>std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">&gt;</span>  <span class="comment">// abstract</span>

<span class="special">&gt;</span> <span class="identifier">bm_type</span><span class="special">;</span>
<span class="keyword">typedef</span> <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">value_type</span> <span class="identifier">book</span><span class="special">;</span>

<span class="identifier">bm_type