learning-sicp

My embarrassing half assed SICP run.
git clone https://kaka.farm/~git/learning-sicp
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exercise-60.scm (870B)

      1 ;; Exercise 2.60 XXX
      2 
      3 (define (exercise-2.60)
      4   ;; I don't get it. Am I supposed to let these sets explode by just appending
      5   ;; more and more stuff to them?
      6 
      7   (define (element-of-set? x set)
      8     (cond
      9      ((null? set) #f)
     10      ((equal? x (car set)) #t)
     11      (else (element-of-set? x (cdr set)))))
     12 
     13   (define (adjoin-set x set)
     14     (cons x set))
     15 
     16   (define (union-set set1 set2)
     17     (append set1 set2))
     18 
     19   (define (intersection-set set1 set2)
     20     (cond
     21      ((or (null? set1)
     22           (null? set2)) '())
     23      ((equal? (car set1) (element-of-set? (car set1)
     24                                           set2))
     25       (adjoin-set (car set1)
     26                   (intersection-set (cdr set1)
     27                                     set2)))
     28      (else (intersection-set (cdr set1)
     29                              set2))))
     30 
     31   (test-begin "2.60")
     32   (test-end "2.60"))
     33 
     34 (exercise-2.60)
     35