Lecture 21 Objectives

At the end of today's class you should

KNOW:

That format creates a string by dropping data into the ~a in the string
That begin can be used to run any number of Scheme expressions, but only returns the result of the last expression
When to use begin
That local can be used to give names to the results of intermediate computations
That it is OK to define a function which takes no inputs

BE ABLE TO:

Write programs that change the values of variables

Sample Exam Question:

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

;; an order is a (make-order string list-of-string symbol)
(define-struct order (name titles status))

;; orderlist:  list-of-order
;; stores the orders that customers have placed

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

Write a function remove-shipped that removes all orders with the status 'shipped from orderlist

;; remove-shipped: -> void
;; removes all orders with status 'shipped from orderlist
;; EFFECT:  changes orderlist to exclude shipped orders