练习2.73-练习2.74

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版权声明：本文为博主原创文章，转载请注明出处：http://blog.jerkybible.com/2014/02/07/2014-02-07-练习2.73-练习2.74/
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1.练习2.73
a
没有必要
b

(define (insert-sum-proc)
  (define (deriv-sum exp var)
    (make-sum (deriv (car exp) var)
              (deriv (cadr exp) var)))
  (put 'deriv '+ deriv-sum)
  'done)

(define (insert-mult-proc)
  (define (deriv-mult exp var)
    (make-sum
     (make-product (car exp)
                   (deriv (cadr exp) var))
     (make-product (deriv (car exp) var)
                   (cadr exp))))
  (put 'deriv '* deriv-mult)
  'done)

cd
改变put和get的顺序
2.练习2.74
a

;;提供分支机构的名称，即brcanch
(define (get-record branch name)
  (cond ((null? branch) false)
        ((null? name) false)
        (else ((get 'get-record branch) name))))

;;提供分支机构的名称,即brcanch
(define (get-salary branch name)
  (cond ((null? branch) false)
        ((null? name) false)
        (else ((get 'get-salary branch) name))))

(define (find-employee-record name branchs)
  (if (null? branchs)
      false
      (let ((record ((get 'get-record (branch-name (car branchs))) name)))
        (if (null? record)
            (find-employee-record name (cdr branchs))
            record))))

d将新人事的方法注册到表中，即put进去。