Re: [Haskell-cafe] IO is not a monad

On Tue, 2007-01-23 at 13:35 +0200, Yitzchak Gale wrote:

<troll>

Prelude> let f .! g = ((.) $! f) $! g Prelude> let f = undefined :: Int -> IO Int Prelude> f `seq` 42 *** Exception: Prelude.undefined Prelude> ((>>= f) . return) `seq` 42 42 Prelude> ((>>= f) .! return) `seq` 42 42

</troll>

Perhaps I'm missing something but I don't see what's wrong. I think what you're saying is that you want (>>=) to be strict in it's second argument. I don't see that this is a requirement of the monad laws. You'll note that you get the same behaviour for other monads like Maybe and []. I recall that there is some infidelity in standard implementations of the IO monad, but I don't think this is it. Duncan