ecial">::</span><span class="identifier">base_type</span><span class="special">(</span><span class="identifier">start</span><span class="special">)</span>
    <span class="special">{</span>
        <span class="keyword">using</span> <span class="identifier">qi</span><span class="special">::</span><span class="identifier">eps</span><span class="special">;</span>
        <span class="keyword">using</span> <span class="identifier">qi</span><span class="special">::</span><span class="identifier">lit</span><span