er is needed, overload the policy
            class <code class="computeroutput"><span class="identifier">real_policies</span><span class="special">&lt;</span><span class="identifier">Num</span><span class="special">&gt;</span></code>
            and use it as a template parameter to the <code class="computeroutput"><span class="identifier">real_generator</span><span class="special">&lt;&gt;</span></code> real number generator. For instance:
          </p>
<pre class="programlisting"><span class="comment">/