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<title>Issue 2808: Requirements for fpos and stateT</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#Resolved">Resolved</a> status.</em></p>
<h3 id="2808"><a href="lwg-defects.html#2808">2808</a>. Requirements for <code>fpos</code> and <code>stateT</code></h3>
<p><b>Section:</b> 31.5.3.3 <a href="https://wg21.link/fpos.operations">[fpos.operations]</a> <b>Status:</b> <a href="lwg-active.html#Resolved">Resolved</a>
 <b>Submitter:</b> Great Britain <b>Opened:</b> 2016-11-09 <b>Last modified:</b> 2020-05-12</p>
<p><b>Priority: </b>4
</p>
<p><b>View all other</b> <a href="lwg-index.html#fpos.operations">issues</a> in [fpos.operations].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#Resolved">Resolved</a> status.</p>
<p><b>Discussion:</b></p>
<p>
<b>Addresses GB 60</b>
</p>
<p>
The requirements on the <code>stateT</code> type used 
to instantiate class template <code>fpos</code> are not 
clear, and the following Table 108 &mdash; "Position 
type requirements" is a bit of a mess. This is 
old wording, and should be cleaned up with better
terminology from the Clause 17 Requirements. For example, 
<code>stateT</code> might be require <code>CopyConstructible</code>?, 
<code>CopyAssignable</code>?, and <code>Destructible</code>. Several 
entries in the final column of the table appear to be 
post-conditions, but without the <code>post</code> markup to 
clarify they are not assertions or preconditions. They 
frequently refer to identifiers that do not apply to all 
entries in their corresponding <code>Expression</code> 
column, leaving some expressions without a clearly defined semantic.
If <code>stateT</code> is a trivial type, is <code>fpos</code> also a 
trivial type, or is a default constructor not required/supported?
</p>
<p>
Proposed change:
<p/>
Clarify the requirements and the table.
</p>

<p><i>[Issues Telecon 16-Dec-2016]</i></p>

<p>Priority 4; no consensus for any concrete change</p>

<p><i>[2019-03-17; Daniel comments]</i></p>

<p>
With the acceptance of <a href="https://wg21.link/p0759r1">P0759R1</a> at the Rapperswil 2018 meeting
this issue should be closed as <b>Resolved</b> (Please note that this paper resolves a historic
NB comment that was originally written against C++17 but was at that time responded: "invite a paper 
if anybody wants to change it - no concensus for change").
</p>

<p><i>[2020-05-12; Reflector discussions]</i></p>

<p>
Resolved by <a href="https://wg21.link/p0759r1">P0759R1</a>.
</p>


<p><b>Rationale:</b></p>
Resolved by <a href="https://wg21.link/p0759r1">P0759R1</a>.


<p id="res-2808"><b>Proposed resolution:</b></p>





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