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<div><h2 class="title">
<a name="iterator"></a>Chapter&#160;1.&#160;Boost.Iterator</h2></div>
<div><div class="author"><h3 class="author">
<span class="firstname">David</span> <span class="surname">Abrahams</span>
</h3></div></div>
<div><div class="author"><h3 class="author">
<span class="firstname">Jeremy</span> <span class="surname">Siek</span>
</h3></div></div>
<div><div class="author"><h3 class="author">
<span class="firstname">Thomas</span> <span class="surname">Witt</span>
</h3></div></div>
<div><p class="copyright">Copyright &#169; 2003, 2005 David Abrahams Jeremy Siek Thomas
Witt</p></div>
<div><div class="legalnotice">
<a name="iterator.legal"></a><p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at &lt;ulink url="http://www.boost.org/LICENSE_1_0.txt"&gt;
http://www.boost.org/LICENSE_1_0.txt &lt;/ulink&gt;)
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<div class="toc">
<p><b>Table of Contents</b></p>
<dl class="toc">
<dt><span class="section"><a href="index.html#iterator.intro">Introduction</a></span></dt>
<dt><span class="section"><a href="iterator/concepts.html">Iterator Concepts</a></span></dt>
<dd><dl>
<dt><span class="section"><a href="iterator/concepts.html#iterator.concepts.concepts_access">Access</a></span></dt>
<dt><span class="section"><a href="iterator/concepts/concepts_traversal.html">Traversal</a></span></dt>
</dl></dd>
<dt><span class="section"><a href="iterator/generic.html">Generic Iterators</a></span></dt>
<dd><dl>
<dt><span class="section"><a href="iterator/generic.html#iterator.generic.facade">Iterator Facade</a></span></dt>
<dd><dl>
<dt><span class="section"><a href="iterator/generic.html#iterator.generic.facade.facade_reference">Reference</a></span></dt>
<dt><span class="section"><a href="iterator/generic.html#iterator.generic.facade.facade_tutorial">Tutorial</a></span></dt>
</dl></dd>
<dt><span class="section"><a href="iterator/generic/adaptor.html">Iterator Adaptor</a></span></dt>
<dd><dl>
<dt><span class="section"><a href="iterator/generic/adaptor.html#iterator.generic.adaptor.adaptor_reference">Reference</a></span></dt>
<dt><span class="section"><a href="iterator/generic/adaptor/adaptor_tutorial.html">Tutorial</a></span></dt>
</dl></dd>
</dl></dd>
<dt><span class="section"><a href="iterator/specialized.html">Specialized Adaptors</a></span></dt>
<dd><dl>
<dt><span class="section"><a href="iterator/specialized.html#iterator.specialized.counting">Counting Iterator</a></span></dt>
<dt><span class="section"><a href="iterator/specialized/filter.html">Filter Iterator</a></span></dt>
<dt><span class="section"><a href="iterator/specialized/function_output.html">Function Output
Iterator</a></span></dt>
<dt><span class="section"><a href="iterator/specialized/indirect.html">Indirect Iterator</a></span></dt>
<dt><span class="section"><a href="iterator/specialized/permutation.html">Permutation Iterator</a></span></dt>
<dt><span class="section"><a href="iterator/specialized/reverse.html">Reverse Iterator</a></span></dt>
<dt><span class="section"><a href="iterator/specialized/shared_container.html">Shared Container
Iterator</a></span></dt>
<dd><dl>
<dt><span class="section"><a href="iterator/specialized/shared_container.html#iterator.specialized.shared_container.shared_container_type">The
Shared Container Iterator Type</a></span></dt>
<dt><span class="section"><a href="iterator/specialized/shared_container/shared_container_object_generator.html">The
Shared Container Iterator Object Generator</a></span></dt>
<dt><span class="section"><a href="iterator/specialized/shared_container/shared_container_generator.html">The
Shared Container Iterator Range Generator</a></span></dt>
</dl></dd>
<dt><span class="section"><a href="iterator/specialized/transform.html">Transform Iterator</a></span></dt>
<dt><span class="section"><a href="iterator/specialized/zip.html">Zip Iterator</a></span></dt>
<dd><dl>
<dt><span class="section"><a href="iterator/specialized/zip.html#iterator.specialized.zip.zip_example">Example</a></span></dt>
<dt><span class="section"><a href="iterator/specialized/zip/zip_reference.html">Reference</a></span></dt>
</dl></dd>
</dl></dd>
<dt><span class="section"><a href="iterator/utilities.html">Utilities</a></span></dt>
<dd><dl>
<dt><span class="section"><a href="iterator/utilities.html#iterator.utilities.archetypes">Iterator Archetypes</a></span></dt>
<dt><span class="section"><a href="iterator/utilities/concept_checking.html">Concept Checking</a></span></dt>
<dt><span class="section"><a href="iterator/utilities/traits.html">Iterator Traits</a></span></dt>
<dt><span class="section"><a href="iterator/utilities/utilities.html">Iterator Utilities</a></span></dt>
<dd><dl>
<dt><span class="section"><a href="iterator/utilities/utilities.html#iterator.utilities.utilities.utilities_traits">Traits</a></span></dt>
<dt><span class="section"><a href="iterator/utilities/utilities/utilities_testing.html">Testing
and Concept Checking</a></span></dt>
</dl></dd>
</dl></dd>
<dt><span class="section"><a href="iterator/upgrading.html">Upgrading from the old Boost Iterator
Adaptor Library</a></span></dt>
<dt><span class="section"><a href="iterator/history.html">History</a></span></dt>
</dl>
</div>
<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="iterator.intro"></a><a class="link" href="index.html#iterator.intro" title="Introduction">Introduction</a>
</h2></div></div></div>
<p>
The Boost Iterator Library contains two parts. The first is a system of <a href="http://www.boost.org/more/generic_programming.html#concept" target="_top">concepts</a>
which extend the C++ standard iterator requirements. The second is a framework
of components for building iterators based on these extended concepts and includes
several useful iterator adaptors. The extended iterator concepts have been
carefully designed so that old-style iterators can fit in the new concepts
and so that new-style iterators will be compatible with old-style algorithms,
though algorithms may need to be updated if they want to take full advantage
of the new-style iterator capabilities. Several components of this library
have been accepted into the C++ standard technical report. The components of
the Boost Iterator Library replace the older Boost Iterator Adaptor Library.
</p>
<h3>
<a name="iterator.intro.h0"></a>
<span class="phrase"><a name="iterator.intro.new_style_iterators"></a></span><a class="link" href="index.html#iterator.intro.new_style_iterators">New-Style
Iterators</a>
</h3>
<p>
The iterator categories defined in C++98 are extremely limiting because they
bind together two orthogonal concepts: traversal and element access. For example,
because a random access iterator is required to return a reference (and not
a proxy) when dereferenced, it is impossible to capture the capabilities of
<code class="computeroutput"><span class="identifier">vector</span><span class="special">&lt;</span><span class="keyword">bool</span><span class="special">&gt;::</span><span class="identifier">iterator</span></code>
using the C++98 categories. This is the infamous "<code class="computeroutput"><span class="identifier">vector</span><span class="special">&lt;</span><span class="keyword">bool</span><span class="special">&gt;</span></code>
is not a container, and its iterators aren't random access iterators",
debacle about which Herb Sutter wrote two papers for the standards comittee
(<a href="http://www.gotw.ca/publications/N1185.pdf" target="_top">N1185</a> and
<a href="http://www.gotw.ca/publications/N1211.pdf" target="_top">N1211</a>), and
a <a href="http://www.gotw.ca/gotw/050.htm" target="_top">Guru of the Week</a>. New-style
iterators go well beyond patching up <code class="computeroutput"><span class="identifier">vector</span><span class="special">&lt;</span><span class="keyword">bool</span><span class="special">&gt;</span></code>,
though: there are lots of other iterators already in use which can't be adequately
represented by the existing concepts. For details about the new iterator concepts,
see our <a href="./new-iter-concepts.html" target="_top">Standard Proposal for New-Style
Iterators</a>.
</p>
<h3>
<a name="iterator.intro.h1"></a>
<span class="phrase"><a name="iterator.intro.iterator_facade_and_adaptor"></a></span><a class="link" href="index.html#iterator.intro.iterator_facade_and_adaptor">Iterator
Facade and Adaptor</a>
</h3>
<p>
Writing standard-conforming iterators is tricky, but the need comes up often.
In order to ease the implementation of new iterators, the Boost.Iterator library
provides the <a href="./iterator_facade.html" target="_top">facade</a> class template,
which implements many useful defaults and compile-time checks designed to help
the iterator author ensure that his iterator is correct.
</p>
<p>
It is also common to define a new iterator that is similar to some underlying
iterator or iterator-like type, but that modifies some aspect of the underlying
type's behavior. For that purpose, the library supplies the <a href="./iterator_adaptor.html" target="_top">adaptor</a>
class template, which is specially designed to take advantage of as much of
the underlying type's behavior as possible.
</p>
<p>
Both <a href="./iterator_facade.html" target="_top">facade</a> and <a href="./iterator_adaptor.html" target="_top">adaptor</a>
as well as many of the <code class="computeroutput"><span class="identifier">specialized</span>
<span class="identifier">adaptors</span></code>_ mentioned below have been
proposed for standardization (<a href="./facade-and-adaptor.html" target="_top">Standard
Proposal For Iterator Facade and Adaptor</a>).
</p>
<h3>
<a name="iterator.intro.h2"></a>
<span class="phrase"><a name="iterator.intro.specialized_adaptors"></a></span><a class="link" href="index.html#iterator.intro.specialized_adaptors">Specialized
Adaptors</a>
</h3>
<p>
The iterator library supplies a useful suite of standard-conforming iterator
templates based on the Boost <a class="link" href="index.html#iterator.intro.iterator_facade_and_adaptor">iterator
facade and adaptor</a> templates.
</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<a href="./counting_iterator.html" target="_top"><code class="computeroutput"><span class="identifier">counting_iterator</span></code></a>:
an iterator over a sequence of consecutive values. Implements a "lazy
sequence"
</li>
<li class="listitem">
<a href="./filter_iterator.html" target="_top"><code class="computeroutput"><span class="identifier">filter_iterator</span></code></a>:
an iterator over the subset of elements of some sequence which satisfy
a given predicate
</li>
<li class="listitem">
<a href="./function_output_iterator.html" target="_top"><code class="computeroutput"><span class="identifier">function_output_iterator</span></code></a>:
an output iterator wrapping a unary function object; each time an element
is written into the dereferenced iterator, it is passed as a parameter
to the function object.
</li>
<li class="listitem">
<a href="./indirect_iterator.html" target="_top"><code class="computeroutput"><span class="identifier">indirect_iterator</span></code></a>:
an iterator over the objects <span class="bold"><strong>pointed-to</strong></span>
by the elements of some sequence.
</li>
<li class="listitem">
<a href="./permutation_iterator.html" target="_top"><code class="computeroutput"><span class="identifier">permutation_iterator</span></code></a>:
an iterator over the elements of some random-access sequence, rearranged
according to some sequence of integer indices.
</li>
<li class="listitem">
<p class="simpara">
<a href="./reverse_iterator.html" target="_top"><code class="computeroutput"><span class="identifier">reverse_iterator</span></code></a>:
an iterator which traverses the elements of some bidirectional sequence
in reverse. Corrects many of the shortcomings of C++98's
</p>
<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">reverse_iterator</span></pre>
<p class="simpara">
.
</p>
</li>
<li class="listitem">
<a href="./shared_container_iterator.html" target="_top"><code class="computeroutput"><span class="identifier">shared_container_iterator</span></code></a>:
an iterator over elements of a container whose lifetime is maintained by
a <a href="../../smart_ptr/shared_ptr.htm" target="_top"><code class="computeroutput"><span class="identifier">shared_ptr</span></code></a>
stored in the iterator.
</li>
<li class="listitem">
<p class="simpara">
<a href="./transform_iterator.html" target="_top"><code class="computeroutput"><span class="identifier">transform_iterator</span></code></a>:
an iterator over elements which are the result of applying some functional
transformation to the elements of an underlying sequence. This component
also replaces the old
</p>
<pre class="programlisting"><span class="identifier">projection_iterator_adaptor</span></pre>
<p class="simpara">
.
</p>
</li>
<li class="listitem">
<a href="./zip_iterator.html" target="_top"><code class="computeroutput"><span class="identifier">zip_iterator</span></code></a>:
an iterator over tuples of the elements at corresponding positions of heterogeneous
underlying iterators.
</li>
</ul></div>
<h3>
<a name="iterator.intro.h3"></a>
<span class="phrase"><a name="iterator.intro.iterator_utilities"></a></span><a class="link" href="index.html#iterator.intro.iterator_utilities">Iterator
Utilities</a>
</h3>
<h4>
<a name="iterator.intro.h4"></a>
<span class="phrase"><a name="iterator.intro.traits"></a></span><a class="link" href="index.html#iterator.intro.traits">Traits</a>
</h4>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<a href="./pointee.html" target="_top"><code class="computeroutput"><span class="identifier">pointee</span><span class="special">.</span><span class="identifier">hpp</span></code></a>:
Provides the capability to deduce the referent types of pointers, smart
pointers and iterators in generic code. Used in <a href="./indirect_iterator.html" target="_top"><code class="computeroutput"><span class="identifier">indirect_iterator</span></code></a>.
</li>
<li class="listitem">
<a href="./iterator_traits.html" target="_top"><code class="computeroutput"><span class="identifier">iterator_traits</span><span class="special">.</span><span class="identifier">hpp</span></code></a>:
Provides <a href="../../mpl/doc/index.html" target="_top"><span class="bold"><strong>MPL</strong></span></a>
compatible metafunctions which retrieve an iterator's traits. Also corrects
for the deficiencies of broken implementations of <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">iterator_traits</span></code>.
</li>
</ul></div>
<p>
[* |interoperable|_ (PDF__): Provides an <a href="../../mpl/doc/index.html" target="_top"><span class="bold"><strong>MPL</strong></span></a> compatible metafunction for testing iterator
interoperability ]
</p>
<h4>
<a name="iterator.intro.h5"></a>
<span class="phrase"><a name="iterator.intro.testing_and_concept_checking"></a></span><a class="link" href="index.html#iterator.intro.testing_and_concept_checking">Testing
and Concept Checking</a>
</h4>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<a href="./iterator_concepts.html" target="_top"><code class="computeroutput"><span class="identifier">iterator_concepts</span><span class="special">.</span><span class="identifier">hpp</span></code></a>:
Concept checking classes for the new iterator concepts.
</li>
<li class="listitem">
<a href="./iterator_archetypes.html" target="_top"><code class="computeroutput"><span class="identifier">iterator_archetypes</span><span class="special">.</span><span class="identifier">hpp</span></code></a>:
Concept archetype classes for the new iterators concepts.
</li>
</ul></div>
</div>
</div>
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<td align="left"><p><small>Last revised: December 22, 2016 at 12:43:11 GMT</small></p></td>
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