Keith Wansbrough writes:
Count me as a vote for the better-but-slightly-slower wc.
How about the attached program? On my machine it faster than Tomasz's version, and I think it's still a fairly clean source code. Using some random large file for input, I got these results with time(1): real 0m33.883s -- getarray/unsafeRead user 0m22.594s sys 0m2.493s real 0m30.435s -- hgetbuf/peek user 0m13.958s sys 0m2.814s Peter module Main ( main ) where import System.IO import Foreign bufsize :: Int -- our I/O buffer size bufsize = 4096 type Count = Int32 data CountingState = ST !Bool !Count !Count !Count deriving (Show) initCST :: CountingState initCST = ST True 0 0 0 wc :: Char -> CountingState -> CountingState wc '\n' (ST _ l w c) = (ST True (l+1) w (c+1)) wc ' ' (ST _ l w c) = (ST True l w (c+1)) wc '\t' (ST _ l w c) = (ST True l w (c+1)) wc _ (ST True l w c) = (ST False l (w+1) (c+1)) wc _ (ST False l w c) = (ST False l w (c+1)) countBuf :: Ptr Word8 -> Int -> CountingState -> IO CountingState countBuf _ 0 st@(ST _ _ _ _) = return st countBuf ptr n st@(ST _ _ _ _) = do c <- fmap (toEnum . fromEnum) (peek ptr) countBuf (ptr `plusPtr` 1) (n - 1) (wc c st) loop :: Handle -> Ptr Word8 -> CountingState -> IO CountingState loop h ptr st@(ST _ _ _ _) = do rc <- hGetBuf h ptr bufsize if rc == 0 then return st else countBuf ptr rc st >>= (loop h ptr $!) main :: IO () main = do allocaArray bufsize $ \ptr -> do ST _ l w c <- loop stdin ptr initCST putStrLn . shows l . (' ':) . shows w . (' ':) . shows c $ ""