Class 24 Objectives

At the end of today's class you should

KNOW:

How to test functions that change the values of state variables
How to use error to report an error condition
The differences between set! and mutators (set-structure!)

BE ABLE TO:

Develop a set of test cases to adequately test a function that uses set!
Choose set! or set-structure!, as appropriate, to solve a problem

Sample Exam Question:

An online bookstore uses the following data definition and variable to track customers' orders:

;; Order is a (make-order String ListOfString Symbol)
(define-struct order (name titles status))

;; orderlist:  ListOfOrder
;; stores the orders that customers have placed

;; where status is one of 'placed, 'paid, or 'shipped

Write a function change-status that consumes an order and a symbol and changes the order's status to the given symbol.

;; change-status: Order Symbol -> void
;; changes status of given order to given symbol