sicp 2.60

sicp_2_60

(define (element-of-set? x set)
(cond ((null? set) #f)
((= x (car set)) #t)
(else (element-of-set? x (cdr set)))))

(define a '(1 2 3 4 6 6))
(define b '(3 4 5 6 2))

(element-of-set? 3 a)
(element-of-set? 5 a)

(define (adjoin-set x set)
(cons x set))

(define (union-set x y)
  (cond ((null? x) y) 
   (else (union-set (cdr x) (cons (car x) y)))
  )
  )

(define (intersection-set set1 set2)
(cond ((or (null? set1) (null? set2)) '())
((element-of-set? (car set1) set2)
(cons (car set1)
(intersection-set (cdr set1) set2)))
(else (intersection-set (cdr set1) set2))))

(union-set a b)
(intersection-set a b)