public static int GetIndex(PDLBinarySetOperator op)
        {
            switch (op)
            {
            case PDLBinarySetOperator.Intersection: return(0);

            case PDLBinarySetOperator.Union: return(1);

            default: throw new PDLException("undefined operator");
            }
        }
 public static int GetIndex(PDLBinarySetOperator op)
 {
     switch (op)
     {
         case PDLBinarySetOperator.Intersection: return 0;
         case PDLBinarySetOperator.Union: return 1;
         default: throw new PDLException("undefined operator");
     }
 }