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<title>Issue 1180: Missing string_type member typedef in class sub_match</title>
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<p><em>This page is a snapshot from the LWG issues list, see the <a href="lwg-active.html">Library Active Issues List</a> for more information and the meaning of <a href="lwg-active.html#C++11">C++11</a> status.</em></p>
<h3 id="1180"><a href="lwg-defects.html#1180">1180</a>. Missing <code>string_type</code> member typedef in class <code>sub_match</code></h3>
<p><b>Section:</b> 28.6.8.2 <a href="https://wg21.link/re.submatch.members">[re.submatch.members]</a> <b>Status:</b> <a href="lwg-active.html#C++11">C++11</a>
 <b>Submitter:</b> Daniel Kr&uuml;gler <b>Opened:</b> 2009-07-25 <b>Last modified:</b> 2016-01-28</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all issues with</b> <a href="lwg-status.html#C++11">C++11</a> status.</p>
<p><b>Discussion:</b></p>
<p>
The definition of class template <code>sub_match</code> is strongly dependent
on the type <code>basic_string&lt;value_type&gt;</code>, both in interface and effects,
but does not provide a corresponding typedef <code>string_type</code>, as e.g.
class <code>match_results</code> does, which looks like an oversight to me that
should be fixed.
</p>

<p><i>[
2009-11-15 Moved to Tentatively Ready after 5 positive votes on c++std-lib.
]</i></p>



<p id="res-1180"><b>Proposed resolution:</b></p>

<ol>
<li>
<p>
In the class template <code>sub_match</code> synopsis 28.6.8 <a href="https://wg21.link/re.submatch">[re.submatch]</a>/1
change as indicated:
</p>

<blockquote><pre>
template &lt;class BidirectionalIterator&gt;
class sub_match : public std::pair&lt;BidirectionalIterator, BidirectionalIterator&gt; {
public:
  typedef typename iterator_traits&lt;BidirectionalIterator&gt;::value_type value_type;
  typedef typename iterator_traits&lt;BidirectionalIterator&gt;::difference_type difference_type;
  typedef BidirectionalIterator iterator;
  <ins>typedef basic_string&lt;value_type&gt; string_type;</ins>

  bool matched;

  difference_type length() const;
  operator <del>basic_string&lt;value_type&gt;</del><ins>string_type</ins>() const;
  <del>basic_string&lt;value_type&gt;</del><ins>string_type</ins> str() const;
  int compare(const sub_match&amp; s) const;
  int compare(const <del>basic_string&lt;value_type&gt;</del><ins>string_type</ins>&amp; s) const;
  int compare(const value_type* s) const;
};
</pre></blockquote>
</li>

<li>
<p>
In 28.6.8.2 <a href="https://wg21.link/re.submatch.members">[re.submatch.members]</a>/2 change as indicated:
</p>

<blockquote><pre>
operator <del>basic_string&lt;value_type&gt;</del><ins>string_type</ins>() const;
</pre>

<blockquote><p>
<i>Returns:</i> <code>matched ? <del>basic_string&lt;value_type&gt;</del>
<ins>string_type</ins>(first, second) : <del>basic_string&lt;value_type&gt;</del>
<ins>string_type</ins>()</code>.
</p></blockquote>
</blockquote>
</li>

<li>
<p>
In 28.6.8.2 <a href="https://wg21.link/re.submatch.members">[re.submatch.members]</a>/3 change as indicated:
</p>

<blockquote><pre>
<del>basic_string&lt;value_type&gt;</del><ins>string_type</ins> str() const;
</pre>

<blockquote><p>
<i>Returns:</i> <code>matched ? <del>basic_string&lt;value_type&gt;</del>
<ins>string_type</ins>(first, second) : <del>basic_string&lt;value_type&gt;</del>
<ins>string_type</ins>()</code>.
</p></blockquote>
</blockquote>
</li>

<li>
<p>
In 28.6.8.2 <a href="https://wg21.link/re.submatch.members">[re.submatch.members]</a>/5 change as indicated:
</p>

<blockquote><pre>
int compare(const <del>basic_string&lt;value_type&gt;</del><ins>string_type</ins>&amp; s) const;
</pre></blockquote>
</li>
</ol>






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