">struct</span> <span class="identifier">double3_policy</span> <span class="special">:</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">karma</span><span class="special">::</span><span class="identifier">real_policies</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span>
<span class="special">{</span>
    <span class="comment">//  we want