- Haskell-Cafe - Haskell.org

Berlin HUG meeting at Tuesday, March 4th
by Simon Hengel 26 Feb '14

26 Feb '14

Hi, we have regular Haskell meetings in Berlin, but I think it was never officially announced on this list. There is a meetup page [1] and the next meeting is at Tuesday, March 4th Big thanks to Adam for organizing things! One important thing, please join on meetup if you want to come! Cheers, Simon [1] http://www.meetup.com/berlinhug/

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[ANN] profiteur: a tool to visualise GHC .prof files
by Jasper Van der Jeugt 26 Feb '14

26 Feb '14

Hey all, I just released the tool profiteur [1]. You can use it to visualise GHC `.prof` files in a tree map -- I think this makes looking at huge `.prof` files a lot less unwieldy. More information can be found in this blogpost [2]. [1]: http://hackage.haskell.org/package/profiteur [2]: http://jaspervdj.be/posts/2014-02-25-profiteur-ghc-prof-visualiser.html Peace, Jasper

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Q: haskell type inference algorithm paper
by Di Xu 25 Feb '14

25 Feb '14

Hi, all I'm new to haskell, I'm learning haskell for its type system, and I found haskell type inference is excellent, I'm interested in its type inference algorithm, could you give me some paper or material reference that describe the haskell type inference algorithm? I want to port it to typed clojure.

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Haskell minimal (portable) development environment
by dabd 25 Feb '14

25 Feb '14

Hi, I am currently reading through Packer documentation http://www.packer.io/ and vagrant http://www.vagrantup.com/. I would like to set up a minimal reproducible Haskell development environment on Manjaro Linux (64-bit) running on VirtualBox. Does anyone have a Packer template for this distro or a Vagrant box for Haskell development on any other distro? Thanks.

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Fwd: manage effects in a DSL
by Corentin Dupont 25 Feb '14

25 Feb '14

Oleg: Very interresting, thanks. I have some questions: - What do you mean by "The type Cont Int a describes an impure computation, which may abort with an Int value, for example". Aborting with an Int value is akin to exceptions? - for me it's not clear when to choose an "applicative" or a "monadic" DSL? Betsides, what's the rational behind the name "let_" (never seen it before)? Linsey, Jacques: Thanks for the pointer! I learned about data kinds. I tried to apply your suggestions to add a phantom type parameter to Exp. I came up to (I dropped the Free monad idea, which seems unrelated to the problem): > data Eff = Effect | NoEffect > -- first type parameter is used to track effects > data Exp :: Eff -> * -> * where > ReadAccount :: Exp r Int --ReadAccount can be used in whatever monad (with or without effect) > WriteAccount :: Exp NoEffect Int -> Exp Effect () --WriteAccount takes an effect-less expression, and returns an effectfull expression > SetVictory :: Exp NoEffect Bool -> Exp Effect () -- same for SetVictory > OnTimer :: Exp Effect () -> Exp Effect () --OnTime can program whatever expression to be triggered every minutes, in particular effectful ones > Return :: a -> Exp r a > Bind :: Exp r a -> (a -> Exp r b) -> Exp r b This is the (simplified) game state: > data Game = Game { bankAccount :: Int, > victory :: Exp NoEffect Bool, > timerEvent :: Exp Effect ()} > -- victory when account > 100 > victoryRule' :: Exp Effect () > victoryRule' = SetVictory $ do > m <- readAccount > --WriteAccount (return $ m + 1) --won't compile (good) > return (m > 100) > --increase my bank account by 1 every minute > myTimer :: Exp Effect () > myTimer = OnTimer $ do > m <- readAccount > writeAccount (return $ m + 1) Do you have a better name suggestion for Eff? Other pointers where this idiom is realised?? Thanks!! Corentin

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segfault on fromIntegral (floor $ sqrt (-123.123)) == -123.123
by Erik Rantapaa 24 Feb '14

24 Feb '14

I'm getting a segfault on this expression entered into ghci: GHCi, version 7.6.3: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Prelude> fromIntegral (floor $ sqrt (-123.123)) == -123.123 Segmentation fault: 11 I'm running the 32-bit version of the Haskell Platform on OSX. Is this a bug? a problem with my setup? "Just don't take square roots of negative numbers - you should know better!"???

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Munich Haskell Meeting
by Heinrich Hördegen 24 Feb '14

24 Feb '14

Dear all, Wednesday, the 26th of February, our Monthly Haskell Meeting is taking place once again in Munich, Cafe Puck. We start at 19h30. If you plan to join, please go to http://www.haskell-munich.de/dates and hit the button. This time, we will have a guest from India, Raman, who will bring along some boards and shows us how to run PicoLisp [1] on bare metal. There is also work in progress for running Hugs [2] on bare metal. If you are interested in embedded systems, this will be surely an enlightening meeting. Raman is looking also for people from the Haskell community who are willing to help him embed Hugs or some other Haskell programming system on bare metal. If you are interested, I can make the contact. With hope to see many of you on Wednesday, Heinrich [1] http://picolisp.com/wiki/?home [2] http://www.haskell.org/hugs/

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#haddock lives
by Mateusz Kowalczyk 24 Feb '14

24 Feb '14

Hi all, This is just a small heads up that the IRC channel, #haddock (on Freenode) is now revived. Previously any Haddock chatter would have taken place across #ghc, #hackage, #hspec and #haskell which made it difficult to track. Please use this channel if you have questions. Thanks -- Mateusz K.

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Re: [Haskell-cafe] Is the wiki really this out of date?
by Dominic Steinitz 24 Feb '14

24 Feb '14

Daniil Frumin <difrumin <at> gmail.com> writes: > > There are also some interesting charts on ircbrowse: > http://ircbrowse.net/haskell > Very cool! Unless someone objects, I will update the 2009 data on the wiki with these more up-to- date presentations of the data.

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Want to create your first Haskell project?
by Roman Cheplyaka 23 Feb '14

23 Feb '14

Hi, I'd like to see an html test reporter for the tasty testing framework (http://documentup.com/feuerbach/tasty) I could do that myself, but I thought it would be a nice little project for someone who's about to write their first useful piece of Haskell. To participate you need to know Haskell on LYAH level and be good at html/css/js. If you're interested, get in touch. I'll provide help, review your code etc. Roman

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