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<title>Issue 972: The term "Assignable" undefined but still in use</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#NAD_Editorial">NAD Editorial</a> status.</em></p>
<h3 id="972"><a href="lwg-closed.html#972">972</a>. The term "Assignable" undefined but still in use</h3>
<p><b>Section:</b> 16 <a href="https://wg21.link/library">[library]</a> <b>Status:</b> <a href="lwg-active.html#NAD_Editorial">NAD Editorial</a>
 <b>Submitter:</b> Niels Dekker <b>Opened:</b> 2009-01-07 <b>Last modified:</b> 2016-01-28</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View other</b> <a href="lwg-index-open.html#library">active issues</a> in [library].</p>
<p><b>View all other</b> <a href="lwg-index.html#library">issues</a> in [library].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#NAD Editorial">NAD Editorial</a> status.</p>
<p><b>Discussion:</b></p>
<p>
Previous versions of the Draft had a table, defining the Assignable 
requirement.  For example 
<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n2134.pdf">N2134</a>
Table 79, "Assignable requirements". But I guess the term "Assignable" 
is outdated by now, because the current Committee Draft provides 
<code>MoveAssignable</code>, <code>CopyAssignable</code>, and <code>TriviallyCopyAssignable</code> concepts 
instead. And as far as I can see, it no longer has a definition of 
<code>Assignable</code>. (Please correct me if I'm wrong.) Still the word 
"Assignable" is used in eight places in the Draft, 
<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2800.pdf">N2800</a>.
</p>

<p>
Are all of those instances of "<code>Assignable</code>" to be replaced by "<code>CopyAssignable</code>"? 
</p>

<p><i>[
Batavia (2009-05):
]</i></p>

<blockquote><p>
Move to NAD Editorial.
</p></blockquote>


<p id="res-972"><b>Proposed resolution:</b></p>

<p>
Change Exception Propagation 17.9.7 <a href="https://wg21.link/propagation">[propagation]</a>:
</p>
<blockquote><p>
<code>exception_ptr</code> shall be <code>DefaultConstructible</code>, <code>CopyConstructible</code>,
<code><ins>Copy</ins>Assignable</code> and <code>EqualityComparable</code>.
</p></blockquote>

<p>
Change Class template reference_wrapper 22.10.6 <a href="https://wg21.link/refwrap">[refwrap]</a>:
</p>
<blockquote><p>
<code>reference_wrapper&lt;T&gt;</code> is a <code>CopyConstructible</code> and <code><ins>Copy</ins>Assignable</code> 
wrapper around a reference to an object of type <code>T</code>.
</p></blockquote>
<p>
Change Placeholders 22.10.15.5 <a href="https://wg21.link/func.bind.place">[func.bind.place]</a>:
</p>
<blockquote><p>
It is implementation defined whether placeholder types are <code><ins>Copy</ins>Assignable</code>. 
<code><ins>Copy</ins>Assignable</code> placeholders' copy assignment operators shall not throw exceptions.
</p></blockquote>
<p>
Change Class template shared_ptr 20.3.2.2 <a href="https://wg21.link/util.smartptr.shared">[util.smartptr.shared]</a>:
</p>
<blockquote><p>
Specializations of <code>shared_ptr</code> shall be <code>CopyConstructible</code>, <code><ins>Copy</ins>Assignable</code>, and <code>LessThanComparable</code>...
</p></blockquote>
<p>
Change Class template weak_ptr 20.3.2.3 <a href="https://wg21.link/util.smartptr.weak">[util.smartptr.weak]</a>:
</p>
<blockquote><p>
Specializations of <code>weak_ptr</code> shall be <code>CopyConstructible</code>, <code><ins>Copy</ins>Assignable</code>, and <code>LessThanComparable</code>...
</p></blockquote>
<p>
Change traits typedefs 27.2.3 <a href="https://wg21.link/char.traits.typedefs">[char.traits.typedefs]</a> (note: including deletion of reference to 23.1!):
</p>
<blockquote><p>
<i>Requires:</i> <code>state_type</code> shall meet the requirements of <code><ins>Copy</ins>Assignable</code><del> 
(23.1)</del>, <code>CopyConstructible</code> (20.1.8), and <code>DefaultConstructible</code> types.
</p></blockquote>
<p>
Change Class seed_seq 29.5.8.1 <a href="https://wg21.link/rand.util.seedseq">[rand.util.seedseq]</a> (note again: including deletion of reference to 23.1!):
</p>
<blockquote><p>
In addition to the requirements set forth below, instances of
<code>seed_seq</code> shall meet the requirements of <code>CopyConstructible</code> (20.1.8) and of <code><ins>Copy</ins>Assignable</code><del> (23.1)</del>.
</p></blockquote>

<p>
Note: The proposed resolution of this issue does not deal with the
instance of the term "Assignable" in 99 [auto.ptr], as this is dealt
with more specifically by LWG <a href="lwg-closed.html#973" title="auto_ptr characteristics (Status: NAD Editorial)">973</a><sup><a href="https://cplusplus.github.io/LWG/issue973" title="Latest snapshot">(i)</a></sup>, "<code>auto_ptr</code> characteristics", submitted
by Maarten Hilferink.
</p>






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