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10 Commits

Author SHA1 Message Date
Vladimir Prus
cc5b3f5ad0 Branch for merging Boost.Build and Boost.Jam completely.
[SVN r59143]
2010-01-19 20:47:20 +00:00
Dave Abrahams
ac522bc9e1 category of each component iterator is reduced to a known category before we try to find a minimum.
Closes #1517


[SVN r58012]
2009-11-28 18:53:43 +00:00
Dave Abrahams
4c60e26bf8 Made sure that iterator_facade's nested `::pointer` type is always
the same as what's returned from operator->.  For input iterators,
that wasn't always the case (see operator_arrow_proxy).

Fixes #1019.


[SVN r57989]
2009-11-28 05:12:29 +00:00
Troy D. Straszheim
d11c7a3ec4 rm cmake from trunk. I'm not entirely sure this is necessary to satisfy the inspect script, but I'm not taking any chances, and it is easy to put back
[SVN r56942]
2009-10-17 02:07:38 +00:00
Troy D. Straszheim
76fd8e27fb Copyrights on CMakeLists.txt to keep them from clogging up the inspect
reports.  This is essentially the same commit as r55095 on the release
branch.



[SVN r55159]
2009-07-26 00:49:56 +00:00
John Maddock
f2433c63d5 Add PDF generation options to fix external links to point to the web site.
Added a few more Boostbook based libs that were missed first time around.
Fixed PDF naming issues.

[SVN r51284]
2009-02-17 10:05:58 +00:00
Michael A. Jackson
55c08b706c Updating dependency information for modularized libraries.
[SVN r49628]
2008-11-07 17:05:27 +00:00
Michael A. Jackson
835498603d Updating CMake files to latest trunk. Added dependency information for regression tests and a few new macros for internal use.
[SVN r49627]
2008-11-07 17:02:56 +00:00
Michael A. Jackson
b0ec5a759b Continuing merge of CMake build system files into trunk with the encouragement of Doug Gregor
[SVN r49510]
2008-11-01 13:15:41 +00:00
Nicola Musatti
e06c4b3279 Applied patch from ticket #2344
[SVN r49227]
2008-10-09 21:49:48 +00:00
9 changed files with 45 additions and 482 deletions

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GNUmakefile

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@@ -16,5 +16,7 @@ boostbook standalone
<xsl:param>toc.max.depth=3
<xsl:param>toc.section.depth=3
<xsl:param>chunk.section.depth=4
<format>pdf:<xsl:param>boost.url.prefix=http://www.boost.org/doc/libs/release/libs/iterator/doc
;

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<meta name="date" content="2003-11-19" />
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<body>
<div class="document" id="problem-with-is-writable-and-is-swappable-in-n1550">
<h1 class="title">Problem with <tt class="docutils literal"><span class="pre">is_writable</span></tt> and <tt class="docutils literal"><span class="pre">is_swappable</span></tt> in <a class="reference" href="http://www.boost-consulting.com/writing/n1550.html">N1550</a></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 and Jeremy Siek</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:jsiek&#64;osl.iu.edu">jsiek&#64;osl.iu.edu</a></td></tr>
<tr><th class="docinfo-name">Organization:</th>
<td><a class="first reference" href="http://www.boost-consulting.com">Boost Consulting</a>, Indiana University Bloomington</td></tr>
<tr><th class="docinfo-name">Date:</th>
<td>2003-11-19</td></tr>
<tr><th class="docinfo-name">Copyright:</th>
<td>Copyright David Abrahams, Jeremy Siek 2003. Use, modification and
distribution is subject to the Boost Software License,
Version 1.0. (See accompanying file LICENSE_1_0.txt or copy
at <a class="reference" href="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</a>)</td></tr>
</tbody>
</table>
<div class="contents topic">
<p class="topic-title first"><a id="table-of-contents" name="table-of-contents">Table of Contents</a></p>
<ul class="simple">
<li><a class="reference" href="#introduction" id="id1" name="id1">Introduction</a></li>
<li><a class="reference" href="#proposed-resolution" id="id2" name="id2">Proposed Resolution</a></li>
<li><a class="reference" href="#rationale" id="id3" name="id3">Rationale</a></li>
</ul>
</div>
<div class="section">
<h1><a class="toc-backref" href="#id1" id="introduction" name="introduction">Introduction</a></h1>
<p>The <tt class="docutils literal"><span class="pre">is_writable</span></tt> and <tt class="docutils literal"><span class="pre">is_swappable</span></tt> traits classes in <a class="reference" href="http://www.boost-consulting.com/writing/n1550.html">N1550</a>
provide a mechanism for determining at compile time if an iterator
type is a model of the new Writable Iterator and Swappable Iterator
concepts, analogous to <tt class="docutils literal"><span class="pre">iterator_traits&lt;X&gt;::iterator_category</span></tt>
for the old iterator concepts. For backward compatibility,
<tt class="docutils literal"><span class="pre">is_writable</span></tt> and <tt class="docutils literal"><span class="pre">is_swappable</span></tt> not only work with new
iterators, but they also are intended to work for old
iterators (iterators that meet the requirements for one of the
iterator concepts in the current standard). In the case of old
iterators, the writability and swapability is deduced based on the
<tt class="docutils literal"><span class="pre">iterator_category</span></tt> and also the <tt class="docutils literal"><span class="pre">reference</span></tt> type. The
specification for this deduction gives false positives for forward
iterators that have non-assignable value types.</p>
<p>To review, the part of the <tt class="docutils literal"><span class="pre">is_writable</span></tt> trait definition which
applies to old iterators is:</p>
<pre class="literal-block">
if (cat is convertible to output_iterator_tag)
return true;
else if (cat is convertible to forward_iterator_tag
and iterator_traits&lt;Iterator&gt;::reference is a
mutable reference)
return true;
else
return false;
</pre>
<p>Suppose the <tt class="docutils literal"><span class="pre">value_type</span></tt> of the iterator <tt class="docutils literal"><span class="pre">It</span></tt> has a private
assignment operator:</p>
<pre class="literal-block">
class B {
public:
...
private:
B&amp; operator=(const B&amp;);
};
</pre>
<p>and suppose the <tt class="docutils literal"><span class="pre">reference</span></tt> type of the iterator is <tt class="docutils literal"><span class="pre">B&amp;</span></tt>. In
that case, <tt class="docutils literal"><span class="pre">is_writable&lt;It&gt;::value</span></tt> will be true when in fact
attempting to write into <tt class="docutils literal"><span class="pre">B</span></tt> will cause an error.</p>
<p>The same problem applies to <tt class="docutils literal"><span class="pre">is_swappable</span></tt>.</p>
</div>
<div class="section">
<h1><a class="toc-backref" href="#id2" id="proposed-resolution" name="proposed-resolution">Proposed Resolution</a></h1>
<ol class="arabic">
<li><p class="first">Remove the <tt class="docutils literal"><span class="pre">is_writable</span></tt> and <tt class="docutils literal"><span class="pre">is_swappable</span></tt> traits, and remove the
requirements in the Writable Iterator and Swappable Iterator concepts
that require their models to support these traits.</p>
</li>
<li><p class="first">Change the <tt class="docutils literal"><span class="pre">is_readable</span></tt> specification to be:
<tt class="docutils literal"><span class="pre">is_readable&lt;X&gt;::type</span></tt> is <tt class="docutils literal"><span class="pre">true_type</span></tt> if the
result type of <tt class="docutils literal"><span class="pre">X::operator*</span></tt> is convertible to
<tt class="docutils literal"><span class="pre">iterator_traits&lt;X&gt;::value_type</span></tt> and is <tt class="docutils literal"><span class="pre">false_type</span></tt>
otherwise. Also, <tt class="docutils literal"><span class="pre">is_readable</span></tt> is required to satisfy
the requirements for the UnaryTypeTrait concept
(defined in the type traits proposal).</p>
<p>Remove the requirement for support of the <tt class="docutils literal"><span class="pre">is_readable</span></tt> trait from
the Readable Iterator concept.</p>
</li>
<li><p class="first">Remove the <tt class="docutils literal"><span class="pre">iterator_tag</span></tt> class.</p>
</li>
<li><p class="first">Change the specification of <tt class="docutils literal"><span class="pre">traversal_category</span></tt> to:</p>
<pre class="literal-block">
traversal-category(Iterator) =
let cat = iterator_traits&lt;Iterator&gt;::iterator_category
if (cat is convertible to incrementable_iterator_tag)
return cat; // Iterator is a new iterator
else if (cat is convertible to random_access_iterator_tag)
return random_access_traversal_tag;
else if (cat is convertible to bidirectional_iterator_tag)
return bidirectional_traversal_tag;
else if (cat is convertible to forward_iterator_tag)
return forward_traversal_tag;
else if (cat is convertible to input_iterator_tag)
return single_pass_iterator_tag;
else if (cat is convertible to output_iterator_tag)
return incrementable_iterator_tag;
else
return null_category_tag;
</pre>
</li>
</ol>
</div>
<div class="section">
<h1><a class="toc-backref" href="#id3" id="rationale" name="rationale">Rationale</a></h1>
<ol class="arabic simple">
<li>There are two reasons for removing <tt class="docutils literal"><span class="pre">is_writable</span></tt>
and <tt class="docutils literal"><span class="pre">is_swappable</span></tt>. The first is that we do not know of
a way to fix the specification so that it gives the correct
answer for all iterators. Second, there was only a weak
motivation for having <tt class="docutils literal"><span class="pre">is_writable</span></tt> and <tt class="docutils literal"><span class="pre">is_swappable</span></tt>
there in the first place. The main motivation was simply
uniformity: we have tags for the old iterator categories
so we should have tags for the new iterator categories.
While having tags and the capability to dispatch based
on the traversal categories is often used, we see
less of a need for dispatching based on writability
and swappability, since typically algorithms
that need these capabilities have no alternative if
they are not provided.</li>
<li>We discovered that the <tt class="docutils literal"><span class="pre">is_readable</span></tt> trait can be implemented
using only the iterator type itself and its <tt class="docutils literal"><span class="pre">value_type</span></tt>.
Therefore we remove the requirement for <tt class="docutils literal"><span class="pre">is_readable</span></tt> from the
Readable Iterator concept, and change the definition of
<tt class="docutils literal"><span class="pre">is_readable</span></tt> so that it works for any iterator type.</li>
<li>The purpose of the <tt class="docutils literal"><span class="pre">iterator_tag</span></tt> class was to
bundle the traversal and access category tags
into the <tt class="docutils literal"><span class="pre">iterator_category</span></tt> typedef.
With <tt class="docutils literal"><span class="pre">is_writable</span></tt> and <tt class="docutils literal"><span class="pre">is_swappable</span></tt> gone, and
<tt class="docutils literal"><span class="pre">is_readable</span></tt> no longer in need of special hints,
there is no reason for iterators to provide
information about the access capabilities of an iterator.
Thus there is no need for the <tt class="docutils literal"><span class="pre">iterator_tag</span></tt>. The
traversal tag can be directly used for the
<tt class="docutils literal"><span class="pre">iterator_category</span></tt>. If a new iterator is intended to be backward
compatible with old iterator concepts, a tag type
that is convertible to both one of the new traversal tags
and also to an old iterator tag can be created and use
for the <tt class="docutils literal"><span class="pre">iterator_category</span></tt>.</li>
<li>The changes to the specification of <tt class="docutils literal"><span class="pre">traversal_category</span></tt> are a
direct result of the removal of <tt class="docutils literal"><span class="pre">iterator_tag</span></tt>.</li>
</ol>
</div>
</div>
</body>
</html>

0
doc/rst2html Normal file → Executable file
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@@ -1,17 +0,0 @@
# Copyright David Abrahams 2006. Distributed under 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)
test-suite iterator_examples
: [ run reverse_iterator.cpp ]
[ run node_iterator1.cpp ]
[ run node_iterator2.cpp ]
[ run node_iterator3.cpp ]
[ run counting_iterator_example.cpp ]
[ run filter_iterator_example.cpp ]
[ run func_output_iter_example.cpp ]
[ run indirect_iterator_example.cpp ]
[ run permutation_iter_example.cpp ]
[ run reverse_iterator_example.cpp ]
[ run transform_iterator_example.cpp ]
;

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@@ -105,6 +105,7 @@ namespace boost
typedef typename remove_const<ValueParam>::type value_type;
// Not the real associated pointer type
typedef typename mpl::eval_if<
boost::detail::iterator_writability_disabled<ValueParam,Reference>
, add_pointer<const value_type>
@@ -617,6 +618,12 @@ namespace boost
Value, CategoryOrTraversal, Reference, Difference
> associated_types;
typedef boost::detail::operator_arrow_result<
typename associated_types::value_type
, Reference
, typename associated_types::pointer
> pointer_;
protected:
// For use by derived classes
typedef iterator_facade<Derived,Value,CategoryOrTraversal,Reference,Difference> iterator_facade_;
@@ -626,7 +633,9 @@ namespace boost
typedef typename associated_types::value_type value_type;
typedef Reference reference;
typedef Difference difference_type;
typedef typename associated_types::pointer pointer;
typedef typename pointer_::type pointer;
typedef typename associated_types::iterator_category iterator_category;
reference operator*() const
@@ -634,18 +643,9 @@ namespace boost
return iterator_core_access::dereference(this->derived());
}
typename boost::detail::operator_arrow_result<
value_type
, reference
, pointer
>::type
operator->() const
pointer operator->() const
{
return boost::detail::operator_arrow_result<
value_type
, reference
, pointer
>::make(*this->derived());
return pointer_::make(*this->derived());
}
typename boost::detail::operator_brackets_result<Derived,Value,reference>::type

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@@ -357,7 +357,7 @@ namespace boost {
{
typedef typename tuple_impl_specific::tuple_meta_transform<
IteratorTuple
, iterator_traversal<>
, pure_traversal_tag<iterator_traversal<> >
>::type tuple_of_traversal_tags;
typedef typename tuple_impl_specific::tuple_meta_accumulate<

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@@ -87,6 +87,10 @@ struct input_iter
}
};
template <class T, class U>
void same_type(U const&)
{ BOOST_MPL_ASSERT((boost::is_same<T,U>)); }
int main()
{
int state = 0;
@@ -101,6 +105,8 @@ int main()
input_iter p;
(*p).mutator();
p->mutator();
same_type<input_iter::pointer>(p.operator->());
return boost::report_errors();
}

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@@ -46,6 +46,7 @@
#include <vector>
#include <list>
#include <set>
#include <string>
#include <functional>
#include <boost/tuple/tuple.hpp>
#include <boost/iterator/transform_iterator.hpp>
@@ -60,6 +61,27 @@ struct pure_traversal
typename boost::iterator_traversal<It>::type
>
{};
/// Tests for https://svn.boost.org/trac/boost/ticket/1517
int to_value(int const &v)
{
return v;
}
void category_test()
{
std::list<int> rng1;
std::string rng2;
boost::make_zip_iterator(
boost::make_tuple(
boost::make_transform_iterator(rng1.begin(), &to_value), // BidirectionalInput
rng2.begin() // RandomAccess
)
);
}
///
/////////////////////////////////////////////////////////////////////////////
//
@@ -70,6 +92,8 @@ struct pure_traversal
int main( void )
{
category_test();
std::cout << "\n"
<< "***********************************************\n"
<< "* *\n"