;; 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 8.4.1) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ())))
(require picturing-programs)

; Worked exercise 8.4.1

; Model: a number representing the x coordinate of the calendar

; Assumes you did exercise 8.2.2 or 8.3.3, producing a draw handler named calendar-at-x.

(define (calendar-at-x x)
  (place-image pic:calendar x 50 (rectangle 500 100 "solid" "white")))

; Mouse handler:
; add1-on-mouse : number(x) number(mouse-x) number(mouse-y) event -> number
(check-expect
 (add1-on-mouse 3 29 348 "blarg") 4)
(check-expect
 (add1-on-mouse 15 503 6 "glink") 16)
(define (add1-on-mouse x mouse-x mouse-y event)
  ; x number
  ; mouse-x number (ignore)
  ; mouse-y number (ignore)
  ; event whatever (ignore)
  (+ x 1) ; or, if you prefer, (add1 x)
  )

; sub2-on-key : number (x) key -> number
(check-expect (sub2-on-key 7 "dummy argument") 5)
(check-expect (sub2-on-key 2 "whatever") 0)
(define (sub2-on-key x key)
  ; x number
  ; key whatever (ignore)
  (- x 2)
  )

(big-bang 250
          (on-draw calendar-at-x)
          (on-mouse add1-on-mouse)
          (on-key sub2-on-key))