an class="special">,</span> 
                                  <span class="identifier">Time</span> end_time<span class="special">,</span> <span class="identifier">Time</span> dt<span class="special">)</span><span class="special">;</span>

      <span class="comment">// Second version to solve the forwarding problem, can be called with Boost.Range as start_state. </span>
      <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Stepper<span class="spec