Exercise 2.33 · 习题

Exercise 2.33: Fill in the missing expressions
to complete the following definitions of some basic list-manipulation
operations as accumulations:

(define (map p sequence)
(accumulate (lambda (x y) ⟨??⟩)
nil sequence))

(define (append seq1 seq2)
(accumulate cons ⟨??⟩ ⟨??⟩))

(define (length sequence)

(accumulate ⟨??⟩ 0 sequence))

练习 2.33：填写缺失的表达式，将下列一些基本表操作定义完成，使它们成为累积操作：

(define (map p sequence)
(accumulate (lambda (x y) ⟨??⟩)
nil sequence))

(define (append seq1 seq2)
(accumulate cons ⟨??⟩ ⟨??⟩))

(define (length sequence)
(accumulate ⟨??⟩ 0 sequence))