;; The first three lines of this file were inserted by DrRacket. They record metadata
;; about the language level of this file in a form that our tools can easily process.
#reader(lib "htdp-beginner-reader.ss" "lang")((modname lect08-structs) (read-case-sensitive #t) (teachpacks ((lib "universe.ss" "teachpack" "2htdp"))) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ((lib "universe.ss" "teachpack" "2htdp")))))
; Data definition:

; A book is:
;   (make-book [string] [string] [number] [boolean])
;
(define-struct book (title author pages copyR?))

; Examples of the data:
(make-book "The Soul of Wit" "Shorty" 0 false)
(define b1 (make-book "The Cat in the Hat" "Seuss" 31 true))


; Note that 'define-struct' automagically creates
; functions for us:
; Constructor:
;   make-book: string, string, number, boolean -> book
; Selectors:
;   book-title  : book -> string
;   book-author : book -> string
;   book-pages  : book -> number
;   book-copyR? : book -> boolean
; Predicate:
;   book? : ANY -> boolean


; A dvd is:
; (make-dvd [string] [natNum] [symbol])
;
(define-struct dvd (title time rating))

; example of the data:
(define once (make-dvd "Once" 153 'PG-13))

(dvd-time once)

; watch? : dvd -> boolean
; Given a particular DVD, should we invest our precious time in watching it?
;
(define (watch? a-dvd)
  #f)

(check-expect (watch? once) #f)
(check-expect (watch? (make-dvd "Bill&Ted's Excellent Adventure"
                                90
                                'PG))
              #t)
;(watch? (make-dvd "Wolf of Wall Street" 170 'R) #t)
;(watch? (make-dvd "Scary Movie" 105 'R) #t)

#; template
#;(define (watch? a-dvd)
  ...(dvd-title a-dvd)
  ...(dvd-time a-dvd)
  ...(dvd-rating a-dvd))
         
(define (watch? a-dvd)
  (or (< (dvd-time a-dvd) 110)
      (symbol=? (dvd-rating a-dvd) 'R)))
         
         
         
         
         
         



          
          
          
          
          







; read-time: book -> number
; How long does it take to read `a-book`, in hours?
;
(define (read-time a-book)
  -99)

(check-expect (read-time (make-book "The Soul of Wit" "Shorty" 0 false)) 0)
(check-expect (read-time b1) (+ 1 2/60))

;;; AFTER making the test cases, we go back and write the code: