identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special">&lt;</span>
              <span class="identifier">State</span> <span class="special">,</span>
              <span class="identifier">Stepper</span><span class="special">::</span><span class="identifier">time_type</span> <span class="special">&gt;</span></code>
            </li>
<li class="listitem">
              <code class="computeroutput"><span class="identifier">reference_type</span></code> is