;; file: 3_01.rkt

(#%require rackunit)

(define (make-accumulator initial-value)
  (let ((cached initial-value))
    (lambda (x)
      (set! cached (+ x cached))
      cached)))

(define A (make-accumulator 5))

(check-equal? (A 10) 15)
(check-equal? (A 10) 25)

3_02

;; file: 3_02.rkt

(#%require rackunit)

(define (make-monitored fn)
  (let ((call-count 0))
    (lambda (x)
      (if (eq? x 'how-many-calls?)
          call-count
          (let ((result (fn x)))
            (set! call-count (inc call-count))
            result)))))

(define s (make-monitored sqrt))

(check-equal? (s 100) 10)

(check-equal? (s 'how-many-calls?) 1)

3_03

;; file: 3_03.rkt
;; 3_03 / 3_04 / 3_07

(#%require rackunit)
(#%require (prefix racket: racket))
(racket:provide make-account)

(define (make-account balance initial-password)
  (define (withdraw amount)
    (if (>= balance amount)
        (begin (set! balance (- balance amount))
               balance)
        "Insufficient funds"))
  (define (deposit amount)
    (set! balance (+ balance amount))
    balance)
  (define (dispatch m)
    (cond ((eq? m 'withdraw) withdraw)
          ((eq? m 'deposit) deposit)
          (else (error "Unknown request -- MAKE-ACCOUNT"
                       m))))
  (define (password-dispatch password m)
    (if (not (eq? password initial-password))
        (lambda (amount)
          "Incorrect password")
        (dispatch m)))
  password-dispatch)

(define acc (make-account 100 'secret-password))

(check-equal? ((acc 'secret-password 'withdraw) 40) 60)

(check-equal? ((acc 'some-other-password 'deposit) 50) "Incorrect password")

3_04

;; file: 3_04.rkt
;; 3_03 / 3_04 / 3_07


(#%require rackunit)

(define (make-account balance initial-password)
  (define (withdraw amount)
    (if (>= balance amount)
        (begin (set! balance (- balance amount))
               balance)
        "Insufficient funds"))
  (define (deposit amount)
    (set! balance (+ balance amount))
    balance)
  (define (call-the-cops amount)
    'call-the-cops)
  (define (dispatch m)
    (cond ((eq? m 'withdraw) withdraw)
          ((eq? m 'deposit) deposit)
          ((eq? m 'call-the-cops) call-the-cops)
          (else (error "Unknown request -- MAKE-ACCOUNT"
                       m))))
  (let ((wrong-password-count 0))
    (define (password-dispatch password m)
      (if (not (eq? password initial-password))
          (begin
            (set! wrong-password-count (inc wrong-password-count))
            (if (>= wrong-password-count 7)
                (dispatch 'call-the-cops)
                (lambda (amount)
                  "Incorrect password")))
          (dispatch m)))
    
    password-dispatch))

(define acc (make-account 100 'secret-password))

(check-equal? ((acc 'secret-password 'withdraw) 40) 60)

(check-equal? ((acc 'some-other-password 'deposit) 50) "Incorrect password")
(check-equal? ((acc 'some-other-password 'deposit) 50) "Incorrect password")
(check-equal? ((acc 'some-other-password 'deposit) 50) "Incorrect password")
(check-equal? ((acc 'some-other-password 'deposit) 50) "Incorrect password")
(check-equal? ((acc 'some-other-password 'deposit) 50) "Incorrect password")
(check-equal? ((acc 'some-other-password 'deposit) 50) "Incorrect password")
(check-equal? ((acc 'some-other-password 'deposit) 50) 'call-the-cops)

3_05

;; file: 3_05.rkt

3_06

;; file: 3_06.rkt
(#%require rackunit)

(define (rand-update x)
  (let ((a 27) (b 26) (m 127))
    (modulo (+ (* a x) b) m)))

(define random-init 7)

(define rand
  (let ((x random-init))
    (define (reset new-value)
      (set! x new-value))
    (define (generate)
      (set! x (rand-update x))
      x)
    (define (dispatch m)
      (cond ((eq? m 'generate)
             (generate))
            ((eq? m 'reset)
             reset)))
    dispatch))


(check-equal? (rand 'generate) 88)
(check-equal? (rand 'generate) 116)
(check-equal? (rand 'generate) 110)

((rand 'reset) 7)

(check-equal? (rand 'generate) 88)
(check-equal? (rand 'generate) 116)
(check-equal? (rand 'generate) 110)

3_07

;; file: 3_07.rkt
;; 3_03 / 3_04 / 3_07
(#%require rackunit)
(#%require (prefix racket: racket))
(racket:require (racket:only-in "3_03.rkt" make-account))


(define (make-joint account account-password new-password)
  (define (dispatch password m)
    (if (not (eq? password new-password))
        (lambda (amount)
          "Incorrect password")
        (account account-password m)))
  dispatch)

(define peter-acc (make-account 100 'open-sesame))
(check-equal? ((peter-acc 'open-sesame 'withdraw) 40) 60)

(define paul-acc
  (make-joint peter-acc 'open-sesame 'rosebud))

(check-equal? ((paul-acc 'rosebud 'withdraw) 40) 20)

3_08

;; file: 3_08.rkt

(#%require rackunit)
(define make-f nil)
(define f nil)

(define (make-f-1)
  (let ((cached 'undefined))
    (define (inner-f x)
      (if (eq? cached 'undefined)
          (begin
            (set! cached x)
            x)
          0))
    inner-f))

(set! make-f make-f-1)
(set! f (make-f))
(check-equal? (let ((x (f 0))
                    (y (f 1)))
                (+ x y))
              0)
(set! f (make-f))
(check-equal? (let ((y (f 1))
                    (x (f 0)))
                (+ x y))
              1)


(define (make-f-2)
  ((lambda (old)
     (define (inner-f x)
       (let ((temp old))
         (set! old x)
         temp))
     inner-f)
   0))

(set! make-f make-f-2)
(set! f (make-f))
(check-equal? (let ((x (f 0))
                    (y (f 1)))
                (+ x y))
              0)
(set! f (make-f))
(check-equal? (let ((y (f 1))
                    (x (f 0)))
                (+ x y))
              1)

3_09

;; file: 3_09.rkt

3_10

;; file: 3_10.rkt

3_11

;; file: 3_11.rkt

3_12

;; file: 3_12.rkt
;; 3_12 / 5_22
(#%require rackunit)
(#%require "../allcode/helper/my-util.rkt")
(#%require (prefix racket: racket))
(#%require threading)

;; TODO

(define (append x y)
  (if (null? x)
      y
      (cons (car x) (append (cdr x) y))))

(define (append! x y)
  (set-cdr! (last-pair x) y)
  x)

(define (last-pair x)
  (if (null? (cdr x))
      x
      (last-pair (cdr x))))

(define x1 '(1 2))
(define y1 '(3 4))
(check-equal? (append x1 y1)
              '(1 2 3 4))
(check-equal? x1 '(1 2))
(check-equal? y1 '(3 4))

(define x2 '(1 2))
(define y2 '(3 4))
(check-equal? (append! x2 y2)
              '(1 2 3 4))
(check-equal? x2 '(1 2 3 4))
(check-equal? y2 '(3 4))