On Thu, 2009-07-02 at 15:43 +0400, Bulat Ziganshin wrote:
> Hello Maciej,
>
> Thursday, July 2, 2009, 3:31:59 PM, you wrote:
>
> > class (Monad m, Monoid v) => MonadInput v m where
> > -- | Gets an element from input (line of text [with \n], 4096 bytes,
> > -- or something like that). mzero on end
> > getChunk :: m v
> > class (Monad m, Monoid v) => MonadOutput v m where
> > -- | Puts an element
> > putChunk :: v -> m ()
>
> how about interact function?
>
Well. As far as I know there is no way of using it with network.
Additionally there is hard to put monadic code in it:
myFunc :: (MonadInput i, MonadOutput o) =>
(String -> m a) -> MyMonad i o m [a]
If m == IO - which may be a case in normal code it requires
unsafePerformIO with all it's problems. In testing I can use pipes and
Identity simplifying the whole testing - allowing user to use it's own
monads.
The other problem is that the order sometimes matters. Consider:
main = interact (\x -> "What's your name?\n" ++ "Hello:\n" ++ x)
For human being it is annoying but sometimes it is for example against
RFC.
Regards
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