1 (define *op-table* (make-has-table 'equal))
2 (define (put op type proc)
3     (hash-table-put! *op-table* (list op type) proc))
4 (define (get op type)
5     (hash-table-get *op-table* (list op type) '()))
6 
7 (define (install-deriv-package)
8   (define (make-sum a1 a2) (list '+ a1 a2))
9   (define (addend s) (car s))
10   (define (augend s) (cadr s))
11   (define (make-product m1 m2) (list '* m1 m2))
12   (define (multiplier p) (car p))
13   (define (multiplicand p) (cadr p))
14   (define (deriv-sum exp var)
15     (make-sum (deriv (addend exp) var)
16 	      (deriv (augend exp) var)))
17   (define (deriv-product exp var)
18     (make-sum
19      (make-product (multiplier exp)
20 		   (deriv (multiplicand exp) var))
21      (make-product (deriv (multiplier exp) var)
22 		   (multiplicand exp))))
23   (define (make-exponentiation base exp)
24     (list '** base exp))
25   (define (base s) (car s))
26   (define (exponent s) (cadr s))
27   (define (deriv-exponentiation exp var)
28     (make-product
29      (make-product
30       (exponent exp)
31       (make-exponentiation
32        (base exp)
33        (- (exponent exp) 1)))
34      (deriv (base exp) var)))
35   (put 'deriv '** deriv-exponentiation)
36   (put 'deriv '+ deriv-sum)
37   (put 'deriv '* deriv-product))
38