_GENERATE</span><span class="special">(</span><span class="identifier">half_pi</span><span class="special">);</span>
<span class="special">}</span>
</pre>
<p>
      The output from the program is a snippet of C++ code (actually a macro call)
      that can be cut and pasted into <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">math</span><span class="special">/</span><span class="identifier">constants</span><span class="special">/</span