
</span>
<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> TypeOut<span class="special">,</span> <span class="keyword">typename</span> TypeIn<span class="special">&gt;</span> 
  <span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span><span class="special">&lt;</span> <span class="identifier">TypeOut</span> <span class="special">&gt;</span> <span class="identifier">convert</span><span class="special"