Import source

simple/README

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+*Simple coin tosser*
+
+Simulate the results of a coin toss experiment.
+
+eg. (chart-scores (sample-scores 200 20)) will yield:
+
+-13	
+-12	*
+-11	
+-10	*******
+-9	
+-8	*******
+-7	
+-6	*****************
+-5	
+-4	*******************
+-3	
+-2	*************************
+-1	
+0	*********************************
+1	
+2	******************************
+3	
+4	*****************************
+5	
+6	*******************
+7	
+8	***********
+9	
+10	**
+11	
+12	
+13	

simple/project.clj

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+(defproject coins "1.0.0"
+  :description "coin tossing"
+  :dev-dependencies [])

simple/src/coins.clj

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+(use '[clojure.string :only (join)])
+
+(defn coin-toss
+  "Tosses a fair coin and returns true for heads, false for tails"
+  []
+  (= 1 (rand-int 2)))
+
+(defn toss-score
+  "Win $1 for heads, lose $1 for tails"
+  [toss]
+  (if toss 1 -1))
+
+(defn count-winnings
+  "Figure out the net result for a sequence of tosses"
+  [results]
+  (reduce + (map toss-score results)))
+
+(defn sample-score
+  "Run an experiment of n tosses and figure out the result"
+  [n]
+  (count-winnings (repeatedly n coin-toss)))
+
+(defn sample-scores
+  "Run a sequence of experiments n times with m tosses"
+  [n m]
+  (repeatedly n #(sample-score m)))
+
+(defn tally-scores
+  "Return a map of frequency of results"
+  [scores]
+  (let
+      ;; define an auxiliary function that registers a
+      ;; score into a map holding all the score tallies
+      [tally-score (fn [results score]
+                     (if-let [prev-count (results score)]
+                       (assoc results score (inc prev-count))
+                       (assoc results score 1)))]
+    (reduce tally-score {} scores)))
+
+(defn chart-scores
+  "Given a list of scores, print a simple ASCII frequency graph"
+  [scores]
+  (let [tally (tally-scores scores)
+        low (apply min (keys tally))
+        high (apply max (keys tally))
+        r (inc (max (Math/abs low) high))]
+    (doseq [val (range (- r) (inc r))]
+      (print val)
+      (print "\t")
+      (if-let [c (tally val)]
+        (print (join (repeat c "*"))))
+      (println)
+    )))