_discrete&lt;boost::gregorian::date_duration&gt;">is_discrete</a><span class="special">&lt;</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">gregorian</span><span class="special">::</span><span class="identifier">date_duration</span><span class="special">&gt;</span><span class="special">;</span>
    <span class="keyword">template</span><span class="special">&lt;</span><span class="special">&gt;</span> <span class="keyword">struct</span> <a class="link" href=