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<title>Issue 3302: Range adaptor objects keys and values are unspecified</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++20">C++20</a> status.</em></p>
<h3 id="3302"><a href="lwg-defects.html#3302">3302</a>. Range adaptor objects <code>keys</code> and <code>values</code> are unspecified</h3>
<p><b>Section:</b> 25.2 <a href="https://wg21.link/ranges.syn">[ranges.syn]</a> <b>Status:</b> <a href="lwg-active.html#C++20">C++20</a>
 <b>Submitter:</b> Michel Morin <b>Opened:</b> 2019-10-04 <b>Last modified:</b> 2021-02-25</p>
<p><b>Priority: </b>1
</p>
<p><b>View other</b> <a href="lwg-index-open.html#ranges.syn">active issues</a> in [ranges.syn].</p>
<p><b>View all other</b> <a href="lwg-index.html#ranges.syn">issues</a> in [ranges.syn].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#C++20">C++20</a> status.</p>
<p><b>Discussion:</b></p>
<p>
This issue was submitted as editorial issue 
<a href="https://github.com/cplusplus/draft/issues/3231">cplusplus/draft#3231</a> but had been
classified as non-editorial.
<p/>
<code>keys</code> and <code>values</code> are listed in 25.2 <a href="https://wg21.link/ranges.syn">[ranges.syn]</a>, but not specified.
It seems that <a href="https://wg21.link/p1035r7">P1035R7</a> forgot to specify them (as 
<code>elements&lt;0&gt;</code> and <code>elements&lt;1&gt;</code>).
</p>

<p><i>[2019-10-31 Issue Prioritization]</i></p>

<p>Priority to 1 after reflector discussion.</p>
<p><i>[2019-11 Wednesday night issue processing in Belfast.]</i></p>

<p>Status to Ready.</p>


<p id="res-3302"><b>Proposed resolution:</b></p>
<p>This wording is relative to <a href="https://wg21.link/n4830">N4830</a>.</p>

<ol>
<li><p>Modify 25.2 <a href="https://wg21.link/ranges.syn">[ranges.syn]</a>, header <code>&lt;ranges&gt;</code> synopsis, as indicated:</p>

<blockquote>
<pre>
namespace std::ranges {
  [&hellip;]
  
  template&lt;class R&gt;
    using keys_view = elements_view&lt;all_view&lt;R&gt;, 0&gt;;
  template&lt;class R&gt;
    using values_view = elements_view&lt;all_view&lt;R&gt;, 1&gt;;
  namespace views {
    template&lt;size_t N&gt;
      inline constexpr <i>unspecified</i> elements = <i>unspecified</i>;
    inline constexpr <ins>auto</ins><del><i>unspecified</i></del> keys = <ins>elements&lt;0&gt;</ins><del><i>unspecified</i></del>;
    inline constexpr <ins>auto</ins><del><i>unspecified</i></del> values = <ins>elements&lt;1&gt;</ins><del><i>unspecified</i></del>;
  }  
}
[&hellip;]
</pre>
</blockquote>
</li>

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