first version of montyhall.rkt

montyhall.bak

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+#lang sicp
+

montyhall.rkt

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+#lang racket
+
+(define num-doors 3)
+
+(define (num-to-list n)
+  (define (to-list-rec c n)
+    (if (> c n)
+        (quote())
+        (cons c (to-list-rec (+ c 1) n))))
+  (to-list-rec 1 n))
+
+;this is a test. all comments are function tests
+;(num-to-list 3)
+
+(define (remove-door n list)
+  (cond
+    ((null? list)(quote()))
+    ((= (car list) n)(remove-door n (cdr list)))
+    (else(cons (car list)(remove-door n (cdr list))))))
+
+
+;(pick 1 '(alpha delta doggmega))
+;(pick 2 '(alpha delta doggmega))
+;(pick 3 '(alpha delta doggmega))
+
+(define (a-trial)
+
+  (define prize-door
+    (+ 1 (random num-doors)))
+
+  (define first-pick
+    (+ 1 (random num-doors))) 
+  (newline)
+  (newline)
+  (display "prize door: ")
+  (display prize-door)
+
+  ;to remove unnecessary trials where 'player' selects correct door or a door with a prize is revealed remove these from initial list
+  (define doors
+    (num-to-list num-doors))
+  (newline)
+  (display "initial pick: ")(display first-pick)
+  ;get a wonk, a door that isn't the prize door and isn't the initial door. There will always be one more door that is a wonk
+  ;regardless of whether initial pick is correct or not. 
+  (define wonk (car(remove-door first-pick(remove-door prize-door doors))))
+
+  (newline)
+  (display "wonk: ")
+  (display wonk)
+
+  (define remaining-doors (remove-door wonk doors))  
+
+  (newline)
+  (display "remaining doors: ")
+  (display remaining-doors)
+  ;switch doors; this is where most people assume there is a 50/50 chance
+  (define second-pick (car(remove-door first-pick remaining-doors)))
+  (newline)
+  (display "second pick: ")
+  (display second-pick)
+
+  (if(= prize-door second-pick)
+     true
+     false)
+)
+
+(define (monty-hall n)
+  (define total-trials n)
+  (define (monty-hall-iter n right wrong)
+    (cond
+      ((= n 0)(newline)(newline)(display "ratio correct: ")(display (/ right total-trials)))
+      ((a-trial)(newline)(display "correct")(monty-hall-iter (- n 1) (+ 1 right) wrong))
+      (else (newline)(display "incorrect")(monty-hall-iter (- n 1) right (+ 1 wrong)))))
+  (monty-hall-iter n 0 0))
+
+;run simulation 1000 times
+(monty-hall 1000)
+
+;(remove-door 1 (num-to-list 3))
+;(remove-door 2 (num-to-list 3))
+;(remove-door 3 (num-to-list 3))
+