On Thu, Sep 30, 2004 at 09:49:46AM -0400, Kevin Everets wrote:
> I took Georg's, fixed the word count logic and added prettier
> printing, and then combined it with Sam's main (which I find more
> elegant, but others may find less straightforward). I think it
> strikes a good balance between efficiency and elegance.
Then how about a solution like this: I took your program but used
my fast fileIterate instead of ,,foldl over getContents''.
I also added {-# OPTIONS -funbox-strict-fields #-}, and played a bit
to get the best optimisations from GHC.
It's about 7 times faster this way, but it's still two times slower than
the solution I sent to shootout.
Devilish plan: Maybe we could have some variants of fileIterate in GHC's
libraries? ;->
I remember that someone proposed similar functions on haskell's lists
some time ago, but can't remember who.
Best regards,
Tom
--
.signature: Too many levels of symbolic links
{-# OPTIONS -funbox-strict-fields #-}
import System.IO
import Data.Array.IO
import Data.Array.Base
import Data.Word
import Data.Int
import List
import Char
main = fileIterate stdin wc' (C 0 0 0 False) >>= putStrLn . showC
data C = C !Int !Int !Int !Bool deriving Show
-- Line Word Char InWord
showC (C l w c _) = show l ++ " " ++ show w ++ " " ++ show c
wc' :: C -> Char -> C
wc' (C l w c _) '\n' = C (l+1) w (c+1) False
wc' (C l w c _) ' ' = C l w (c+1) False
wc' (C l w c _) '\t' = C l w (c+1) False
wc' (C l w c False) _ = C l (w+1) (c+1) True
wc' (C l w c True) _ = C l w (c+1) True
--------------------------------------------------------------------------------
{-# INLINE fileIterate #-}
fileIterate :: Handle -> (a -> Char -> a) -> a -> IO a
fileIterate h f a0 = do
buf <- newArray_ (0, bufSize - 1) :: IO (IOUArray Int Word8)
let loop i n a
| i `seq` n `seq` a `seq` False = undefined
| i == n =
do n' <- hGetArray h buf bufSize
if n' == 0
then return a
else loop 0 n' a
| otherwise =
do c <- fmap (toEnum . fromEnum) (readArray buf i)
loop (i + 1) n (f a c)
loop 0 0 a0
where
bufSize :: Int
bufSize = 4096
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