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fgrsnau/Petersburg.hs

Last active September 8, 2015 10:56
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  1. fgrsnau revised this gist Sep 8, 2015. 1 changed file with 1 addition and 2 deletions.
    3 changes: 1 addition & 2 deletions Petersburg.hs
    View file
    Original file line number Diff line number Diff line change
    @@ -4,7 +4,6 @@ module Main where
    import Data.List
    import Data.List.Split
    import Data.Ratio
    import System.IO.Unsafe
    import System.Random

    data Coin = Head | Tail deriving (Eq, Enum, Read, Show)
    @@ -21,4 +20,4 @@ main = do
    let outcomes = product . map (const (2 :: Integer)) <$> trials

    let average = let n = 1e7 in sum (take n outcomes) % (fromIntegral n)
    print (fromRational average)
    print (fromRational average)
  2. fgrsnau created this gist Sep 8, 2015.
    24 changes: 24 additions & 0 deletions Petersburg.hs
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,24 @@
    {-# LANGUAGE NumDecimals #-}
    module Main where

    import Data.List
    import Data.List.Split
    import Data.Ratio
    import System.IO.Unsafe
    import System.Random

    data Coin = Head | Tail deriving (Eq, Enum, Read, Show)

    instance Random Coin where
    randomR (lo, hi ) g = let (x, g') = randomR (fromEnum lo, fromEnum hi) g
    in (toEnum x, g')
    random = randomR (Head, Tail)

    main :: IO ()
    main = do
    coins <- randoms <$> newStdGen
    let trials = splitWhen (== Head) coins
    let outcomes = product . map (const (2 :: Integer)) <$> trials

    let average = let n = 1e7 in sum (take n outcomes) % (fromIntegral n)
    print (fromRational average)