1 (define
false #f)
2 (define
true #t)
3
4 (define (make-
table)
5 (let ((local-table
'()))
6
7 (define (make-tree key value left-branch right-
branch)
8 (list (cons key value) left-branch right-
branch))
9
10 (define (record-
key tree)
11 (caar tree))
12
13 (define (record-
value)
14 (cdar tree))
15
16 (define (left-
sub tree)
17 (cadr tree))
18
19 (define (right-
sub tree)
20 (caddr tree))
21
22 (define (record tree)
23 (car tree))
24
25 (define (lookup key)
26 (define (lookup-
helper tree)
27 (
if (
null?
tree)
28 false
29 (
if (= (record-
key tree) key)
30 (record-
value tree)
31 (
if (< (record-
key tree) key)
32 (lookup-helper (left-
sub tree))
33 (lookup-helper (right-
sub tree))))))
34 (lookup-helper local-
table))
35
36 (define (insert!
key value)
37 (define (insert-helper!
tree)
38 (
if (
null?
tree)
39 (
set! tree (make-tree key value
'() '()))
40 (
if (= (record-
key tree) key)
41 (
set-cdr!
(record tree) value)
42 (
if (< (record-
key tree) key)
43 (insert-helper! (left-
sub tree))
44 (insert-helper! (right-
sub tree))))))
45 (insert-helper! local-
table)
46 'ok)
47
48 (define (print-
table)
49 (display local-
table)
50 (newline))
51
52 (define (dispatch m)
53 (cond ((eq? m
'print-table) print-table)
54 ((eq? m
'insert!) insert!)
55 ((eq? m
'lookup) lookup)
56 (
else (error
"Unknow operation --TABLE" m))))
57
58 dispatch))
59
60 (define t1 (make-
table))
61 ((t1
'print-table))
62 ((t1
'lookup) 4)
63 ((t1
'insert!) 4 'lan)
64 ((t1
'insert!) 5 'tian)
65 ((t1
'print-table))
insert! 部分有问题明明set！ 了 local-table 却没有什么效果，可能是我对环境模型的理解不够导致的。 参考
转载于:https://www.cnblogs.com/tclan126/p/6850959.html
