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-intermediate-reader.ss" "lang")((modname 19.2.2) (read-case-sensitive #t) (teachpacks ((lib "draw.ss" "teachpack" "htdp"))) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ((lib "draw.ss" "teachpack" "htdp")))))
4 ;sort : (X X -> boolean) (listof X) -> (listof X)
5 ;Given a-lox and op, sort the SchemeData.
6 
7 ;insert : (X X -> boolean) X (listof X) -> (listof X)
8 ;Given op, an-x and a-lox, insert an-x in the proper position in a-lox by using op.
9 (define (sort-lox op a-lox)
10   (local ((define (sort op a-lox)
11             (cond
12               [(empty? a-lox) empty]
13               [(cons? a-lox) (insert op
14                                      (first a-lox)
15                                      (sort op (rest a-lox)))]))
16           (define (insert op an-x a-lox)
17             (cond
18               [(empty? a-lox) (cons an-x empty)]
19               [(op an-x (first a-lox)) (cons an-x a-lox)]
20               [else (cons (first a-lox) (insert op an-x (rest a-lox)))])))
21     (sort op a-lox)))
22 
23 (define-struct ir (name price))
24 
25 ;An inventory record (ir) is a structure
26 ;(make-ir n p)
27 ;where n is a symbol and p is a number.
28 
29 ;An inventory is a (listof ir).
30 
31 ;<ir? : ir ir -> boolean
32 ;Given ir1 and ir2, returns true if the price of ir1 is less than that of ir2.
33 (define (<ir? ir1 ir2)
34   (< (ir-price ir1)
35      (ir-price ir2)))
36 
37 ;>ir? : ir ir -> boolean
38 ;Given ir1 and ir2, returns true if the price of ir1 is less than that of ir2.
39 
40 (define (>ir? ir1 ir2)
41   (> (ir-price ir1)
42      (ir-price ir2)))
43 
44 
45 
46 (define ir-list (list (make-ir 'WaterGun 5.50)
47                       (make-ir 'PencilCase 1.25)
48                       (make-ir 'Eraser 0.75)
49                       (make-ir 'CellPhone 25.50)
50                       (make-ir 'Doll 8.75)
51                       (make-ir 'Helmet 15.75)))
52