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A few fixes

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[SVN r23542]
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2004-07-14 12:33:36 +00:00
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@ -3,16 +3,15 @@
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<title>New Iterator Concepts</title>
<meta name="author" content="David Abrahams, Jeremy Siek, Thomas Witt" />
<meta name="organization" content="Boost Consulting, Indiana University Open Systems Lab, Zephyr Associates, Inc." />
<meta name="date" content="2004-04-06" />
<meta name="date" content="2004-07-14" />
<meta name="copyright" content="Copyright David Abrahams, Jeremy Siek, and Thomas Witt 2003. All rights reserved" />
<link rel="stylesheet" href="default.css" type="text/css" />
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<body>
<div class="document" id="new-iterator-concepts">
<h1 class="title">New Iterator Concepts</h1>
<table class="docinfo" frame="void" rules="none">
<col class="docinfo-name" />
@ -26,7 +25,7 @@
<td><a class="first reference" href="http://www.boost-consulting.com">Boost Consulting</a>, Indiana University <a class="reference" href="http://www.osl.iu.edu">Open Systems
Lab</a>, <a class="last reference" href="http://www.styleadvisor.com">Zephyr Associates, Inc.</a></td></tr>
<tr><th class="docinfo-name">Date:</th>
<td>2004-04-06</td></tr>
<td>2004-07-14</td></tr>
<tr class="field"><th class="docinfo-name">Number:</th><td class="field-body">This is a revised version of <a class="reference" href="http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/papers/2003/n1550.html">n1550</a>=03-0133, which was
accepted for Technical Report 1 by the C++ standard
committee's library working group. This proposal is a
@ -37,6 +36,7 @@ revision of paper <a class="reference" href="http://anubis.dkuug.dk/jtc1/sc22/wg
2003. All rights reserved</td></tr>
</tbody>
</table>
<div class="document" id="new-iterator-concepts">
<!-- Version 1.25 of this ReStructuredText document is the same as
n1550_, the paper accepted by the LWG. -->
<table class="field-list" frame="void" rules="none">
@ -52,7 +52,7 @@ of iterators that are used in practice.</td>
</tbody>
</table>
<div class="contents topic" id="table-of-contents">
<p class="topic-title"><a name="table-of-contents">Table of Contents</a></p>
<p class="topic-title first"><a name="table-of-contents">Table of Contents</a></p>
<ul class="simple">
<li><a class="reference" href="#motivation" id="id1" name="id1">Motivation</a></li>
<li><a class="reference" href="#impact-on-the-standard" id="id2" name="id2">Impact on the Standard</a><ul>
@ -107,7 +107,7 @@ geared towards iterator traversal (hence the category names), while
requirements that address value access sneak in at various places. The
following table gives a summary of the current value access
requirements in the iterator categories.</p>
<table border class="table">
<table border="1" class="table">
<colgroup>
<col width="31%" />
<col width="69%" />
@ -364,7 +364,7 @@ for value type <tt class="literal"><span class="pre">T</span></tt> if, in additi
Copy Constructible, the following expressions are valid and respect
the stated semantics. <tt class="literal"><span class="pre">U</span></tt> is the type of any specified member of
type <tt class="literal"><span class="pre">T</span></tt>.</p>
<table border class="table">
<table border="1" class="table">
<colgroup>
<col width="28%" />
<col width="20%" />
@ -406,7 +406,7 @@ non-cv-qualified type</td>
if, in addition to <tt class="literal"><span class="pre">X</span></tt> being Copy Constructible, the following
expressions are valid and respect the stated semantics. Writable
Iterators have an associated <em>set of value types</em>.</p>
<table border class="table">
<table border="1" class="table">
<colgroup>
<col width="37%" />
<col width="21%" />
@ -435,7 +435,7 @@ value types of <tt class="literal"><span class="pre">X</span></tt></td>
<p>A class or built-in type <tt class="literal"><span class="pre">X</span></tt> models the <em>Swappable Iterator</em> concept
if, in addition to <tt class="literal"><span class="pre">X</span></tt> being Copy Constructible, the following
expressions are valid and respect the stated semantics.</p>
<table border class="table">
<table border="1" class="table">
<colgroup>
<col width="37%" />
<col width="19%" />
@ -457,17 +457,16 @@ exchanged</td>
</tr>
</tbody>
</table>
<dl>
<dt>[<em>Note:</em> An iterator that is a model of the <em>Readable</em> and <em>Writable Iterator</em> concepts</dt>
<dd>is also a model of <em>Swappable Iterator</em>. <em>--end note</em>]</dd>
</dl>
<p>[<em>Note:</em> An iterator that is a model of the <a class="reference" href="#readable-iterator">Readable Iterator</a> and
<a class="reference" href="#writable-iterator">Writable Iterator</a> concepts is also a model of <em>Swappable
Iterator</em>. <em>--end note</em>]</p>
</div>
<div class="section" id="lvalue-iterators-lib-lvalue-iterators">
<h4><a class="toc-backref" href="#id14" name="lvalue-iterators-lib-lvalue-iterators">Lvalue Iterators [lib.lvalue.iterators]</a></h4>
<p>The <em>Lvalue Iterator</em> concept adds the requirement that the return
type of <tt class="literal"><span class="pre">operator*</span></tt> type be a reference to the value type of the
iterator.</p>
<table border class="table">
<table border="1" class="table">
<colgroup>
<col width="22%" />
<col width="19%" />
@ -487,14 +486,15 @@ iterator.</p>
<td><tt class="literal"><span class="pre">T</span></tt> is <em>cv</em>
<tt class="literal"><span class="pre">iterator_traits&lt;X&gt;::value_type</span></tt>
where <em>cv</em> is an optional
cv-qualification.
pre: <tt class="literal"><span class="pre">a</span></tt> is
dereferenceable. If <tt class="literal"><span class="pre">a</span>
<span class="pre">==</span> <span class="pre">b</span></tt> then <tt class="literal"><span class="pre">*a</span></tt> is
equivalent to <tt class="literal"><span class="pre">*b</span></tt>.</td>
cv-qualification. pre: <tt class="literal"><span class="pre">a</span></tt> is
dereferenceable.</td>
</tr>
</tbody>
</table>
<p>If <tt class="literal"><span class="pre">X</span></tt> is a <a class="reference" href="#writable-iterator">Writable Iterator</a> then <tt class="literal"><span class="pre">a</span> <span class="pre">==</span> <span class="pre">b</span></tt> if and only if
<tt class="literal"><span class="pre">*a</span></tt> is the same object as <tt class="literal"><span class="pre">*b</span></tt>. If <tt class="literal"><span class="pre">X</span></tt> is a <a class="reference" href="#readable-iterator">Readable
Iterator</a> then <tt class="literal"><span class="pre">a</span> <span class="pre">==</span> <span class="pre">b</span></tt> implies <tt class="literal"><span class="pre">*a</span></tt> is the same object as
<tt class="literal"><span class="pre">*b</span></tt>.</p>
</div>
</div>
<div class="section" id="iterator-traversal-concepts-lib-iterator-traversal">
@ -509,18 +509,18 @@ type <tt class="literal"><span class="pre">X</span></tt>, <tt class="literal"><s
concept if, in addition to <tt class="literal"><span class="pre">X</span></tt> being Assignable and Copy
Constructible, the following expressions are valid and respect the
stated semantics.</p>
<table border class="table">
<table border="1" class="table">
<colgroup>
<col width="39%" />
<col width="37%" />
<col width="24%" />
<col width="38%" />
<col width="23%" />
</colgroup>
<thead valign="bottom">
<tr><th colspan="3">Incrementable Iterator Requirements (in addition to Assignable, Copy Constructible)</th>
</tr>
<tr><th>Expression</th>
<th>Return Type</th>
<th>Assertion/Semantics</th>
<th>Assertion</th>
</tr>
</thead>
<tbody valign="top">
@ -529,15 +529,12 @@ stated semantics.</p>
<td><tt class="literal"><span class="pre">&amp;r</span> <span class="pre">==</span> <span class="pre">&amp;++r</span></tt></td>
</tr>
<tr><td><tt class="literal"><span class="pre">r++</span></tt></td>
<td><tt class="literal"><span class="pre">X</span></tt></td>
<td><pre class="first last literal-block">
{
X tmp = r;
++r;
return tmp;
}
</pre>
</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
</tr>
<tr><td><tt class="literal"><span class="pre">*r++</span></tt></td>
<td>&nbsp;</td>
<td>&nbsp;</td>
</tr>
<tr><td><tt class="literal"><span class="pre">iterator_traversal&lt;X&gt;::type</span></tt></td>
<td>Convertible to
@ -546,6 +543,11 @@ stated semantics.</p>
</tr>
</tbody>
</table>
<p>If <tt class="literal"><span class="pre">X</span></tt> is a <a class="reference" href="#writable-iterator">Writable Iterator</a> then <tt class="literal"><span class="pre">X</span> <span class="pre">a(r++);</span></tt> is equivalent
to <tt class="literal"><span class="pre">X</span> <span class="pre">a(r);</span> <span class="pre">++r;</span></tt> and <tt class="literal"><span class="pre">*r++</span> <span class="pre">=</span> <span class="pre">o</span></tt> is equivalent
to <tt class="literal"><span class="pre">*r</span> <span class="pre">=</span> <span class="pre">o;</span> <span class="pre">++r</span></tt>.
If <tt class="literal"><span class="pre">X</span></tt> is a <a class="reference" href="#readable-iterator">Readable Iterator</a> then <tt class="literal"><span class="pre">T</span> <span class="pre">z(*r++);</span></tt> is equivalent
to <tt class="literal"><span class="pre">T</span> <span class="pre">z(*r);</span> <span class="pre">++r;</span></tt>.</p>
<!-- TR1: incrementable_iterator_tag changed to
incrementable_traversal_tag for consistency. -->
</div>
@ -554,25 +556,29 @@ incrementable_traversal_tag for consistency. -->
<p>A class or built-in type <tt class="literal"><span class="pre">X</span></tt> models the <em>Single Pass Iterator</em>
concept if the following expressions are valid and respect the stated
semantics.</p>
<table border class="table">
<table border="1" class="table">
<colgroup>
<col width="36%" />
<col width="33%" />
<col width="31%" />
<col width="32%" />
<col width="29%" />
<col width="13%" />
<col width="27%" />
</colgroup>
<thead valign="bottom">
<tr><th colspan="3">Single Pass Iterator Requirements (in addition to Incrementable Iterator and Equality
<tr><th colspan="4">Single Pass Iterator Requirements (in addition to Incrementable Iterator and Equality
Comparable)</th>
</tr>
<tr><th>Expression</th>
<th>Return Type</th>
<th>Assertion/Semantics /
<th>Operational
Semantics</th>
<th>Assertion/
Pre-/Post-condition</th>
</tr>
</thead>
<tbody valign="top">
<tr><td><tt class="literal"><span class="pre">++r</span></tt></td>
<td><tt class="literal"><span class="pre">X&amp;</span></tt></td>
<td>&nbsp;</td>
<td>pre: <tt class="literal"><span class="pre">r</span></tt> is
dereferenceable; post:
<tt class="literal"><span class="pre">r</span></tt> is dereferenceable or
@ -580,17 +586,20 @@ dereferenceable; post:
</tr>
<tr><td><tt class="literal"><span class="pre">a</span> <span class="pre">==</span> <span class="pre">b</span></tt></td>
<td>convertible to <tt class="literal"><span class="pre">bool</span></tt></td>
<td>&nbsp;</td>
<td><tt class="literal"><span class="pre">==</span></tt> is an equivalence
relation over its domain</td>
</tr>
<tr><td><tt class="literal"><span class="pre">a</span> <span class="pre">!=</span> <span class="pre">b</span></tt></td>
<td>convertible to <tt class="literal"><span class="pre">bool</span></tt></td>
<td><tt class="literal"><span class="pre">!(a</span> <span class="pre">==</span> <span class="pre">b)</span></tt></td>
<td>&nbsp;</td>
</tr>
<tr><td><tt class="literal"><span class="pre">iterator_traversal&lt;X&gt;::type</span></tt></td>
<td>Convertible to
<tt class="literal"><span class="pre">single_pass_traversal_tag</span></tt></td>
<td>&nbsp;</td>
<td>&nbsp;</td>
</tr>
</tbody>
</table>
@ -603,7 +612,7 @@ single_pass_traversal_tag for consistency -->
concept if, in addition to <tt class="literal"><span class="pre">X</span></tt> meeting the requirements of Default
Constructible and Single Pass Iterator, the following expressions are
valid and respect the stated semantics.</p>
<table border class="table">
<table border="1" class="table">
<colgroup>
<col width="38%" />
<col width="34%" />
@ -650,34 +659,39 @@ forward_traversal_tag for consistency -->
Iterator</em> concept if, in addition to <tt class="literal"><span class="pre">X</span></tt> meeting the requirements of
Forward Traversal Iterator, the following expressions are valid and
respect the stated semantics.</p>
<table border class="table">
<table border="1" class="table">
<colgroup>
<col width="38%" />
<col width="37%" />
<col width="25%" />
<col width="33%" />
<col width="32%" />
<col width="14%" />
<col width="21%" />
</colgroup>
<thead valign="bottom">
<tr><th colspan="3">Bidirectional Traversal Iterator Requirements (in addition to Forward Traversal
<tr><th colspan="4">Bidirectional Traversal Iterator Requirements (in addition to Forward Traversal
Iterator)</th>
</tr>
<tr><th>Expression</th>
<th>Return Type</th>
<th>Assertion/Semantics /
<th>Operational
Semantics</th>
<th>Assertion/
Pre-/Post-condition</th>
</tr>
</thead>
<tbody valign="top">
<tr><td><tt class="literal"><span class="pre">--r</span></tt></td>
<td><tt class="literal"><span class="pre">X&amp;</span></tt></td>
<td>pre: there exists
<td>&nbsp;</td>
<td><p class="first">pre: there exists
<tt class="literal"><span class="pre">s</span></tt> such that <tt class="literal"><span class="pre">r</span>
<span class="pre">==</span> <span class="pre">++s</span></tt>. post:
<tt class="literal"><span class="pre">s</span></tt> is
dereferenceable.
<tt class="literal"><span class="pre">--(++r)</span> <span class="pre">==</span> <span class="pre">r</span></tt>.
dereferenceable.</p>
<p class="last"><tt class="literal"><span class="pre">++(--r)</span> <span class="pre">==</span> <span class="pre">r</span></tt>.
<tt class="literal"><span class="pre">--r</span> <span class="pre">==</span> <span class="pre">--s</span></tt>
implies <tt class="literal"><span class="pre">r</span> <span class="pre">==</span>
<span class="pre">s</span></tt>. <tt class="literal"><span class="pre">&amp;r</span> <span class="pre">==</span> <span class="pre">&amp;--r</span></tt>.</td>
<span class="pre">s</span></tt>. <tt class="literal"><span class="pre">&amp;r</span> <span class="pre">==</span> <span class="pre">&amp;--r</span></tt>.</p>
</td>
</tr>
<tr><td><tt class="literal"><span class="pre">r--</span></tt></td>
<td>convertible to <tt class="literal"><span class="pre">const</span> <span class="pre">X&amp;</span></tt></td>
@ -689,11 +703,13 @@ implies <tt class="literal"><span class="pre">r</span> <span class="pre">==</spa
}
</pre>
</td>
<td>&nbsp;</td>
</tr>
<tr><td><tt class="literal"><span class="pre">iterator_traversal&lt;X&gt;::type</span></tt></td>
<td>Convertible to
<tt class="literal"><span class="pre">bidirectional_traversal_tag</span></tt></td>
<td>&nbsp;</td>
<td>&nbsp;</td>
</tr>
</tbody>
</table>
@ -707,7 +723,7 @@ Iterator</em> concept if the following expressions are valid and respect
the stated semantics. In the table below, <tt class="literal"><span class="pre">Distance</span></tt> is
<tt class="literal"><span class="pre">iterator_traits&lt;X&gt;::difference_type</span></tt> and <tt class="literal"><span class="pre">n</span></tt> represents a
constant object of type <tt class="literal"><span class="pre">Distance</span></tt>.</p>
<table border class="table">
<table border="1" class="table">
<colgroup>
<col width="28%" />
<col width="30%" />
@ -772,14 +788,14 @@ value <tt class="literal"><span class="pre">n</span></tt> of
<tr><td><tt class="literal"><span class="pre">a[n]</span></tt></td>
<td>convertible to T</td>
<td><tt class="literal"><span class="pre">*(a</span> <span class="pre">+</span> <span class="pre">n)</span></tt></td>
<td>pre: a is a <a class="reference" href="#readable-iterator">readable
iterator</a></td>
<td>pre: a is a <a class="reference" href="#readable-iterator">Readable
Iterator</a></td>
</tr>
<tr><td><tt class="literal"><span class="pre">a[n]</span> <span class="pre">=</span> <span class="pre">v</span></tt></td>
<td>convertible to T</td>
<td><tt class="literal"><span class="pre">*(a</span> <span class="pre">+</span> <span class="pre">n)</span> <span class="pre">=</span> <span class="pre">v</span></tt></td>
<td>pre: a is a <a class="reference" href="#writable-iterator">writable
iterator</a></td>
<td>pre: a is a <a class="reference" href="#writable-iterator">Writable
Iterator</a></td>
</tr>
<tr><td><tt class="literal"><span class="pre">a</span> <span class="pre">&lt;</span> <span class="pre">b</span></tt></td>
<td>convertible to <tt class="literal"><span class="pre">bool</span></tt></td>
@ -823,7 +839,7 @@ respect the stated semantics. In the tables below, <tt class="literal"><span cla
of type <tt class="literal"><span class="pre">X</span></tt>, <tt class="literal"><span class="pre">y</span></tt> is an object of type <tt class="literal"><span class="pre">Y</span></tt>, <tt class="literal"><span class="pre">Distance</span></tt> is
<tt class="literal"><span class="pre">iterator_traits&lt;Y&gt;::difference_type</span></tt>, and <tt class="literal"><span class="pre">n</span></tt> represents a
constant object of type <tt class="literal"><span class="pre">Distance</span></tt>.</p>
<table border class="table">
<table border="1" class="table">
<colgroup>
<col width="13%" />
<col width="27%" />
@ -864,7 +880,7 @@ constant object of type <tt class="literal"><span class="pre">Distance</span></t
</table>
<p>If <tt class="literal"><span class="pre">X</span></tt> and <tt class="literal"><span class="pre">Y</span></tt> both model Random Access Traversal Iterator then
the following additional requirements must be met.</p>
<table border class="table">
<table border="1" class="table">
<colgroup>
<col width="12%" />
<col width="25%" />
@ -998,5 +1014,10 @@ LocalWords: incrementable xxx min prev inplace png oldeqnew AccessTag struct
LocalWords: TraversalTag typename lvalues DWA Hmm JGS mis enum -->
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