class="special">&lt;</span><span class="identifier">construct_from_string</span><span class="special">&gt;());</span>
            <span class="special">}</span>
         <span class="special">};</span> <span class="comment">// template &lt;class T&gt; struct constant_pi</span>
      <span class="special">}</span> <span class="comment">//  namespace detail</span>

      <span class="comment">// The actual forwarding function (including policy to control precision).</span>
      <span class="keyword">template