>
<p>
      5. The complete program to generate the constant <code class="computeroutput"><span class="identifier">half_pi</span></code>
      using function <code class="computeroutput"><span class="identifier">calculate_half_pi</span></code>
      is then:
    </p>
<pre class="programlisting"><span class="preprocessor">#define</span> <span class="identifier">USE_CPP_FLOAT</span> <span class="comment">// If required.</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span c