>

<span class="keyword">struct</span> <a class="link" href="iterator.html" title="Struct iterator">iterator</a> <span class="special">{</span>
  <span class="comment">// types</span>
  <span class="keyword">typedef</span> <span class="keyword">decltype</span><span class="special">(</span><span class="identifier">sample_merge</span><span class="special">(</span><span class="special">*</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">declval</span><span class="