tor</span> last<span class="special">)</span><span class="special">;</span></pre></div>
<div class="refsect1">
<a name="idp119020496"></a><h2>Description</h2>
<p>This routine takes in a set of requests stored in the iterator range <code class="computeroutput"></code>[first,last) and waits until at least one of the requests has completed. It then completes all of the requests it can, partitioning the input sequence into pending requests followed by completed requests. If an output iterator is provided, <code