On Wed, Jun 3, 2009 at 8:42 AM, Daniel Fischer <daniel.is.fischer@web.de> wrote:

Am Mittwoch 03 Juni 2009 06:12:46 schrieb Michael Snoyman:

> I made two changes:
>
> 1. You had the arguments to M.lookup backwards.
> 2. lookup does not return any generalized Monad, just Maybe (I think that
> should be changed).

Data.Map.lookup used to return a value in any monad you wanted, I believe until 6.8
inclusive.
I don't think it's going to change again soon.

Is there a reason why it only returns in the Maybe monad? I often times have to write a liftMaybe function to deal with that.

Michael