quicksort.hs

import Data.List

quicksort :: Ord a => [a] -> [a]
quicksort [] = []
quicksort xs = quicksort lessThanPivot ++ equalToPivot ++ quicksort greaterThanPivot
  where
    (lessThanPivot, equalToPivot, greaterThanPivot) = epart (head xs) xs
    epart :: Ord a => a -> [a] -> ([a], [a], [a])
    epart n xs = inner ([], [], []) xs
      where
        inner a [] = a
        inner (l, e, g) (y:ys)
          | y < n = inner (y : l, e, g) ys
          | y > n = inner (l, e, y : g) ys
          | otherwise = inner (l, y : e, g) ys

main :: IO ()
main = do
  print $ quicksort [9,5,2,1,4,0,-1,10,100,50,49,124,83,70,21]
  print $ quicksort "as;ldjfoiajewo;iqjew;oijwe"