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<h1 class="title">The Boost.Iterator Library <a class="reference" href="../../../index.htm"><img alt="Boost" src="../../../boost.png" /></a></h1>
<div class="document" id="the-boost-iterator-library-logo">
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<h1 class="title">The Boost.Iterator Library <a class="reference" href="../../../index.htm"><img alt="Boost" src="../../../boost.png" /></a></h1>
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@ -28,7 +28,7 @@ Lab</a>, <a class="reference" href="http://www.styleadvisor.com">Zephyr Associat
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@ -65,7 +65,7 @@ older Boost Iterator Adaptor Library.</td>
<li><a class="reference" href="#history" id="id29" name="id29">History</a></li>
</ul>
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<div class="section" id="new-style-iterators">
<h1><a class="toc-backref" href="#id22" name="new-style-iterators">New-Style Iterators</a></h1>
<p>The iterator categories defined in C++98 are extremely limiting
@ -73,12 +73,12 @@ 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
<tt class="literal"><span class="pre">vector&lt;bool&gt;::iterator</span></tt> using the C++98 categories. This is the
infamous &quot;<tt class="literal"><span class="pre">vector&lt;bool&gt;</span></tt> is not a container, and its iterators
<tt class="docutils literal"><span class="pre">vector&lt;bool&gt;::iterator</span></tt> using the C++98 categories. This is the
infamous &quot;<tt class="docutils literal"><span class="pre">vector&lt;bool&gt;</span></tt> is not a container, and its iterators
aren't random access iterators&quot;, debacle about which Herb Sutter
wrote two papers for the standards comittee (<a class="reference" href="http://www.gotw.ca/publications/N1185.pdf">n1185</a> and <a class="reference" href="http://www.gotw.ca/publications/N1211.pdf">n1211</a>),
and a <a class="reference" href="http://www.gotw.ca/gotw/050.htm">Guru of the Week</a>. New-style iterators go well beyond
patching up <tt class="literal"><span class="pre">vector&lt;bool&gt;</span></tt>, though: there are lots of other
patching up <tt class="docutils literal"><span class="pre">vector&lt;bool&gt;</span></tt>, 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</p>
@ -89,23 +89,23 @@ concepts, see our</p>
<h1><a class="toc-backref" href="#id23" name="iterator-facade-and-adaptor">Iterator Facade and Adaptor</a></h1>
<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 <tt class="literal"><span class="pre">iterator_facade</span></tt> class template,
the Boost.Iterator library provides the <tt class="docutils literal"><span class="pre">iterator_facade</span></tt> 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 <tt class="literal"><span class="pre">iterator_adaptor</span></tt> class template, which is specially
library supplies the <tt class="docutils literal"><span class="pre">iterator_adaptor</span></tt> class template, which is specially
designed to take advantage of as much of the underlying type's
behavior as possible.</p>
<p>The documentation for these two classes can be found at the following
web pages:</p>
<ul class="simple">
<li><a class="reference" href="iterator_facade.html"><tt class="literal"><span class="pre">iterator_facade</span></tt></a> (<a class="reference" href="iterator_facade.pdf">PDF</a>)</li>
<li><a class="reference" href="iterator_adaptor.html"><tt class="literal"><span class="pre">iterator_adaptor</span></tt></a> (<a class="reference" href="iterator_adaptor.pdf">PDF</a>)</li>
<li><a class="reference" href="iterator_facade.html"><tt class="docutils literal"><span class="pre">iterator_facade</span></tt></a> (<a class="reference" href="iterator_facade.pdf">PDF</a>)</li>
<li><a class="reference" href="iterator_adaptor.html"><tt class="docutils literal"><span class="pre">iterator_adaptor</span></tt></a> (<a class="reference" href="iterator_adaptor.pdf">PDF</a>)</li>
</ul>
<p>Both <tt class="literal"><span class="pre">iterator_facade</span></tt> and <tt class="literal"><span class="pre">iterator_adaptor</span></tt> as well as many of the <a class="reference" href="#specialized-adaptors">specialized
<p>Both <tt class="docutils literal"><span class="pre">iterator_facade</span></tt> and <tt class="docutils literal"><span class="pre">iterator_adaptor</span></tt> as well as many of the <a class="reference" href="#specialized-adaptors">specialized
adaptors</a> mentioned below have been proposed for standardization,
and accepted into the first C++ technical report; see our</p>
<blockquote>
@ -117,27 +117,27 @@ and accepted into the first C++ technical report; see our</p>
<p>The iterator library supplies a useful suite of standard-conforming
iterator templates based on the Boost <a class="reference" href="#iterator-facade-and-adaptor">iterator facade and adaptor</a>.</p>
<ul class="simple">
<li><a class="reference" href="counting_iterator.html"><tt class="literal"><span class="pre">counting_iterator</span></tt></a> (<a class="reference" href="counting_iterator.pdf">PDF</a>): an iterator over a sequence of consecutive values.
<li><a class="reference" href="counting_iterator.html"><tt class="docutils literal"><span class="pre">counting_iterator</span></tt></a> (<a class="reference" href="counting_iterator.pdf">PDF</a>): an iterator over a sequence of consecutive values.
Implements a &quot;lazy sequence&quot;</li>
<li><a class="reference" href="filter_iterator.html"><tt class="literal"><span class="pre">filter_iterator</span></tt></a> (<a class="reference" href="filter_iterator.pdf">PDF</a>): an iterator over the subset of elements of some
<li><a class="reference" href="filter_iterator.html"><tt class="docutils literal"><span class="pre">filter_iterator</span></tt></a> (<a class="reference" href="filter_iterator.pdf">PDF</a>): an iterator over the subset of elements of some
sequence which satisfy a given predicate</li>
<li><a class="reference" href="function_output_iterator.html"><tt class="literal"><span class="pre">function_output_iterator</span></tt></a> (<a class="reference" href="function_output_iterator.pdf">PDF</a>): an output iterator wrapping a unary function
<li><a class="reference" href="function_output_iterator.html"><tt class="docutils literal"><span class="pre">function_output_iterator</span></tt></a> (<a class="reference" href="function_output_iterator.pdf">PDF</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><a class="reference" href="indirect_iterator.html"><tt class="literal"><span class="pre">indirect_iterator</span></tt></a> (<a class="reference" href="indirect_iterator.pdf">PDF</a>): an iterator over the objects <em>pointed-to</em> by the
<li><a class="reference" href="indirect_iterator.html"><tt class="docutils literal"><span class="pre">indirect_iterator</span></tt></a> (<a class="reference" href="indirect_iterator.pdf">PDF</a>): an iterator over the objects <em>pointed-to</em> by the
elements of some sequence.</li>
<li><a class="reference" href="permutation_iterator.html"><tt class="literal"><span class="pre">permutation_iterator</span></tt></a> (<a class="reference" href="permutation_iterator.pdf">PDF</a>): an iterator over the elements of some random-access
<li><a class="reference" href="permutation_iterator.html"><tt class="docutils literal"><span class="pre">permutation_iterator</span></tt></a> (<a class="reference" href="permutation_iterator.pdf">PDF</a>): an iterator over the elements of some random-access
sequence, rearranged according to some sequence of integer indices.</li>
<li><a class="reference" href="reverse_iterator.html"><tt class="literal"><span class="pre">reverse_iterator</span></tt></a> (<a class="reference" href="reverse_iterator.pdf">PDF</a>): an iterator which traverses the elements of some
<li><a class="reference" href="reverse_iterator.html"><tt class="docutils literal"><span class="pre">reverse_iterator</span></tt></a> (<a class="reference" href="reverse_iterator.pdf">PDF</a>): an iterator which traverses the elements of some
bidirectional sequence in reverse. Corrects many of the
shortcomings of C++98's <tt class="literal"><span class="pre">std::reverse_iterator</span></tt>.</li>
<li><a class="reference" href="../../utility/shared_container_iterator.html"><tt class="literal"><span class="pre">shared_container_iterator</span></tt></a>: an iterator over elements of a container whose
lifetime is maintained by a <a class="reference" href="../../smart_ptr/shared_ptr.htm"><tt class="literal"><span class="pre">shared_ptr</span></tt></a> stored in the iterator.</li>
<li><a class="reference" href="transform_iterator.html"><tt class="literal"><span class="pre">transform_iterator</span></tt></a> (<a class="reference" href="transform_iterator.pdf">PDF</a>): an iterator over elements which are the result of
shortcomings of C++98's <tt class="docutils literal"><span class="pre">std::reverse_iterator</span></tt>.</li>
<li><a class="reference" href="../../utility/shared_container_iterator.html"><tt class="docutils literal"><span class="pre">shared_container_iterator</span></tt></a>: an iterator over elements of a container whose
lifetime is maintained by a <a class="reference" href="../../smart_ptr/shared_ptr.htm"><tt class="docutils literal"><span class="pre">shared_ptr</span></tt></a> stored in the iterator.</li>
<li><a class="reference" href="transform_iterator.html"><tt class="docutils literal"><span class="pre">transform_iterator</span></tt></a> (<a class="reference" href="transform_iterator.pdf">PDF</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
<tt class="literal"><span class="pre">projection_iterator_adaptor</span></tt>.</li>
<li><a class="reference" href="zip_iterator.html"><tt class="literal"><span class="pre">zip_iterator</span></tt></a> (<a class="reference" href="zip_iterator.pdf">PDF</a>): an iterator over tuples of the elements at corresponding
<tt class="docutils literal"><span class="pre">projection_iterator_adaptor</span></tt>.</li>
<li><a class="reference" href="zip_iterator.html"><tt class="docutils literal"><span class="pre">zip_iterator</span></tt></a> (<a class="reference" href="zip_iterator.pdf">PDF</a>): an iterator over tuples of the elements at corresponding
positions of heterogeneous underlying iterators.</li>
</ul>
</div>
@ -146,12 +146,12 @@ positions of heterogeneous underlying iterators.</li>
<div class="section" id="traits">
<h2><a class="toc-backref" href="#id26" name="traits">Traits</a></h2>
<ul class="simple">
<li><a class="reference" href="pointee.html"><tt class="literal"><span class="pre">pointee.hpp</span></tt></a> (<a class="reference" href="pointee.pdf">PDF</a>): Provides the capability to deduce the referent types
<li><a class="reference" href="pointee.html"><tt class="docutils literal"><span class="pre">pointee.hpp</span></tt></a> (<a class="reference" href="pointee.pdf">PDF</a>): Provides the capability to deduce the referent types
of pointers, smart pointers and iterators in generic code. Used
in <tt class="literal"><span class="pre">indirect_iterator</span></tt>.</li>
<li><a class="reference" href="iterator_traits.html"><tt class="literal"><span class="pre">iterator_traits.hpp</span></tt></a> (<a class="reference" href="iterator_traits.pdf">PDF</a>): Provides <a class="reference" href="../../mpl/doc/index.html">MPL</a>-compatible metafunctions which
in <tt class="docutils literal"><span class="pre">indirect_iterator</span></tt>.</li>
<li><a class="reference" href="iterator_traits.html"><tt class="docutils literal"><span class="pre">iterator_traits.hpp</span></tt></a> (<a class="reference" href="iterator_traits.pdf">PDF</a>): Provides <a class="reference" href="../../mpl/doc/index.html">MPL</a>-compatible metafunctions which
retrieve an iterator's traits. Also corrects for the deficiencies
of broken implementations of <tt class="literal"><span class="pre">std::iterator_traits</span></tt>.</li>
of broken implementations of <tt class="docutils literal"><span class="pre">std::iterator_traits</span></tt>.</li>
</ul>
<!-- * |interoperable|_ (PDF__): Provides an MPL_\ -compatible metafunction for
testing iterator interoperability -->
@ -160,35 +160,35 @@ testing iterator interoperability -->
<div class="section" id="testing-and-concept-checking">
<h2><a class="toc-backref" href="#id27" name="testing-and-concept-checking">Testing and Concept Checking</a></h2>
<ul class="simple">
<li><a class="reference" href="iterator_concepts.html"><tt class="literal"><span class="pre">iterator_concepts.hpp</span></tt></a> (<a class="reference" href="iterator_concepts.pdf">PDF</a>): Concept checking classes for the new iterator concepts.</li>
<li><a class="reference" href="iterator_archetypes.html"><tt class="literal"><span class="pre">iterator_archetypes.hpp</span></tt></a> (<a class="reference" href="iterator_archetypes.pdf">PDF</a>): Concept archetype classes for the new iterators concepts.</li>
<li><a class="reference" href="iterator_concepts.html"><tt class="docutils literal"><span class="pre">iterator_concepts.hpp</span></tt></a> (<a class="reference" href="iterator_concepts.pdf">PDF</a>): Concept checking classes for the new iterator concepts.</li>
<li><a class="reference" href="iterator_archetypes.html"><tt class="docutils literal"><span class="pre">iterator_archetypes.hpp</span></tt></a> (<a class="reference" href="iterator_archetypes.pdf">PDF</a>): Concept archetype classes for the new iterators concepts.</li>
</ul>
</div>
</div>
<div class="section" id="upgrading-from-the-old-boost-iterator-adaptor-library">
<h1><a class="toc-backref" href="#id28" name="upgrading-from-the-old-boost-iterator-adaptor-library">Upgrading from the old Boost Iterator Adaptor Library</a></h1>
<a class="target" id="upgrading" name="upgrading"></a><p>If you have been using the old Boost Iterator Adaptor library to
implement iterators, you probably wrote a <tt class="literal"><span class="pre">Policies</span></tt> class which
implement iterators, you probably wrote a <tt class="docutils literal"><span class="pre">Policies</span></tt> class which
captures the core operations of your iterator. In the new library
design, you'll move those same core operations into the body of the
iterator class itself. If you were writing a family of iterators,
you probably wrote a <a class="reference" href="../../../more/generic_programming.html#type_generator">type generator</a> to build the
<tt class="literal"><span class="pre">iterator_adaptor</span></tt> specialization you needed; in the new library
<tt class="docutils literal"><span class="pre">iterator_adaptor</span></tt> specialization you needed; in the new library
design you don't need a type generator (though may want to keep it
around as a compatibility aid for older code) because, due to the
use of the Curiously Recurring Template Pattern (CRTP) <a class="citation-reference" href="#cop95" id="id21" name="id21">[Cop95]</a>,
you can now define the iterator class yourself and acquire
functionality through inheritance from <tt class="literal"><span class="pre">iterator_facade</span></tt> or
<tt class="literal"><span class="pre">iterator_adaptor</span></tt>. As a result, you also get much finer control
functionality through inheritance from <tt class="docutils literal"><span class="pre">iterator_facade</span></tt> or
<tt class="docutils literal"><span class="pre">iterator_adaptor</span></tt>. As a result, you also get much finer control
over how your iterator works: you can add additional constructors,
or even override the iterator functionality provided by the
library.</p>
<p>If you're looking for the old <tt class="literal"><span class="pre">projection_iterator</span></tt> component,
its functionality has been merged into <tt class="literal"><span class="pre">transform_iterator</span></tt>: as
long as the function object's <tt class="literal"><span class="pre">result_type</span></tt> (or the <tt class="literal"><span class="pre">Reference</span></tt>
<p>If you're looking for the old <tt class="docutils literal"><span class="pre">projection_iterator</span></tt> component,
its functionality has been merged into <tt class="docutils literal"><span class="pre">transform_iterator</span></tt>: as
long as the function object's <tt class="docutils literal"><span class="pre">result_type</span></tt> (or the <tt class="docutils literal"><span class="pre">Reference</span></tt>
template argument, if explicitly specified) is a true reference
type, <tt class="literal"><span class="pre">transform_iterator</span></tt> will behave like
<tt class="literal"><span class="pre">projection_iterator</span></tt> used to.</p>
type, <tt class="docutils literal"><span class="pre">transform_iterator</span></tt> will behave like
<tt class="docutils literal"><span class="pre">projection_iterator</span></tt> used to.</p>
</div>
<div class="section" id="history">
<h1><a class="toc-backref" href="#id29" name="history">History</a></h1>
@ -212,11 +212,11 @@ policies into the iterator class itself. Thomas Witt expressed
interest and became the voice of strict compile-time checking for
the project, adding uses of the SFINAE technique to eliminate false
converting constructors and operators from the overload set. He
also recognized the need for a separate <tt class="literal"><span class="pre">iterator_facade</span></tt>, and
factored it out of <tt class="literal"><span class="pre">iterator_adaptor</span></tt>. Finally, after a
also recognized the need for a separate <tt class="docutils literal"><span class="pre">iterator_facade</span></tt>, and
factored it out of <tt class="docutils literal"><span class="pre">iterator_adaptor</span></tt>. Finally, after a
near-complete rewrite of the prototype, they came up with the
library you see today.</p>
<table class="citation" frame="void" id="cop95" rules="none">
<table class="docutils citation" frame="void" id="cop95" rules="none">
<colgroup><col class="label" /><col /></colgroup>
<tbody valign="top">
<tr><td class="label"><a class="fn-backref" href="#id21" name="cop95">[Cop95]</a></td><td>[Coplien, 1995] Coplien, J., Curiously Recurring Template
@ -232,7 +232,7 @@ LocalWords: incrementable xxx min prev inplace png oldeqnew AccessTag struct
LocalWords: TraversalTag typename lvalues DWA Hmm JGS -->
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