an class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Type<span class="special">&gt;</span> 
  <span class="keyword">struct</span> <a class="link" href="map/on_invertible__idp41617456.html" title="Struct template on_invertible&lt;Type, false&gt;">on_invertible</a><span class="special">&lt;</span><span class="identifier">Type</span><span class="special">,</span> <span class="keyword">false</span><span class="special">&gt;</span> <span class="special">{</span