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Added zip_iterator docs

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::
template<typename IteratorTuple>
zip_iterator<IteratorTuple>
make_zip_iterator(IteratorTuple t);
:Returns: An instance of ``zip_iterator<IteratorTuple>`` with ``m_iterator_tuple``
initialized to ``t``.

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<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<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 0.3.1: http://docutils.sourceforge.net/" />
<title>Zip Iterator</title>
<meta name="author" content="David Abrahams, Thomas Becker" />
<meta name="organization" content="Boost Consulting, Zephyr Associates, Inc." />
<meta name="date" content="2004-01-19" />
<meta name="copyright" content="Copyright David Abrahams and Thomas Becker 2003. All rights reserved" />
<link rel="stylesheet" href="default.css" type="text/css" />
</head>
<body>
<div class="document" id="zip-iterator">
<h1 class="title">Zip Iterator</h1>
<table class="docinfo" frame="void" rules="none">
<col class="docinfo-name" />
<col class="docinfo-content" />
<tbody valign="top">
<tr><th class="docinfo-name">Author:</th>
<td>David Abrahams, Thomas Becker</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="last reference" href="mailto:thomas&#64;styleadvisor.com">thomas&#64;styleadvisor.com</a></td></tr>
<tr><th class="docinfo-name">Organization:</th>
<td><a class="first reference" href="http://www.boost-consulting.com">Boost Consulting</a>, <a class="last reference" href="http://www.styleadvisor.com">Zephyr Associates, Inc.</a></td></tr>
<tr><th class="docinfo-name">Date:</th>
<td>2004-01-19</td></tr>
<tr><th class="docinfo-name">Copyright:</th>
<td>Copyright David Abrahams and Thomas Becker 2003. All rights reserved</td></tr>
</tbody>
</table>
<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">abstract:</th><td class="field-body">The zip iterator provides the ability to parallel-iterate
over several controlled sequences simultaneously. A zip
iterator is constructed from a tuple of iterators. Moving
the zip iterator moves all the iterators in parallel.
Dereferencing the zip iterator returns a tuple that contains
the results of dereferencing the individual iterators.</td>
</tr>
</tbody>
</table>
<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="#zip-iterator-synopsis" id="id2" name="id2"><tt class="literal"><span class="pre">zip_iterator</span></tt> synopsis</a></li>
<li><a class="reference" href="#zip-iterator-requirements" id="id3" name="id3"><tt class="literal"><span class="pre">zip_iterator</span></tt> requirements</a></li>
<li><a class="reference" href="#zip-iterator-models" id="id4" name="id4"><tt class="literal"><span class="pre">zip_iterator</span></tt> models</a></li>
<li><a class="reference" href="#zip-iterator-operations" id="id5" name="id5"><tt class="literal"><span class="pre">zip_iterator</span></tt> operations</a></li>
<li><a class="reference" href="#examples" id="id6" name="id6">Examples</a></li>
</ul>
</div>
<div class="section" id="zip-iterator-synopsis">
<h1><a class="toc-backref" href="#id2" name="zip-iterator-synopsis"><tt class="literal"><span class="pre">zip_iterator</span></tt> synopsis</a></h1>
<pre class="literal-block">
template&lt;typename IteratorTuple&gt;
class zip_iterator
{
public:
typedef /* see below */ reference;
typedef reference value_type;
typedef value_type* pointer;
typedef /* see below */ difference_type;
typedef /* see below */ iterator_category;
zip_iterator();
zip_iterator(IteratorTuple iterator_tuple);
template&lt;typename OtherIteratorTuple&gt;
zip_iterator(
const zip_iterator&lt;OtherIteratorTuple&gt;&amp; other
, typename enable_if_convertible&lt;
OtherIteratorTuple
, IteratorTuple&gt;::type* = 0 // exposition only
);
const IteratorTuple&amp; get_iterator_tuple() const;
private:
IteratorTuple m_iterator_tuple; // exposition only
};
template&lt;typename IteratorTuple&gt;
zip_iterator&lt;IteratorTuple&gt;
make_zip_iterator(IteratorTuple t);
</pre>
<p>The <tt class="literal"><span class="pre">reference</span></tt> member of <tt class="literal"><span class="pre">zip_iterator</span></tt> is the type of the tuple
made of the reference types of the iterator types in the <tt class="literal"><span class="pre">IteratorTuple</span></tt>
argument.</p>
<p>The <tt class="literal"><span class="pre">difference_type</span></tt> member of <tt class="literal"><span class="pre">zip_iterator</span></tt> is the <tt class="literal"><span class="pre">difference_type</span></tt>
of the first of the iterator types in the <tt class="literal"><span class="pre">IteratorTuple</span></tt> argument.</p>
<p>The <tt class="literal"><span class="pre">iterator_category</span></tt> member of <tt class="literal"><span class="pre">zip_iterator</span></tt> is convertible to the
minimum of the traversal categories of the iterator types in the <tt class="literal"><span class="pre">IteratorTuple</span></tt>
argument. For example, if the <tt class="literal"><span class="pre">zip_iterator</span></tt> holds only vector
iterators, then <tt class="literal"><span class="pre">iterator_category</span></tt> is convertible to
<tt class="literal"><span class="pre">boost::random_access_traversal_tag</span></tt>. If you add a list iterator, then
<tt class="literal"><span class="pre">iterator_category</span></tt> will be convertible to <tt class="literal"><span class="pre">boost::bidirectional_traversal_tag</span></tt>,
but no longer to <tt class="literal"><span class="pre">boost::random_access_traversal_tag</span></tt>.</p>
</div>
<div class="section" id="zip-iterator-requirements">
<h1><a class="toc-backref" href="#id3" name="zip-iterator-requirements"><tt class="literal"><span class="pre">zip_iterator</span></tt> requirements</a></h1>
<p>All iterator types in the argument <tt class="literal"><span class="pre">IteratorTuple</span></tt> shall model Readable Iterator.</p>
</div>
<div class="section" id="zip-iterator-models">
<h1><a class="toc-backref" href="#id4" name="zip-iterator-models"><tt class="literal"><span class="pre">zip_iterator</span></tt> models</a></h1>
<p>The resulting <tt class="literal"><span class="pre">zip_iterator</span></tt> models Readable Iterator.</p>
<p>The fact that the <tt class="literal"><span class="pre">zip_iterator</span></tt> models only Readable Iterator does not
prevent you from modifying the values that the individual iterators point
to. The tuple returned by the <tt class="literal"><span class="pre">zip_iterator</span></tt>'s <tt class="literal"><span class="pre">operator*</span></tt> is a tuple
constructed from the reference types of the individual iterators, not
their value types. For example, if <tt class="literal"><span class="pre">zip_it</span></tt> is a <tt class="literal"><span class="pre">zip_iterator</span></tt> whose
first member iterator is an <tt class="literal"><span class="pre">std::vector&lt;double&gt;::iterator</span></tt>, then the
following line will modify the value which the first member iterator of
<tt class="literal"><span class="pre">zip_it</span></tt> currently points to:</p>
<pre class="literal-block">
zip_it-&gt;get&lt;0&gt;() = 42.0;
</pre>
<p>Consider the set of standard traversal concepts obtained by taking
the most refined standard traversal concept modeled by each individual
iterator type in the <tt class="literal"><span class="pre">IteratorTuple</span></tt> argument.The <tt class="literal"><span class="pre">zip_iterator</span></tt>
models the least refined standard traversal concept in this set.</p>
<p><tt class="literal"><span class="pre">zip_iterator&lt;IteratorTuple1&gt;</span></tt> is interoperable with
<tt class="literal"><span class="pre">zip_iterator&lt;IteratorTuple2&gt;</span></tt> if and only if <tt class="literal"><span class="pre">IteratorTuple1</span></tt>
is interoperable with <tt class="literal"><span class="pre">IteratorTuple2</span></tt>.</p>
</div>
<div class="section" id="zip-iterator-operations">
<h1><a class="toc-backref" href="#id5" name="zip-iterator-operations"><tt class="literal"><span class="pre">zip_iterator</span></tt> operations</a></h1>
<p>In addition to the operations required by the concepts modeled by
<tt class="literal"><span class="pre">zip_iterator</span></tt>, <tt class="literal"><span class="pre">zip_iterator</span></tt> provides the following
operations.</p>
<p><tt class="literal"><span class="pre">zip_iterator();</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">zip_iterator</span></tt> with <tt class="literal"><span class="pre">m_iterator_tuple</span></tt>
default constructed.</td>
</tr>
</tbody>
</table>
<p><tt class="literal"><span class="pre">zip_iterator(IteratorTuple</span> <span class="pre">iterator_tuple);</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">zip_iterator</span></tt> with <tt class="literal"><span class="pre">m_iterator_tuple</span></tt>
initialized to <tt class="literal"><span class="pre">iterator_tuple</span></tt>.</td>
</tr>
</tbody>
</table>
<pre class="literal-block">
template&lt;typename OtherIteratorTuple&gt;
zip_iterator(
const zip_iterator&lt;OtherIteratorTuple&gt;&amp; other
, typename enable_if_convertible&lt;
OtherIteratorTuple
, IteratorTuple&gt;::type* = 0 // exposition only
);
</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">zip_iterator</span></tt> that is a copy of <tt class="literal"><span class="pre">other</span></tt>.</td>
</tr>
<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><tt class="literal"><span class="pre">OtherIteratorTuple</span></tt> is implicitly convertible to <tt class="literal"><span class="pre">IteratorTuple</span></tt>.</td>
</tr>
</tbody>
</table>
<p><tt class="literal"><span class="pre">const</span> <span class="pre">IteratorTuple&amp;</span> <span class="pre">get_iterator_tuple()</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">m_iterator_tuple</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">A tuple consisting of the results of dereferencing all iterators in
<tt class="literal"><span class="pre">m_iterator_tuple</span></tt>.</td>
</tr>
</tbody>
</table>
<p><tt class="literal"><span class="pre">zip_iterator&amp;</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">Increments each iterator in <tt class="literal"><span class="pre">m_iterator_tuple</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>
</tbody>
</table>
<p><tt class="literal"><span class="pre">zip_iterator&amp;</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">Decrements each iterator in <tt class="literal"><span class="pre">m_iterator_tuple</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>
</tbody>
</table>
<pre class="literal-block">
template&lt;typename IteratorTuple&gt;
zip_iterator&lt;IteratorTuple&gt;
make_zip_iterator(IteratorTuple t);
</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">zip_iterator&lt;IteratorTuple&gt;</span></tt> with <tt class="literal"><span class="pre">m_iterator_tuple</span></tt>
initialized to <tt class="literal"><span class="pre">t</span></tt>.</td>
</tr>
</tbody>
</table>
<pre class="literal-block">
template&lt;typename IteratorTuple&gt;
zip_iterator&lt;IteratorTuple&gt;
make_zip_iterator(IteratorTuple t);
</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">zip_iterator&lt;IteratorTuple&gt;</span></tt> with <tt class="literal"><span class="pre">m_iterator_tuple</span></tt>
initialized to <tt class="literal"><span class="pre">t</span></tt>.</td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="examples">
<h1><a class="toc-backref" href="#id6" name="examples">Examples</a></h1>
<p>There are two main types of applications of the <tt class="literal"><span class="pre">zip_iterator</span></tt>. The first
one concerns runtime efficiency: If one has several controlled sequences
of the same length that must be somehow processed, e.g., with the
<tt class="literal"><span class="pre">for_each</span></tt> algorithm, then it is more efficient to perform just
one parallel-iteration rather than several individual iterations. For an
example, assume that <tt class="literal"><span class="pre">vect_of_doubles</span></tt> and <tt class="literal"><span class="pre">vect_of_ints</span></tt>
are two vectors of equal length containing doubles and ints, respectively,
and consider the following two iterations:</p>
<pre class="literal-block">
std::vector&lt;double&gt;::const_iterator beg1 = vect_of_doubles.begin();
std::vector&lt;double&gt;::const_iterator end1 = vect_of_doubles.end();
std::vector&lt;int&gt;::const_iterator beg2 = vect_of_ints.begin();
std::vector&lt;int&gt;::const_iterator end2 = vect_of_ints.end();
std::for_each(beg1, end1, func_0());
std::for_each(beg2, end2, func_1());
</pre>
<p>These two iterations can now be replaced with a single one as follows:</p>
<pre class="literal-block">
std::for_each(
boost::make_zip_iterator(
boost::make_tuple(beg1, beg2)
),
boost::make_zip_iterator(
boost::make_tuple(end1, end2)
),
zip_func()
);
</pre>
<p>A non-generic implementation of <tt class="literal"><span class="pre">zip_func</span></tt> could look as follows:</p>
<pre class="literal-block">
struct zip_func :
public std::unary_function&lt;const boost::tuple&lt;const double&amp;, const int&amp;&gt;&amp;, void&gt;
{
void operator()(const boost::tuple&lt;const double&amp;, const int&amp;&gt;&amp; t) const
{
m_f0(t.get&lt;0&gt;());
m_f1(t.get&lt;1&gt;());
}
private:
func_0 m_f0;
func_1 m_f1;
};
</pre>
<p>The second important application of the <tt class="literal"><span class="pre">zip_iterator</span></tt> is as a building block
to make combining iterators. A combining iterator is an iterator
that parallel-iterates over several controlled sequences and, upon
dereferencing, returns the result of applying a functor to the values of the
sequences at the respective positions. This can now be achieved by using the
<tt class="literal"><span class="pre">zip_iterator</span></tt> in conjunction with the <tt class="literal"><span class="pre">transform_iterator</span></tt>.</p>
<p>Suppose, for example, that you have two vectors of doubles, say
<tt class="literal"><span class="pre">vect_1</span></tt> and <tt class="literal"><span class="pre">vect_2</span></tt>, and you need to expose to a client
a controlled sequence containing the products of the elements of
<tt class="literal"><span class="pre">vect_1</span></tt> and <tt class="literal"><span class="pre">vect_2</span></tt>. Rather than placing these products
in a third vector, you can use a combining iterator that calculates the
products on the fly. Let us assume that <tt class="literal"><span class="pre">tuple_multiplies</span></tt> is a
functor that works like <tt class="literal"><span class="pre">std::multiplies</span></tt>, except that it takes
its two arguments packaged in a tuple. Then the two iterators
<tt class="literal"><span class="pre">it_begin</span></tt> and <tt class="literal"><span class="pre">it_end</span></tt> defined below delimit a controlled
sequence containing the products of the elements of <tt class="literal"><span class="pre">vect_1</span></tt> and
<tt class="literal"><span class="pre">vect_2</span></tt>:</p>
<pre class="literal-block">
typedef boost::tuple&lt;
std::vector&lt;double&gt;::const_iterator,
std::vector&lt;double&gt;::const_iterator
&gt; the_iterator_tuple;
typedef boost::zip_iterator&lt;
the_iterator_tuple
&gt; the_zip_iterator;
typedef boost::transform_iterator&lt;
tuple_multiplies&lt;double&gt;,
the_zip_iterator
&gt; the_transform_iterator;
the_transform_iterator it_begin(
the_zip_iterator(
the_iterator_tuple(
vect_1.begin(),
vect_2.begin()
)
),
tuple_multiplies&lt;double&gt;()
);
the_transform_iterator it_end(
the_zip_iterator(
the_iterator_tuple(
vect_1.end(),
vect_2.end()
)
),
tuple_multiplies&lt;double&gt;()
);
</pre>
<p>The source code for these examples can be found <a class="reference" href="../example/zip_iterator_examples.cpp">here</a>.</p>
</div>
</div>
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+++++++++++++
Zip Iterator
+++++++++++++
:Author: David Abrahams, Thomas Becker
:Contact: dave@boost-consulting.com, thomas@styleadvisor.com
:organization: `Boost Consulting`_, `Zephyr Associates, Inc.`_
:date: $Date$
:copyright: Copyright David Abrahams and Thomas Becker 2003. All rights reserved
.. _`Boost Consulting`: http://www.boost-consulting.com
.. _`Zephyr Associates, Inc.`: http://www.styleadvisor.com
:abstract:
.. include:: zip_iterator_abstract.rst
.. contents:: Table of Contents
``zip_iterator`` synopsis
...............................
.. include:: zip_iterator_ref.rst
.. include:: make_zip_iterator.rst
.. include:: zip_iterator_eg.rst

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The zip iterator provides the ability to parallel-iterate
over several controlled sequences simultaneously. A zip
iterator is constructed from a tuple of iterators. Moving
the zip iterator moves all the iterators in parallel.
Dereferencing the zip iterator returns a tuple that contains
the results of dereferencing the individual iterators.

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Examples
........
There are two main types of applications of the ``zip_iterator``. The first
one concerns runtime efficiency: If one has several controlled sequences
of the same length that must be somehow processed, e.g., with the
``for_each`` algorithm, then it is more efficient to perform just
one parallel-iteration rather than several individual iterations. For an
example, assume that ``vect_of_doubles`` and ``vect_of_ints``
are two vectors of equal length containing doubles and ints, respectively,
and consider the following two iterations:
::
std::vector<double>::const_iterator beg1 = vect_of_doubles.begin();
std::vector<double>::const_iterator end1 = vect_of_doubles.end();
std::vector<int>::const_iterator beg2 = vect_of_ints.begin();
std::vector<int>::const_iterator end2 = vect_of_ints.end();
std::for_each(beg1, end1, func_0());
std::for_each(beg2, end2, func_1());
These two iterations can now be replaced with a single one as follows:
::
std::for_each(
boost::make_zip_iterator(
boost::make_tuple(beg1, beg2)
),
boost::make_zip_iterator(
boost::make_tuple(end1, end2)
),
zip_func()
);
A non-generic implementation of ``zip_func`` could look as follows:
::
struct zip_func :
public std::unary_function<const boost::tuple<const double&, const int&>&, void>
{
void operator()(const boost::tuple<const double&, const int&>& t) const
{
m_f0(t.get<0>());
m_f1(t.get<1>());
}
private:
func_0 m_f0;
func_1 m_f1;
};
The second important application of the ``zip_iterator`` is as a building block
to make combining iterators. A combining iterator is an iterator
that parallel-iterates over several controlled sequences and, upon
dereferencing, returns the result of applying a functor to the values of the
sequences at the respective positions. This can now be achieved by using the
``zip_iterator`` in conjunction with the ``transform_iterator``.
Suppose, for example, that you have two vectors of doubles, say
``vect_1`` and ``vect_2``, and you need to expose to a client
a controlled sequence containing the products of the elements of
``vect_1`` and ``vect_2``. Rather than placing these products
in a third vector, you can use a combining iterator that calculates the
products on the fly. Let us assume that ``tuple_multiplies`` is a
functor that works like ``std::multiplies``, except that it takes
its two arguments packaged in a tuple. Then the two iterators
``it_begin`` and ``it_end`` defined below delimit a controlled
sequence containing the products of the elements of ``vect_1`` and
``vect_2``:
::
typedef boost::tuple<
std::vector<double>::const_iterator,
std::vector<double>::const_iterator
> the_iterator_tuple;
typedef boost::zip_iterator<
the_iterator_tuple
> the_zip_iterator;
typedef boost::transform_iterator<
tuple_multiplies<double>,
the_zip_iterator
> the_transform_iterator;
the_transform_iterator it_begin(
the_zip_iterator(
the_iterator_tuple(
vect_1.begin(),
vect_2.begin()
)
),
tuple_multiplies<double>()
);
the_transform_iterator it_end(
the_zip_iterator(
the_iterator_tuple(
vect_1.end(),
vect_2.end()
)
),
tuple_multiplies<double>()
);
The source code for these examples can be found `here`__.
__ ../example/zip_iterator_examples.cpp

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::
template<typename IteratorTuple>
class zip_iterator
{
public:
typedef /* see below */ reference;
typedef reference value_type;
typedef value_type* pointer;
typedef /* see below */ difference_type;
typedef /* see below */ iterator_category;
zip_iterator();
zip_iterator(IteratorTuple iterator_tuple);
template<typename OtherIteratorTuple>
zip_iterator(
const zip_iterator<OtherIteratorTuple>& other
, typename enable_if_convertible<
OtherIteratorTuple
, IteratorTuple>::type* = 0 // exposition only
);
const IteratorTuple& get_iterator_tuple() const;
private:
IteratorTuple m_iterator_tuple; // exposition only
};
template<typename IteratorTuple>
zip_iterator<IteratorTuple>
make_zip_iterator(IteratorTuple t);
The ``reference`` member of ``zip_iterator`` is the type of the tuple
made of the reference types of the iterator types in the ``IteratorTuple``
argument.
The ``difference_type`` member of ``zip_iterator`` is the ``difference_type``
of the first of the iterator types in the ``IteratorTuple`` argument.
The ``iterator_category`` member of ``zip_iterator`` is convertible to the
minimum of the traversal categories of the iterator types in the ``IteratorTuple``
argument. For example, if the ``zip_iterator`` holds only vector
iterators, then ``iterator_category`` is convertible to
``boost::random_access_traversal_tag``. If you add a list iterator, then
``iterator_category`` will be convertible to ``boost::bidirectional_traversal_tag``,
but no longer to ``boost::random_access_traversal_tag``.
``zip_iterator`` requirements
...................................
All iterator types in the argument ``IteratorTuple`` shall model Readable Iterator.
``zip_iterator`` models
.............................
The resulting ``zip_iterator`` models Readable Iterator.
The fact that the ``zip_iterator`` models only Readable Iterator does not
prevent you from modifying the values that the individual iterators point
to. The tuple returned by the ``zip_iterator``'s ``operator*`` is a tuple
constructed from the reference types of the individual iterators, not
their value types. For example, if ``zip_it`` is a ``zip_iterator`` whose
first member iterator is an ``std::vector<double>::iterator``, then the
following line will modify the value which the first member iterator of
``zip_it`` currently points to:
::
zip_it->get<0>() = 42.0;
Consider the set of standard traversal concepts obtained by taking
the most refined standard traversal concept modeled by each individual
iterator type in the ``IteratorTuple`` argument.The ``zip_iterator``
models the least refined standard traversal concept in this set.
``zip_iterator<IteratorTuple1>`` is interoperable with
``zip_iterator<IteratorTuple2>`` if and only if ``IteratorTuple1``
is interoperable with ``IteratorTuple2``.
``zip_iterator`` operations
.................................
In addition to the operations required by the concepts modeled by
``zip_iterator``, ``zip_iterator`` provides the following
operations.
``zip_iterator();``
:Returns: An instance of ``zip_iterator`` with ``m_iterator_tuple``
default constructed.
``zip_iterator(IteratorTuple iterator_tuple);``
:Returns: An instance of ``zip_iterator`` with ``m_iterator_tuple``
initialized to ``iterator_tuple``.
::
template<typename OtherIteratorTuple>
zip_iterator(
const zip_iterator<OtherIteratorTuple>& other
, typename enable_if_convertible<
OtherIteratorTuple
, IteratorTuple>::type* = 0 // exposition only
);
:Returns: An instance of ``zip_iterator`` that is a copy of ``other``.
:Requires: ``OtherIteratorTuple`` is implicitly convertible to ``IteratorTuple``.
``const IteratorTuple& get_iterator_tuple() const;``
:Returns: ``m_iterator_tuple``
``reference operator*() const;``
:Returns: A tuple consisting of the results of dereferencing all iterators in
``m_iterator_tuple``.
``zip_iterator& operator++();``
:Effects: Increments each iterator in ``m_iterator_tuple``.
:Returns: ``*this``
``zip_iterator& operator--();``
:Effects: Decrements each iterator in ``m_iterator_tuple``.
:Returns: ``*this``
::
template<typename IteratorTuple>
zip_iterator<IteratorTuple>
make_zip_iterator(IteratorTuple t);
:Returns: An instance of ``zip_iterator<IteratorTuple>`` with ``m_iterator_tuple``
initialized to ``t``.