This seems to be the Haskell equivalent
downs
default_357-line at yahoo.de
Sun Dec 20 04:37:21 PST 2009
according to http://www.mail-archive.com/haskell-cafe%40haskell.org/msg63381.html
I'll let this speak for itself.
import Data.Array.Base (unsafeRead, unsafeWrite)
import Data.Array.ST
import Control.Monad.ST
myqsort :: STUArray s Int Int -> Int -> Int -> ST s ()
myqsort a lo hi
| lo < hi = do
let lscan p h i
| i < h = do
v <- unsafeRead a i
if p < v then return i else lscan p h (i+1)
| otherwise = return i
rscan p l i
| l < i = do
v <- unsafeRead a i
if v < p then return i else rscan p l (i-1)
| otherwise = return i
swap i j = do
v <- unsafeRead a i
unsafeRead a j >>= unsafeWrite a i
unsafeWrite a j v
sloop p l h
| l < h = do
l1 <- lscan p h l
h1 <- rscan p l1 h
if (l1 < h1) then (swap l1 h1 >> sloop p l1 h1) else return
l1
| otherwise = return l
piv <- unsafeRead a hi
i <- sloop piv lo hi
swap i hi
myqsort a lo (i-1)
myqsort a (i+1) hi
| otherwise = return ()
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