SICP的一些练习题

1 (define (MaxSum x y z)
2   (+ (cond ((or (> x y) (> x z)) x)
3            (else 0))
4      (cond ((or (> y x) (> y z)) y)
5            (else 0))
6      (cond ((or (> z x) (> z y)) z)
7            (else 0))))
8 (MaxSum 5 3 10)

 1 (define (Abs x)
 2   (cond ((> x 0) x)
 3         ((= x 0) 0)
 4         ((< x 0) (- x))))
 5 (define (Square x) (* x x))
 6 (define (Average x y)
 7   (/ (+ x y) 2))
 8 (define (Improve guess x)
 9   (Average guess (/ x guess)))
10 (define (GoodEnough? guess x)
11   (< (Abs (- (Square guess) x)) 0.001))
12 (define (SqrtIter guess x)
13   (if (GoodEnough? guess x)
14       guess
15       (SqrtIter (Improve guess x)
16                 x)))
17 (SqrtIter 1 2)