Lecture 17 Objectives

At the end of today's class you should

KNOW:

Why it is sometimes necessary to write a function where the contract specifies two possible return types

BE ABLE TO:

Write a function that specifies two return types in the contract

Sample Exam Question:

(This is trickier than what would normally be asked on an exam)

Using the definition of person given below, write the function last-blue:

;; a person is a (make-person string symbol)
(define-struct person (name eye))

;; a list-of-person is either
;; empty, or
;; (cons person list-of-person)

;; last-blue:  list-of-person -> person or false
;; finds the last person in a list of person who has blue eyes