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vitapluvia/permu.hs

Created July 3, 2017 01:47
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permutations in haskell
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permu.hs
import Data.List (nub)
disperse :: a -> [a] -> [[a]]
disperse value arr =
map (\(start, ending) -> start ++ [value] ++ ending) .
map (\char -> splitAt char arr) $ [0..length arr]
permu :: Ord a => [a] -> [[a]]
permu [] = [[]]
permu (x:xs) = concatMap (disperse x) $ permu xs
main = mapM_ putStrLn $ nub $ permu ['a'..'d']
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