Racket translation of "Reversing the technical interview"

reversing-the-technical-interview.rkt

#lang racket

; read this, and check back here as you go for racket code
; https://aphyr.com/posts/340-reversing-the-technical-interview

(define (cons h t)
  (lambda (p)
    (if p
        h
        t)))

;;; some extra stuff
(define-syntax list
  (syntax-rules ()
    [(list elem) (cons elem #f)]
    [(list elem rest ...) (cons elem (list rest ...))]))

(define (first l)
  (l #t))

(define (rest l)
  (l #f))
;;; ----
   
(define (nth l n)
  (when l
    (if (= 0 n)
        (l true)
        (nth (l false) (sub1 n)))))

(define (prn-list l)
  (display "(")
  (define (loop l)
    (if (not l)
        (displayln ")")
        (begin
          (display (l true))
          (when (l false)
            (display " "))
          (loop (l false)))))
  (loop l))

(define (reverse l)
  (define (loop r l)
    (if l
        (loop (cons (l true) r) (l false))
        r))
  (loop #f l))

(prn-list (reverse (cons 1 (cons 2 (cons 3 #f)))))
; (prn-list (reverse (list 1 2 3)))