private static String round(String num, int length) {  // used by realToString
      if (num.indexOf('.') < 0)
         return num;
      if (num.length() <= length)
         return num;
      if (num.charAt(length) >= '5' && num.charAt(length) != '.') {
         char[] temp = new char[length+1];
         int ct = length;
         boolean rounding = true;
         for (int i = length-1; i >= 0; i--) {
            temp[ct] = num.charAt(i); 
            if (rounding && temp[ct] != '.') {
               if (temp[ct] < '9') {
                  temp[ct]++;
                  rounding = false;
               }
               else
                  temp[ct] = '0';
            }
            ct--;
         }
         if (rounding) {
            temp[ct] = '1';
            ct--;
         }
         // ct is -1 or 0
         return new String(temp,ct+1,length-ct);
      }
      else 
         return num.substring(0,length);
      
   }