Object-oriented Software in Ada 95

92 Packages as classes
6.14 Exercises
Construct the following classes:
• Account_with_overdraft
Construct a class which represents an account on which a customer is allowed to go overdrawn. You
should restrict the amount the customer is allowed to go overdrawn. The methods of this class are:
Method
Responsibility
Balance
Deliver the balance of the account.
Deposit
Deposit money into the account
Set_Overdraft_Limit Set the overdraft limit.
Statement
Print a statement of the current balance of
the account.
Withdraw
Withdraw money from the account.
• Cinema Performance Attendance
A class Performance, an instance of which represents the seats at a particular showing of a film, has
the following methods:
Method
Book_seats
Cancel
Sales
Seats_Free
Responsibility
Book n seats at the performance.
Unbook n seats.
Return the value of the seats sold at this
performance.
Return the number of seats that are still
unsold.
Thus on an instance of Performance the following actions can be performed:
• Book a number of seats
• Find out the number of unsold seats at the performance
• Cancel the booking for n seats.
• Return the value of the seats sold at this performance.
• Library Book
A class to represent a book in a library, such that the following operations can be processed:
(a)
(b)
(c)
(d)
Loan the book.
Mark the book as being reserved. Only one outstanding reservation is allowed on a book.
Ask if a book can be loaned. A book can only be loaned if it is not already on loan or is not
reserved.
Return the book.
© M A Smith - May not be reproduced without permission