lass="keyword">typename</span> Type<span class="special">,</span> <span class="keyword">bool</span> is_total<span class="special">&gt;</span> 
  <span class="keyword">struct</span> <a class="link" href="map/on_definedness.html" title="Struct template on_definedness">on_definedness</a> <span class="special">{</span>
  <span class="special">}</span><span class="special">;</span>
  <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Type<span class="speci