Chapter 2, Building Abstractions with Data
Section - 2.3 Symbolic Data
Exercise 2.57
We can just change procedures augend and multiplicand. Its interesting to see that how abstraction takes care of the rest.
1
2
3
4
5
6
7
8
9
10
11
12
13
(define (augend s)
(if (null? (cdddr s))
(caddr s)
(cons '+ (cddr s))
)
)
(define (multiplicand p)
(if (null? (cdddr p))
(caddr p)
(cons '* (cddr p))
)
)
Test/Output:
1
2
3
> (display (deriv '(* x y (+ x 3)) 'x))
(+ (* x y) (* y (+ x 3)))
>