1 #lang sicp
2
3 (#%require sicp-
pict)
4
5 (define (origin-
frame frame)
6 (car frame))
7
8 (define (edge1-
frame frame)
9 (cadr frame))
10
11 (define (edge2-
frame frame)
12 (caddr frame))
13
14 (define (make-
vect a b)
15 (cons a b))
16
17 (define (xcor-
vect v)
18 (car v))
19
20 (define (ycor-
vect v)
21 (cdr v))
22
23 (define (add-
vect v1 v2)
24 (make-vect (+ (xcor-
vect v1)
25 (xcor-
vect v2))
26 (+ (ycor-
vect v1)
27 (ycor-
vect v2))))
28
29 (define (sub-
vect v1 v2)
30 (make-vect (- (xcor-
vect v1)
31 (xcor-
vect v2))
32 (- (ycor-
vect v1)
33 (ycor-
vect v2))))
34
35 (define (scale-
vect s v1)
36 (make-vect (* s (xcor-
vect v1))
37 (* s (ycor-
vect v1))))
38
39 (define (frame-coord-
map frame)
40 (lambda (v)
41 (add-
vect
42 (origin-
frame frame)
43 (add-vect (scale-vect (xcor-
vect v)
44 (edge1-
frame frame))
45 (scale-vect (ycor-
vect v)
46 (edge2-
frame frame))))))
47 ;;;;;;;;;;;;;;;;;;;
2.50
48 (define (transform-
painter painter origin corner1 corner2)
49 (lambda (frame)
50 (let ((m (frame-coord-
map frame)))
51 (let ((
new-
origin (m origin)))
52 (painter
53 (make-frame
new-
origin
54 (sub-vect (m corner1)
new-
origin)
55 (sub-vect (m corner2)
new-
origin)))))))
56
57 (define (flip-
horiz painter)
58 (transform-
painter painter
59 (make-vect
1.0 0.0)
60 (make-vect
0.0 0.0)
61 (make-vect
1.0 1.0)))
62
63 (define (roate90 painter)
64 (transform-
painter painter
65 (make-vect
1.0 0.0)
66 (make-vect
1.0 1.0)
67 (make-vect
0.0 0.0)))
68
69 (define (roate180 painter)
70 (transform-
painter painter
71 (make-vect
1.0 1.0)
72 (make-vect
0.0 1.0)
73 (make-vect
1.0 0.0)))
74
75 (define (roate270 painter)
76 (transform-
painter painter
77 (make-vect
0.0 1.0)
78 (make-vect
0.0 0.0)
79 (make-vect
1.0 1.0)))
80
81 ;;;;;;;;;;;;;;;;;
2.51
82 (define (my-
below painter1 painter2)
83 (let ((split-point (make-vect
0.0 0.5)))
84 (let ((paint-
up
85 (transform-
painter painter2
86 split-
point
87 (make-vect
1.0 0.5)
88 (make-vect
0.0 1.0)))
89 (paint-
bottom
90 (transform-
painter painter1
91 (make-vect
0.0 0.0)
92 (make-vect
1.0 0.0)
93 split-
point)))
94 (lambda (frame)
95 (paint-
up frame)
96 (paint-
bottom frame)))))
97
98 (define (my-
below2 painter1 painter2)
99 (roate270 (beside (roate90 painter1) (roate90 painter2))))
1.理解painter是个过程接受frame参数，即在frame中画painter
2.frame-coord-map 中将一个单位正方形中的点映射到一个新框架中
3.transform-painter 则是将painter映射到一个新框架中返回的也是一个过程，也可以理解为返回一个painter
转载于:https://www.cnblogs.com/tclan126/p/6431103.html
相关资源：数据结构—成绩单生成器
