At 5:27 PM -0800 2/18/05, Isaac Jones wrote:

John Goerzen writes:

...

Here's an alternative:

module Main where

(snip john's version)

And what list would be complete without a points-free version. It doesn't operate on stdin, though like John's does:

pointsFreeCat :: IO () pointsFreeCat = getArgs >>= mapM readFile >>= putStrLn . concat

-- And a regular version for reference

cat2 :: IO () cat2 = do a <- getArgs lines <- mapM readFile a putStrLn $ concat lines

peace,

isaac

You probably want `putStr` instead of `putStrLn`, as the latter introduces a gratuitous newline at the end of the concatenated contents. Dean

Bjorn Bringert said:

Or why not the two characters shorter, but much less readable:

pointsFreeCat' = getArgs >>= mapM_ ((>>= putStr) . readFile)

or maybe:

pointsFreeCat'' = getArgs >>= mapM_ (putStr >>. readFile)

(>>.) :: (b -> IO c) -> (a -> IO b) -> a -> IO c (>>.) = (.) . flip (>>=)

Is (>>.) in the standard libs? If not, should it be? I'm sure there is a shorter definition of (>>.) that I haven't thought of.

/Bjorn

Or even: k :: Monad m => (a -> m b) -> Kleisli m a b k = Kleisli runKleisli :: Monad m => Kleisli m a b -> (a -> m b) runKleisli (Kleisli f) = f cat :: IO () cat = getArgs >>= (runKleisli $ (k $ mapM readFile) >>> (k $ mapM_ putStr)) after noticing that (>>.) is pretty similar to (<<<) when we lift (a -> IO b) to (Kleisli IO a b). It is pretty disappointing that runKleisli isn't defined so that I can be cool and completely point free too ;) /Andreas -- some cannot be created more equal than others