1 ;; The first three lines of this file were inserted by DrScheme. They record metadata
2 ;; about the language level of this file in a form that our tools can easily process.
3 #reader(lib "htdp-advanced-reader.ss" "lang")((modname |40.1|) (read-case-sensitive #t) (teachpacks ((lib "guess-gui.ss" "teachpack" "htdp") (lib "guess.ss" "teachpack" "htdp") (lib "gui.ss" "teachpack" "htdp") (lib "draw.ss" "teachpack" "htdp"))) (htdp-settings #(#t constructor repeating-decimal #t #t none #f ((lib "guess-gui.ss" "teachpack" "htdp") (lib "guess.ss" "teachpack" "htdp") (lib "gui.ss" "teachpack" "htdp") (lib "draw.ss" "teachpack" "htdp")))))
4 #|
5 Exercise 40.1.3.   Show how to implement the following structure definitions as functions:
6 
7    1. (define-struct movie (title producer))
8    2. (define-struct boyfriend (name hair eyes phone))
9    3. (define-struct cheerleader (name number))
10    4. (define-struct CD (artist title price))
11    5. (define-struct sweater (material size producer))
12 
13 Pick one and demonstrate that the expected laws hold.    Solution
14 |#
15 
16 (define (make-movie title producer)
17   (local ((define title0 title)
18           (define producer0 producer)
19           (define (service-manager msg)
20             (cond
21               [(equal? msg 'title) title0]
22               [(equal? msg 'producer) producer0])))
23     service-manager))
24 
25 (define (movie-title amovie)
26   (amovie 'title))
27 
28 (define (movie-producer amovie)
29   (amovie 'producer))
30 
31 (define SciFi (make-movie 'StarWars 'GeorgeLucas))
32 (movie-title SciFi)
33 (movie-producer SciFi)
34 
35 (define (make-boyfriend name hair eyes phone)
36   (lambda (selector)
37     (selector name hair eyes phone)))
38 (define (boyfriend-name aboyfriend)
39   (aboyfriend (lambda (name hair eyes phone) name)))
40 (define (boyfriend-hair aboyfriend)
41   (aboyfriend (lambda (name hair eyes phone) hair)))
42 (define (boyfriend-eyes aboyfriend)
43   (aboyfriend (lambda (name hair eyes phone) eyes)))
44 (define (boyfriend-phone aboyfriend)
45   (aboyfriend (lambda (name hair eyes phone) phone)))
46 
47 (define Aaron (make-boyfriend 'Aaron 'black 'black 715))
48 (boyfriend-name Aaron)
49 (boyfriend-hair Aaron)
50 (boyfriend-eyes Aaron)
51 (boyfriend-phone Aaron)
52 
53 (define (make-cheerleader name number)
54   (lambda (selector)
55     (selector name number)))
56 (define (cheerleader-name acheerleader)
57   (acheerleader (lambda (name number) name)))
58    
59 (define (cheerleader-number acheerleader)
60   (acheerleader (lambda (name number) number)))
61 
62 (define Abbo (make-cheerleader 'Abbo 53535))
63 (cheerleader-name Abbo)
64 (cheerleader-number Abbo)
65 
66 (define (make-CD artist title price)
67   (local ((define artist0 artist)
68           (define title0 title)
69           (define price0 price)
70           (define (service-manager msg)
71             (cond
72               [(equal? msg 'artist) artist0]
73               [(equal? msg 'title) title0]
74               [(equal? msg 'price) price0])))
75     service-manager))
76 
77 (define (CD-artist aCD)
78   (aCD 'artist))
79 
80 (define (CD-title aCD)
81   (aCD 'title))
82 
83 (define (CD-price aCD)
84   (aCD 'price))
85 
86 (define BeeGees (make-CD 'BeeGees 'SaturdayNightFever 9.99))
87 (CD-artist BeeGees)
88 (CD-title BeeGees)
89 (CD-price BeeGees)
90 
91 (define (make-sweater material size producer)
92   (lambda (selector)
93     (selector material size producer)))
94 (define (sweater-material asweater)
95   (asweater (lambda (material size producer) material)))
96 (define (sweater-size asweater)
97   (asweater (lambda (material size producer) size)))
98 (define (sweater-producer asweater)
99   (asweater (lambda (material size producer) producer)))
100 
101 (define YellowJacket (make-sweater 'Cotton 'Large 'Unknown))
102 (sweater-material YellowJacket)
103 (sweater-size YellowJacket)
104 (sweater-producer YellowJacket)