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std_transform.html

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    25. 

  25. <div class="section">
    26. 

  26. <div class="titlepage"><div><div><h3 class="title">
    27. 

  27. <a name="boost_icl.examples.std_transform"></a><a class="link" href="std_transform.html" title="Std transform">Std transform</a>
    28. 

  28. </h3></div></div></div>
    29. 

  29. <p>
    30. 

  30.         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>
    31. 

  31.         can be used to fill interval containers from std containers of user defined
    32. 

  32.         objects. We need a function, that maps the <span class="emphasis"><em>user defined object</em></span>
    33. 

  33.         into the <span class="emphasis"><em>segement type</em></span> of an interval map or the <span class="emphasis"><em>interval
    34. 

  34.         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>
    35. 

  35.         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>
    36. 

  36.         to transform the user objects into interval containers.
    37. 

  37.       </p>
    38. 

  38. <p>
    39. 

  39. </p>
    40. 

  40. <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">iostream</span><span class="special">&gt;</span>
    41. 

  41. <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">vector</span><span class="special">&gt;</span>
    42. 

  42. <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">algorithm</span><span class="special">&gt;</span>
    43. 

  43. <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>
    44. 

  44. <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">separate_interval_set</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
    45. 

  45. 

  46. <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">std</span><span class="special">;</span>
    47. 

  47. <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">;</span>
    48. 

  48. <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>
    49. 

  49. 

  50. <span class="comment">// Suppose we are working with a class called MyObject, containing some</span>
    51. 

  51. <span class="comment">// information about interval bounds e.g. _from, _to and some data members</span>
    52. 

  52. <span class="comment">// that carry associated information like e.g. _value.</span>
    53. 

  53. <span class="keyword">class</span> <span class="identifier">MyObject</span>
    54. 

  54. <span class="special">{</span>
    55. 

  55. <span class="keyword">public</span><span class="special">:</span>
    56. 

  56.     <span class="identifier">MyObject</span><span class="special">(){}</span>
    57. 

  57.     <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>
    58. 

  58.     <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>
    59. 

  59.     <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>
    60. 

  60.     <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>
    61. 

  61. <span class="keyword">private</span><span class="special">:</span>
    62. 

  62.     <span class="keyword">int</span> <span class="identifier">_from</span><span class="special">;</span>
    63. 

  63.     <span class="keyword">int</span> <span class="identifier">_to</span><span class="special">;</span>
    64. 

  64.     <span class="keyword">int</span> <span class="identifier">_value</span><span class="special">;</span>
    65. 

  65. <span class="special">};</span>
    66. 

  66. 

  67. <span class="comment">// ... in order to use the std::transform algorithm to fill</span>
    68. 

  68. <span class="comment">// interval maps with MyObject data we need a function</span>
    69. 

  69. <span class="comment">// 'to_segment' that maps an object of type MyObject into</span>
    70. 

  70. <span class="comment">// the value type to the interval map we want to tranform to ...</span>
    71. 

  71. <span class="identifier">pair</span><span class="special">&lt;</span><span class="identifier">discrete_interval</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;,</span> <span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">to_segment</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">MyObject</span><span class="special">&amp;</span> <span class="identifier">myObj</span><span class="special">)</span>
    72. 

  72. <span class="special">{</span>
    73. 

  73.     <span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special">&lt;</span> <span class="identifier">discrete_interval</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;,</span> <span class="keyword">int</span> <span class="special">&gt;</span>
    74. 

  74.         <span class="special">(</span><span class="identifier">discrete_interval</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;::</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>
    75. 

  75. <span class="special">}</span>
    76. 

  76. 

  77. <span class="comment">// ... there may be another function that returns the interval</span>
    78. 

  78. <span class="comment">// of an object only</span>
    79. 

  79. <span class="identifier">discrete_interval</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">to_interval</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">MyObject</span><span class="special">&amp;</span> <span class="identifier">myObj</span><span class="special">)</span>
    80. 

  80. <span class="special">{</span>
    81. 

  81.     <span class="keyword">return</span> <span class="identifier">discrete_interval</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;::</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>
    82. 

  82. <span class="special">}</span>
    83. 

  83. 

  84. 

  85. <span class="comment">// ... make_object computes a sequence of objects to test.</span>
    86. 

  86. <span class="identifier">vector</span><span class="special">&lt;</span><span class="identifier">MyObject</span><span class="special">&gt;</span> <span class="identifier">make_objects</span><span class="special">()</span>
    87. 

  87. <span class="special">{</span>
    88. 

  88.     <span class="identifier">vector</span><span class="special">&lt;</span><span class="identifier">MyObject</span><span class="special">&gt;</span> <span class="identifier">object_vec</span><span class="special">;</span>
    89. 

  89.     <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>
    90. 

  90.     <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>
    91. 

  91.     <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>
    92. 

  92.     <span class="keyword">return</span> <span class="identifier">object_vec</span><span class="special">;</span>
    93. 

  93. <span class="special">}</span>
    94. 

  94. 

  95. <span class="comment">// ... show_objects displays the sequence of input objects.</span>
    96. 

  96. <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">&lt;</span><span class="identifier">MyObject</span><span class="special">&gt;&amp;</span> <span class="identifier">objects</span><span class="special">)</span>
    97. 

  97. <span class="special">{</span>
    98. 

  98.     <span class="identifier">vector</span><span class="special">&lt;</span><span class="identifier">MyObject</span><span class="special">&gt;::</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>
    99. 

  99.     <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>
    100. 

  100.     <span class="special">{</span>
    101. 

  101.         <span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"(["</span> <span class="special">&lt;&lt;</span> <span class="identifier">iter</span><span class="special">-&gt;</span><span class="identifier">from</span><span class="special">()</span> <span class="special">&lt;&lt;</span> <span class="string">","</span> <span class="special">&lt;&lt;</span> <span class="identifier">iter</span><span class="special">-&gt;</span><span class="identifier">to</span><span class="special">()</span> <span class="special">&lt;&lt;</span> <span class="string">"],"</span>
    102. 

  102.              <span class="special">&lt;&lt;</span> <span class="identifier">iter</span><span class="special">-&gt;</span><span class="identifier">value</span><span class="special">()</span> <span class="special">&lt;&lt;</span> <span class="string">")"</span><span class="special">;</span>
    103. 

  103.         <span class="special">++</span><span class="identifier">iter</span><span class="special">;</span>
    104. 

  104.     <span class="special">}</span>
    105. 

  105. <span class="special">}</span>
    106. 

  106. 

  107. 

  108. <span class="keyword">void</span> <span class="identifier">std_transform</span><span class="special">()</span>
    109. 

  109. <span class="special">{</span>
    110. 

  110.     <span class="comment">// This time we want to transform objects into a splitting interval map:</span>
    111. 

  111.     <span class="identifier">split_interval_map</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span><span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">segmap</span><span class="special">;</span>
    112. 

  112.     <span class="identifier">vector</span><span class="special">&lt;</span><span class="identifier">MyObject</span><span class="special">&gt;</span> <span class="identifier">myObjects</span> <span class="special">=</span> <span class="identifier">make_objects</span><span class="special">();</span>
    113. 

  113. 

  114.     <span class="comment">// Display the input</span>
    115. 

  115.     <span class="identifier">cout</span> <span class="special">&lt;&lt;</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">&lt;&lt;</span> <span class="string">"\n\n"</span><span class="special">;</span>
    116. 

  116. 

  117.     <span class="comment">// Use an icl::inserter to fill the interval map via inserts</span>
    118. 

  118.     <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>
    119. 

  119.                    <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>
    120. 

  120.                    <span class="identifier">to_segment</span><span class="special">);</span>
    121. 

  121.     <span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"icl::inserting: "</span> <span class="special">&lt;&lt;</span> <span class="identifier">segmap</span> <span class="special">&lt;&lt;</span> <span class="identifier">endl</span><span class="special">;</span>
    122. 

  122.     <span class="identifier">segmap</span><span class="special">.</span><span class="identifier">clear</span><span class="special">();</span>
    123. 

  123. 

  124.     <span class="comment">// In order to compute aggregation results on associated values, we</span>
    125. 

  125.     <span class="comment">// usually want to use an icl::adder instead of an std or icl::inserter</span>
    126. 

  126.     <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>
    127. 

  127.                    <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>
    128. 

  128.                    <span class="identifier">to_segment</span><span class="special">);</span>
    129. 

  129.     <span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"icl::adding   : "</span> <span class="special">&lt;&lt;</span> <span class="identifier">segmap</span> <span class="special">&lt;&lt;</span> <span class="string">"\n\n"</span><span class="special">;</span>
    130. 

  130. 

  131.     <span class="identifier">separate_interval_set</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">segset</span><span class="special">;</span>
    132. 

  132.     <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>
    133. 

  133.                    <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>
    134. 

  134.     <span class="comment">// could be a  icl::inserter(segset, segset.end()), here: same effect </span>
    135. 

  135.                    <span class="identifier">to_interval</span><span class="special">);</span>
    136. 

  136. 

  137.     <span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"Using std::transform to fill a separate_interval_set:\n\n"</span><span class="special">;</span>
    138. 

  138.     <span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"icl::adding   : "</span> <span class="special">&lt;&lt;</span> <span class="identifier">segset</span> <span class="special">&lt;&lt;</span> <span class="string">"\n\n"</span><span class="special">;</span>
    139. 

  139. <span class="special">}</span>
    140. 

  140. 

  141. 

  142. <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
    143. 

  143. <span class="special">{</span>
    144. 

  144.     <span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"&gt;&gt;  Interval Container Library: Example std_transform.cpp  &lt;&lt;\n"</span><span class="special">;</span>
    145. 

  145.     <span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"------------------------------------------------------------\n"</span><span class="special">;</span>
    146. 

  146.     <span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"Using std::transform to fill a split_interval_map:\n\n"</span><span class="special">;</span>
    147. 

  147. 

  148.     <span class="identifier">std_transform</span><span class="special">();</span>
    149. 

  149.     <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
    150. 

  150. <span class="special">}</span>
    151. 

  151. 

  152. <span class="comment">// Program output:</span>
    153. 

  153. <span class="comment">/*----------------------------------------------------------
    154. 

  154. &gt;&gt;  Interval Container Library: Example std_transform.cpp  &lt;&lt;
    155. 

  155. ------------------------------------------------------------
    156. 

  156. Using std::transform to fill a split_interval_map:
    157. 

  157. 

  158. input sequence: ([2,3],1)([4,4],1)([1,2],1)
    159. 

  159. 

  160. icl::inserting: {([1,2)-&gt;1)([2,3]-&gt;1)([4,4]-&gt;1)}
    161. 

  161. icl::adding   : {([1,2)-&gt;1)([2,2]-&gt;2)((2,3]-&gt;1)([4,4]-&gt;1)}
    162. 

  162. 

  163. Using std::transform to fill a separate_interval_set:
    164. 

  164. 

  165. icl::adding   : {[1,3][4,4]}
    166. 

  166. ----------------------------------------------------------*/</span>
    167. 

  167. </pre>
    168. 

  168. <p>
    169. 

  169.       </p>
    170. 

  170. <p>
    171. 

  171.         To get clear about the different behaviors of interval containers in the
    172. 

  172.         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
    173. 

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