1 (#%require (only racket/
base random))
2
3 ;;;;;;;;;
3.5
4 (define (estimate-
integral expriment x1 x2 y1 y2 trials)
5 (let ((length (abs (-
x2 x1)))
6 (high (abs (-
y2 y1))))
7 (* (* high length) (monte-
carlo trials expriment))))
8
9 (define (monte-
carlo trials expriment)
10 (define (iter trials-remaining trials-
passed)
11 (cond ((= trials-remaining
0)
12 (/ trials-
passed trials))
13 ((expriment)
14 (iter (- trials-remaining
1) (+ trials-passed
1)))
15 (
else
16 (iter (- trials-remaining
1) trials-
passed))))
17 (iter trials
0))
18
19 ;(define p1
20 ; (let ((x (random-
in-range -
1 1))
21 ; (y (random-
in-range -
1 1)))
22 ; (<= (+ (square x) (square y))
1)))
23 (#%require (only racket/
base random))
24
25 ;;;;;;;;;
3.5
26 (define (estimate-
integral expriment x1 x2 y1 y2 trials)
27 (let ((length (abs (-
x2 x1)))
28 (high (abs (-
y2 y1))))
29 (* (* high length) (monte-
carlo trials expriment))))
30
31 (define (monte-
carlo trials expriment)
32 (define (iter trials-remaining trials-
passed)
33 (cond ((= trials-remaining
0)
34 (/ trials-
passed trials))
35 ((expriment)
36 (iter (- trials-remaining
1) (+ trials-passed
1)))
37 (
else
38 (iter (- trials-remaining
1) trials-
passed))))
39 (iter trials
0))
40
41 ;(define p1
42 ; (let ((x (random-
in-range -
1 1))
43 ; (y (random-
in-range -
1 1)))
44 ; (<= (+ (square x) (square y))
1)))
45
46 (define p
47 (lambda ()
48 (let ((x (random-
in-range
0 2))
49 (y (random-
in-range
0 2)))
50 (>=
1 (+ (square (- x
1)) (square (- y
1)))))))
51
52 (define (random-
in-
range low high)
53 (let ((range (-
high low)))
54 (+
low (random range))))
55
56 (define square
57 (lambda (x) (*
x x)))
58
59 (exact->inexact (estimate-integral p
0 2 0 2 1000))
60
61 ;;;;;;;;
3.6
62 (define rand-init
1)
63
64 (define rand-
update
65 (lambda (x)
66 (+ x
1)))
67
68 (define rand
69 (let ((x rand-
init))
70
71 (define reset
72 (lambda (value)
73 (
set!
x value)))
74
75 (define generate
76 (begin(
set! x (rand-
update x))
77 x))
78
79 (define (dispatch x)
80 (cond ((eq? x
'generate) generate)
81 ((eq? x
'reset) reset)
82 (
else (error
"No such method -- rand" a))))
83 dispatch))
84
85 (define rand1
86 (let ((x rand-
init))
87 (define (dispatch message)
88 (cond ((eq? message
'generate)
89 (begin (
set! x (rand-
update x))
90 x))
91 ((eq? message
'reset)
92 (lambda (
new-value) (
set! x
new-
value)))))
93 dispatch))
94
95 (define rand2
96 (let ((x rand-
init))
97 (define (generate)
98 (
set! x (rand-
update x))
99 x)
100 (define (reset n)
101 (
set!
x n))
102 (define (dispatch a)
103 (cond ((eq?
'generate a) (generate))
104 ((eq?
'reset a) reset)
105 (
else (error
"No such method -- rand" a))))
106 dispatch))
107
108
109
110 ;(rand
'generate)
111 ;(rand
'generate)
112 ;(rand
'generate)
113 ;((rand
'reset) 3)
114 ;(rand
'generate)
115
116 (rand2
'generate)
117 (rand2
'generate)
118 (rand2
'generate)
119 ((rand2
'reset) 3)
120 (rand2
'generate)
1.被注释掉的p 不是一个过程，而是一个值 如果把rand-in-range 放后面会报错
2.也是同样的情况被注释掉的rand过程中 我试图直接把generate做成一个值，但是总是得不到正确的结果，
我想可能是因为，当generate 为数值时，它的数值的取决于rand中的x，而在这里就会 出现 x一直为
rand-init。如果把generate 做成一个无参过程，除了开始之外就不会依赖于rand 中的x了，从而每次都会update
自己的x了，可能和作用域有关
转载于:https://www.cnblogs.com/tclan126/p/6531978.html
相关资源：数据结构—成绩单生成器
