SICP的一些练习题

1.3 较大两个数之和

 (define (MaxSum x y z)
   (+ (cond ((or (> x y) (> x z)) x)
            (else ))
      (cond ((or (> y x) (> y z)) y)
            (else ))
      (cond ((or (> z x) (> z y)) z)
            (else ))))
 (MaxSum   )

较大两个数之和

牛顿迭代

 (define (Abs x)
   (cond ((> x ) x)
         ((= x ) )
         ((< x ) (- x))))
 (define (Square x) (* x x))
 (define (Average x y)
   (/ (+ x y) ))
 (define (Improve guess x)
   (Average guess (/ x guess)))
 (define (GoodEnough? guess x)
   (< (Abs (- (Square guess) x)) 0.001))
 (define (SqrtIter guess x)
   (if (GoodEnough? guess x)
       guess
       (SqrtIter (Improve guess x)
                 x)))
 (SqrtIter  )

牛顿迭代

一个表的最后一个表

 (define (last-pair lst)
   (if (<= (length lst) )
       lst
       (last-pair (cdr lst))))

最后一个表

集合操作

 (define (element-of-set? x set)
   (cond ((null? set) false)
         ((equal? x (car set)) true)
         (else (element-of-set? x (cdr set)))))

 (define (adjoin-set x set)
   (if (element-of-set? x set)
       set
       (cons x set)))

 (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))))

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

 (define set1 (list    ))
 (define set2 (list    ))
 (element-of-set?  set1)
 (element-of-set?  set1)
 (intersection-set set1 set2)
 (union-set set1 set2)

集合