ns every 
   point contained in the first window but not contained in the 
   second window. 

   Fortran offers no satisfactory floating point representation 
   of open intervals. Thus, for floating point windows we must 
   return the closure of the set theoretical difference.
 </PRE>
<h4><a name="Examples">Examples</a></h4>
<PRE>
 
   Let a contain the intervals 

      [ 1, 3 ]  [ 7, 11 ]  [ 23, 27 ] 

   and b contain the intervals 

      [ 2, 4 ]  [ 8, 10 ]  [ 16, 18 ] 

   Then the difference of a 