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

[Brent Yorgey]

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