span>
<span class="identifier">MyObject</span><span class="special">(){}</span>
<span class="identifier">MyObject</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">from</span><span class="special">,</span> <span class="keyword">int</span> <span class="identifier">to</span><span class="special">,</span> <span class="keyword">int</span> <span class="identifier">value</span><span class="special">):</span> <span class="identifier">_from</span><span class="special">(</span><span class="identifier">from</span><span class="special">),</span> <span class="identifier">_to</span><span class="special">(</span><span class="identifier">to</span><span class="special">),</span> <span class="identifier">_value</span><span class="special">(</span><span class="identifier">value</span><span class="special">){}</span>
<span class="keyword">int</span> <span class="identifier">from</span><span class="special">()</span><span class="keyword">const</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">_from</span><span class="special">;}</span>
<span class="keyword">int</span> <span class="identifier">to</span><span class="special">()</span><span class="keyword">const</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">_to</span><span class="special">;}</span>
<span class="keyword">int</span> <span class="identifier">value</span><span class="special">()</span><span class="keyword">const</span><span class="special">{</span><span class="keyword">return</span> <span class="identifier">_value</span><span class="special">;}</span>
<span class="keyword">private</span><span class="special">:</span>
<span class="keyword">int</span> <span class="identifier">_from</span><span class="special">;</span>
<span class="keyword">int</span> <span class="identifier">_to</span><span class="special">;</span>
<span class="keyword">int</span> <span class="identifier">_value</span><span class="special">;</span>
<span class="special">};</span>
<span class="comment">// ... in order to use the std::transform algorithm to fill
</span><span class="comment">// interval maps with MyObject data we need a function
</span><span class="comment">// 'to_segment' that maps an object of type MyObject into
</span><span class="comment">// the value type to the interval map we want to tranform to ...
</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">discrete_interval</span><span class="special"><</span><span class="keyword">int</span><span class="special">>,</span> <span class="keyword">int</span><span class="special">></span> <span class="identifier">to_segment</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">MyObject</span><span class="special">&</span> <span class="identifier">myObj</span><span class="special">)</span>
<span class="special">{</span>
<span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span> <span class="identifier">discrete_interval</span><span class="special"><</span><span class="keyword">int</span><span class="special">>,</span> <span class="keyword">int</span> <span class="special">></span>
<span class="special">(</span><span class="identifier">discrete_interval</span><span class="special"><</span><span class="keyword">int</span><span class="special">>::</span><span class="identifier">closed</span><span class="special">(</span><span class="identifier">myObj</span><span class="special">.</span><span class="identifier">from</span><span class="special">(),</span> <span class="identifier">myObj</span><span class="special">.</span><span class="identifier">to</span><span class="special">()),</span> <span class="identifier">myObj</span><span class="special">.</span><span class="identifier">value</span><span class="special">());</span>
<span class="special">}</span>
<span class="comment">// ... there may be another function that returns the interval
</span><span class="comment">// of an object only
</span><span class="identifier">discrete_interval</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">to_interval</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">MyObject</span><span class="special">&</span> <span class="identifier">myObj</span><span class="special">)</span>
<span class="special">{</span>
<span class="keyword">return</span> <span class="identifier">discrete_interval</span><span class="special"><</span><span class="keyword">int</span><span class="special">>::</span><span class="identifier">closed</span><span class="special">(</span><span class="identifier">myObj</span><span class="special">.</span><span class="identifier">from</span><span class="special">(),</span> <span class="identifier">myObj</span><span class="special">.</span><span class="identifier">to</span><span class="special">());</span>
<span class="special">}</span>
<span class="comment">// ... make_object computes a sequence of objects to test.
</span><span class="identifier">vector</span><span class="special"><</span><span class="identifier">MyObject</span><span class="special">></span> <span class="identifier">make_objects</span><span class="special">()</span>
<span class="special">{</span>
<span class="identifier">vector</span><span class="special"><</span><span class="identifier">MyObject</span><span class="special">></span> <span class="identifier">object_vec</span><span class="special">;</span>
<span class="identifier">object_vec</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="identifier">MyObject</span><span class="special">(</span><span class="number">2</span><span class="special">,</span><span class="number">3</span><span class="special">,</span><span class="number">1</span><span class="special">));</span>
<span class="identifier">object_vec</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="identifier">MyObject</span><span class="special">(</span><span class="number">4</span><span class="special">,</span><span class="number">4</span><span class="special">,</span><span class="number">1</span><span class="special">));</span>
<span class="identifier">object_vec</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="identifier">MyObject</span><span class="special">(</span><span class="number">1</span><span class="special">,</span><span class="number">2</span><span class="special">,</span><span class="number">1</span><span class="special">));</span>
<span class="keyword">return</span> <span class="identifier">object_vec</span><span class="special">;</span>
<span class="special">}</span>
<span class="comment">// ... show_objects displays the sequence of input objects.
</span><span class="keyword">void</span> <span class="identifier">show_objects</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">vector</span><span class="special"><</span><span class="identifier">MyObject</span><span class="special">>&</span> <span class="identifier">objects</span><span class="special">)</span>
<span class="special">{</span>
<span class="identifier">vector</span><span class="special"><</span><span class="identifier">MyObject</span><span class="special">>::</span><span class="identifier">const_iterator</span> <span class="identifier">iter</span> <span class="special">=</span> <span class="identifier">objects</span><span class="special">.</span><span class="identifier">begin</span><span class="special">();</span>
<span class="keyword">while</span><span class="special">(</span><span class="identifier">iter</span> <span class="special">!=</span> <span class="identifier">objects</span><span class="special">.</span><span class="identifier">end</span><span class="special">())</span>
<span class="special">{</span>
<span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"(["</span> <span class="special"><<</span> <span class="identifier">iter</span><span class="special">-></span><span class="identifier">from</span><span class="special">()</span> <span class="special"><<</span> <span class="string">","</span> <span class="special"><<</span> <span class="identifier">iter</span><span class="special">-></span><span class="identifier">to</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"],"</span>
<span class="special"><<</span> <span class="identifier">iter</span><span class="special">-></span><span class="identifier">value</span><span class="special">()</span> <span class="special"><<</span> <span class="string">")"</span><span class="special">;</span>
<span class="special">++</span><span class="identifier">iter</span><span class="special">;</span>
<span class="special">}</span>
<span class="special">}</span>
<span class="keyword">void</span> <span class="identifier">std_transform</span><span class="special">()</span>
<span class="special">{</span>
<span class="comment">// This time we want to transform objects into a splitting interval map:
</span> <span class="identifier">split_interval_map</span><span class="special"><</span><span class="keyword">int</span><span class="special">,</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">segmap</span><span class="special">;</span>
<span class="identifier">vector</span><span class="special"><</span><span class="identifier">MyObject</span><span class="special">></span> <span class="identifier">myObjects</span> <span class="special">=</span> <span class="identifier">make_objects</span><span class="special">();</span>
<span class="comment">// Display the input
</span> <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"input sequence: "</span><span class="special">;</span> <span class="identifier">show_objects</span><span class="special">(</span><span class="identifier">myObjects</span><span class="special">);</span> <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"\n\n"</span><span class="special">;</span>
<span class="comment">// Use an icl::inserter to fill the interval map via inserts
</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">transform</span><span class="special">(</span><span class="identifier">myObjects</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">myObjects</span><span class="special">.</span><span class="identifier">end</span><span class="special">(),</span>
<span class="identifier">icl</span><span class="special">::</span><span class="identifier">inserter</span><span class="special">(</span><span class="identifier">segmap</span><span class="special">,</span> <span class="identifier">segmap</span><span class="special">.</span><span class="identifier">end</span><span class="special">()),</span>
<span class="identifier">to_segment</span><span class="special">);</span>
<span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"icl::inserting: "</span> <span class="special"><<</span> <span class="identifier">segmap</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span>
<span class="identifier">segmap</span><span class="special">.</span><span class="identifier">clear</span><span class="special">();</span>
<span class="comment">// In order to compute aggregation results on associated values, we
</span> <span class="comment">// usually want to use an icl::adder instead of an std or icl::inserter
</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">transform</span><span class="special">(</span><span class="identifier">myObjects</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">myObjects</span><span class="special">.</span><span class="identifier">end</span><span class="special">(),</span>
<span class="identifier">icl</span><span class="special">::</span><span class="identifier">adder</span><span class="special">(</span><span class="identifier">segmap</span><span class="special">,</span> <span class="identifier">segmap</span><span class="special">.</span><span class="identifier">end</span><span class="special">()),</span>
<span class="identifier">to_segment</span><span class="special">);</span>
<span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"icl::adding : "</span> <span class="special"><<</span> <span class="identifier">segmap</span> <span class="special"><<</span> <span class="string">"\n\n"</span><span class="special">;</span>
<span class="identifier">separate_interval_set</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">segset</span><span class="special">;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">transform</span><span class="special">(</span><span class="identifier">myObjects</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">myObjects</span><span class="special">.</span><span class="identifier">end</span><span class="special">(),</span>
<span class="identifier">icl</span><span class="special">::</span><span class="identifier">adder</span> <span class="special">(</span><span class="identifier">segset</span><span class="special">,</span> <span class="identifier">segset</span><span class="special">.</span><span class="identifier">end</span><span class="special">()),</span>
<span class="comment">// could be a icl::inserter(segset, segset.end()), here: same effect
</span> <span class="identifier">to_interval</span><span class="special">);</span>
<span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Using std::transform to fill a separate_interval_set:\n\n"</span><span class="special">;</span>
<span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"icl::adding : "</span> <span class="special"><<</span> <span class="identifier">segset</span> <span class="special"><<</span> <span class="string">"\n\n"</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: Example std_transform.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">cout</span> <span class="special"><<</span> <span class="string">"Using std::transform to fill a split_interval_map:\n\n"</span><span class="special">;</span>
<span class="identifier">std_transform</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: Example std_transform.cpp <<
------------------------------------------------------------
Using std::transform to fill a split_interval_map:
input sequence: ([2,3],1)([4,4],1)([1,2],1)
icl::inserting: {([1,2)->1)([2,3]->1)([4,4]->1)}
icl::adding : {([1,2)->1)([2,2]->2)((2,3]->1)([4,4]->1)}
Using std::transform to fill a separate_interval_set:
icl::adding : {[1,3][4,4]}
----------------------------------------------------------*/</span>
</pre>
<p>
</p>
<p>
</p>
<p>
To get clear about the different behaviors of interval containers in the
example, you may want to refer to the section about <a class="link" href="../../index.html#boost_icl.introduction.interval_combining_styles" title="Interval Combining Styles">interval
combining styles</a> that uses the same data.
</p>
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<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>
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