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<meta name="generator" content="Docutils 0.3.0: http://docutils.sourceforge.net/" />
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<title>Counting 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="2003-09-14" />
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<meta name="copyright" content="Copyright David Abrahams, Jeremy Siek, and Thomas Witt 2003. All rights reserved" />
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/*
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:Author: David Goodger
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<body>
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<div class="document" id="counting-iterator">
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@ -231,45 +40,32 @@ Railway Operation and Construction</a></td></tr>
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</tr>
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</tbody>
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</table>
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<p>The counting iterator adaptor implements dereference by returning a
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||||
reference to the base object. The other operations are implemented by
|
||||
the base <tt class="literal"><span class="pre">m_iterator</span></tt>, as per the inheritance from
|
||||
<tt class="literal"><span class="pre">iterator_adaptor</span></tt>.</p>
|
||||
<p><tt class="literal"><span class="pre">counting_iterator</span></tt> adapts an arithmetic type, such as <tt class="literal"><span class="pre">int</span></tt>, by
|
||||
adding an <tt class="literal"><span class="pre">operator*</span></tt> that returns the current value of the 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="#counting-iterator-requirements" id="id1" name="id1"><tt class="literal"><span class="pre">counting_iterator</span></tt> requirements</a></li>
|
||||
<li><a class="reference" href="#counting-iterator-operations" id="id2" name="id2"><tt class="literal"><span class="pre">counting_iterator</span></tt> operations</a></li>
|
||||
<li><a class="reference" href="#counting-iterator-models" id="id2" name="id2"><tt class="literal"><span class="pre">counting_iterator</span></tt> models</a></li>
|
||||
<li><a class="reference" href="#counting-iterator-operations" id="id3" name="id3"><tt class="literal"><span class="pre">counting_iterator</span></tt> operations</a></li>
|
||||
<li><a class="reference" href="#example" id="id4" name="id4">Example</a></li>
|
||||
</ul>
|
||||
</div>
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||||
<pre class="literal-block">
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||||
template <
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||||
class Incrementable
|
||||
, unsigned Access = use_default_access
|
||||
, class Traversal = use_default
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||||
, class CategoryOrTraversal = use_default
|
||||
, class Difference = use_default
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||||
>
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||||
class counting_iterator
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||||
: public iterator_adaptor<
|
||||
counting_iterator<Incrementable, Access, Traversal, Difference>
|
||||
, Incrementable
|
||||
, Incrementable
|
||||
, Access
|
||||
, /* see details for traversal category */
|
||||
, Incrementable const&
|
||||
, Incrementable const*
|
||||
, /* distance = Difference or a signed integral type */>
|
||||
{
|
||||
friend class iterator_core_access;
|
||||
public:
|
||||
counting_iterator();
|
||||
counting_iterator(counting_iterator const& rhs);
|
||||
counting_iterator(Incrementable x);
|
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explicit counting_iterator(Incrementable x);
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Incrementable base() const;
|
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private:
|
||||
typename counting_iterator::reference dereference() const
|
||||
{
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||||
return this->base_reference();
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||||
}
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Incrementable current; // exposition
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||||
};
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||||
</pre>
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<dl>
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||||
@ -281,8 +77,11 @@ the cases when the <tt class="literal"><span class="pre">Incrementable</span></t
|
||||
<h1><a class="toc-backref" href="#id1" name="counting-iterator-requirements"><tt class="literal"><span class="pre">counting_iterator</span></tt> requirements</a></h1>
|
||||
<p>The <tt class="literal"><span class="pre">Incrementable</span></tt> type must be Default Constructible, Copy
|
||||
Constructible, and Assignable. The default distance is
|
||||
an implementation defined signed integegral type.</p>
|
||||
<p>The resulting <tt class="literal"><span class="pre">counting_iterator</span></tt> models Readable Lvalue Iterator.</p>
|
||||
an implementation defined signed integral type.</p>
|
||||
</div>
|
||||
<div class="section" id="counting-iterator-models">
|
||||
<h1><a class="toc-backref" href="#id2" name="counting-iterator-models"><tt class="literal"><span class="pre">counting_iterator</span></tt> models</a></h1>
|
||||
<p><tt class="literal"><span class="pre">counting_iterator</span></tt> models Readable Lvalue Iterator.</p>
|
||||
<p>Furthermore, if you wish to create a counting iterator that is a Forward
|
||||
Traversal Iterator, then the following expressions must be valid:</p>
|
||||
<pre class="literal-block">
|
||||
@ -306,7 +105,7 @@ i < j
|
||||
</pre>
|
||||
</div>
|
||||
<div class="section" id="counting-iterator-operations">
|
||||
<h1><a class="toc-backref" href="#id2" name="counting-iterator-operations"><tt class="literal"><span class="pre">counting_iterator</span></tt> operations</a></h1>
|
||||
<h1><a class="toc-backref" href="#id3" name="counting-iterator-operations"><tt class="literal"><span class="pre">counting_iterator</span></tt> operations</a></h1>
|
||||
<p><tt class="literal"><span class="pre">counting_iterator();</span></tt></p>
|
||||
<table class="field-list" frame="void" rules="none">
|
||||
<col class="field-name" />
|
||||
@ -325,23 +124,90 @@ i < j
|
||||
</tr>
|
||||
</tbody>
|
||||
</table>
|
||||
<p><tt class="literal"><span class="pre">counting_iterator(Incrementable</span> <span class="pre">x);</span></tt></p>
|
||||
<p><tt class="literal"><span class="pre">explicit</span> <span class="pre">counting_iterator(Incrementable</span> <span class="pre">x);</span></tt></p>
|
||||
<table class="field-list" frame="void" rules="none">
|
||||
<col class="field-name" />
|
||||
<col class="field-body" />
|
||||
<tbody valign="top">
|
||||
<tr class="field"><th class="field-name">Returns:</th><td class="field-body">An instance of <tt class="literal"><span class="pre">counting_iterator</span></tt> with its base
|
||||
object copy constructed from <tt class="literal"><span class="pre">x</span></tt>.</td>
|
||||
<tr class="field"><th class="field-name">Returns:</th><td class="field-body">An instance of <tt class="literal"><span class="pre">counting_iterator</span></tt> with <tt class="literal"><span class="pre">current</span></tt>
|
||||
constructed from <tt class="literal"><span class="pre">x</span></tt>.</td>
|
||||
</tr>
|
||||
</tbody>
|
||||
</table>
|
||||
<p><tt class="literal"><span class="pre">reference</span> <span class="pre">operator*()</span> <span class="pre">const;</span></tt></p>
|
||||
<table class="field-list" frame="void" rules="none">
|
||||
<col class="field-name" />
|
||||
<col class="field-body" />
|
||||
<tbody valign="top">
|
||||
<tr class="field"><th class="field-name">Returns:</th><td class="field-body"><tt class="literal"><span class="pre">current</span></tt></td>
|
||||
</tr>
|
||||
</tbody>
|
||||
</table>
|
||||
<p><tt class="literal"><span class="pre">counting_iterator&</span> <span class="pre">operator++();</span></tt></p>
|
||||
<table class="field-list" frame="void" rules="none">
|
||||
<col class="field-name" />
|
||||
<col class="field-body" />
|
||||
<tbody valign="top">
|
||||
<tr class="field"><th class="field-name">Effects:</th><td class="field-body"><tt class="literal"><span class="pre">++current</span></tt></td>
|
||||
</tr>
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||||
</tbody>
|
||||
</table>
|
||||
<p><tt class="literal"><span class="pre">Incrementable</span> <span class="pre">base()</span> <span class="pre">const;</span></tt></p>
|
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<table class="field-list" frame="void" rules="none">
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<col class="field-name" />
|
||||
<col class="field-body" />
|
||||
<tbody valign="top">
|
||||
<tr class="field"><th class="field-name">Returns:</th><td class="field-body"><tt class="literal"><span class="pre">current</span></tt></td>
|
||||
</tr>
|
||||
</tbody>
|
||||
</table>
|
||||
<pre class="literal-block">
|
||||
template <class Incrementable>
|
||||
counting_iterator<Incrementable>
|
||||
make_counting_iterator(Incrementable x)
|
||||
</pre>
|
||||
<table class="field-list" frame="void" rules="none">
|
||||
<col class="field-name" />
|
||||
<col class="field-body" />
|
||||
<tbody valign="top">
|
||||
<tr class="field"><th class="field-name">Returns:</th><td class="field-body">An instance of <tt class="literal"><span class="pre">counting_iterator<Incrementable></span></tt>
|
||||
with <tt class="literal"><span class="pre">current</span></tt> constructed from <tt class="literal"><span class="pre">x</span></tt>.</td>
|
||||
</tr>
|
||||
</tbody>
|
||||
</table>
|
||||
</div>
|
||||
<div class="section" id="example">
|
||||
<h1><a class="toc-backref" href="#id4" name="example">Example</a></h1>
|
||||
<p>This example fills an array with numbers and a second array with
|
||||
pointers into the first array, using <tt class="literal"><span class="pre">counting_iterator</span></tt> for both
|
||||
tasks. Finally <tt class="literal"><span class="pre">indirect_iterator</span></tt> is used to print out the numbers
|
||||
into the first array via indirection through the second array.</p>
|
||||
<pre class="literal-block">
|
||||
int N = 7;
|
||||
std::vector<int> numbers;
|
||||
typedef std::vector<int>::iterator n_iter;
|
||||
std::copy(boost::counting_iterator<int>(0),
|
||||
boost::counting_iterator<int>(N),
|
||||
std::back_inserter(numbers));
|
||||
|
||||
std::vector<std::vector<int>::iterator> pointers;
|
||||
std::copy(boost::make_counting_iterator(numbers.begin()),
|
||||
boost::make_counting_iterator(numbers.end()),
|
||||
std::back_inserter(pointers));
|
||||
|
||||
std::cout << "indirectly printing out the numbers from 0 to "
|
||||
<< N << std::endl;
|
||||
std::copy(boost::make_indirect_iterator(pointers.begin()),
|
||||
boost::make_indirect_iterator(pointers.end()),
|
||||
std::ostream_iterator<int>(std::cout, " "));
|
||||
std::cout << std::endl;
|
||||
</pre>
|
||||
<p>The output is:</p>
|
||||
<pre class="literal-block">
|
||||
indirectly printing out the numbers from 0 to 7
|
||||
0 1 2 3 4 5 6
|
||||
</pre>
|
||||
</div>
|
||||
<hr class="footer" />
|
||||
<div class="footer">
|
||||
<a class="reference" href="counting_iterator.rst">View document source</a>.
|
||||
Generated on: 2003-11-24 05:00 UTC.
|
||||
Generated by <a class="reference" href="http://docutils.sourceforge.net/">Docutils</a> from <a class="reference" href="http://docutils.sourceforge.net/rst.html">reStructuredText</a> source.
|
||||
</div>
|
||||
</body>
|
||||
</html>
|
||||
|
@ -21,3 +21,6 @@
|
||||
.. contents:: Table of Contents
|
||||
|
||||
.. include:: counting_iterator_ref.rst
|
||||
.. include:: make_counting_iterator.rst
|
||||
|
||||
.. include:: counting_iterator_eg.rst
|
||||
|
@ -1,5 +1,2 @@
|
||||
The counting iterator adaptor implements dereference by returning a
|
||||
reference to the base object. The other operations are implemented by
|
||||
the base ``m_iterator``, as per the inheritance from
|
||||
``iterator_adaptor``.
|
||||
|
||||
``counting_iterator`` adapts an arithmetic type, such as ``int``, by
|
||||
adding an ``operator*`` that returns the current value of the object.
|
||||
|
35
doc/counting_iterator_eg.rst
Normal file
35
doc/counting_iterator_eg.rst
Normal file
@ -0,0 +1,35 @@
|
||||
|
||||
Example
|
||||
-------
|
||||
|
||||
This example fills an array with numbers and a second array with
|
||||
pointers into the first array, using ``counting_iterator`` for both
|
||||
tasks. Finally ``indirect_iterator`` is used to print out the numbers
|
||||
into the first array via indirection through the second array.
|
||||
|
||||
::
|
||||
|
||||
int N = 7;
|
||||
std::vector<int> numbers;
|
||||
typedef std::vector<int>::iterator n_iter;
|
||||
std::copy(boost::counting_iterator<int>(0),
|
||||
boost::counting_iterator<int>(N),
|
||||
std::back_inserter(numbers));
|
||||
|
||||
std::vector<std::vector<int>::iterator> pointers;
|
||||
std::copy(boost::make_counting_iterator(numbers.begin()),
|
||||
boost::make_counting_iterator(numbers.end()),
|
||||
std::back_inserter(pointers));
|
||||
|
||||
std::cout << "indirectly printing out the numbers from 0 to "
|
||||
<< N << std::endl;
|
||||
std::copy(boost::make_indirect_iterator(pointers.begin()),
|
||||
boost::make_indirect_iterator(pointers.end()),
|
||||
std::ostream_iterator<int>(std::cout, " "));
|
||||
std::cout << std::endl;
|
||||
|
||||
|
||||
The output is::
|
||||
|
||||
indirectly printing out the numbers from 0 to 7
|
||||
0 1 2 3 4 5 6
|
@ -2,31 +2,18 @@
|
||||
|
||||
template <
|
||||
class Incrementable
|
||||
, unsigned Access = use_default_access
|
||||
, class Traversal = use_default
|
||||
, class CategoryOrTraversal = use_default
|
||||
, class Difference = use_default
|
||||
>
|
||||
class counting_iterator
|
||||
: public iterator_adaptor<
|
||||
counting_iterator<Incrementable, Access, Traversal, Difference>
|
||||
, Incrementable
|
||||
, Incrementable
|
||||
, Access
|
||||
, /* see details for traversal category */
|
||||
, Incrementable const&
|
||||
, Incrementable const*
|
||||
, /* distance = Difference or a signed integral type */>
|
||||
{
|
||||
friend class iterator_core_access;
|
||||
public:
|
||||
counting_iterator();
|
||||
counting_iterator(counting_iterator const& rhs);
|
||||
counting_iterator(Incrementable x);
|
||||
explicit counting_iterator(Incrementable x);
|
||||
Incrementable base() const;
|
||||
private:
|
||||
typename counting_iterator::reference dereference() const
|
||||
{
|
||||
return this->base_reference();
|
||||
}
|
||||
Incrementable current; // exposition
|
||||
};
|
||||
|
||||
|
||||
@ -39,28 +26,29 @@
|
||||
|
||||
The ``Incrementable`` type must be Default Constructible, Copy
|
||||
Constructible, and Assignable. The default distance is
|
||||
an implementation defined signed integegral type.
|
||||
an implementation defined signed integral type.
|
||||
|
||||
The resulting ``counting_iterator`` models Readable Lvalue Iterator.
|
||||
|
||||
``counting_iterator`` models
|
||||
----------------------------
|
||||
|
||||
``counting_iterator`` models Readable Lvalue Iterator.
|
||||
|
||||
Furthermore, if you wish to create a counting iterator that is a Forward
|
||||
Traversal Iterator, then the following expressions must be valid:
|
||||
::
|
||||
Traversal Iterator, then the following expressions must be valid::
|
||||
|
||||
Incrementable i, j;
|
||||
++i // pre-increment
|
||||
i == j // operator equal
|
||||
|
||||
If you wish to create a counting iterator that is a
|
||||
Bidirectional Traversal Iterator, then pre-decrement is also required:
|
||||
::
|
||||
Bidirectional Traversal Iterator, then pre-decrement is also required::
|
||||
|
||||
--i
|
||||
|
||||
If you wish to create a counting iterator that is a Random Access
|
||||
Traversal Iterator, then these additional expressions are also
|
||||
required:
|
||||
::
|
||||
required::
|
||||
|
||||
counting_iterator::difference_type n;
|
||||
i += n
|
||||
@ -84,8 +72,22 @@ required:
|
||||
|
||||
|
||||
|
||||
``counting_iterator(Incrementable x);``
|
||||
``explicit counting_iterator(Incrementable x);``
|
||||
|
||||
:Returns: An instance of ``counting_iterator`` with its base
|
||||
object copy constructed from ``x``.
|
||||
:Returns: An instance of ``counting_iterator`` with ``current``
|
||||
constructed from ``x``.
|
||||
|
||||
|
||||
``reference operator*() const;``
|
||||
|
||||
:Returns: ``current``
|
||||
|
||||
|
||||
``counting_iterator& operator++();``
|
||||
|
||||
:Effects: ``++current``
|
||||
|
||||
|
||||
``Incrementable base() const;``
|
||||
|
||||
:Returns: ``current``
|
Reference in New Issue
Block a user