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implementation module RandomGetallen
import StdEnv, Random
random_n :: Int RandomSeed -> ([Int],RandomSeed)
random_n 0 seed = ([], seed)
random_n n seed = ([r:rs], s`)
where
(rs,s`) = random_n (n-1) s
(r,s) = random seed
random_inf :: RandomSeed -> [Int]
random_inf s = iterateSt random s
iterateSt :: (s -> (a,s)) s -> [a]
iterateSt f s = [a : iterateSt f s`]
where
(a,s`) = f s
shuffle :: [a] RandomSeed -> [a]
shuffle xs s = (perms xs)!!(fst (random s) rem (factorial (length xs)))
perms :: [a] -> [[a]]
perms [] = [[]]
perms xs = [[xs!!i : xs`] \\ i <- [0..length xs - 1] , xs` <- perms (take i xs ++ drop (i+1) xs)]
factorial :: Int -> Int
factorial 0 = 1
factorial n = n * factorial (n-1)
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