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<title>Issue 1398: Users should be able to specialize functors without depending on whole &lt;functional&gt; header</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">NAD</a> status.</em></p>
<h3 id="1398"><a href="lwg-closed.html#1398">1398</a>. Users should be able to specialize functors without depending on whole <code>&lt;functional&gt;</code> header</h3>
<p><b>Section:</b> 22.10 <a href="https://wg21.link/function.objects">[function.objects]</a> <b>Status:</b> <a href="lwg-active.html#NAD">NAD</a>
 <b>Submitter:</b> BSI <b>Opened:</b> 2010-08-25 <b>Last modified:</b> 2016-01-28</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all other</b> <a href="lwg-index.html#function.objects">issues</a> in [function.objects].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#NAD">NAD</a> status.</p>
<p><b>Discussion:</b></p>
<p><b>Addresses GB-96</b></p>
<p>
The function templates <code>hash</code>, <code>less</code> and <code>equal_to</code>
are important customization points for user-defined types to
be supported by several standard containers. These are
accessed through the <code>&lt;functional&gt;</code> header which has
grown significantly larger in C++0x, exposing many more
facilities than a user is likely to need through there own
header, simply to declare the necessary specialization.
There should be a smaller header available for users to
make the necessary customization.
</p>

<p><i>[
Resolution proposed by ballot comment
]</i></p>

<p>
Provide a tiny forwarding header for important
functor types in the <code>&lt;functional&gt;</code> header that a
user may want to specialize. This should contain
the template declaration for <code>equal_to</code>, <code>hash</code> and
<code>less</code>.
</p>

<p><i>[
Rapperswill summary
]</i></p>

<p>Alisdair: Would recommend NAD unless someone takes the issue. </p>

<p>Daniel: Volunteers to write a paper for this. </p>

<p><i>[
2010-11-07 Daniel provides a paper available on the Batavia document list
]</i></p>


<p><i>[
2010 Batavia:
]</i></p>

<p>
Closed as NAD - the consensus was that forwarding headers such as
<code>&lt;iosfwd&gt;</code> do not bring the expected benefits, and are
not widely used (to the surprise of some active users in the room!).
Without real experience reporting a benefit, there is no further interest
in pursuing this issue as an extension - hence NAD rather than NAD Future.
</p>



<p><b>Rationale:</b></p><p>No consensus to make a change</p>

<p id="res-1398"><b>Proposed resolution:</b></p>
<p>
See paper &quot;Forwarding <code>&lt;functional&gt;</code> functor templates&quot;
on the Batavia LWG document list
</p>





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