Homework 5: A Rational Calculator

Summary: In this assignment, you will develop a simple calculator which uses rational numbers as its primary data type.

Key Topical Goals: Java basics, Loops, Strings

Assigned: Thursday, 1 April 2004

Due: 10:00 a..m, Friday, 9 April 2004

Assignment

Before break, we started to design a rational number class. It's time to finish that class and put it to use.

Write a simple calculator that can work with rational numbers. You should write a register-based calculator with three named registers (a, b, and c) and one unnamed primary register. (A register is something in which you store a value.) Your calculator should support the following commands:

• P (print): Prints the value in the primary register.
• S register (store): Copies the value from the primary register to the named register.
• L register (load): Loads the value from the named register into the primary register.
• + register-or-rational (add): Adds the given value to the primary register and stores the result in the primary register.
• - register-or-rational (subtract): Subtracts the given value from the primary register and stores the result in the primary register.
• * register-or-rational (multiply): Multiplies the primary register by the given value and stores the result in the primary register.
• / register-or-rational (divide): Divides the primary register by the given value and stores the result in the primary register.
• = rational (assign): Stores the given rational in the primary register.
• Q (quit): Quit the program.

For example,

% java RationalCalculator
Command: = 5
Command: P
5
Command: + 3
Command: * 5
Command: P
40
Command: S a
Command: = 5
Command: P
5
Command: / a
Command: P
1/8
Command: + 1/3
Command: P
11/24
Command: Q