Question

The private member function DayofYear: :check_date in Display 10.4 allows some illegal dates to get through, such as February \(30 .\) Redefine the member function DayofYear: :check_date so that it ends the program whenever it finds any illegal date. Allow February to contain 29 days, so you account for leap years. (Hint: This is a bit tedious and the function definition is a bit long, but it is not very difficult.

Short answer

Answer: The redefined DayofYear::check_date function handles illegal dates by first checking if the given year is a leap year (divisible by 4, not divisible by 100, or divisible by 400). Based on the month, it then checks if the day value is within the valid range for that month, considering leap years for February. If the day is out of the valid range, the function outputs an error message and terminates the program.

Step-by-step solution

Identify rules for validating dates

To validate the date, we need to consider the days range for each month in any year: - January: 1-31 - February: 1-28 (or 1-29 in leap years) - March: 1-31 - April: 1-30 - May: 1-31 - June: 1-30 - July: 1-31 - August: 1-31 - September: 1-30 - October: 1-31 - November: 1-30 - December: 1-31 And be aware of the leap year rule: - Leap year occurs when the year is divisible by 4, not divisible by 100, or divisible by 400.

Create the DayofYear::check_date function

Before we continue, make sure you understand the code from Display 10.4, including the class definition and the implementation of check_date function. Now, redefine the DayofYear::check_date function to follow these basic rules: 1. Check if the year is a leap year. If it meets the aforementioned conditions, set a variable flag (e.g., isLeapYear) to true. 2. Based on the month, check if the day value is within the valid range for that month. If the day is out of the range, output an error message and end the program. 3. If the function has not ended the program, it proceeds through the Days without any issue. ```cpp //Definition of member function check_date void DayofYear::check_date() { bool isLeapYear = ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0)); int daysInMonth; if(month == 2) daysInMonth = (isLeapYear) ? 29 : 28; else if(month == 4 || month == 6 || month == 9 || month == 11) daysInMonth = 30; else daysInMonth = 31; if(day <= 0 || day > daysInMonth) { std::cout << "Illegal date! Program will terminate." << std::endl; exit(1); } } ``` Now, the DayofYear::check_date function will correctly handle illegal dates, including the leap years, and terminate the program when it encounters an illegal date.