;; The first three lines of this file were inserted by DrScheme. They record metadata
;; about the language level of this file in a form that our tools can easily process.
#reader(lib "htdp-intermediate-reader.ss" "lang")((modname 14.1.1) (read-case-sensitive #t) (teachpacks ((lib "draw.ss" "teachpack" "htdp") (lib "arrow.ss" "teachpack" "htdp"))) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ((lib "draw.ss" "teachpack" "htdp") (lib "arrow.ss" "teachpack" "htdp")))))
(define list-a (list 0 1 2 3 4 5))
(define list-b (cons 0 (cons 1 (cons 2 (cons 3 (cons 4 (cons 5 empty)))))))
(define list-c (list (list 'adam 0) (list 'eve 1) (list 'louisXIV 2)))
(define list-d (cons (cons 'adam (cons 0 empty))
                     (cons (cons 'eve (cons 1 empty))
                           (cons (cons 'louisXIV (cons 2 empty)) empty))))


;Data Definition
;A mixed-list is either
;1. an empty list
;2. (cons ns ml) where ns is either a number or a symbol
;and ml is a mixed-list
;3. (cons ml1 ml2) where ml1 and ml2 are both mixed-lists.
;
;
;
;list=? : mixed-list mixed-list -> boolean
;Compares list1 and list2 and returns true if equal,
;false otherwise.

(define (list=? list1 list2)
  (cond
    [(and
      (empty? list1)
      (empty? list2)) true]
    [(or
      (empty? list1)
      (empty? list2)) false]
    [(and (symbol? (first list1))
          (symbol? (first list2))
          (symbol=? (first list1) (first list2)))
     (list=? (rest list1) (rest list2))]
    [(and (number? (first list1))
          (number? (first list2))
          (= (first list1) (first list2)))
     (list=? (rest list1) (rest list2))]
    [(and
      (cons? (first list1))
      (cons? (first list2))
      (list=? (first list1) (first list2)))
     (list=? (rest list1) (rest list2))]
    [else false]))

(define list-e (cons (cons 1 (cons 2 empty)) empty))
(define list-f (list (list 1 2)))
;(list=? list-g list-h) is incorrect for this case
(define list-g (cons 'a
                     (cons (cons 1 empty)
                           (cons false empty))))
(define list-h (list 'a (cons 1 empty) false))

(cons (cons 1 (cons 2 empty)) 
      (cons (cons 2 (cons 3 empty)) empty))
(list (list 1 2)
      (list 2 3))

(cons 'a (list 0 false))
(cons 'a (cons 0 (cons false empty)))
(list 'a 0 false)

(list (cons 1 (cons 13 empty)))
(cons (cons 1 (cons 13 empty)) empty)
(list (list 1 13))

(list empty empty (cons 1 empty))
(cons empty
      (cons empty
            (cons (cons 1 empty) empty)))
(list empty empty (list 1))

(cons 'a (cons (list 1) (list false empty)))
(cons 'a (cons (cons 1 empty) (cons false (cons empty empty))))
(list 'a (list 1) false empty)

(list (symbol=? 'a 'b) (symbol=? 'c 'c) false)
(list false true false)
(cons false
      (cons true
            (cons false empty)))

(list (+ 10 20) (* 10 20) (/ 10 20))
(list 30 200 0.5)
(cons 30
      (cons 200
            (cons 0.5)))

(list 'dana 'jane 'mary 'laura)
(cons 'dana
      (cons 'jane
            (cons 'mary
                  (cons 'laura))))

(first (list 1 2 3))
1
(rest (list 1 2 3))
(list 2 3)
(cons 2 (cons 3 empty))

'(1 a 2 b 3 c)
(list 1 'a 2 'b 3 'c)

'((alan 1000)
  (barb 2000)
  (carl 1500)
  (dawn 2300))
(list (list 'alan 1000)
      (list 'barb 2000)
      (list 'carl 1500)
      (list 'dawn 2300))

'((My First Paper)
  (Sean Fisler)
  (Section 1 
    (Subsection 1 Life is difficult)
    (Subsection 2 But learning things makes it interesting))
  (Section 2
    Conclusion? What conclusion?))  
(list (list 'My 'First 'Paper)
      (list 'Sean 'Fisler)
      (list 'Section 1
            (list 'Subsection 1 'Life 'is 'difficult)
            (list 'Subsection 2 'But 'learning 'things 'makes 'it 'interesting))
      (list 'Section 2
            (list 'Conclusion? 'What 'conclusion?))