SICP Exercise 2.35

2022-01-14

Question

Redefine count-leaves from 2.2.2 as an accumulation:

(define (count-leaves t)
  (accumulate ⟨??⟩ ⟨??⟩ (map ⟨??⟩ ⟨??⟩)))

Answer

(define (count-leaves t)
  (accumulate +
              0
              (map (λ (x)
                     (if (pair? x)
                         (count-leaves x)
                         1))
                   t)))

; testing:
(define x (cons (list 1 2) (list 3 4)))
(count-leaves (list x x))

Results: