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You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than "Re: Contents of Beginners digest..." Today's Topics: 1. Re: Maybe monad and computations (Daniel Trstenjak) 2. Re: Maybe monad and computations (Emmanuel Touzery) 3. Re: Maybe monad and computations (Daniel Trstenjak) ---------------------------------------------------------------------- Message: 1 Date: Sat, 7 Sep 2013 09:49:16 +0200 From: Daniel Trstenjak <daniel.trsten...@gmail.com> To: The Haskell-Beginners Mailing List - Discussion of primarilybeginner-level topics related to Haskell <beginners@haskell.org> Cc: The Haskell-Beginners Mailing List - Discussion of primarilybeginner-level topics related to Haskell <beginners@haskell.org> Subject: Re: [Haskell-beginners] Maybe monad and computations Message-ID: <07edb9e0-b233-42b4-8dac-e77fea745...@gmail.com> Content-Type: text/plain; charset=us-ascii > I thought I understood it, but looking at the difference in behaviour in the > examples I posted, maybe I don't. I would try to add a type signature for liftM2, perhaps you're than getting a more helpful error message. Greetings, Daniel ------------------------------ Message: 2 Date: Sat, 7 Sep 2013 10:01:14 +0200 From: Emmanuel Touzery <etouz...@gmail.com> To: The Haskell-Beginners Mailing List - Discussion of primarily beginner-level topics related to Haskell <beginners@haskell.org> Subject: Re: [Haskell-beginners] Maybe monad and computations Message-ID: <CAC42Reni0ENzM-Y9Muy3=30MXLPv46+a+FRgJS=ar1dmzav...@mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" I got an helpful answer on stackoverflow that probably explains it all. Otherwise if i add the type, i'll have to bind it to a concrete monad due to the lack of typeclasses, that's why i didn't put a type. Thanks again. On Sep 7, 2013 9:50 AM, "Daniel Trstenjak" <daniel.trsten...@gmail.com> wrote: > > I thought I understood it, but looking at the difference in behaviour in > the examples I posted, maybe I don't. > > I would try to add a type signature for liftM2, perhaps you're than > getting a more helpful error message. > > Greetings, > Daniel > _______________________________________________ > Beginners mailing list > Beginners@haskell.org > http://www.haskell.org/mailman/listinfo/beginners > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.haskell.org/pipermail/beginners/attachments/20130907/e2e804fb/attachment-0001.html> ------------------------------ Message: 3 Date: Sat, 7 Sep 2013 10:28:38 +0200 From: Daniel Trstenjak <daniel.trsten...@gmail.com> To: The Haskell-Beginners Mailing List - Discussion of primarilybeginner-level topics related to Haskell <beginners@haskell.org> Cc: The Haskell-Beginners Mailing List - Discussion of primarilybeginner-level topics related to Haskell <beginners@haskell.org> Subject: Re: [Haskell-beginners] Maybe monad and computations Message-ID: <e149bac8-2e67-4d9f-b209-d901c1d77...@gmail.com> Content-Type: text/plain; charset="us-ascii" Am 07.09.2013 um 10:01 schrieb Emmanuel Touzery <etouz...@gmail.com>: > I got an helpful answer on stackoverflow that probably explains it all. > Otherwise if i add the type, i'll have to bind it to a concrete monad due to > the lack of typeclasses, that's why i didn't put a type. Thanks again. > Ok, that explains a lot. But if you need this kind of operation a lot, you could still have something like: liftMaybe2 :: (a -> b -> c) -> Maybe a -> Maybe b -> Maybe c liftMaybe2 f (Just a) (Just b) = Just $ f a b liftMaybe2 _ _ _ = Nothing Greetings, Daniel -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.haskell.org/pipermail/beginners/attachments/20130907/7ea82956/attachment-0001.html> ------------------------------ Subject: Digest Footer _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners ------------------------------ End of Beginners Digest, Vol 63, Issue 12 *****************************************