protected void checkTypeOfOperands (List<Expression> operands)
    {
        List<Class<?>> expectedOperandTypes = getOperandTypes();
        if (expectedOperandTypes == null) return;
        boolean statusCheck = true;
        for (int i = 0; i < operands.size(); i++)
        {
            statusCheck =
                statusCheck && isCorrectInstance(operands.get(i), expectedOperandTypes.get(i));
            if (statusCheck == false)
                 throw new ParserException("Incorrect type of operand(s). Should be " +
                                           expectedOperandTypes.toString());
        }
    }