void parseLoopParameters(String[] fields) throws Exception {
    fieldCount = 0;
    for (int i = 0; i < fields.length; i++)
      propertyReferenced[i] = false;

    propertyCount = fields.length;
    while (true) {
      String str = tokenizer.peekToken();
      if (str == null) {
        fieldCount = 0;
        break;
      }
      if (str.charAt(0) != '_')
        break;
      tokenizer.getTokenPeeked();
      fieldTypes[fieldCount] = NONE;
      for (int i = fields.length; --i >= 0;)
        if (isMatch(str, fields[i])) {
          fieldTypes[fieldCount] = i;
          propertyReferenced[i] = true;
          break;
        }
      fieldCount++;
    }
    if (fieldCount > 0)
      loopData = new String[fieldCount];
  }