Project:
 ```1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 ``` ```; guess the number (define rand #f) (define randint #f) (let ((two31 #x80000000) (a (make-vector 56 -1)) (fptr #f)) (define (mod-diff x y) (modulo (- x y) two31)) ; generic version ; (define (mod-diff x y) (logand (- x y) #x7FFFFFFF)) ; fast version (define (flip-cycle) (do ((ii 1 (+ ii 1)) (jj 32 (+ jj 1))) ((< 55 jj)) (vector-set! a ii (mod-diff (vector-ref a ii) (vector-ref a jj)))) (do ((ii 25 (+ ii 1)) (jj 1 (+ jj 1))) ((< 55 ii)) (vector-set! a ii (mod-diff (vector-ref a ii) (vector-ref a jj)))) (set! fptr 54) (vector-ref a 55)) (define (init-rand seed) (let* ((seed (mod-diff seed 0)) (prev seed) (next 1)) (vector-set! a 55 prev) (do ((i 21 (modulo (+ i 21) 55))) ((zero? i)) (vector-set! a i next) (set! next (mod-diff prev next)) (set! seed (+ (quotient seed 2) (if (odd? seed) #x40000000 0))) (set! next (mod-diff next seed)) (set! prev (vector-ref a i))) (flip-cycle) (flip-cycle) (flip-cycle) (flip-cycle) (flip-cycle))) (define (next-rand) (if (negative? (vector-ref a fptr)) (flip-cycle) (let ((next (vector-ref a fptr))) (set! fptr (- fptr 1)) next))) (define (unif-rand m) (let ((t (- two31 (modulo two31 m)))) (let loop ((r (next-rand))) (if (<= t r) (loop (next-rand)) (modulo r m))))) (init-rand 19380110) ; happy birthday donald e knuth (set! rand (lambda seed (cond ((null? seed) (/ (next-rand) two31)) ((eq? (car seed) 'get) (cons fptr (vector->list a))) ((eq? (car seed) 'set) (set! fptr (caadr seed)) (set! a (list->vector (cdadr seed)))) (else (/ (init-rand (modulo (numerator (inexact->exact (car seed))) two31)) two31))))) (set! randint (lambda args (cond ((null? (cdr args)) (if (< (car args) two31) (unif-rand (car args)) (floor (* (next-rand) (car args))))) ((< (car args) (cadr args)) (let ((span (- (cadr args) (car args)))) (+ (car args) (if (< span two31) (unif-rand span) (floor (* (next-rand) span)))))) (else (let ((span (- (car args) (cadr args)))) (- (car args) (if (< span two31) (unif-rand span) (floor (* (next-rand) span)))))))))) (define (show . msg) (for-each display msg)) (define (show-line . msg) (apply show msg) (newline)) (define (get-yes-no) (let ((answer (char-downcase (string-ref (symbol->string (read)) 0)))) (if (member answer '(#\y #\n)) answer (begin (show-line "Please answer yes or no.") (get-yes-no))))) (define (human-plays limit) (let ((n (randint 1 limit))) (show-line "I am thinking of a number from 1 to " limit) (display "What is your guess? ") (let loop ((g (read)) (k 0)) (cond ((< g n) (show-line "Your guess is less than my number.") (show "What is your next guess? ") (loop (read) (+ k 1))) ((< n g) (show-line "My number is less than your guess.") (show "What is your next guess? ") (loop (read) (+ k 1))) (else (show-line "You guessed my number " n " in " k " tries!") k))))) (define (computer-plays limit) (show-line "Think of a number from 1 to " limit ".") (let loop ((lo 1) (hi limit) (k 0)) (let ((mid (quotient (+ lo hi) 2))) (cond ((= lo mid) (show-line "I guessed your number " lo " in " k " tries.") k) (else (show "Is your number less than " mid "? ") (case (get-yes-no) ((#\y) (loop lo mid (+ k 1))) ((#\n) (loop mid hi (+ k 1))))))))) (define (play limit) (show-line "Let's play Guess-The-Number!") (show-line "You go first.") (let ((k-human (human-plays limit))) (show-line "Now it's my turn.") (let ((k-computer (computer-plays limit))) (cond ((< k-human k-computer) (show-line "You made less guesses than me.") (show-line "You win! Congratulations!")) ((< k-computer k-human) (show-line "I made less guesses than you.") (show-line "I win. Better luck next time!")) (else (show-line "We both made the same number of guesses.") (show-line "The game is a tie. Good game!"))) (show "Would you like to play again? ") (if (char=? (get-yes-no) #\y) (play limit) (show-line "Thanks for playing! Good-bye!"))))) (play 100) ```
 ```1 2 3 4 5 ``` ```Let's play Guess-The-Number! You go first. I am thinking of a number from 1 to 100 What is your guess? Disallowed system call: SYS__newselect```