;;;;;;; Side effects (aka immorality) in Scheme

;; Output using display and newline
;; (two equivalent ways)

(define print
  (lambda (lst)
    (if (null? lst)
        'done
        ; The first way: use begin
        (begin (display (car lst))
               (newline)
               (print (cdr lst))))))

(define print
  (lambda (lst)
    (if (null? lst)
        'done
        ; The second way: use let
        (let ((garbage (display (car lst))))
          (let ((garbage2 (newline)))
            (print (cdr lst)))))))

;; Mutating variables using set!, set-car!, and set-cdr!

(let ((lst (cons 10 (cons 20 (cons 30 '())))))
  (begin (set! lst '())
         lst))

(let ((list1 (cons 10 (cons 20 (cons 30 '())))))
  (let ((list2 list1))
    (begin (set-car! list1 'apple)
           list2)))

(let ((list1 (cons 10 (cons 20 (cons 30 '())))))
  (let ((list2 list1))
    (begin (set-cdr! list1 '())
           list2)))