十一去喀纳斯玩了2天,今天恢复,才几天没看书再看到代码就感到有点陌生了。。
Exercise 2.35
Redefine count-leaves from Section 2.2.2 as an accumulation:
(define (count-leaves t)(accumulate ⟨??⟩ ⟨??⟩ (map ⟨??⟩ ⟨??⟩)))
这道题难度不大,利用 enumerate-tree 和 accumulate 很容易就能实现。
(define (count-leaves t)(accumulate+0(map (lambda (x) (if (null? x) 0 1)) (enumerate-tree t))))(define x (cons (list 1 2) (list 1 3 0 5 0 1)))
(count-leaves x)
(count-leaves (list x x)); 执行结果
10
20