SICP Practice

#lang racket

(define (fold-right op initial sequence)
(if (null? sequence)
    initial
    (op (car sequence)
        (fold-right op initial (cdr sequence)))))

(define (fold-left op initial sequence)
(define (iter result rest)
    (if (null? rest)
        result
        (iter (op result (car rest))
            (cdr rest))))
(iter initial sequence))

(fold-right / 1 (list 1 2 3))          ; 1 1/2
(fold-left / 1 (list 1 2 3))           ; 1/6
(fold-right list '() (list 1 2 3))     ; '(1 (2 (3 ())))
(fold-left list '() (list 1 2 3))      ; '(((() 1 ) 2) 3)