Re: [Haskell-beginners] I don't understand mapM in mapM id (Just 1, Nothing, Just 3)

On Mon, Jun 06, 2011 at 09:08:40AM +0800, Haisheng Wu wrote:

Thanks Senastian!

I would refine the equality as below:

sequence [Just 2, Nothing] = do x <- Just 2 y <- sequence [Nothing] return (x:y) = Just 2 >>= \x -> sequence [Nothing] >>= \y -> return (x:y) = Nothing >>= \y -> return (2:y) = Nothing

Yes, exactly. -Brent