Lecture 20 Objectives

At the end of today's class you should

KNOW:

What a variable is
How to make Scheme remember a result that changes over time
Why set! can't be used to change the value of a function argument
How to test functions that change the values of variables
How to use error to report an error condition

BE ABLE TO:

Use set! to redefine a named variable
Document variables
Document a function that changes the value of a variable
Develop a set of test cases to adequately test a function that uses set!

Sample Exam Question:

Using the data definitions for account and list-of-account that we defined in class, write a function withdraw-funds that takes an account number and an amount of money and adjusts the balance in the given account by subtracting the amount of the withdrawal. If the original amount of the balance is less than the amount to be withdrawn, print an error message.