Michael Snoyman wrote: > On Wed, Jun 3, 2009 at 8:42 AM, Daniel Fischer > <daniel.is.fisc...@web.de>wrote: > > Am Mittwoch 03 Juni 2009 06:12:46 schrieb Michael Snoyman: > > > 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.
Here's the proposal that changed it: http://hackage.haskell.org/trac/ghc/ticket/2309 The discussion about the proposal can be found here: http://www.haskell.org/pipermail/libraries/2008-May/009698.html (There's even the suggestion of adding a function like liftMaybe to Data.Maybe, but apparently nobody turned that into a formal proposal.) Regards, Bertram _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe