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<title>Issue 2949: Unclear complexity requirements: space vs. time</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#New">New</a> status.</em></p>
<h3 id="2949"><a href="lwg-active.html#2949">2949</a>. Unclear complexity requirements: space vs. time</h3>
<p><b>Section:</b> 16 <a href="https://wg21.link/library">[library]</a> <b>Status:</b> <a href="lwg-active.html#New">New</a>
 <b>Submitter:</b> Jens Maurer <b>Opened:</b> 2017-03-20 <b>Last modified:</b> 2017-07-15</p>
<p><b>Priority: </b>4
</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#New">New</a> status.</p>
<p><b>Discussion:</b></p>
<p>
This is from editorial issue <a href="https://github.com/cplusplus/draft/issues/1088">#1088</a>:
<p/>
It is not always made explicit whether the requirement is referring to time or space complexity, or both.
</p>
<blockquote>
<p>
"Linear time." vs. "Linear."<br/>
"Constant time." vs. "Constant."
</p>
</blockquote>
<p>
16.3.2.4 <a href="https://wg21.link/structure.specifications">[structure.specifications]</a> says that the <i>Complexity</i> element specifies "the time and/or space
complexity of the function", so being explicit about this would be good.
<p/>
Examples:
</p>
<ul>
<li><p>[sequence.reqmts] <code>a.clear()</code></p></li>
<li><p>[deque.cons]</p></li>
<li><p>[vector.cons]</p></li>
<li><p>[map.cons]</p></li>
<li><p>[multimap.cons]</p></li>
<li><p>[set.cons]</p></li>
<li><p>[multiset.cons]</p></li>
<li><p>[unord.map.cnstr]</p></li>
<li><p>[unord.multimap.cnstr]</p></li>
</ul>
<p>
etc.
</p>

<p><i>[2017-07 Toronto Wed Issue Prioritization]</i></p>

<p>Priority 4; Robert to look at</p>


<p id="res-2949"><b>Proposed resolution:</b></p>





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