an class="keyword">typename</span> System<span class="special">&gt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special">&lt;</span> <span class="identifier">time_type</span><span class="special">,</span> <span class="identifier">time_type</span> <span class="special">&gt;</span> <a class="link" href="dense_output_r_idp20189216.html#idp20198416-bb"><span class="identifier">do_step</span></a><span class="special">(</span><span clas