tasks a-s

Task/Probabilistic-choice/Haskell/probabilistic-choice.hs

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+import System.Random
+import Data.List
+import Control.Monad
+import Control.Arrow
+
+labels = ["aleph", "beth", "gimel", "daleth", "he", "waw", "zayin", "heth" ]
+piv n = take n . (++  repeat ' ')
+
+main = do
+  g <- newStdGen
+  let rs,ps :: [Float]
+      rs = take 1000000 $ randomRs(0,1) g
+      ps = ap (++) (return. (1 -) .sum) $ map recip [5..11]
+      sps = scanl1 (+) ps
+      qs = (\xs -> map ((/1000000.0).fromIntegral.length. flip filter xs. (==))sps)
+           $ map (head . flip dropWhile sps . (>)) rs
+  putStrLn $ "       expected     actual"
+  mapM_ putStrLn $ zipWith3
+               (\l s c-> (piv 7 l) ++ (piv 13 $ show $ s)
+                    ++(piv 12 $ show $ c)) labels ps qs