pan class="identifier">string</span> <span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Tin<span class="special">,</span> <span class="keyword">typename</span> Signature<span class="special">,</span> 
           <span class="keyword">typename</span>  <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span cl