<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Issue 2435: reference_wrapper::operator()'s Remark should be deleted</title>
<meta property="og:title" content="Issue 2435: reference_wrapper::operator()'s Remark should be deleted">
<meta property="og:description" content="C++ library issue. Status: C++17">
<meta property="og:url" content="https://cplusplus.github.io/LWG/issue2435.html">
<meta property="og:type" content="website">
<meta property="og:image" content="http://cplusplus.github.io/LWG/images/cpp_logo.png">
<meta property="og:image:alt" content="C++ logo">
<style>
  p {text-align:justify}
  li {text-align:justify}
  pre code.backtick::before { content: "`" }
  pre code.backtick::after { content: "`" }
  blockquote.note
  {
    background-color:#E0E0E0;
    padding-left: 15px;
    padding-right: 15px;
    padding-top: 1px;
    padding-bottom: 1px;
  }
  ins {background-color:#A0FFA0}
  del {background-color:#FFA0A0}
  table.issues-index { border: 1px solid; border-collapse: collapse; }
  table.issues-index th { text-align: center; padding: 4px; border: 1px solid; }
  table.issues-index td { padding: 4px; border: 1px solid; }
  table.issues-index td:nth-child(1) { text-align: right; }
  table.issues-index td:nth-child(2) { text-align: left; }
  table.issues-index td:nth-child(3) { text-align: left; }
  table.issues-index td:nth-child(4) { text-align: left; }
  table.issues-index td:nth-child(5) { text-align: center; }
  table.issues-index td:nth-child(6) { text-align: center; }
  table.issues-index td:nth-child(7) { text-align: left; }
  table.issues-index td:nth-child(5) span.no-pr { color: red; }
  @media (prefers-color-scheme: dark) {
     html {
        color: #ddd;
        background-color: black;
     }
     ins {
        background-color: #225522
     }
     del {
        background-color: #662222
     }
     a {
        color: #6af
     }
     a:visited {
        color: #6af
     }
     blockquote.note
     {
        background-color: rgba(255, 255, 255, .10)
     }
  }
</style>
</head>
<body>
<hr>
<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++17">C++17</a> status.</em></p>
<h3 id="2435"><a href="lwg-defects.html#2435">2435</a>. <code>reference_wrapper::operator()</code>'s Remark should be deleted</h3>
<p><b>Section:</b> 22.10.6.5 <a href="https://wg21.link/refwrap.invoke">[refwrap.invoke]</a> <b>Status:</b> <a href="lwg-active.html#C++17">C++17</a>
 <b>Submitter:</b> Stephan T. Lavavej <b>Opened:</b> 2014-10-01 <b>Last modified:</b> 2017-07-30</p>
<p><b>Priority: </b>4
</p>
<p><b>View all other</b> <a href="lwg-index.html#refwrap.invoke">issues</a> in [refwrap.invoke].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#C++17">C++17</a> status.</p>
<p><b>Discussion:</b></p>
<p>
22.10.6.5 <a href="https://wg21.link/refwrap.invoke">[refwrap.invoke]</a>/2 is no longer useful. (It was originally TR1 2.1.2.4 [tr.util.refwrp.invoke]/2.)  
First, we already have the As If Rule (6.10.1 <a href="https://wg21.link/intro.execution">[intro.execution]</a>/1) and the STL Implementers Can Be Sneaky Rule 
(16.4.6.5 <a href="https://wg21.link/member.functions">[member.functions]</a>). Second, with variadic templates and other C++11/14 tech, this can be implemented 
exactly as depicted.
</p>

<p><i>[2015-05, Lenexa]</i></p>

<p>
DK: I don't see a defect here<br/>
STL: the issue is that the standard is overly verbose, we don't need this sentence. It's redundant.<br/>
MC: does anyone think this paragraph has value?<br/>
JW: it has negative value. reading it makes me wonder if there's some reason I would want to provide a set of overloaded 
functions, maybe there's some problem with doing it the obvious way that I'm not clever enough to see.<br/>
Move to Ready status: 8 in favor, none against. 
</p>


<p id="res-2435"><b>Proposed resolution:</b></p>
<p>
This wording is relative to N3936.
</p>

<ol>
<li><p>Change 22.10.6.5 <a href="https://wg21.link/refwrap.invoke">[refwrap.invoke]</a> p2 as depicted:</p>

<blockquote>
<pre>
template &lt;class... ArgTypes&gt;
  result_of_t&lt;T&amp;(ArgTypes&amp;&amp;...)>
    operator()(ArgTypes&amp;&amp;... args) const;
</pre>
<blockquote>
<p>
-1- <i>Returns</i>: <code>INVOKE(get(), std::forward&lt;ArgTypes&gt;(args)...)</code>. (20.9.2)
<p/>
<del>-2- <i>Remark</i>: <code>operator()</code> is described for exposition only. Implementations are not required to provide an
actual <code>reference_wrapper::operator()</code>. Implementations are permitted to support <code>reference_wrapper</code> function 
invocation through multiple overloaded operators or through other means.</del>
</p>
</blockquote>
</blockquote>
</li>
</ol>






</body>
</html>
