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			192 lines
		
	
	
		
			9.5 KiB
		
	
	
	
		
			HTML
		
	
	
	
	
	
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<meta name="generator" content="Docutils 0.5: http://docutils.sourceforge.net/" />
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<title>Function Output Iterator</title>
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<meta name="author" content="David Abrahams, Jeremy Siek, Thomas Witt" />
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<meta name="organization" content="Boost Consulting, Indiana University Open Systems Lab, University of Hanover Institute for Transport Railway Operation and Construction" />
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<meta name="date" content="2006-09-11" />
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<meta name="copyright" content="Copyright David Abrahams, Jeremy Siek, and Thomas Witt 2003." />
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<link rel="stylesheet" href="../../../rst.css" type="text/css" />
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<body>
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<div class="document" id="function-output-iterator">
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<h1 class="title">Function Output Iterator</h1>
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<table class="docinfo" frame="void" rules="none">
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<col class="docinfo-name" />
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<col class="docinfo-content" />
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<tbody valign="top">
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<tr><th class="docinfo-name">Author:</th>
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<td>David Abrahams, Jeremy Siek, Thomas Witt</td></tr>
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<tr><th class="docinfo-name">Contact:</th>
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<td><a class="first reference external" href="mailto:dave@boost-consulting.com">dave@boost-consulting.com</a>, <a class="reference external" href="mailto:jsiek@osl.iu.edu">jsiek@osl.iu.edu</a>, <a class="last reference external" href="mailto:witt@ive.uni-hannover.de">witt@ive.uni-hannover.de</a></td></tr>
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<tr><th class="docinfo-name">Organization:</th>
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<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
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Lab</a>, University of Hanover <a class="last reference external" href="http://www.ive.uni-hannover.de">Institute for Transport
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Railway Operation and Construction</a></td></tr>
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<tr><th class="docinfo-name">Date:</th>
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<td>2006-09-11</td></tr>
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<tr><th class="docinfo-name">Copyright:</th>
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<td>Copyright David Abrahams, Jeremy Siek, and Thomas Witt 2003.</td></tr>
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</tbody>
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</table>
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<!-- Distributed under the Boost -->
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<!-- Software License, Version 1.0. (See accompanying -->
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<!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
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<table class="docutils field-list" frame="void" rules="none">
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<tr class="field"><th class="field-name">abstract:</th><td class="field-body"><!-- Copyright David Abrahams 2006. Distributed under the Boost -->
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<!-- Software License, Version 1.0. (See accompanying -->
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<!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
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The function output iterator adaptor makes it easier to create custom
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output iterators. The adaptor takes a unary function and creates a
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model of Output Iterator. Each item assigned to the output iterator is
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passed as an argument to the unary function.  The motivation for this
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iterator is that creating a conforming output iterator is non-trivial,
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particularly because the proper implementation usually requires a
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proxy object.</td>
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</tr>
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</tbody>
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</table>
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<div class="contents topic" id="table-of-contents">
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<p class="topic-title first">Table of Contents</p>
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<ul class="simple">
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<li><a class="reference internal" href="#header" id="id1">Header</a></li>
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<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>
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<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>
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<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>
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<li><a class="reference internal" href="#example" id="id5">Example</a></li>
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</ul>
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</div>
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<!-- Copyright David Abrahams 2006. Distributed under the Boost -->
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<!-- Software License, Version 1.0. (See accompanying -->
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<!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
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<div class="section" id="header">
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<h1><a class="toc-backref" href="#id1">Header</a></h1>
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<pre class="literal-block">
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#include <boost/function_output_iterator.hpp>
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</pre>
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<pre class="literal-block">
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template <class UnaryFunction>
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class function_output_iterator {
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public:
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  typedef std::output_iterator_tag iterator_category;
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  typedef void                     value_type;
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  typedef void                     difference_type;
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  typedef void                     pointer;
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  typedef void                     reference;
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  explicit function_output_iterator();
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  explicit function_output_iterator(const UnaryFunction& f);
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  /* see below */ operator*();
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  function_output_iterator& operator++();
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  function_output_iterator& operator++(int);
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private:
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  UnaryFunction m_f;     // exposition only
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};
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</pre>
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</div>
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<div class="section" id="function-output-iterator-requirements">
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<h1><a class="toc-backref" href="#id2"><tt class="docutils literal"><span class="pre">function_output_iterator</span></tt> requirements</a></h1>
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<p><tt class="docutils literal"><span class="pre">UnaryFunction</span></tt> must be Assignable and Copy Constructible.</p>
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</div>
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<div class="section" id="function-output-iterator-models">
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<h1><a class="toc-backref" href="#id3"><tt class="docutils literal"><span class="pre">function_output_iterator</span></tt> models</a></h1>
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<p><tt class="docutils literal"><span class="pre">function_output_iterator</span></tt> is a model of the Writable and
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Incrementable Iterator concepts.</p>
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</div>
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<div class="section" id="function-output-iterator-operations">
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<h1><a class="toc-backref" href="#id4"><tt class="docutils literal"><span class="pre">function_output_iterator</span></tt> operations</a></h1>
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<p><tt class="docutils literal"><span class="pre">explicit</span> <span class="pre">function_output_iterator(const</span> <span class="pre">UnaryFunction&</span> <span class="pre">f</span> <span class="pre">=</span> <span class="pre">UnaryFunction());</span></tt></p>
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<table class="docutils field-list" frame="void" rules="none">
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<col class="field-body" />
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<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>
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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>
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</tr>
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</tbody>
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</table>
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<p><tt class="docutils literal"><span class="pre">operator*();</span></tt></p>
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<table class="docutils field-list" frame="void" rules="none">
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<col class="field-name" />
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<col class="field-body" />
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<tbody valign="top">
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<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>
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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>
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</tr>
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</tbody>
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</table>
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<p><tt class="docutils literal"><span class="pre">function_output_iterator&</span> <span class="pre">operator++();</span></tt></p>
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<table class="docutils field-list" frame="void" rules="none">
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<col class="field-name" />
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<col class="field-body" />
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<tbody valign="top">
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<tr class="field"><th class="field-name">Returns:</th><td class="field-body"><tt class="docutils literal"><span class="pre">*this</span></tt></td>
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</tr>
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</tbody>
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</table>
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<p><tt class="docutils literal"><span class="pre">function_output_iterator&</span> <span class="pre">operator++(int);</span></tt></p>
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<table class="docutils field-list" frame="void" rules="none">
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<col class="field-name" />
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<col class="field-body" />
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<tbody valign="top">
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<tr class="field"><th class="field-name">Returns:</th><td class="field-body"><tt class="docutils literal"><span class="pre">*this</span></tt></td>
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</tr>
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</tbody>
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</table>
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<!-- Copyright David Abrahams 2006. Distributed under the Boost -->
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<!-- Software License, Version 1.0. (See accompanying -->
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<!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
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</div>
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<div class="section" id="example">
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<h1><a class="toc-backref" href="#id5">Example</a></h1>
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<pre class="literal-block">
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struct string_appender
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{
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    string_appender(std::string& s)
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        : m_str(&s)
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    {}
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    void operator()(const std::string& x) const
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    {
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        *m_str += x;
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    }
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    std::string* m_str;
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};
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int main(int, char*[])
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{
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  std::vector<std::string> x;
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  x.push_back("hello");
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  x.push_back(" ");
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  x.push_back("world");
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  x.push_back("!");
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  std::string s = "";
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  std::copy(x.begin(), x.end(),
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            boost::make_function_output_iterator(string_appender(s)));
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  std::cout << s << std::endl;
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  return 0;
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}
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</pre>
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</div>
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</div>
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