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[SVN r29099]
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Dave Abrahams
2005-05-20 15:32:55 +00:00
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@ -3,7 +3,7 @@
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="generator" content="Docutils 0.3.6: http://docutils.sourceforge.net/" />
<meta name="generator" content="Docutils 0.3.8: http://docutils.sourceforge.net/" />
<title>Counting 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" />
@ -12,6 +12,7 @@
<link rel="stylesheet" href="default.css" type="text/css" />
</head>
<body>
<div class="document" id="counting-iterator">
<h1 class="title">Counting Iterator</h1>
<table class="docinfo" frame="void" rules="none">
<col class="docinfo-name" />
@ -31,20 +32,19 @@ Railway Operation and Construction</a></td></tr>
<td>Copyright David Abrahams, Jeremy Siek, and Thomas Witt 2003.</td></tr>
</tbody>
</table>
<div class="document" id="counting-iterator">
<table class="field-list" frame="void" rules="none">
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">abstract:</th><td class="field-body"><p class="first">How would you fill up a vector with the numbers zero
through one hundred using <tt class="literal"><span class="pre">std::copy()</span></tt>? The only iterator
through one hundred using <tt class="docutils literal"><span class="pre">std::copy()</span></tt>? The only iterator
operation missing from builtin integer types is an
<tt class="literal"><span class="pre">operator*()</span></tt> that returns the current value of the integer.
<tt class="docutils literal"><span class="pre">operator*()</span></tt> that returns the current value of the integer.
The counting iterator adaptor adds this crucial piece of
functionality to whatever type it wraps. One can use the
counting iterator adaptor not only with integer types, but with
any incrementable type.</p>
<p class="last"><tt class="literal"><span class="pre">counting_iterator</span></tt> adapts an object by adding an <tt class="literal"><span class="pre">operator*</span></tt> that
<p class="last"><tt class="docutils literal"><span class="pre">counting_iterator</span></tt> adapts an object by adding an <tt class="docutils literal"><span class="pre">operator*</span></tt> that
returns the current value of the object. All other iterator operations
are forwarded to the adapted object.</p>
</td>
@ -54,15 +54,15 @@ are forwarded to the adapted object.</p>
<div class="contents topic" id="table-of-contents">
<p class="topic-title first"><a name="table-of-contents">Table of Contents</a></p>
<ul class="simple">
<li><a class="reference" href="#counting-iterator-synopsis" id="id2" name="id2"><tt class="literal"><span class="pre">counting_iterator</span></tt> synopsis</a></li>
<li><a class="reference" href="#counting-iterator-requirements" id="id3" name="id3"><tt class="literal"><span class="pre">counting_iterator</span></tt> requirements</a></li>
<li><a class="reference" href="#counting-iterator-models" id="id4" name="id4"><tt class="literal"><span class="pre">counting_iterator</span></tt> models</a></li>
<li><a class="reference" href="#counting-iterator-operations" id="id5" name="id5"><tt class="literal"><span class="pre">counting_iterator</span></tt> operations</a></li>
<li><a class="reference" href="#counting-iterator-synopsis" id="id2" name="id2"><tt class="docutils literal"><span class="pre">counting_iterator</span></tt> synopsis</a></li>
<li><a class="reference" href="#counting-iterator-requirements" id="id3" name="id3"><tt class="docutils literal"><span class="pre">counting_iterator</span></tt> requirements</a></li>
<li><a class="reference" href="#counting-iterator-models" id="id4" name="id4"><tt class="docutils literal"><span class="pre">counting_iterator</span></tt> models</a></li>
<li><a class="reference" href="#counting-iterator-operations" id="id5" name="id5"><tt class="docutils literal"><span class="pre">counting_iterator</span></tt> operations</a></li>
<li><a class="reference" href="#example" id="id6" name="id6">Example</a></li>
</ul>
</div>
<div class="section" id="counting-iterator-synopsis">
<h1><a class="toc-backref" href="#id2" name="counting-iterator-synopsis"><tt class="literal"><span class="pre">counting_iterator</span></tt> synopsis</a></h1>
<h1><a class="toc-backref" href="#id2" name="counting-iterator-synopsis"><tt class="docutils literal"><span class="pre">counting_iterator</span></tt> synopsis</a></h1>
<pre class="literal-block">
template &lt;
class Incrementable
@ -89,10 +89,10 @@ private:
Incrementable m_inc; // exposition
};
</pre>
<p>If the <tt class="literal"><span class="pre">Difference</span></tt> argument is <tt class="literal"><span class="pre">use_default</span></tt> then
<tt class="literal"><span class="pre">difference_type</span></tt> is an unspecified signed integral
type. Otherwise <tt class="literal"><span class="pre">difference_type</span></tt> is <tt class="literal"><span class="pre">Difference</span></tt>.</p>
<p><tt class="literal"><span class="pre">iterator_category</span></tt> is determined according to the following
<p>If the <tt class="docutils literal"><span class="pre">Difference</span></tt> argument is <tt class="docutils literal"><span class="pre">use_default</span></tt> then
<tt class="docutils literal"><span class="pre">difference_type</span></tt> is an unspecified signed integral
type. Otherwise <tt class="docutils literal"><span class="pre">difference_type</span></tt> is <tt class="docutils literal"><span class="pre">Difference</span></tt>.</p>
<p><tt class="docutils literal"><span class="pre">iterator_category</span></tt> is determined according to the following
algorithm:</p>
<pre class="literal-block">
if (CategoryOrTraversal is not use_default)
@ -105,31 +105,31 @@ else
iterator_traversal&lt;Incrementable&gt;::type,
Incrementable, const Incrementable&amp;)
</pre>
<dl>
<dl class="docutils">
<dt>[<em>Note:</em> implementers are encouraged to provide an implementation of</dt>
<dd><tt class="literal"><span class="pre">operator-</span></tt> and a <tt class="literal"><span class="pre">difference_type</span></tt> that avoids overflows in
the cases where <tt class="literal"><span class="pre">std::numeric_limits&lt;Incrementable&gt;::is_specialized</span></tt>
<dd><tt class="docutils literal"><span class="pre">operator-</span></tt> and a <tt class="docutils literal"><span class="pre">difference_type</span></tt> that avoids overflows in
the cases where <tt class="docutils literal"><span class="pre">std::numeric_limits&lt;Incrementable&gt;::is_specialized</span></tt>
is true.]</dd>
</dl>
</div>
<div class="section" id="counting-iterator-requirements">
<h1><a class="toc-backref" href="#id3" 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> argument shall be Copy Constructible and Assignable.</p>
<p>If <tt class="literal"><span class="pre">iterator_category</span></tt> is convertible to <tt class="literal"><span class="pre">forward_iterator_tag</span></tt>
or <tt class="literal"><span class="pre">forward_traversal_tag</span></tt>, the following must be well-formed:</p>
<h1><a class="toc-backref" href="#id3" name="counting-iterator-requirements"><tt class="docutils literal"><span class="pre">counting_iterator</span></tt> requirements</a></h1>
<p>The <tt class="docutils literal"><span class="pre">Incrementable</span></tt> argument shall be Copy Constructible and Assignable.</p>
<p>If <tt class="docutils literal"><span class="pre">iterator_category</span></tt> is convertible to <tt class="docutils literal"><span class="pre">forward_iterator_tag</span></tt>
or <tt class="docutils literal"><span class="pre">forward_traversal_tag</span></tt>, the following must be well-formed:</p>
<pre class="literal-block">
Incrementable i, j;
++i; // pre-increment
i == j; // operator equal
</pre>
<p>If <tt class="literal"><span class="pre">iterator_category</span></tt> is convertible to
<tt class="literal"><span class="pre">bidirectional_iterator_tag</span></tt> or <tt class="literal"><span class="pre">bidirectional_traversal_tag</span></tt>,
<p>If <tt class="docutils literal"><span class="pre">iterator_category</span></tt> is convertible to
<tt class="docutils literal"><span class="pre">bidirectional_iterator_tag</span></tt> or <tt class="docutils literal"><span class="pre">bidirectional_traversal_tag</span></tt>,
the following expression must also be well-formed:</p>
<pre class="literal-block">
--i
</pre>
<p>If <tt class="literal"><span class="pre">iterator_category</span></tt> is convertible to
<tt class="literal"><span class="pre">random_access_iterator_tag</span></tt> or <tt class="literal"><span class="pre">random_access_traversal_tag</span></tt>,
<p>If <tt class="docutils literal"><span class="pre">iterator_category</span></tt> is convertible to
<tt class="docutils literal"><span class="pre">random_access_iterator_tag</span></tt> or <tt class="docutils literal"><span class="pre">random_access_traversal_tag</span></tt>,
the following must must also be valid:</p>
<pre class="literal-block">
counting_iterator::difference_type n;
@ -139,92 +139,92 @@ i &lt; j;
</pre>
</div>
<div class="section" id="counting-iterator-models">
<h1><a class="toc-backref" href="#id4" name="counting-iterator-models"><tt class="literal"><span class="pre">counting_iterator</span></tt> models</a></h1>
<p>Specializations of <tt class="literal"><span class="pre">counting_iterator</span></tt> model Readable Lvalue
<h1><a class="toc-backref" href="#id4" name="counting-iterator-models"><tt class="docutils literal"><span class="pre">counting_iterator</span></tt> models</a></h1>
<p>Specializations of <tt class="docutils literal"><span class="pre">counting_iterator</span></tt> model Readable Lvalue
Iterator. In addition, they model the concepts corresponding to the
iterator tags to which their <tt class="literal"><span class="pre">iterator_category</span></tt> is convertible.
Also, if <tt class="literal"><span class="pre">CategoryOrTraversal</span></tt> is not <tt class="literal"><span class="pre">use_default</span></tt> then
<tt class="literal"><span class="pre">counting_iterator</span></tt> models the concept corresponding to the iterator
tag <tt class="literal"><span class="pre">CategoryOrTraversal</span></tt>. Otherwise, if
<tt class="literal"><span class="pre">numeric_limits&lt;Incrementable&gt;::is_specialized</span></tt>, then
<tt class="literal"><span class="pre">counting_iterator</span></tt> models Random Access Traversal Iterator.
Otherwise, <tt class="literal"><span class="pre">counting_iterator</span></tt> models the same iterator traversal
concepts modeled by <tt class="literal"><span class="pre">Incrementable</span></tt>.</p>
<p><tt class="literal"><span class="pre">counting_iterator&lt;X,C1,D1&gt;</span></tt> is interoperable with
<tt class="literal"><span class="pre">counting_iterator&lt;Y,C2,D2&gt;</span></tt> if and only if <tt class="literal"><span class="pre">X</span></tt> is
interoperable with <tt class="literal"><span class="pre">Y</span></tt>.</p>
iterator tags to which their <tt class="docutils literal"><span class="pre">iterator_category</span></tt> is convertible.
Also, if <tt class="docutils literal"><span class="pre">CategoryOrTraversal</span></tt> is not <tt class="docutils literal"><span class="pre">use_default</span></tt> then
<tt class="docutils literal"><span class="pre">counting_iterator</span></tt> models the concept corresponding to the iterator
tag <tt class="docutils literal"><span class="pre">CategoryOrTraversal</span></tt>. Otherwise, if
<tt class="docutils literal"><span class="pre">numeric_limits&lt;Incrementable&gt;::is_specialized</span></tt>, then
<tt class="docutils literal"><span class="pre">counting_iterator</span></tt> models Random Access Traversal Iterator.
Otherwise, <tt class="docutils literal"><span class="pre">counting_iterator</span></tt> models the same iterator traversal
concepts modeled by <tt class="docutils literal"><span class="pre">Incrementable</span></tt>.</p>
<p><tt class="docutils literal"><span class="pre">counting_iterator&lt;X,C1,D1&gt;</span></tt> is interoperable with
<tt class="docutils literal"><span class="pre">counting_iterator&lt;Y,C2,D2&gt;</span></tt> if and only if <tt class="docutils literal"><span class="pre">X</span></tt> is
interoperable with <tt class="docutils literal"><span class="pre">Y</span></tt>.</p>
</div>
<div class="section" id="counting-iterator-operations">
<h1><a class="toc-backref" href="#id5" name="counting-iterator-operations"><tt class="literal"><span class="pre">counting_iterator</span></tt> operations</a></h1>
<h1><a class="toc-backref" href="#id5" name="counting-iterator-operations"><tt class="docutils literal"><span class="pre">counting_iterator</span></tt> operations</a></h1>
<p>In addition to the operations required by the concepts modeled by
<tt class="literal"><span class="pre">counting_iterator</span></tt>, <tt class="literal"><span class="pre">counting_iterator</span></tt> provides the following
<tt class="docutils literal"><span class="pre">counting_iterator</span></tt>, <tt class="docutils literal"><span class="pre">counting_iterator</span></tt> provides the following
operations.</p>
<p><tt class="literal"><span class="pre">counting_iterator();</span></tt></p>
<table class="field-list" frame="void" rules="none">
<p><tt class="docutils literal"><span class="pre">counting_iterator();</span></tt></p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><tt class="literal"><span class="pre">Incrementable</span></tt> is Default Constructible.</td>
<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><tt class="docutils literal"><span class="pre">Incrementable</span></tt> is Default Constructible.</td>
</tr>
<tr class="field"><th class="field-name">Effects:</th><td class="field-body">Default construct the member <tt class="literal"><span class="pre">m_inc</span></tt>.</td>
<tr class="field"><th class="field-name">Effects:</th><td class="field-body">Default construct the member <tt class="docutils literal"><span class="pre">m_inc</span></tt>.</td>
</tr>
</tbody>
</table>
<p><tt class="literal"><span class="pre">counting_iterator(counting_iterator</span> <span class="pre">const&amp;</span> <span class="pre">rhs);</span></tt></p>
<table class="field-list" frame="void" rules="none">
<p><tt class="docutils literal"><span class="pre">counting_iterator(counting_iterator</span> <span class="pre">const&amp;</span> <span class="pre">rhs);</span></tt></p>
<table class="docutils 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">Construct member <tt class="literal"><span class="pre">m_inc</span></tt> from <tt class="literal"><span class="pre">rhs.m_inc</span></tt>.</td>
<tr class="field"><th class="field-name">Effects:</th><td class="field-body">Construct member <tt class="docutils literal"><span class="pre">m_inc</span></tt> from <tt class="docutils literal"><span class="pre">rhs.m_inc</span></tt>.</td>
</tr>
</tbody>
</table>
<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">
<p><tt class="docutils literal"><span class="pre">explicit</span> <span class="pre">counting_iterator(Incrementable</span> <span class="pre">x);</span></tt></p>
<table class="docutils 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">Construct member <tt class="literal"><span class="pre">m_inc</span></tt> from <tt class="literal"><span class="pre">x</span></tt>.</td>
<tr class="field"><th class="field-name">Effects:</th><td class="field-body">Construct member <tt class="docutils literal"><span class="pre">m_inc</span></tt> from <tt class="docutils 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">
<p><tt class="docutils literal"><span class="pre">reference</span> <span class="pre">operator*()</span> <span class="pre">const;</span></tt></p>
<table class="docutils 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">m_inc</span></tt></td>
<tr class="field"><th class="field-name">Returns:</th><td class="field-body"><tt class="docutils literal"><span class="pre">m_inc</span></tt></td>
</tr>
</tbody>
</table>
<p><tt class="literal"><span class="pre">counting_iterator&amp;</span> <span class="pre">operator++();</span></tt></p>
<table class="field-list" frame="void" rules="none">
<p><tt class="docutils literal"><span class="pre">counting_iterator&amp;</span> <span class="pre">operator++();</span></tt></p>
<table class="docutils 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">++m_inc</span></tt></td>
<tr class="field"><th class="field-name">Effects:</th><td class="field-body"><tt class="docutils literal"><span class="pre">++m_inc</span></tt></td>
</tr>
<tr class="field"><th class="field-name">Returns:</th><td class="field-body"><tt class="literal"><span class="pre">*this</span></tt></td>
<tr class="field"><th class="field-name">Returns:</th><td class="field-body"><tt class="docutils literal"><span class="pre">*this</span></tt></td>
</tr>
</tbody>
</table>
<p><tt class="literal"><span class="pre">counting_iterator&amp;</span> <span class="pre">operator--();</span></tt></p>
<table class="field-list" frame="void" rules="none">
<p><tt class="docutils literal"><span class="pre">counting_iterator&amp;</span> <span class="pre">operator--();</span></tt></p>
<table class="docutils 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">--m_inc</span></tt></td>
<tr class="field"><th class="field-name">Effects:</th><td class="field-body"><tt class="docutils literal"><span class="pre">--m_inc</span></tt></td>
</tr>
<tr class="field"><th class="field-name">Returns:</th><td class="field-body"><tt class="literal"><span class="pre">*this</span></tt></td>
<tr class="field"><th class="field-name">Returns:</th><td class="field-body"><tt class="docutils literal"><span class="pre">*this</span></tt></td>
</tr>
</tbody>
</table>
<p><tt class="literal"><span class="pre">Incrementable</span> <span class="pre">const&amp;</span> <span class="pre">base()</span> <span class="pre">const;</span></tt></p>
<table class="field-list" frame="void" rules="none">
<p><tt class="docutils literal"><span class="pre">Incrementable</span> <span class="pre">const&amp;</span> <span class="pre">base()</span> <span class="pre">const;</span></tt></p>
<table class="docutils 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">m_inc</span></tt></td>
<tr class="field"><th class="field-name">Returns:</th><td class="field-body"><tt class="docutils literal"><span class="pre">m_inc</span></tt></td>
</tr>
</tbody>
</table>
@ -232,12 +232,12 @@ operations.</p>
template &lt;class Incrementable&gt;
counting_iterator&lt;Incrementable&gt; make_counting_iterator(Incrementable x);
</pre>
<table class="field-list" frame="void" rules="none">
<table class="docutils 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&lt;Incrementable&gt;</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 class="field"><th class="field-name">Returns:</th><td class="field-body">An instance of <tt class="docutils literal"><span class="pre">counting_iterator&lt;Incrementable&gt;</span></tt>
with <tt class="docutils literal"><span class="pre">current</span></tt> constructed from <tt class="docutils literal"><span class="pre">x</span></tt>.</td>
</tr>
</tbody>
</table>
@ -245,8 +245,8 @@ with <tt class="literal"><span class="pre">current</span></tt> constructed from
<div class="section" id="example">
<h1><a class="toc-backref" href="#id6" 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
pointers into the first array, using <tt class="docutils literal"><span class="pre">counting_iterator</span></tt> for both
tasks. Finally <tt class="docutils 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;
@ -276,7 +276,7 @@ indirectly printing out the numbers from 0 to 7
<p>The source code for this example can be found <a class="reference" href="../example/counting_iterator_example.cpp">here</a>.</p>
</div>
</div>
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