iterator/doc/function_output_iterator.html
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<title>Function Output Iterator</title>
<meta name="author" content="David Abrahams, Jeremy Siek, Thomas Witt" />
<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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<div class="document" id="function-output-iterator">
<h1 class="title">Function Output Iterator</h1>
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<tr><th class="docinfo-name">Author:</th>
<td>David Abrahams, Jeremy Siek, Thomas Witt</td></tr>
<tr><th class="docinfo-name">Contact:</th>
<td><a class="first reference" href="mailto:dave&#64;boost-consulting.com">dave&#64;boost-consulting.com</a>, <a class="reference" href="mailto:jsiek&#64;osl.iu.edu">jsiek&#64;osl.iu.edu</a>, <a class="last reference" href="mailto:witt&#64;ive.uni-hannover.de">witt&#64;ive.uni-hannover.de</a></td></tr>
<tr><th class="docinfo-name">Organization:</th>
<td><a class="first reference" href="http://www.boost-consulting.com">Boost Consulting</a>, Indiana University <a class="reference" href="http://www.osl.iu.edu">Open Systems
Lab</a>, University of Hanover <a class="last reference" href="http://www.ive.uni-hannover.de">Institute for Transport
Railway Operation and Construction</a></td></tr>
<tr><th class="docinfo-name">Date:</th>
<td>2003-08-05</td></tr>
<tr><th class="docinfo-name">Copyright:</th>
<td>Copyright Dave Abrahams, Jeremy Siek, and Thomas Witt 2003. All rights reserved</td></tr>
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<tr class="field"><th class="field-name">abstract:</th><td class="field-body"></td>
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<p>The function output iterator adaptor makes it easier to create custom
output iterators. The adaptor takes a unary function and creates a
model of Output Iterator. Each item assigned to the output iterator is
passed as an argument to the unary function. The motivation for this
iterator is that creating a conforming output iterator is non-trivial,
particularly because the proper implementation usually requires a
proxy object.</p>
<div class="contents topic" id="table-of-contents">
<p class="topic-title"><a name="table-of-contents">Table of Contents</a></p>
<ul class="simple">
<li><a class="reference" href="#function-output-iterator-requirements" id="id1" name="id1"><tt class="literal"><span class="pre">function_output_iterator</span></tt> requirements</a></li>
<li><a class="reference" href="#function-output-iterator-operations" id="id2" name="id2"><tt class="literal"><span class="pre">function_output_iterator</span></tt> operations</a></li>
<li><a class="reference" href="#function-output-iterator-output-proxy-operations" id="id3" name="id3"><tt class="literal"><span class="pre">function_output_iterator::output_proxy</span></tt> operations</a></li>
</ul>
</div>
<pre class="literal-block">
template &lt;class UnaryFunction&gt;
class function_output_iterator {
public:
typedef iterator_tag&lt;
writable_iterator_tag
, incrementable_traversal_tag
&gt; iterator_category;
typedef void value_type;
typedef void difference_type;
typedef void pointer;
typedef void reference;
explicit function_output_iterator(const UnaryFunction&amp; f = UnaryFunction());
struct output_proxy {
output_proxy(UnaryFunction&amp; f);
template &lt;class T&gt; output_proxy&amp; operator=(const T&amp; value);
};
output_proxy operator*();
function_output_iterator&amp; operator++();
function_output_iterator&amp; operator++(int);
};
</pre>
<div class="section" id="function-output-iterator-requirements">
<h1><a class="toc-backref" href="#id1" name="function-output-iterator-requirements"><tt class="literal"><span class="pre">function_output_iterator</span></tt> requirements</a></h1>
<p>The <tt class="literal"><span class="pre">UnaryFunction</span></tt> must be Assignable, Copy Constructible, and the
expression <tt class="literal"><span class="pre">f(x)</span></tt> must be valid, where <tt class="literal"><span class="pre">f</span></tt> is an object of type
<tt class="literal"><span class="pre">UnaryFunction</span></tt> and <tt class="literal"><span class="pre">x</span></tt> is an object of a type accepted by <tt class="literal"><span class="pre">f</span></tt>.
The resulting <tt class="literal"><span class="pre">function_output_iterator</span></tt> is a model of the Writable
and Incrementable Iterator concepts.</p>
</div>
<div class="section" id="function-output-iterator-operations">
<h1><a class="toc-backref" href="#id2" name="function-output-iterator-operations"><tt class="literal"><span class="pre">function_output_iterator</span></tt> operations</a></h1>
<p><tt class="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>
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<tr class="field"><th class="field-name">Returns:</th><td class="field-body">An instance of <tt class="literal"><span class="pre">function_output_iterator</span></tt> with
<tt class="literal"><span class="pre">f</span></tt> stored as a data member.</td>
</tr>
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<p><tt class="literal"><span class="pre">output_proxy</span> <span class="pre">operator*();</span></tt></p>
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<tr class="field"><th class="field-name">Returns:</th><td class="field-body">An instance of <tt class="literal"><span class="pre">output_proxy</span></tt> constructed with
a copy of the unary function <tt class="literal"><span class="pre">f</span></tt>.</td>
</tr>
</tbody>
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<p><tt class="literal"><span class="pre">function_output_iterator&amp;</span> <span class="pre">operator++();</span></tt></p>
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<tr class="field"><th class="field-name">Returns:</th><td class="field-body"><tt class="literal"><span class="pre">*this</span></tt></td>
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<p><tt class="literal"><span class="pre">function_output_iterator&amp;</span> <span class="pre">operator++(int);</span></tt></p>
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<tr class="field"><th class="field-name">Returns:</th><td class="field-body"><tt class="literal"><span class="pre">*this</span></tt></td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="function-output-iterator-output-proxy-operations">
<h1><a class="toc-backref" href="#id3" name="function-output-iterator-output-proxy-operations"><tt class="literal"><span class="pre">function_output_iterator::output_proxy</span></tt> operations</a></h1>
<p><tt class="literal"><span class="pre">output_proxy(UnaryFunction&amp;</span> <span class="pre">f);</span></tt></p>
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<tr class="field"><th class="field-name">Returns:</th><td class="field-body">An instance of <tt class="literal"><span class="pre">output_proxy</span></tt> with <tt class="literal"><span class="pre">f</span></tt> stored as
a data member.</td>
</tr>
</tbody>
</table>
<p><tt class="literal"><span class="pre">template</span> <span class="pre">&lt;class</span> <span class="pre">T&gt;</span> <span class="pre">output_proxy&amp;</span> <span class="pre">operator=(const</span> <span class="pre">T&amp;</span> <span class="pre">value);</span></tt></p>
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<tr class="field"><th class="field-name">Effects:</th><td class="field-body"><pre class="first last literal-block">
m_f(value);
return *this;
</pre>
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