Created
December 25, 2012 08:19
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(define (random-in-range low high) | |
(let ((range (- high low))) | |
(+ low (random range)))) | |
(define (experiment x1 x2 y1 y2) | |
(let ((a (random-in-range x1 x2)) | |
(b (random-in-range y1 y2)) | |
(c (/ (+ x1 x2) 2.0)) | |
(d (/ (+ y1 y2) 2.0)) | |
(r (/ (- x1 x2) 2.0))) | |
(<= (+ (square (- a c)) | |
(square (- b d))) | |
(square r)))) | |
(define (monte-carlo p x1 x2 y1 y2 trials) | |
(define (iter trials-remaining trials-passed) | |
(cond ((= trials-remaining 0) | |
(/ (* 1.0 trials-passed) trials)) | |
((p x1 x2 y1 y2) | |
(iter (- trials-remaining 1) (+ 1 trials-passed))) | |
(else | |
(iter (- trials-remaining 1) trials-passed)))) | |
(iter trials 0)) | |
;; 3.5 | |
(define (pi) | |
(* 4.0 (monte-carlo experiment 0 1.0 0 1.0 10000))) | |
;; 3.6 | |
(define rand | |
(let ((x random-init)) | |
(lambda (m) | |
(cond ((eq? m 'generate) (set! x (rand-update x)) x) | |
((eq? m 'reset) (lambda (y) (set! x y))) | |
(else (error "Sorry")))))) |
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