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recursive datakinds

haskell-cafe - Fri, 05/29/2015 - 4:47pm
Hello, If I were trying to do something like creating types like.... what about Cafe2.lhs:23:30: Occurs check: cannot construct the infinite type: b ~ a : b Expected type: MyList b Actual type: MyList (a : b) Relevant bindings include myrecursivelist :: MyList (a : b) (bound at Cafe2.lhs:23:3) In the second argument of 'MyCons', namely 'myrecursivelist' In the expression: MyCons 1 myrecursivelist can I "fix" this somehow? I obviously want the type of myrecursivelist to be MyList '[Integer, Integer, Integer, Integer, Integer, Integer, Integer, Integer,.....] Something like a completely nonsensical... MyList (Fix (Integer ': )) P.S. Yes, I barely understand "fix" as a function, let alone a data type. CONFIDENTIALITY NOTICE This e-mail (and any attached files) is confidential and protected by copyright (and other intellectual property rights). If you are not the intended recipient please e-mail the sender and then delete the email and any attached files immediate
Categories: Offsite Discussion

Holden Karau: Learning Spark - now updated for Spark 1.3

Planet Haskell - Fri, 05/29/2015 - 4:30pm
I'm pleased to announce, albeit somewhat late, that the Learning Spark book has been updated for Spark 1.3+, including Spark SQL's DataFrames and . In the process we also fixed a large number of errata issues reported, so please keep reporting issues so we can keep improving.
Categories: Offsite Blogs

LPMR 2015 - Associated events - DEADLINES

General haskell list - Fri, 05/29/2015 - 3:48pm
[apologies for multiple or cross- posting] The LPNMR 2015 Program Committee is evaluating the submitted papers, and notifications of acceptance are expected soon. However, we would like to remember that this year's edition comes along with a very rich set of associated events: 4 Workshops, the ADT 2015 conference, the joint ADT/LPNMR Doctoral Consortium, not to mention the 6th Answer Set Programming Competition. Quite a rich menu, right? Deadlines are approaching for such events, and this is intended as a gentle reminder: * GTTV'15: June 22, 2015 * ALPP 2015: July 15, 2015 * NLPAR 2015: June 22, 2015 * LNMR'15: June 22, 2015 * ADT 2015: time over * Joint LPNMR-ADT Doctoral Consortium: June 1, 2015 * Answer Set Programming Competition ASPCOMP: June 1, 2015 More details can be found here: http://lpnmr2015.mat.unical.it/associated-events
Categories: Incoming News

Edward Z. Yang: Ubuntu Vivid upgrade (Xmonad)

Planet Haskell - Fri, 05/29/2015 - 12:09pm

Another half year, another Ubuntu upgrade. This upgrade went essentially smoothly: the only things that stopped working were my xbindkeys bindings for volume and suspend, which were easy to fix.

Volume up and down

If you previously had:

#Volume Up "pactl set-sink-volume 0 -- +5%" m:0x10 + c:123 Mod2 + XF86AudioRaiseVolume

this syntax no longer works: you must place the double dash earlier in the command, as so:

#Volume Up "pactl -- set-sink-volume 0 +5%" m:0x10 + c:123 Mod2 + XF86AudioRaiseVolume

Do the same for volume down.

Suspend

If you previously had:

#Sleep "dbus-send --system --print-reply --dest="org.freedesktop.UPower" /org/freedesktop/UPower org.freedesktop.UPower.Suspend" m:0x10 + c:150 Mod2 + XF86Sleep

UPower no longer handles suspend; you have to send the command to login:

#Sleep "dbus-send --system --print-reply --dest=org.freedesktop.login1 /org/freedesktop/login1 org.freedesktop.login1.Manager.Suspend boolean:true" m:0x10 + c:150 Mod2 + XF86Sleep
Categories: Offsite Blogs

Motivation for lens?

Haskell on Reddit - Fri, 05/29/2015 - 10:57am

Hi all,

I've been studying Haskell idioms for quite a while, but I've never picked up /u/edwardkmett's lens. I think the main reason is because to this day I'm not sure what it's supposed to be for.

After reading about them for years, I recently learned that conduit and pipes were libraries for a certain IO pattern ("iterated IO"?) In the past, every time I'd asked about them, people told me about things you could do with them, but they never told me what problem it was trying to solve.

What problem is lens trying to solve? How does it succeed and how does it fail?

submitted by PM_ME_UR_OBSIDIAN
[link] [59 comments]
Categories: Incoming News

Two years R&D engineer position available in ComputerScience & Arts, Bordeaux, France

General haskell list - Fri, 05/29/2015 - 10:25am
Inria Bordeaux opens a R&D engineer position in the PoSET research project, located at LaBRI, Bordeaux, France Object: research and development on new modeling and programing methods for realtime computerized artistic systems. Duration: two years from Autumn 2015. Where : Inria Bordeaux/CNRS LaBRI, within the research project PoSET. Salary: from 2000 to 2500 Euros monthly netto (including health insurance) depending on candidate qualification. Keywords: functional programing (Haskell or Ocaml), reactive programming, real-time system, graphical modeling, computational music, science and arts. More details below. To apply, send CV and motivation letter to David Janin, david.janin< at >labri.fr ********************* ** Research Context The Inria research project PoSET is a new research team in Bordeaux with four permanent researchers and at least as many PhD students. It aims at developing a new approach to the design, implementation and execution of complex interactive media systems such as augmented musica
Categories: Incoming News

Haskell wiki: user account

haskell-cafe - Fri, 05/29/2015 - 9:46am
Hi there, I'd like to get a user account for the Haskell wiki. Desired username: Jubobs Cheers
Categories: Offsite Discussion

Consecutive FFI calls

glasgow-user - Fri, 05/29/2015 - 8:52am
(cross-posted from ghc-dev and the cafe, with apologies to cross-subscribers) Hi, If I make a sequence of FFI calls (on a single Haskell thread) but which end up being called from different OS threads, is there any kind of ordering guarantee given? More specifically, is there a full memory barrier at the point where a Haskell thread migrates to a new OS thread? Many thanks, David
Categories: Offsite Discussion

Anyone using Tidal/emacs like emacs-live/overtone?

haskell-cafe - Fri, 05/29/2015 - 8:49am
Does anyone have a working setup where you enter Haskell code from the tidal library and use a keybinding to execute that statement (or multiple)? Basically wanting to try livecoding Tidal code like all the overtone videos: https://vimeo.com/22798433
Categories: Offsite Discussion

Type inference doesn't always calculate the mostgeneric type?

haskell-cafe - Thu, 05/28/2015 - 9:54pm
Hello, I'm new here. Sorry if this question has already been asked. I have noticed something strange about type inference. Prelude> :t abs abs :: Num a => a -> a Prelude> let mapabs = map abs Prelude> :t mapabs mapabs :: [Integer] -> [Integer] Prelude> :t (map abs) (map abs) :: Num b => [b] -> [b] I think that "mapabs" and "map abs" should have the same generic type. In a program I can force the type like this: mapabs = map abs mapabs' :: (Num a) => [a] -> [a] mapabs' = map abs but mapabs still have the type [Integer] -> [Integer] Are there any reason for this? Regards, Christophe Delord.
Categories: Offsite Discussion

Status of Acid-State and IxSet

haskell-cafe - Thu, 05/28/2015 - 7:05pm
Hello, for a project I decided to use Acid-State and IxSet, and was pretty happy with them. I enjoyed working with Haskell structures for storing and querying data, and my data could fit in memory. However, now I've moved to GHC 7.10, and for example syb-with-class, a dependency of ixset, does not build with template-haskell 2.10. So I'm wondering, are these projects still alive and kicking? Are if I want some memory based storage and indexing, should I look at some other projects (maybe VCache http://hackage.haskell.org/package/vcache). Or is it just bad timing and GHC 7.10 compatible versions of these libraries are in the works? Thanks!
Categories: Offsite Discussion

Consecutive FFI calls

haskell-cafe - Thu, 05/28/2015 - 5:24pm
Hi, If I make a sequence of FFI calls (on a single Haskell thread) but which end up being called from different OS threads, is there any kind of ordering guarantee given? More specifically, is there a full memory barrier at the point where a Haskell thread migrates to a new OS thread? Many thanks, David
Categories: Offsite Discussion

Chicago Lambdajam 2015 Schedule is Posted

Haskell on Reddit - Thu, 05/28/2015 - 5:09pm

The schedule has been posted for Chicago Lambdajam 2015. Haskell talks by Conal Elliot and Ranjit Jhala; the rest seem to be Erlang/Scala/Clojure/Racket flavored. With the high attendance at LambdaConf2015 in Boulder this year, are many planning on attending Lambdajam?

submitted by crb002
[link] [2 comments]
Categories: Incoming News

My biggest difficulty/annoyance in learning Haskell is all the 1-letter variable names

Haskell on Reddit - Thu, 05/28/2015 - 4:28pm

Look, I get that Haskell has a mathematical foundation. But honestly, every example that teaches some Haskell concept seems to use meaningless 1-letter variable names in every single spot. It's just so frustrating. I'm sure I'm not the only one who feels this way.

I feel like I could learn these concepts a lot easier if their examples were written using actual words.

submitted by MrCatholic
[link] [69 comments]
Categories: Incoming News