Boost_1_39_0/libs/iterator/doc/function_output_iterator.html

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   7 <title>Function Output Iterator</title>
   8 <meta name="author" content="David Abrahams, Jeremy Siek, Thomas Witt" />
   9 <meta name="organization" content="Boost Consulting, Indiana University Open Systems Lab, University of Hanover Institute for Transport Railway Operation and Construction" />
  10 <meta name="date" content="2006-09-11" />
  11 <meta name="copyright" content="Copyright David Abrahams, Jeremy Siek, and Thomas Witt 2003." />
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  15 <div class="document" id="function-output-iterator">
  16 <h1 class="title">Function Output Iterator</h1>
  17 <table class="docinfo" frame="void" rules="none">
  18 <col class="docinfo-name" />
  19 <col class="docinfo-content" />
  20 <tbody valign="top">
  21 <tr><th class="docinfo-name">Author:</th>
  22 <td>David Abrahams, Jeremy Siek, Thomas Witt</td></tr>
  23 <tr><th class="docinfo-name">Contact:</th>
  24 <td><a class="first reference external" href="mailto:dave&#64;boost-consulting.com">dave&#64;boost-consulting.com</a>, <a class="reference external" href="mailto:jsiek&#64;osl.iu.edu">jsiek&#64;osl.iu.edu</a>, <a class="last reference external" href="mailto:witt&#64;ive.uni-hannover.de">witt&#64;ive.uni-hannover.de</a></td></tr>
  25 <tr><th class="docinfo-name">Organization:</th>
  26 <td><a class="first reference external" href="http://www.boost-consulting.com">Boost Consulting</a>, Indiana University <a class="reference external" href="http://www.osl.iu.edu">Open Systems
  27 Lab</a>, University of Hanover <a class="last reference external" href="http://www.ive.uni-hannover.de">Institute for Transport
  28 Railway Operation and Construction</a></td></tr>
  29 <tr><th class="docinfo-name">Date:</th>
  30 <td>2006-09-11</td></tr>
  31 <tr><th class="docinfo-name">Copyright:</th>
  32 <td>Copyright David Abrahams, Jeremy Siek, and Thomas Witt 2003.</td></tr>
  33 </tbody>
  34 </table>
  35 <!-- Distributed under the Boost -->
  36 <!-- Software License, Version 1.0. (See accompanying -->
  37 <!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
  38 <table class="docutils field-list" frame="void" rules="none">
  39 <col class="field-name" />
  40 <col class="field-body" />
  41 <tbody valign="top">
  42 <tr class="field"><th class="field-name">abstract:</th><td class="field-body"><!-- Copyright David Abrahams 2006. Distributed under the Boost -->
  43 <!-- Software License, Version 1.0. (See accompanying -->
  44 <!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
  45 The function output iterator adaptor makes it easier to create custom
  46 output iterators. The adaptor takes a unary function and creates a
  47 model of Output Iterator. Each item assigned to the output iterator is
  48 passed as an argument to the unary function.  The motivation for this
  49 iterator is that creating a conforming output iterator is non-trivial,
  50 particularly because the proper implementation usually requires a
  51 proxy object.</td>
  52 </tr>
  53 </tbody>
  54 </table>
  55 <div class="contents topic" id="table-of-contents">
  56 <p class="topic-title first">Table of Contents</p>
  57 <ul class="simple">
  58 <li><a class="reference internal" href="#header" id="id1">Header</a></li>
  59 <li><a class="reference internal" href="#function-output-iterator-requirements" id="id2"><tt class="docutils literal"><span class="pre">function_output_iterator</span></tt> requirements</a></li>
  60 <li><a class="reference internal" href="#function-output-iterator-models" id="id3"><tt class="docutils literal"><span class="pre">function_output_iterator</span></tt> models</a></li>
  61 <li><a class="reference internal" href="#function-output-iterator-operations" id="id4"><tt class="docutils literal"><span class="pre">function_output_iterator</span></tt> operations</a></li>
  62 <li><a class="reference internal" href="#example" id="id5">Example</a></li>
  63 </ul>
  64 </div>
  65 <!-- Copyright David Abrahams 2006. Distributed under the Boost -->
  66 <!-- Software License, Version 1.0. (See accompanying -->
  67 <!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
  68 <div class="section" id="header">
  69 <h1><a class="toc-backref" href="#id1">Header</a></h1>
  70 <pre class="literal-block">
  71 #include &lt;boost/function_output_iterator.hpp&gt;
  72 </pre>
  73 <pre class="literal-block">
  74 template &lt;class UnaryFunction&gt;
  75 class function_output_iterator {
  76 public:
  77   typedef std::output_iterator_tag iterator_category;
  78   typedef void                     value_type;
  79   typedef void                     difference_type;
  80   typedef void                     pointer;
  81   typedef void                     reference;
  82
  83   explicit function_output_iterator();
  84
  85   explicit function_output_iterator(const UnaryFunction&amp; f);
  86
  87   /* see below */ operator*();
  88   function_output_iterator&amp; operator++();
  89   function_output_iterator&amp; operator++(int);
  90 private:
  91   UnaryFunction m_f;     // exposition only
  92 };
  93 </pre>
  94 </div>
  95 <div class="section" id="function-output-iterator-requirements">
  96 <h1><a class="toc-backref" href="#id2"><tt class="docutils literal"><span class="pre">function_output_iterator</span></tt> requirements</a></h1>
  97 <p><tt class="docutils literal"><span class="pre">UnaryFunction</span></tt> must be Assignable and Copy Constructible.</p>
  98 </div>
  99 <div class="section" id="function-output-iterator-models">
 100 <h1><a class="toc-backref" href="#id3"><tt class="docutils literal"><span class="pre">function_output_iterator</span></tt> models</a></h1>
 101 <p><tt class="docutils literal"><span class="pre">function_output_iterator</span></tt> is a model of the Writable and
 102 Incrementable Iterator concepts.</p>
 103 </div>
 104 <div class="section" id="function-output-iterator-operations">
 105 <h1><a class="toc-backref" href="#id4"><tt class="docutils literal"><span class="pre">function_output_iterator</span></tt> operations</a></h1>
 106 <p><tt class="docutils literal"><span class="pre">explicit</span> <span class="pre">function_output_iterator(const</span> <span class="pre">UnaryFunction&amp;</span> <span class="pre">f</span> <span class="pre">=</span> <span class="pre">UnaryFunction());</span></tt></p>
 107 <table class="docutils field-list" frame="void" rules="none">
 108 <col class="field-name" />
 109 <col class="field-body" />
 110 <tbody valign="top">
 111 <tr class="field"><th class="field-name">Effects:</th><td class="field-body">Constructs an instance of <tt class="docutils literal"><span class="pre">function_output_iterator</span></tt>
 112 with <tt class="docutils literal"><span class="pre">m_f</span></tt> constructed from <tt class="docutils literal"><span class="pre">f</span></tt>.</td>
 113 </tr>
 114 </tbody>
 115 </table>
 116 <p><tt class="docutils literal"><span class="pre">operator*();</span></tt></p>
 117 <table class="docutils field-list" frame="void" rules="none">
 118 <col class="field-name" />
 119 <col class="field-body" />
 120 <tbody valign="top">
 121 <tr class="field"><th class="field-name">Returns:</th><td class="field-body">An object <tt class="docutils literal"><span class="pre">r</span></tt> of unspecified type such that <tt class="docutils literal"><span class="pre">r</span> <span class="pre">=</span> <span class="pre">t</span></tt>
 122 is equivalent to <tt class="docutils literal"><span class="pre">m_f(t)</span></tt> for all <tt class="docutils literal"><span class="pre">t</span></tt>.</td>
 123 </tr>
 124 </tbody>
 125 </table>
 126 <p><tt class="docutils literal"><span class="pre">function_output_iterator&amp;</span> <span class="pre">operator++();</span></tt></p>
 127 <table class="docutils field-list" frame="void" rules="none">
 128 <col class="field-name" />
 129 <col class="field-body" />
 130 <tbody valign="top">
 131 <tr class="field"><th class="field-name">Returns:</th><td class="field-body"><tt class="docutils literal"><span class="pre">*this</span></tt></td>
 132 </tr>
 133 </tbody>
 134 </table>
 135 <p><tt class="docutils literal"><span class="pre">function_output_iterator&amp;</span> <span class="pre">operator++(int);</span></tt></p>
 136 <table class="docutils field-list" frame="void" rules="none">
 137 <col class="field-name" />
 138 <col class="field-body" />
 139 <tbody valign="top">
 140 <tr class="field"><th class="field-name">Returns:</th><td class="field-body"><tt class="docutils literal"><span class="pre">*this</span></tt></td>
 141 </tr>
 142 </tbody>
 143 </table>
 144 <!-- Copyright David Abrahams 2006. Distributed under the Boost -->
 145 <!-- Software License, Version 1.0. (See accompanying -->
 146 <!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
 147 </div>
 148 <div class="section" id="example">
 149 <h1><a class="toc-backref" href="#id5">Example</a></h1>
 150 <pre class="literal-block">
 151 struct string_appender
 152 {
 153     string_appender(std::string&amp; s)
 154         : m_str(&amp;s)
 155     {}
 156
 157     void operator()(const std::string&amp; x) const
 158     {
 159         *m_str += x;
 160     }
 161
 162     std::string* m_str;
 163 };
 164
 165 int main(int, char*[])
 166 {
 167   std::vector&lt;std::string&gt; x;
 168   x.push_back(&quot;hello&quot;);
 169   x.push_back(&quot; &quot;);
 170   x.push_back(&quot;world&quot;);
 171   x.push_back(&quot;!&quot;);
 172
 173   std::string s = &quot;&quot;;
 174   std::copy(x.begin(), x.end(),
 175             boost::make_function_output_iterator(string_appender(s)));
 176
 177   std::cout &lt;&lt; s &lt;&lt; std::endl;
 178
 179   return 0;
 180 }
 181 </pre>
 182 </div>
 183 </div>
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