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 ``` ```; gb-flip (define two31 #x80000000) (define a (make-vector 56 -1)) (define fptr #f) (define (mod-diff x y) (modulo (- x y) two31)) ; use this if you have logand ; (define (mod-diff x y) ; (logand (- x y) #x7FFFFFFF)) (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))))) (define (test-flip) (init-rand -314159) (when (not (= (next-rand) 119318998)) (error 'test-flip "Failure on the first try!")) (do ((j 1 (+ j 1))) ((< 133 j)) (next-rand)) (when (not (= (unif-rand #x55555555) 748103812)) (error 'test-flip "Failure on the second try!")) (display "OK, the gb-flip routines seem to work!") (newline)) (test-flip) ```
 ```1 ``` ```OK, the gb-flip routines seem to work! ```