. 
 </PRE>
<h4><a name="Exceptions">Exceptions</a></h4>
<PRE>
 
   Error free. 
 </PRE>
<h4><a name="Files">Files</a></h4>
<PRE>
 
   None. 
 </PRE>
<h4><a name="Particulars">Particulars</a></h4>
<PRE>
 
   The first time the function is referenced, the value is computed 
   as shown above. The value is saved, and returned directly upon 
   subsequent reference. 
 </PRE>
<h4><a name="Examples">Examples</a></h4>
<PRE>
 
   The subroutine shown below illustrates the use of <b>halfpi_c</b>. 
 
            void