;; 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-intermediate-lambda-reader.ss" "lang")((modname week7_w_binary_full) (read-case-sensitive #t) (teachpacks ((lib "image.ss" "teachpack" "htdp"))) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ((lib "image.ss" "teachpack" "htdp")))))
;; make-secret : number -> (number -> symbol)
;; makes up a secret and then returns
;; a function that lets you guess the secret
(define (make-secret n)
  (local [(define secret (random n))]
    (lambda (guess)
      (cond
        [(< guess secret) 'toosmall]
        [(= guess secret) 'yes]
        [(> guess secret) 'toobig]))))

;;guess-helper-binary-search: (number -> symbol) number number
; guesses number using binary search, assuming number is less than or equal to "above" and greater than or equal to "below"
(define (guess-helper-binary-search secret below above)
  (local [(define guess (quotient (+ below above) 2))
          (define ans (secret guess))]
    (cond
      [(symbol=? ans 'yes) guess]
      [(symbol=? ans 'toosmall) (guess-helper-binary-search secret (+ guess 1) above)]
      [(symbol=? ans 'toobig) (guess-helper-binary-search secret below (- guess 1))])))


(define sec1 (make-secret 4))
(guess-helper-binary-search sec1 0 4)
(define sec2 (make-secret 4))
(guess-helper-binary-search sec2 0 4)
(define sec4 (make-secret 4))
(guess-helper-binary-search sec4 0 4)