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Fixed up definition of facade's iterator_category

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fixed table widths in new-iter-concepts

cross-referenced interoperability concept in iterator_facade_tutorial

iterator_traversal can't satisfy UnaryTypeTrait: that's a boolean trait.


[SVN r21742]
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Dave Abrahams 2004-01-14 23:23:54 +00:00
parent 42147b9e86
commit f1f6262be7
7 changed files with 394 additions and 318 deletions
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65
doc/facade-and-adaptor.html
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@ -693,28 +693,53 @@ template <class Derived, class V, class TC, class R, class D>
Derived operator+ (iterator_facade<Derived, V, TC, R, D> const&,
typename Derived::difference_type n)
</pre>
<a class="target" id="iterator-category" name="iterator-category"></a><p>The <tt class="literal"><span class="pre">iterator_category</span></tt> member of <tt class="literal"><span class="pre">iterator_facade</span></tt> is
<tt class="literal"><span class="pre">facade_iterator_category(CategoryOrTraversal,</span> <span class="pre">value_type,</span>
<span class="pre">reference)</span></tt>, as specified by the following pseudo-code:</p>
<a class="target" id="iterator-category" name="iterator-category"></a><p>The <tt class="literal"><span class="pre">iterator_category</span></tt> member of <tt class="literal"><span class="pre">iterator_facade</span></tt> is</p>
<pre class="literal-block">
facade_iterator_category(C, V, R) =
if (C is convertible to input_iterator_tag or output_iterator_tag) then
return C
else if (C is convertible to incrementable_traversal_tag) then
if (R is a reference type
and C is convertible to forward_traversal_tag) then
if (C is convertible to random_access_traversal_tag)
return a type convertible to random_access_iterator_tag
else if (C is convertible to bidirectional_traversal_tag)
return a type convertible to bidirectional_iterator_tag
else
return a type convertible to forward_iterator_tag
else if (C is convertible to single_pass_traversal_tag
and R is convertible to V)
return a type convertible to input_iterator_tag
else
return C
<em>iterator-category</em>(CategoryOrTraversal, value_type, reference)
</pre>
<p>where <em>iterator-category</em> is defined as follows:</p>
<pre class="literal-block">
<em>iterator-category</em>(C,R,V) :=
if (C is convertible to std::input_iterator_tag
|| C is convertible to std::output_iterator_tag
)
return C
else if (C is not convertible to incrementable_traversal_tag)
<em>the program is ill-formed</em>
else return a type X satisfying the following two constraints:
1. X is convertible to X1, and not to any more-derived
type, where X1 is defined by:
if (R is a reference type
&amp;&amp; C is convertible to forward_traversal_tag)
{
if (C is convertible to random_access_traversal_tag)
X1 = random_access_iterator_tag
else if (C is convertible to bidirectional_traversal_tag)
X1 = bidirectional_iterator_tag
else
X1 = forward_iterator_tag
}
else
{
if (C is convertible to single_pass_traversal_tag
&amp;&amp; R is convertible to V)
X1 = input_iterator_tag
else
X1 = C
}
2. <a class="reference" href="new-iter-concepts.html#category-to-traversal"><em>category-to-traversal</em></a>(X) is convertible to the most
derived traversal tag type to which X is also
convertible, and not to any more-derived traversal tag
type.
</pre>
<p>[Note: the intention is to allow <tt class="literal"><span class="pre">iterator_category</span></tt> to be one of
the five original category tags when convertibility to one of the
traversal tags would add no information]</p>
<!-- Copyright David Abrahams 2004. Use, modification and distribution is -->
<!-- subject to the Boost Software License, Version 1.0. (See accompanying -->
<!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->

61
doc/facade_iterator_category.rst
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@ -1,24 +1,49 @@
.. parsed-literal::
*iterator-category*\ (C,R,V) :=
if (C is convertible to std::input_iterator_tag
|| C is convertible to std::output_iterator_tag
)
return C
else if (C is not convertible to incrementable_traversal_tag)
*the program is ill-formed*
::
else return a type X satisfying the following two constraints:
facade_iterator_category(C, V, R) =
if (C is convertible to input_iterator_tag or output_iterator_tag) then
return C
else if (C is convertible to incrementable_traversal_tag) then
if (R is a reference type
and C is convertible to forward_traversal_tag) then
if (C is convertible to random_access_traversal_tag)
return a type convertible to random_access_iterator_tag
else if (C is convertible to bidirectional_traversal_tag)
return a type convertible to bidirectional_iterator_tag
else
return a type convertible to forward_iterator_tag
else if (C is convertible to single_pass_traversal_tag
and R is convertible to V)
return a type convertible to input_iterator_tag
else
return C
1. X is convertible to X1, and not to any more-derived
type, where X1 is defined by:
if (R is a reference type
&& C is convertible to forward_traversal_tag)
{
if (C is convertible to random_access_traversal_tag)
X1 = random_access_iterator_tag
else if (C is convertible to bidirectional_traversal_tag)
X1 = bidirectional_iterator_tag
else
X1 = forward_iterator_tag
}
else
{
if (C is convertible to single_pass_traversal_tag
&& R is convertible to V)
X1 = input_iterator_tag
else
X1 = C
}
2. |category-to-traversal|_\ (X) is convertible to the most
derived traversal tag type to which X is also
convertible, and not to any more-derived traversal tag
type.
.. |category-to-traversal| replace:: *category-to-traversal*
.. _`category-to-traversal`: new-iter-concepts.html#category-to-traversal
[Note: the intention is to allow ``iterator_category`` to be one of
the five original category tags when convertibility to one of the
traversal tags would add no information]
.. Copyright David Abrahams 2004. Use, modification and distribution is
.. subject to the Boost Software License, Version 1.0. (See accompanying

159
doc/iterator_facade.html
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@ -45,43 +45,43 @@ and associated types, to be supplied by a derived iterator class.</td>
<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="#overview" id="id20" name="id20">Overview</a><ul>
<li><a class="reference" href="#usage" id="id21" name="id21">Usage</a></li>
<li><a class="reference" href="#iterator-core-access" id="id22" name="id22">Iterator Core Access</a></li>
<li><a class="reference" href="#operator" id="id23" name="id23"><tt class="literal"><span class="pre">operator[]</span></tt></a></li>
<li><a class="reference" href="#id2" id="id24" name="id24"><tt class="literal"><span class="pre">operator-&gt;</span></tt></a></li>
<li><a class="reference" href="#overview" id="id21" name="id21">Overview</a><ul>
<li><a class="reference" href="#usage" id="id22" name="id22">Usage</a></li>
<li><a class="reference" href="#iterator-core-access" id="id23" name="id23">Iterator Core Access</a></li>
<li><a class="reference" href="#operator" id="id24" name="id24"><tt class="literal"><span class="pre">operator[]</span></tt></a></li>
<li><a class="reference" href="#id2" id="id25" name="id25"><tt class="literal"><span class="pre">operator-&gt;</span></tt></a></li>
</ul>
</li>
<li><a class="reference" href="#reference" id="id25" name="id25">Reference</a><ul>
<li><a class="reference" href="#iterator-facade-requirements" id="id26" name="id26"><tt class="literal"><span class="pre">iterator_facade</span></tt> Requirements</a></li>
<li><a class="reference" href="#iterator-facade-operations" id="id27" name="id27"><tt class="literal"><span class="pre">iterator_facade</span></tt> operations</a></li>
<li><a class="reference" href="#reference" id="id26" name="id26">Reference</a><ul>
<li><a class="reference" href="#iterator-facade-requirements" id="id27" name="id27"><tt class="literal"><span class="pre">iterator_facade</span></tt> Requirements</a></li>
<li><a class="reference" href="#iterator-facade-operations" id="id28" name="id28"><tt class="literal"><span class="pre">iterator_facade</span></tt> operations</a></li>
</ul>
</li>
<li><a class="reference" href="#tutorial-example" id="id28" name="id28">Tutorial Example</a><ul>
<li><a class="reference" href="#the-problem" id="id29" name="id29">The Problem</a></li>
<li><a class="reference" href="#a-basic-iterator-using-iterator-facade" id="id30" name="id30">A Basic Iterator Using <tt class="literal"><span class="pre">iterator_facade</span></tt></a><ul>
<li><a class="reference" href="#template-arguments-for-iterator-facade" id="id31" name="id31">Template Arguments for <tt class="literal"><span class="pre">iterator_facade</span></tt></a><ul>
<li><a class="reference" href="#derived" id="id32" name="id32"><tt class="literal"><span class="pre">Derived</span></tt></a></li>
<li><a class="reference" href="#value" id="id33" name="id33"><tt class="literal"><span class="pre">Value</span></tt></a></li>
<li><a class="reference" href="#categoryortraversal" id="id34" name="id34"><tt class="literal"><span class="pre">CategoryOrTraversal</span></tt></a></li>
<li><a class="reference" href="#id10" id="id35" name="id35"><tt class="literal"><span class="pre">Reference</span></tt></a></li>
<li><a class="reference" href="#difference" id="id36" name="id36"><tt class="literal"><span class="pre">Difference</span></tt></a></li>
<li><a class="reference" href="#tutorial-example" id="id29" name="id29">Tutorial Example</a><ul>
<li><a class="reference" href="#the-problem" id="id30" name="id30">The Problem</a></li>
<li><a class="reference" href="#a-basic-iterator-using-iterator-facade" id="id31" name="id31">A Basic Iterator Using <tt class="literal"><span class="pre">iterator_facade</span></tt></a><ul>
<li><a class="reference" href="#template-arguments-for-iterator-facade" id="id32" name="id32">Template Arguments for <tt class="literal"><span class="pre">iterator_facade</span></tt></a><ul>
<li><a class="reference" href="#derived" id="id33" name="id33"><tt class="literal"><span class="pre">Derived</span></tt></a></li>
<li><a class="reference" href="#value" id="id34" name="id34"><tt class="literal"><span class="pre">Value</span></tt></a></li>
<li><a class="reference" href="#categoryortraversal" id="id35" name="id35"><tt class="literal"><span class="pre">CategoryOrTraversal</span></tt></a></li>
<li><a class="reference" href="#id10" id="id36" name="id36"><tt class="literal"><span class="pre">Reference</span></tt></a></li>
<li><a class="reference" href="#difference" id="id37" name="id37"><tt class="literal"><span class="pre">Difference</span></tt></a></li>
</ul>
</li>
<li><a class="reference" href="#constructors-and-data-members" id="id37" name="id37">Constructors and Data Members</a></li>
<li><a class="reference" href="#implementing-the-core-operations" id="id38" name="id38">Implementing the Core Operations</a></li>
<li><a class="reference" href="#constructors-and-data-members" id="id38" name="id38">Constructors and Data Members</a></li>
<li><a class="reference" href="#implementing-the-core-operations" id="id39" name="id39">Implementing the Core Operations</a></li>
</ul>
</li>
<li><a class="reference" href="#a-constant-node-iterator" id="id39" name="id39">A constant <tt class="literal"><span class="pre">node_iterator</span></tt></a></li>
<li><a class="reference" href="#interoperability" id="id40" name="id40">Interoperability</a></li>
<li><a class="reference" href="#telling-the-truth" id="id41" name="id41">Telling the Truth</a></li>
<li><a class="reference" href="#wrap-up" id="id42" name="id42">Wrap Up</a></li>
<li><a class="reference" href="#a-constant-node-iterator" id="id40" name="id40">A constant <tt class="literal"><span class="pre">node_iterator</span></tt></a></li>
<li><a class="reference" href="#interoperability" id="id41" name="id41">Interoperability</a></li>
<li><a class="reference" href="#telling-the-truth" id="id42" name="id42">Telling the Truth</a></li>
<li><a class="reference" href="#wrap-up" id="id43" name="id43">Wrap Up</a></li>
</ul>
</li>
</ul>
</div>
<div class="section" id="overview">
<h1><a class="toc-backref" href="#id20" name="overview">Overview</a></h1>
<h1><a class="toc-backref" href="#id21" name="overview">Overview</a></h1>
<!-- Version 1.1 of this ReStructuredText document corresponds to
n1530_, the paper accepted by the LWG for TR1. -->
<!-- Copyright David Abrahams, Jeremy Siek, and Thomas Witt 2003. All
@ -126,7 +126,7 @@ impossible.</li>
</ol>
</blockquote>
<div class="section" id="usage">
<h2><a class="toc-backref" href="#id21" name="usage">Usage</a></h2>
<h2><a class="toc-backref" href="#id22" name="usage">Usage</a></h2>
<p>The user of <tt class="literal"><span class="pre">iterator_facade</span></tt> derives his iterator class from a
specialization of <tt class="literal"><span class="pre">iterator_facade</span></tt> and passes the derived
iterator class as <tt class="literal"><span class="pre">iterator_facade</span></tt>'s first template parameter.
@ -190,7 +190,7 @@ Iterator or a more-refined iterator concept, a default constructor is
required.</p>
</div>
<div class="section" id="iterator-core-access">
<h2><a class="toc-backref" href="#id22" name="iterator-core-access">Iterator Core Access</a></h2>
<h2><a class="toc-backref" href="#id23" name="iterator-core-access">Iterator Core Access</a></h2>
<p><tt class="literal"><span class="pre">iterator_facade</span></tt> and the operator implementations need to be able
to access the core member functions in the derived class. Making the
core member functions public would expose an implementation detail to
@ -224,7 +224,7 @@ open a safety loophole, as every core member function preserves the
invariants of the iterator.</p>
</div>
<div class="section" id="operator">
<h2><a class="toc-backref" href="#id23" name="operator"><tt class="literal"><span class="pre">operator[]</span></tt></a></h2>
<h2><a class="toc-backref" href="#id24" name="operator"><tt class="literal"><span class="pre">operator[]</span></tt></a></h2>
<p>The indexing operator for a generalized iterator presents special
challenges. A random access iterator's <tt class="literal"><span class="pre">operator[]</span></tt> is only
required to return something convertible to its <tt class="literal"><span class="pre">value_type</span></tt>.
@ -247,7 +247,7 @@ class; it will hide the one supplied by <tt class="literal"><span class="pre">it
clients of her iterator.</p>
<a class="target" id="operator-arrow" name="operator-arrow"></a></div>
<div class="section" id="id2">
<h2><a class="toc-backref" href="#id24" name="id2"><tt class="literal"><span class="pre">operator-&gt;</span></tt></a></h2>
<h2><a class="toc-backref" href="#id25" name="id2"><tt class="literal"><span class="pre">operator-&gt;</span></tt></a></h2>
<p>The <tt class="literal"><span class="pre">reference</span></tt> type of a readable iterator (and today's input
iterator) need not in fact be a reference, so long as it is
convertible to the iterator's <tt class="literal"><span class="pre">value_type</span></tt>. When the <tt class="literal"><span class="pre">value_type</span></tt>
@ -270,7 +270,7 @@ Patterns, C++ Report, February 1995, pp. 24-27.</td></tr>
</div>
</div>
<div class="section" id="reference">
<h1><a class="toc-backref" href="#id25" name="reference">Reference</a></h1>
<h1><a class="toc-backref" href="#id26" name="reference">Reference</a></h1>
<!-- Version 1.3 of this ReStructuredText document corresponds to
n1530_, the paper accepted by the LWG for TR1. -->
<!-- Copyright David Abrahams, Jeremy Siek, and Thomas Witt 2003. All
@ -358,28 +358,53 @@ template &lt;class Derived, class V, class TC, class R, class D&gt;
Derived operator+ (iterator_facade&lt;Derived, V, TC, R, D&gt; const&amp;,
typename Derived::difference_type n)
</pre>
<a class="target" id="iterator-category" name="iterator-category"></a><p>The <tt class="literal"><span class="pre">iterator_category</span></tt> member of <tt class="literal"><span class="pre">iterator_facade</span></tt> is
<tt class="literal"><span class="pre">facade_iterator_category(CategoryOrTraversal,</span> <span class="pre">value_type,</span>
<span class="pre">reference)</span></tt>, as specified by the following pseudo-code:</p>
<a class="target" id="iterator-category" name="iterator-category"></a><p>The <tt class="literal"><span class="pre">iterator_category</span></tt> member of <tt class="literal"><span class="pre">iterator_facade</span></tt> is</p>
<pre class="literal-block">
facade_iterator_category(C, V, R) =
if (C is convertible to input_iterator_tag or output_iterator_tag) then
return C
else if (C is convertible to incrementable_traversal_tag) then
if (R is a reference type
and C is convertible to forward_traversal_tag) then
if (C is convertible to random_access_traversal_tag)
return a type convertible to random_access_iterator_tag
else if (C is convertible to bidirectional_traversal_tag)
return a type convertible to bidirectional_iterator_tag
else
return a type convertible to forward_iterator_tag
else if (C is convertible to single_pass_traversal_tag
and R is convertible to V)
return a type convertible to input_iterator_tag
else
return C
<em>iterator-category</em>(CategoryOrTraversal, value_type, reference)
</pre>
<p>where <em>iterator-category</em> is defined as follows:</p>
<pre class="literal-block">
<em>iterator-category</em>(C,R,V) :=
if (C is convertible to std::input_iterator_tag
|| C is convertible to std::output_iterator_tag
)
return C
else if (C is not convertible to incrementable_traversal_tag)
<em>the program is ill-formed</em>
else return a type X satisfying the following two constraints:
1. X is convertible to X1, and not to any more-derived
type, where X1 is defined by:
if (R is a reference type
&amp;&amp; C is convertible to forward_traversal_tag)
{
if (C is convertible to random_access_traversal_tag)
X1 = random_access_iterator_tag
else if (C is convertible to bidirectional_traversal_tag)
X1 = bidirectional_iterator_tag
else
X1 = forward_iterator_tag
}
else
{
if (C is convertible to single_pass_traversal_tag
&amp;&amp; R is convertible to V)
X1 = input_iterator_tag
else
X1 = C
}
2. <a class="reference" href="new-iter-concepts.html#category-to-traversal"><em>category-to-traversal</em></a>(X) is convertible to the most
derived traversal tag type to which X is also
convertible, and not to any more-derived traversal tag
type.
</pre>
<p>[Note: the intention is to allow <tt class="literal"><span class="pre">iterator_category</span></tt> to be one of
the five original category tags when convertibility to one of the
traversal tags would add no information]</p>
<!-- Copyright David Abrahams 2004. Use, modification and distribution is -->
<!-- subject to the Boost Software License, Version 1.0. (See accompanying -->
<!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
@ -415,7 +440,7 @@ struct enable_if_interoperable
{};
</pre>
<div class="section" id="iterator-facade-requirements">
<h2><a class="toc-backref" href="#id26" name="iterator-facade-requirements"><tt class="literal"><span class="pre">iterator_facade</span></tt> Requirements</a></h2>
<h2><a class="toc-backref" href="#id27" name="iterator-facade-requirements"><tt class="literal"><span class="pre">iterator_facade</span></tt> Requirements</a></h2>
<p>The following table describes the typical valid expressions on
<tt class="literal"><span class="pre">iterator_facade</span></tt>'s <tt class="literal"><span class="pre">Derived</span></tt> parameter, depending on the
iterator concept(s) it will model. The operations in the first
@ -486,7 +511,7 @@ Iterator</td>
</div>
</div>
<div class="section" id="iterator-facade-operations">
<h2><a class="toc-backref" href="#id27" name="iterator-facade-operations"><tt class="literal"><span class="pre">iterator_facade</span></tt> operations</a></h2>
<h2><a class="toc-backref" href="#id28" name="iterator-facade-operations"><tt class="literal"><span class="pre">iterator_facade</span></tt> operations</a></h2>
<p>The operations in this section are described in terms of operations on
the core interface of <tt class="literal"><span class="pre">Derived</span></tt> which may be inaccessible
(i.e. private). The implementation should access these operations
@ -627,7 +652,7 @@ return tmp -= n;
</div>
</div>
<div class="section" id="tutorial-example">
<h1><a class="toc-backref" href="#id28" name="tutorial-example">Tutorial Example</a></h1>
<h1><a class="toc-backref" href="#id29" name="tutorial-example">Tutorial Example</a></h1>
<!-- Copyright David Abrahams 2004. Use, modification and distribution is -->
<!-- subject to the Boost Software License, Version 1.0. (See accompanying -->
<!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
@ -637,7 +662,7 @@ example of a linked list of polymorphic objects. This example was
inspired by a <a class="reference" href="http://thread.gmane.org/gmane.comp.lib.boost.user/5100">posting</a> by Keith Macdonald on the <a class="reference" href="../../../more/mailing_lists.htm#users">Boost-Users</a>
mailing list.</p>
<div class="section" id="the-problem">
<h2><a class="toc-backref" href="#id29" name="the-problem">The Problem</a></h2>
<h2><a class="toc-backref" href="#id30" name="the-problem">The Problem</a></h2>
<p>Say we've written a polymorphic linked list node base class:</p>
<pre class="literal-block">
# include &lt;iostream&gt;
@ -699,7 +724,7 @@ inline std::ostream&amp; operator&lt;&lt;(std::ostream&amp; s, node_base const&a
lists.</p>
</div>
<div class="section" id="a-basic-iterator-using-iterator-facade">
<h2><a class="toc-backref" href="#id30" name="a-basic-iterator-using-iterator-facade">A Basic Iterator Using <tt class="literal"><span class="pre">iterator_facade</span></tt></a></h2>
<h2><a class="toc-backref" href="#id31" name="a-basic-iterator-using-iterator-facade">A Basic Iterator Using <tt class="literal"><span class="pre">iterator_facade</span></tt></a></h2>
<p>We will construct a <tt class="literal"><span class="pre">node_iterator</span></tt> class using inheritance from
<tt class="literal"><span class="pre">iterator_facade</span></tt> to implement most of the iterator's operations.</p>
<pre class="literal-block">
@ -713,24 +738,24 @@ class node_iterator
};
</pre>
<div class="section" id="template-arguments-for-iterator-facade">
<h3><a class="toc-backref" href="#id31" name="template-arguments-for-iterator-facade">Template Arguments for <tt class="literal"><span class="pre">iterator_facade</span></tt></a></h3>
<h3><a class="toc-backref" href="#id32" name="template-arguments-for-iterator-facade">Template Arguments for <tt class="literal"><span class="pre">iterator_facade</span></tt></a></h3>
<p><tt class="literal"><span class="pre">iterator_facade</span></tt> has several template parameters, so we must decide
what types to use for the arguments. The parameters are <tt class="literal"><span class="pre">Derived</span></tt>,
<tt class="literal"><span class="pre">Value</span></tt>, <tt class="literal"><span class="pre">CategoryOrTraversal</span></tt>, <tt class="literal"><span class="pre">Reference</span></tt>, and <tt class="literal"><span class="pre">Difference</span></tt>.</p>
<div class="section" id="derived">
<h4><a class="toc-backref" href="#id32" name="derived"><tt class="literal"><span class="pre">Derived</span></tt></a></h4>
<h4><a class="toc-backref" href="#id33" name="derived"><tt class="literal"><span class="pre">Derived</span></tt></a></h4>
<p>Because <tt class="literal"><span class="pre">iterator_facade</span></tt> is meant to be used with the CRTP
<a class="citation-reference" href="#cop95" id="id8" name="id8">[Cop95]</a> the first parameter is the iterator class name itself,
<tt class="literal"><span class="pre">node_iterator</span></tt>.</p>
</div>
<div class="section" id="value">
<h4><a class="toc-backref" href="#id33" name="value"><tt class="literal"><span class="pre">Value</span></tt></a></h4>
<h4><a class="toc-backref" href="#id34" name="value"><tt class="literal"><span class="pre">Value</span></tt></a></h4>
<p>The <tt class="literal"><span class="pre">Value</span></tt> parameter determines the <tt class="literal"><span class="pre">node_iterator</span></tt>'s
<tt class="literal"><span class="pre">value_type</span></tt>. In this case, we are iterating over <tt class="literal"><span class="pre">node_base</span></tt>
objects, so <tt class="literal"><span class="pre">Value</span></tt> will be <tt class="literal"><span class="pre">node_base</span></tt>.</p>
</div>
<div class="section" id="categoryortraversal">
<h4><a class="toc-backref" href="#id34" name="categoryortraversal"><tt class="literal"><span class="pre">CategoryOrTraversal</span></tt></a></h4>
<h4><a class="toc-backref" href="#id35" name="categoryortraversal"><tt class="literal"><span class="pre">CategoryOrTraversal</span></tt></a></h4>
<p>Now we have to determine which <a class="reference" href="new-iter-concepts.html#iterator-traversal-concepts-lib-iterator-traversal">iterator traversal concept</a> our
<tt class="literal"><span class="pre">node_iterator</span></tt> is going to model. Singly-linked lists only have
forward links, so our iterator can't can't be a <a class="reference" href="new-iter-concepts.html#bidirectional-traversal-iterators-lib-bidirectional-traversal-iterators">bidirectional
@ -750,7 +775,7 @@ end up being <tt class="literal"><span class="pre">std::forward_iterator_tag</sp
</table>
</div>
<div class="section" id="id10">
<h4><a class="toc-backref" href="#id35" name="id10"><tt class="literal"><span class="pre">Reference</span></tt></a></h4>
<h4><a class="toc-backref" href="#id36" name="id10"><tt class="literal"><span class="pre">Reference</span></tt></a></h4>
<p>The <tt class="literal"><span class="pre">Reference</span></tt> argument becomes the type returned by
<tt class="literal"><span class="pre">node_iterator</span></tt>'s dereference operation, and will also be the
same as <tt class="literal"><span class="pre">std::iterator_traits&lt;node_iterator&gt;::reference</span></tt>. The
@ -759,7 +784,7 @@ library's default for this parameter is <tt class="literal"><span class="pre">Va
type, we can omit this argument, or pass <tt class="literal"><span class="pre">use_default</span></tt>.</p>
</div>
<div class="section" id="difference">
<h4><a class="toc-backref" href="#id36" name="difference"><tt class="literal"><span class="pre">Difference</span></tt></a></h4>
<h4><a class="toc-backref" href="#id37" name="difference"><tt class="literal"><span class="pre">Difference</span></tt></a></h4>
<p>The <tt class="literal"><span class="pre">Difference</span></tt> argument determines how the distance between
two <tt class="literal"><span class="pre">node_iterator</span></tt>s will be measured and will also be the
same as <tt class="literal"><span class="pre">std::iterator_traits&lt;node_iterator&gt;::difference_type</span></tt>.
@ -786,7 +811,7 @@ class node_iterator
</div>
</div>
<div class="section" id="constructors-and-data-members">
<h3><a class="toc-backref" href="#id37" name="constructors-and-data-members">Constructors and Data Members</a></h3>
<h3><a class="toc-backref" href="#id38" name="constructors-and-data-members">Constructors and Data Members</a></h3>
<p>Next we need to decide how to represent the iterator's position.
This representation will take the form of data members, so we'll
also need to write constructors to initialize them. The
@ -831,7 +856,7 @@ default constructor to leave <tt class="literal"><span class="pre">m_node</span>
</table>
</div>
<div class="section" id="implementing-the-core-operations">
<h3><a class="toc-backref" href="#id38" name="implementing-the-core-operations">Implementing the Core Operations</a></h3>
<h3><a class="toc-backref" href="#id39" name="implementing-the-core-operations">Implementing the Core Operations</a></h3>
<p>The last step is to implement the <a class="reference" href="#core-operations">core operations</a> required by
the concepts we want our iterator to model. Referring to the
<a class="reference" href="#core-operations">table</a>, we can see that the first three rows are applicable
@ -882,7 +907,7 @@ iterator! For a working example of its use, see <a class="reference" href="../e
</div>
</div>
<div class="section" id="a-constant-node-iterator">
<h2><a class="toc-backref" href="#id39" name="a-constant-node-iterator">A constant <tt class="literal"><span class="pre">node_iterator</span></tt></a></h2>
<h2><a class="toc-backref" href="#id40" name="a-constant-node-iterator">A constant <tt class="literal"><span class="pre">node_iterator</span></tt></a></h2>
<div class="sidebar">
<p class="sidebar-title">Constant and Mutable iterators</p>
<p>The term <strong>mutable iterator</strong> means an iterator through which
@ -983,7 +1008,7 @@ typedef node_iter&lt;node_base const&gt; node_const_iterator;
</pre>
</div>
<div class="section" id="interoperability">
<h2><a class="toc-backref" href="#id40" name="interoperability">Interoperability</a></h2>
<h2><a class="toc-backref" href="#id41" name="interoperability">Interoperability</a></h2>
<p>Our <tt class="literal"><span class="pre">const_node_iterator</span></tt> works perfectly well on its own, but
taken together with <tt class="literal"><span class="pre">node_iterator</span></tt> it doesn't quite meet
expectations. For example, we'd like to be able to pass a
@ -993,7 +1018,7 @@ just as you can with <tt class="literal"><span class="pre">std::list&lt;int&gt;<
<tt class="literal"><span class="pre">node_const_iterator</span></tt> into the same list, we should be able to
compare them for equality.</p>
<p>This expected ability to use two different iterator types together
is known as <strong>interoperability</strong>. Achieving interoperability in
is known as <a class="reference" href="new-iter-concepts.html#interoperable-iterators-lib-interoperable-iterators"><strong>interoperability</strong></a>. Achieving interoperability in
our case is as simple as templatizing the <tt class="literal"><span class="pre">equal</span></tt> function and
adding a templatized converting constructor <a class="footnote-reference" href="#broken" id="id14" name="id14"><sup>3</sup></a> <a class="footnote-reference" href="#random" id="id15" name="id15"><sup>4</sup></a>:</p>
<pre class="literal-block">
@ -1056,7 +1081,7 @@ traversal iterator</a>, we'd have had to templatize its
iterators <a class="reference" href="../example/node_iterator2.cpp">here</a>.</p>
</div>
<div class="section" id="telling-the-truth">
<h2><a class="toc-backref" href="#id41" name="telling-the-truth">Telling the Truth</a></h2>
<h2><a class="toc-backref" href="#id42" name="telling-the-truth">Telling the Truth</a></h2>
<p>Now <tt class="literal"><span class="pre">node_iterator</span></tt> and <tt class="literal"><span class="pre">node_const_iterator</span></tt> behave exactly as
you'd expect... almost. We can compare them and we can convert in
one direction: from <tt class="literal"><span class="pre">node_iterator</span></tt> to <tt class="literal"><span class="pre">node_const_iterator</span></tt>.
@ -1094,7 +1119,7 @@ appropriate:</p>
</pre>
</div>
<div class="section" id="wrap-up">
<h2><a class="toc-backref" href="#id42" name="wrap-up">Wrap Up</a></h2>
<h2><a class="toc-backref" href="#id43" name="wrap-up">Wrap Up</a></h2>
<p>This concludes our <tt class="literal"><span class="pre">iterator_facade</span></tt> tutorial, but before you
stop reading we urge you to take a look at <a class="reference" href="iterator_adaptor.html"><tt class="literal"><span class="pre">iterator_adaptor</span></tt></a>.
There's another way to approach writing these iterators which might

10
doc/iterator_facade_ref.rst
View File

@ -97,9 +97,13 @@ __ brackets_
.. _`iterator category`:
The ``iterator_category`` member of ``iterator_facade`` is
``facade_iterator_category(CategoryOrTraversal, value_type,
reference)``, as specified by the following pseudo-code:
The ``iterator_category`` member of ``iterator_facade`` is
.. parsed-literal::
*iterator-category*\ (CategoryOrTraversal, value_type, reference)
where *iterator-category* is defined as follows:
.. include:: facade_iterator_category.rst

5
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View File

@ -388,7 +388,7 @@ just as you can with ``std::list<int>``\ 's ``iterator`` and
compare them for equality.
This expected ability to use two different iterator types together
is known as **interoperability**. Achieving interoperability in
is known as |interoperability|_. Achieving interoperability in
our case is as simple as templatizing the ``equal`` function and
adding a templatized converting constructor [#broken]_ [#random]_::
@ -432,6 +432,9 @@ adding a templatized converting constructor [#broken]_ [#random]_::
typedef impl::node_iterator<node_base> node_iterator;
typedef impl::node_iterator<node_base const> node_const_iterator;
.. |interoperability| replace:: **interoperability**
.. _interoperability: new-iter-concepts.html#interoperable-iterators-lib-interoperable-iterators
.. [#broken] If you're using an older compiler and it can't handle
this example, see the `example code`__ for workarounds.

95
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View File

@ -476,9 +476,9 @@ type of <tt class="literal"><span class="pre">operator*</span></tt> type be a re
iterator.</p>
<table border class="table">
<colgroup>
<col width="42%" />
<col width="14%" />
<col width="44%" />
<col width="22%" />
<col width="19%" />
<col width="59%" />
</colgroup>
<thead valign="bottom">
<tr><th colspan="3">Lvalue Iterator Requirements</th>
@ -659,12 +659,13 @@ Forward Traversal Iterator, the following expressions are valid and
respect the stated semantics.</p>
<table border class="table">
<colgroup>
<col width="35%" />
<col width="44%" />
<col width="21%" />
<col width="38%" />
<col width="37%" />
<col width="25%" />
</colgroup>
<thead valign="bottom">
<tr><th colspan="3">Bidirectional Traversal Iterator Requirements (in addition to Forward Traversal Iterator)</th>
<tr><th colspan="3">Bidirectional Traversal Iterator Requirements (in addition to Forward Traversal
Iterator)</th>
</tr>
<tr><th>Expression</th>
<th>Return Type</th>
@ -715,10 +716,10 @@ the stated semantics. In the table below, <tt class="literal"><span class="pre"
constant object of type <tt class="literal"><span class="pre">Distance</span></tt>.</p>
<table border class="table">
<colgroup>
<col width="31%" />
<col width="35%" />
<col width="18%" />
<col width="16%" />
<col width="28%" />
<col width="30%" />
<col width="23%" />
<col width="20%" />
</colgroup>
<thead valign="bottom">
<tr><th colspan="4">Random Access Traversal Iterator Requirements (in addition to Bidirectional Traversal Iterator)</th>
@ -831,9 +832,9 @@ of type <tt class="literal"><span class="pre">X</span></tt>, <tt class="literal"
constant object of type <tt class="literal"><span class="pre">Distance</span></tt>.</p>
<table border class="table">
<colgroup>
<col width="30%" />
<col width="34%" />
<col width="36%" />
<col width="13%" />
<col width="27%" />
<col width="60%" />
</colgroup>
<thead valign="bottom">
<tr><th>Expression</th>
@ -872,43 +873,38 @@ constant object of type <tt class="literal"><span class="pre">Distance</span></t
the following additional requirements must be met.</p>
<table border class="table">
<colgroup>
<col width="31%" />
<col width="35%" />
<col width="18%" />
<col width="16%" />
<col width="12%" />
<col width="25%" />
<col width="23%" />
<col width="41%" />
</colgroup>
<thead valign="bottom">
<tr><th>Expression</th>
<th>Return Type</th>
<th>Operational Semantics</th>
<th>Assertion/
Precondition</th>
<th>Assertion/ Precondition</th>
</tr>
</thead>
<tbody valign="top">
<tr><td><tt class="literal"><span class="pre">x</span> <span class="pre">&lt;</span> <span class="pre">y</span></tt></td>
<td>convertible to <tt class="literal"><span class="pre">bool</span></tt></td>
<td><tt class="literal"><span class="pre">y</span> <span class="pre">-</span> <span class="pre">x</span> <span class="pre">&gt;</span> <span class="pre">0</span></tt></td>
<td><tt class="literal"><span class="pre">&lt;</span></tt> is a total
ordering relation</td>
<td><tt class="literal"><span class="pre">&lt;</span></tt> is a total ordering relation</td>
</tr>
<tr><td><tt class="literal"><span class="pre">y</span> <span class="pre">&lt;</span> <span class="pre">x</span></tt></td>
<td>convertible to <tt class="literal"><span class="pre">bool</span></tt></td>
<td><tt class="literal"><span class="pre">x</span> <span class="pre">-</span> <span class="pre">y</span> <span class="pre">&gt;</span> <span class="pre">0</span></tt></td>
<td><tt class="literal"><span class="pre">&lt;</span></tt> is a total
ordering relation</td>
<td><tt class="literal"><span class="pre">&lt;</span></tt> is a total ordering relation</td>
</tr>
<tr><td><tt class="literal"><span class="pre">x</span> <span class="pre">&gt;</span> <span class="pre">y</span></tt></td>
<td>convertible to <tt class="literal"><span class="pre">bool</span></tt></td>
<td><tt class="literal"><span class="pre">y</span> <span class="pre">&lt;</span> <span class="pre">x</span></tt></td>
<td><tt class="literal"><span class="pre">&gt;</span></tt> is a total
ordering relation</td>
<td><tt class="literal"><span class="pre">&gt;</span></tt> is a total ordering relation</td>
</tr>
<tr><td><tt class="literal"><span class="pre">y</span> <span class="pre">&gt;</span> <span class="pre">x</span></tt></td>
<td>convertible to <tt class="literal"><span class="pre">bool</span></tt></td>
<td><tt class="literal"><span class="pre">x</span> <span class="pre">&lt;</span> <span class="pre">y</span></tt></td>
<td><tt class="literal"><span class="pre">&gt;</span></tt> is a total
ordering relation</td>
<td><tt class="literal"><span class="pre">&gt;</span></tt> is a total ordering relation</td>
</tr>
<tr><td><tt class="literal"><span class="pre">x</span> <span class="pre">&gt;=</span> <span class="pre">y</span></tt></td>
<td>convertible to <tt class="literal"><span class="pre">bool</span></tt></td>
@ -933,20 +929,16 @@ ordering relation</td>
<tr><td><tt class="literal"><span class="pre">y</span> <span class="pre">-</span> <span class="pre">x</span></tt></td>
<td><tt class="literal"><span class="pre">Distance</span></tt></td>
<td><tt class="literal"><span class="pre">distance(Y(x),y)</span></tt></td>
<td>pre: there exists a
value <tt class="literal"><span class="pre">n</span></tt> of
<tt class="literal"><span class="pre">Distance</span></tt> such that
<tt class="literal"><span class="pre">x</span> <span class="pre">+</span> <span class="pre">n</span> <span class="pre">==</span> <span class="pre">y</span></tt>. <tt class="literal"><span class="pre">y</span>
<span class="pre">==</span> <span class="pre">x</span> <span class="pre">+</span> <span class="pre">(y</span> <span class="pre">-</span> <span class="pre">x)</span></tt>.</td>
<td>pre: there exists a value <tt class="literal"><span class="pre">n</span></tt> of
<tt class="literal"><span class="pre">Distance</span></tt> such that <tt class="literal"><span class="pre">x</span> <span class="pre">+</span> <span class="pre">n</span> <span class="pre">==</span> <span class="pre">y</span></tt>.
<tt class="literal"><span class="pre">y</span> <span class="pre">==</span> <span class="pre">x</span> <span class="pre">+</span> <span class="pre">(y</span> <span class="pre">-</span> <span class="pre">x)</span></tt>.</td>
</tr>
<tr><td><tt class="literal"><span class="pre">x</span> <span class="pre">-</span> <span class="pre">y</span></tt></td>
<td><tt class="literal"><span class="pre">Distance</span></tt></td>
<td><tt class="literal"><span class="pre">distance(y,Y(x))</span></tt></td>
<td>pre: there exists a
value <tt class="literal"><span class="pre">n</span></tt> of
<tt class="literal"><span class="pre">Distance</span></tt> such that
<tt class="literal"><span class="pre">y</span> <span class="pre">+</span> <span class="pre">n</span> <span class="pre">==</span> <span class="pre">x</span></tt>. <tt class="literal"><span class="pre">x</span>
<span class="pre">==</span> <span class="pre">y</span> <span class="pre">+</span> <span class="pre">(x</span> <span class="pre">-</span> <span class="pre">y)</span></tt>.</td>
<td>pre: there exists a value <tt class="literal"><span class="pre">n</span></tt> of
<tt class="literal"><span class="pre">Distance</span></tt> such that <tt class="literal"><span class="pre">y</span> <span class="pre">+</span> <span class="pre">n</span> <span class="pre">==</span> <span class="pre">x</span></tt>.
<tt class="literal"><span class="pre">x</span> <span class="pre">==</span> <span class="pre">y</span> <span class="pre">+</span> <span class="pre">(x</span> <span class="pre">-</span> <span class="pre">y)</span></tt>.</td>
</tr>
</tbody>
</table>
@ -969,27 +961,30 @@ struct random_access_traversal_tag : bidirectional_traversal_tag { };
</div>
<div class="section" id="addition-to-lib-iterator-traits">
<h2><a class="toc-backref" href="#id23" name="addition-to-lib-iterator-traits">Addition to [lib.iterator.traits]</a></h2>
<p>The <tt class="literal"><span class="pre">is_readable_iterator</span></tt> and <tt class="literal"><span class="pre">iterator_traversal</span></tt> class
templates satisfy the <a class="reference" href="http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/papers/2003/n1519.htm">UnaryTypeTrait</a> requirements.</p>
<p>The <tt class="literal"><span class="pre">is_readable_iterator</span></tt> class
template satisfies the <a class="reference" href="http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/papers/2003/n1519.htm">UnaryTypeTrait</a> requirements.</p>
<p>Given an iterator type <tt class="literal"><span class="pre">X</span></tt>, <tt class="literal"><span class="pre">is_readable_iterator&lt;X&gt;::value</span></tt>
yields <tt class="literal"><span class="pre">true</span></tt> if, for an object <tt class="literal"><span class="pre">a</span></tt> of type <tt class="literal"><span class="pre">X</span></tt>, <tt class="literal"><span class="pre">*a</span></tt> is
convertible to <tt class="literal"><span class="pre">iterator_traits&lt;X&gt;::value_type</span></tt>, and <tt class="literal"><span class="pre">false</span></tt>
otherwise.</p>
<p><tt class="literal"><span class="pre">iterator_traversal&lt;X&gt;::type</span></tt> is defined to be:</p>
<p><tt class="literal"><span class="pre">iterator_traversal&lt;X&gt;::type</span></tt> is</p>
<pre class="literal-block">
traversal-category(X) =
cat = iterator_traits&lt;X&gt;::iterator_category;
if (cat is convertible to incrementable_traversal_tag)
return cat;
else if (cat is convertible to random_access_iterator_tag)
<em>category-to-traversal</em>(iterator_traits&lt;X&gt;::iterator_category)
</pre>
<p>where <em>category-to-traversal</em> is defined as follows</p>
<a class="target" id="category-to-traversal" name="category-to-traversal"></a><pre class="literal-block">
<em>category-to-traversal</em>(C) =
if (C is convertible to incrementable_traversal_tag)
return C;
else if (C is convertible to random_access_iterator_tag)
return random_access_traversal_tag;
else if (cat is convertible to bidirectional_iterator_tag)
else if (C is convertible to bidirectional_iterator_tag)
return bidirectional_traversal_tag;
else if (cat is convertible to forward_iterator_tag)
else if (C is convertible to forward_iterator_tag)
return forward_traversal_tag;
else if (cat is convertible to input_iterator_tag)
else if (C is convertible to input_iterator_tag)
return single_pass_traversal_tag;
else if (cat is convertible to output_iterator_tag)
else if (C is convertible to output_iterator_tag)
return incrementable_traversal_tag;
else
<em>the program is ill-formed</em>

317
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View File

@ -430,20 +430,20 @@ The *Lvalue Iterator* concept adds the requirement that the return
type of ``operator*`` type be a reference to the value type of the
iterator.
+---------------------------------------------------------------------------------+
| Lvalue Iterator Requirements |
+---------------------------------+-----------+-----------------------------------+
|Expression |Return Type|Note/Assertion |
+=================================+===========+===================================+
|``*a`` | ``T&`` |``T`` is *cv* |
| | |``iterator_traits<X>::value_type`` |
| | |where *cv* is an optional |
| | |cv-qualification. |
| | |pre: ``a`` is |
| | |dereferenceable. If ``a |
| | |== b`` then ``*a`` is |
| | |equivalent to ``*b``. |
+---------------------------------+-----------+-----------------------------------+
+-------------------------------------------------------------+
| Lvalue Iterator Requirements |
+-------------+-----------+-----------------------------------+
|Expression |Return Type|Note/Assertion |
+=============+===========+===================================+
|``*a`` | ``T&`` |``T`` is *cv* |
| | |``iterator_traits<X>::value_type`` |
| | |where *cv* is an optional |
| | |cv-qualification. |
| | |pre: ``a`` is |
| | |dereferenceable. If ``a |
| | |== b`` then ``*a`` is |
| | |equivalent to ``*b``. |
+-------------+-----------+-----------------------------------+
@ -561,34 +561,35 @@ Iterator* concept if, in addition to ``X`` meeting the requirements of
Forward Traversal Iterator, the following expressions are valid and
respect the stated semantics.
+--------------------------------------------------------------------------------------------------------+
|Bidirectional Traversal Iterator Requirements (in addition to Forward Traversal Iterator) |
+------------------------------------+---------------------------------------------+---------------------+
|Expression |Return Type |Assertion/Semantics /|
| | |Pre-/Post-condition |
+====================================+=============================================+=====================+
|``--r`` |``X&`` |pre: there exists |
| | |``s`` such that ``r |
| | |== ++s``. post: |
| | |``s`` is |
| | |dereferenceable. |
| | |``--(++r) == r``. |
| | |``--r == --s`` |
| | |implies ``r == |
| | |s``. ``&r == &--r``. |
+------------------------------------+---------------------------------------------+---------------------+
|``r--`` |convertible to ``const X&`` |:: |
| | | |
| | | { |
| | | X tmp = r; |
| | | --r; |
| | | return tmp; |
| | | } |
+------------------------------------+---------------------------------------------+---------------------+
|``iterator_traversal<X>::type`` |Convertible to | |
| |``bidirectional_traversal_tag`` | |
| | | |
+------------------------------------+---------------------------------------------+---------------------+
+--------------------------------------------------------------------------------------+
|Bidirectional Traversal Iterator Requirements (in addition to Forward Traversal |
|Iterator) |
+--------------------------------+-------------------------------+---------------------+
|Expression |Return Type |Assertion/Semantics /|
| | |Pre-/Post-condition |
+================================+===============================+=====================+
|``--r`` |``X&`` |pre: there exists |
| | |``s`` such that ``r |
| | |== ++s``. post: |
| | |``s`` is |
| | |dereferenceable. |
| | |``--(++r) == r``. |
| | |``--r == --s`` |
| | |implies ``r == |
| | |s``. ``&r == &--r``. |
+--------------------------------+-------------------------------+---------------------+
|``r--`` |convertible to ``const X&`` |:: |
| | | |
| | | { |
| | | X tmp = r; |
| | | --r; |
| | | return tmp; |
| | | } |
+--------------------------------+-------------------------------+---------------------+
|``iterator_traversal<X>::type`` |Convertible to | |
| |``bidirectional_traversal_tag``| |
| | | |
+--------------------------------+-------------------------------+---------------------+
.. TR1: bidirectional_traversal_iterator_tag changed to
bidirectional_traversal_tag for consistency
@ -602,60 +603,60 @@ the stated semantics. In the table below, ``Distance`` is
``iterator_traits<X>::difference_type`` and ``n`` represents a
constant object of type ``Distance``.
+----------------------------------------------------------------------------------------------------------------------------------------------+
|Random Access Traversal Iterator Requirements (in addition to Bidirectional Traversal Iterator) |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|Expression |Return Type |Operational Semantics |Assertion/ |
| | | |Precondition |
+===========================================+=================================================+=========================+======================+
|``r += n`` |``X&`` |:: | |
| | | | |
| | | { | |
| | | Distance m = n; | |
| | | if (m >= 0) | |
| | | while (m--) | |
| | | ++r; | |
| | | else | |
| | | while (m++) | |
| | | --r; | |
| | | return r; | |
| | | } | |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|``a + n``, ``n + a`` |``X`` |``{ X tmp = a; return tmp| |
| | |+= n; }`` | |
| | | | |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|``r -= n`` |``X&`` |``return r += -n`` | |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|``a - n`` |``X`` |``{ X tmp = a; return tmp| |
| | |-= n; }`` | |
| | | | |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|``b - a`` |``Distance`` |``a < b ? distance(a,b) |pre: there exists a |
| | |: -distance(b,a)`` |value ``n`` of |
| | | |``Distance`` such that|
| | | |``a + n == b``. ``b |
| | | |== a + (b - a)``. |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|``a[n]`` |convertible to T |``*(a + n)`` |pre: a is a `readable |
| | | |iterator`_ |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|``a[n] = v`` |convertible to T |``*(a + n) = v`` |pre: a is a `writable |
| | | |iterator`_ |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|``a < b`` |convertible to ``bool`` |``b - a > 0`` |``<`` is a total |
| | | |ordering relation |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|``a > b`` |convertible to ``bool`` |``b < a`` |``>`` is a total |
| | | |ordering relation |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|``a >= b`` |convertible to ``bool`` |``!(a < b)`` | |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|``a <= b`` |convertible to ``bool`` |``!(a > b)`` | |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|``iterator_traversal<X>::type`` |Convertible to | | |
| |``random_access_traversal_tag`` | | |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
+------------------------------------------------------------------------------------------------------------------+
|Random Access Traversal Iterator Requirements (in addition to Bidirectional Traversal Iterator) |
+-------------------------------+---------------------------------+-------------------------+----------------------+
|Expression |Return Type |Operational Semantics |Assertion/ |
| | | |Precondition |
+===============================+=================================+=========================+======================+
|``r += n`` |``X&`` |:: | |
| | | | |
| | | { | |
| | | Distance m = n; | |
| | | if (m >= 0) | |
| | | while (m--) | |
| | | ++r; | |
| | | else | |
| | | while (m++) | |
| | | --r; | |
| | | return r; | |
| | | } | |
+-------------------------------+---------------------------------+-------------------------+----------------------+
|``a + n``, ``n + a`` |``X`` |``{ X tmp = a; return tmp| |
| | |+= n; }`` | |
| | | | |
+-------------------------------+---------------------------------+-------------------------+----------------------+
|``r -= n`` |``X&`` |``return r += -n`` | |
+-------------------------------+---------------------------------+-------------------------+----------------------+
|``a - n`` |``X`` |``{ X tmp = a; return tmp| |
| | |-= n; }`` | |
| | | | |
+-------------------------------+---------------------------------+-------------------------+----------------------+
|``b - a`` |``Distance`` |``a < b ? distance(a,b) |pre: there exists a |
| | |: -distance(b,a)`` |value ``n`` of |
| | | |``Distance`` such that|
| | | |``a + n == b``. ``b |
| | | |== a + (b - a)``. |
+-------------------------------+---------------------------------+-------------------------+----------------------+
|``a[n]`` |convertible to T |``*(a + n)`` |pre: a is a `readable |
| | | |iterator`_ |
+-------------------------------+---------------------------------+-------------------------+----------------------+
|``a[n] = v`` |convertible to T |``*(a + n) = v`` |pre: a is a `writable |
| | | |iterator`_ |
+-------------------------------+---------------------------------+-------------------------+----------------------+
|``a < b`` |convertible to ``bool`` |``b - a > 0`` |``<`` is a total |
| | | |ordering relation |
+-------------------------------+---------------------------------+-------------------------+----------------------+
|``a > b`` |convertible to ``bool`` |``b < a`` |``>`` is a total |
| | | |ordering relation |
+-------------------------------+---------------------------------+-------------------------+----------------------+
|``a >= b`` |convertible to ``bool`` |``!(a < b)`` | |
+-------------------------------+---------------------------------+-------------------------+----------------------+
|``a <= b`` |convertible to ``bool`` |``!(a > b)`` | |
+-------------------------------+---------------------------------+-------------------------+----------------------+
|``iterator_traversal<X>::type``|Convertible to | | |
| |``random_access_traversal_tag`` | | |
+-------------------------------+---------------------------------+-------------------------+----------------------+
.. TR1: random_access_traversal_iterator_tag changed to
random_access_traversal_tag for consistency
@ -672,61 +673,52 @@ of type ``X``, ``y`` is an object of type ``Y``, ``Distance`` is
``iterator_traits<Y>::difference_type``, and ``n`` represents a
constant object of type ``Distance``.
+-------------------------------------------+-------------------------------------------------+---------------------------------------------------+
|Expression |Return Type |Assertion/Precondition/Postcondition |
+===========================================+=================================================+===================================================+
|``y = x`` |``Y`` |post: ``y == x`` |
+-------------------------------------------+-------------------------------------------------+---------------------------------------------------+
|``Y(x)`` |``Y`` |post: ``Y(x) == x`` |
+-------------------------------------------+-------------------------------------------------+---------------------------------------------------+
|``x == y`` |convertible to ``bool`` |``==`` is an equivalence relation over its domain. |
+-------------------------------------------+-------------------------------------------------+---------------------------------------------------+
|``y == x`` |convertible to ``bool`` |``==`` is an equivalence relation over its domain. |
+-------------------------------------------+-------------------------------------------------+---------------------------------------------------+
|``x != y`` |convertible to ``bool`` |``bool(a==b) != bool(a!=b)`` over its domain. |
+-------------------------------------------+-------------------------------------------------+---------------------------------------------------+
|``y != x`` |convertible to ``bool`` |``bool(a==b) != bool(a!=b)`` over its domain. |
+-------------------------------------------+-------------------------------------------------+---------------------------------------------------+
+-----------+-----------------------+---------------------------------------------------+
|Expression |Return Type |Assertion/Precondition/Postcondition |
+===========+=======================+===================================================+
|``y = x`` |``Y`` |post: ``y == x`` |
+-----------+-----------------------+---------------------------------------------------+
|``Y(x)`` |``Y`` |post: ``Y(x) == x`` |
+-----------+-----------------------+---------------------------------------------------+
|``x == y`` |convertible to ``bool``|``==`` is an equivalence relation over its domain. |
+-----------+-----------------------+---------------------------------------------------+
|``y == x`` |convertible to ``bool``|``==`` is an equivalence relation over its domain. |
+-----------+-----------------------+---------------------------------------------------+
|``x != y`` |convertible to ``bool``|``bool(a==b) != bool(a!=b)`` over its domain. |
+-----------+-----------------------+---------------------------------------------------+
|``y != x`` |convertible to ``bool``|``bool(a==b) != bool(a!=b)`` over its domain. |
+-----------+-----------------------+---------------------------------------------------+
If ``X`` and ``Y`` both model Random Access Traversal Iterator then
the following additional requirements must be met.
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|Expression |Return Type |Operational Semantics |Assertion/ |
| | | |Precondition |
+===========================================+=================================================+=========================+======================+
|``x < y`` |convertible to ``bool`` |``y - x > 0`` |``<`` is a total |
| | | |ordering relation |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|``y < x`` |convertible to ``bool`` |``x - y > 0`` |``<`` is a total |
| | | |ordering relation |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|``x > y`` |convertible to ``bool`` |``y < x`` |``>`` is a total |
| | | |ordering relation |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|``y > x`` |convertible to ``bool`` |``x < y`` |``>`` is a total |
| | | |ordering relation |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|``x >= y`` |convertible to ``bool`` |``!(x < y)`` | |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|``y >= x`` |convertible to ``bool`` |``!(y < x)`` | |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|``x <= y`` |convertible to ``bool`` |``!(x > y)`` | |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|``y <= x`` |convertible to ``bool`` |``!(y > x)`` | |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|``y - x`` |``Distance`` |``distance(Y(x),y)`` |pre: there exists a |
| | | |value ``n`` of |
| | | |``Distance`` such that|
| | | |``x + n == y``. ``y |
| | | |== x + (y - x)``. |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|``x - y`` |``Distance`` |``distance(y,Y(x))`` |pre: there exists a |
| | | |value ``n`` of |
| | | |``Distance`` such that|
| | | |``y + n == x``. ``x |
| | | |== y + (x - y)``. |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
+-----------+-----------------------+---------------------+--------------------------------------+
|Expression |Return Type |Operational Semantics|Assertion/ Precondition |
+===========+=======================+=====================+======================================+
|``x < y`` |convertible to ``bool``|``y - x > 0`` |``<`` is a total ordering relation |
+-----------+-----------------------+---------------------+--------------------------------------+
|``y < x`` |convertible to ``bool``|``x - y > 0`` |``<`` is a total ordering relation |
+-----------+-----------------------+---------------------+--------------------------------------+
|``x > y`` |convertible to ``bool``|``y < x`` |``>`` is a total ordering relation |
+-----------+-----------------------+---------------------+--------------------------------------+
|``y > x`` |convertible to ``bool``|``x < y`` |``>`` is a total ordering relation |
+-----------+-----------------------+---------------------+--------------------------------------+
|``x >= y`` |convertible to ``bool``|``!(x < y)`` | |
+-----------+-----------------------+---------------------+--------------------------------------+
|``y >= x`` |convertible to ``bool``|``!(y < x)`` | |
+-----------+-----------------------+---------------------+--------------------------------------+
|``x <= y`` |convertible to ``bool``|``!(x > y)`` | |
+-----------+-----------------------+---------------------+--------------------------------------+
|``y <= x`` |convertible to ``bool``|``!(y > x)`` | |
+-----------+-----------------------+---------------------+--------------------------------------+
|``y - x`` |``Distance`` |``distance(Y(x),y)`` |pre: there exists a value ``n`` of |
| | | |``Distance`` such that ``x + n == y``.|
| | | |``y == x + (y - x)``. |
+-----------+-----------------------+---------------------+--------------------------------------+
|``x - y`` |``Distance`` |``distance(y,Y(x))`` |pre: there exists a value ``n`` of |
| | | |``Distance`` such that ``y + n == x``.|
| | | |``x == y + (x - y)``. |
+-----------+-----------------------+---------------------+--------------------------------------+
@ -749,31 +741,38 @@ Addition to [lib.iterator.synopsis]
Addition to [lib.iterator.traits]
=================================
The ``is_readable_iterator`` and ``iterator_traversal`` class
templates satisfy the UnaryTypeTrait_ requirements.
The ``is_readable_iterator`` class
template satisfies the UnaryTypeTrait_ requirements.
Given an iterator type ``X``, ``is_readable_iterator<X>::value``
yields ``true`` if, for an object ``a`` of type ``X``, ``*a`` is
convertible to ``iterator_traits<X>::value_type``, and ``false``
otherwise.
``iterator_traversal<X>::type`` is defined to be:
``iterator_traversal<X>::type`` is
.. parsed-literal::
traversal-category(X) =
cat = iterator_traits<X>::iterator_category;
if (cat is convertible to incrementable_traversal_tag)
return cat;
else if (cat is convertible to random_access_iterator_tag)
*category-to-traversal*\ (iterator_traits<X>::iterator_category)
where *category-to-traversal* is defined as follows
.. _`category-to-traversal`:
.. parsed-literal::
*category-to-traversal*\ (C) =
if (C is convertible to incrementable_traversal_tag)
return C;
else if (C is convertible to random_access_iterator_tag)
return random_access_traversal_tag;
else if (cat is convertible to bidirectional_iterator_tag)
else if (C is convertible to bidirectional_iterator_tag)
return bidirectional_traversal_tag;
else if (cat is convertible to forward_iterator_tag)
else if (C is convertible to forward_iterator_tag)
return forward_traversal_tag;
else if (cat is convertible to input_iterator_tag)
else if (C is convertible to input_iterator_tag)
return single_pass_traversal_tag;
else if (cat is convertible to output_iterator_tag)
else if (C is convertible to output_iterator_tag)
return incrementable_traversal_tag;
else
*the program is ill-formed*