Requires sicp plugin: # raco pkg install sicp

Chapter 2.scm

#lang sicp

(define (accumulate op initial sequence)
  (if (null? sequence)
      initial
      (op (car sequence) (accumulate op initial (cdr sequence)))))

(accumulate + 0 (list 1 2 3))


; Exercise 2.33

(define (map p sequence)
  (accumulate (lambda (x y) (cons (p x) y)) nil sequence))

(define (append seq1 seq2)
  (accumulate cons seq2 seq1))

(define (length sequence)
  (accumulate (lambda (x y) (+ x 1)) 0 sequence))

; Exercise 2.34

(define (horner-eval x coefficient-sequence)
  (accumulate (lambda (this-coeff higher-terms) (+ this-coeff (* x higher-terms)))
              0
              coefficient-sequence))

; (horner-eval 2 (list 1 3 0 5 0 1))

; Exercise 2.35

(define (count-leaves t)
  (accumulate + 0 (map (lambda (x) (if (list? x) (count-leaves x) 1)) t)))