4.3 Exercise 4.3

4.1	Exercise 4.1
4.2	Exercise 4.2
4.3	Exercise 4.3
4.4	Exercise 4.4
4.5	Exercise 4.5
4.6	Exercise 4.6
4.7	Exercise 4.7
4.8	Exercise 4.8
4.9	Exercise 4.9
4.10	Exercise 4.10
4.11	Exercise 4.11
4.12	Exercise 4.12
4.13	Exercise 4.13
4.14	Exercise 4.14
4.15	Exercise 4.15
4.16	Exercise 4.16
4.17	Exercise 4.17
4.18	Exercise 4.18
4.19	Exercise 4.19
4.20	Exercise 4.20
4.21	Exercise 4.21
4.22	Exercise 4.22
4.23	Exercise 4.23
4.24	Exercise 4.24
4.25	Exercise 4.25
4.26	Exercise 4.26
4.27	Exercise 4.27
4.28	Exercise 4.28
4.29	Exercise 4.29
4.30	Exercise 4.30
4.31	Exercise 4.31
4.32	Exercise 4.32
4.33	Exercise 4.33
4.34	Exercise 4.34
4.35	Exercise 4.35
4.36	Exercise 4.36
4.37	Exercise 4.37
4.38	Exercise 4.38
4.39	Exercise 4.39
4.40	Exercise 4.40
4.41	Exercise 4.41
4.42	Exercise 4.42
4.43	Exercise 4.43
4.44	Exercise 4.44
4.45	Exercise 4.45
4.46	Exercise 4.46
4.47	Exercise 4.47
4.48	Exercise 4.48
4.49	Exercise 4.49
4.50	Exercise 4.50
4.51	Exercise 4.51
4.52	Exercise 4.52
4.53	Exercise 4.53
4.54	Exercise 4.54
4.55	Exercise 4.55
4.56	Exercise 4.56
4.57	Exercise 4.57
4.58	Exercise 4.58
4.59	Exercise 4.59
4.60	Exercise 4.60
4.61	Exercise 4.61
4.62	Exercise 4.62
4.63	Exercise 4.63
4.64	Exercise 4.64
4.65	Exercise 4.65
4.66	Exercise 4.66
4.67	Exercise 4.67
4.68	Exercise 4.68
4.69	Exercise 4.69
4.70	Exercise 4.70
4.71	Exercise 4.71

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4.3 Exercise 4.3

We can write the new version of eval like this:

(define (eval- exp env)
  (if (self-evaluating? exp)
      (real-exp exp)
      ((get 'eval (exp-type exp)) (real-exp exp) env)))

(define exp-type car)
(define real-exp cdr)

We would then install the various operations into the table, e.g.:

(put 'eval 'variable (lambda (exp env) (lookup-variable-value exp env)))
(put 'eval 'quoted (lambda (exp env) (text-of-quotation exp)))
...

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1	Chapter 1
2	Chapter 2
3	Chapter 3
4	Chapter 4
5	Chapter 5