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#lang racket
(require 2htdp/universe 2htdp/image)
(struct interval (small big guesses))
;;; constants
(define TEXT-SIZE 12)
(define HELP-TEXT
(text "↑ for larger numbers, ↓ for smaller ones"
TEXT-SIZE
"blue"))
(define HELP-TEXT2
(text "Press = when your number is guessed; q to quit."
TEXT-SIZE
"blue"))
(define COLOR "red")
(define WIDTH (+ (image-width HELP-TEXT2) 10))
(define HEIGHT 150)
(define SIZE 72)
(define TEXT-X 3)
(define TEXT-UPPER-Y 10)
(define TEXT-LOWER-Y 135)
(define GUESSES-SIZE 12)
(define GUESSES-COLOR "green")
(define MT-SC
(place-image/align
HELP-TEXT TEXT-X TEXT-UPPER-Y "left" "top"
(place-image/align
HELP-TEXT2 TEXT-X TEXT-LOWER-Y "left" "bottom"
(empty-scene WIDTH HEIGHT))))
;; main
(define (start lower upper)
(big-bang (interval lower upper 0)
(on-key deal-with-guess)
(to-draw render)
(stop-when single? render-last-scene)))
;; key events
(define (deal-with-guess w key)
(cond [(key=? key "up") (bigger w)]
[(key=? key "down") (smaller w)]
[(key=? key "q") (stop-with w)]
[(key=? key "=") (stop-with w)]
[else w]))
(define (smaller w)
(interval (interval-small w)
(max (interval-small w) (sub1 (guess w)))
(+ 1 (interval-guesses w))))
(define (bigger w)
(interval (min (interval-big w) (add1 (guess w)))
(interval-big w)
(+ 1 (interval-guesses w))))
(define (guess w)
(quotient (+ (interval-small w) (interval-big w)) 2))
(define (render w)
(overlay (overlay/offset
(text (number->string (guess w)) SIZE COLOR) 0 40
(text (number->string (interval-guesses w))
GUESSES-SIZE GUESSES-COLOR))
MT-SC))
(define (render-last-scene w)
(overlay (overlay/offset
(text "End" SIZE COLOR) 0 40
(text (number->string (interval-guesses w))
GUESSES-SIZE GUESSES-COLOR))
MT-SC))
(define (single? w)
(= (interval-small w) (interval-big w)))
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