April 2010 - Haskell-Cafe

ANNOUNCE: Hac phi 2010
by Chris Casinghino 08 Apr '10

08 Apr '10

Greetings, I am very pleased to officially announce Hac phi 2010, a Haskell hackathon/get-together to be held May 21-23 at the University of Pennsylvania in Philadelphia. The hackathon will officially kick off at 2:30 Friday afternoon, and go until 5pm on Sunday (with breaks for sleep, of course). Last year's Hac phi was a lot of fun, and many people have already expressed interest in coming back this year. I want to stress that everyone is welcome---you do not have to be a Haskell guru to attend! Helping hack on someone else's project could be a great way to increase your Haskell-fu. If you plan on coming, please officially register [1]. Registration, travel, lodging and many other details can be found on the Hac phi wiki [2]. Note that we're in a different space this year and may have to cap attendance, so register early. We're also looking for a few people interested in giving short (15-20 min.) talks, probably on Saturday afternoon. Anything of interest to the Haskell community is fair game---a project you've been working on, a paper, a quick tutorial. If you'd like to give a talk, add it on the wiki [3]. Hope to see you in Philadelphia! -The Hac φ team [1] http://haskell.org/haskellwiki/Hac_φ/Register [2] http://haskell.org/haskellwiki/Hac_φ [3] http://haskell.org/haskellwiki/Hac_φ/Talks

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multi-ghc: Managing Multiple GHC Distributions
by Sean Leather 08 Apr '10

08 Apr '10

I created a few tools to help me manage multiple GHC distributions in a Bash shell environment. Perhaps it's useful to others. http://github.com/spl/multi-ghc Feedback welcome. I'd also like to know if something similar exists. Regards, Sean

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Traypoweroff questions
by Luis Cabellos 08 Apr '10

08 Apr '10

Hi, I just put an application into hackage http://hackage.haskell.org/package/traypoweroff. I made this application to allow a tray icon in xmonad to poweroff and reboot my computer. But I dislike two things I made. The first one is the use of */sbin/poweroff* and */sbin/reboot* with system call. I feel than i should be a better way to do the poweroff or the reboot. err <- system "sudo /sbin/reboot" The second issue is, the user need to put into sudoers the permission to execute reboot and poweroff. The use of *sudo* seems a little awkward. I'll like a cleaner installation without force user touch configuration files. myuser ALL=(ALL) NOPASSWD: /sbin/poweroff Thanks for the help, Luis Cabellos p.d: I'll add suspend with pm-suspend command in the next version BTW

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GHC LLVM ARM Cross Compilation
by Nathaniel Neitzke 08 Apr '10

08 Apr '10

I saw the Google Summer of Code project for using LLVM to cross compile for other architectures such as ARM. Professionally I write embedded Linux code that targets ARM processors such as the TI DaVinci DM355 and am very intrigued by the potential use of Haskell for future projects. If I was interested in attempting to add support for LLVM ARM cross-compilation, are there any thoughts on what parts would have to be modified to do so? Or has work already been conducted in this area? ~Nathan

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what are the safety conditions for unsafeIOToST
by Nicolas Frisby 08 Apr '10

08 Apr '10

I haven't been able to find it via Google or Haddock. An old message suggests is was just a matter of exceptions? I only want to use the IO for generating Data.Uniques to pair with STRefs in order to make a map of them. I'm guessing this would be a safe use since it's exception free (... right?). Thanks!

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ANNOUNCE: JSONb-1.0.0
by Jason Dusek 08 Apr '10

08 Apr '10

A new release of JSONb, taking advantage of the latest Attoparsec. http://hackage.haskell.org/package/JSONb-1.0.0 Thanks to Grant Monroe for help with the numerics parser. -- Jason Dusek

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lhaskell.vim: syntax highlighting fix for pragmas and comments in TeX mode
by Tomas Janousek 08 Apr '10

08 Apr '10

Hello cafe :-), you're the maintainer of lhaskell.vim and I'm sending you a patch that fixes the highlighting of curly brackets and anything between them. (Who's supposed to send it to vim maintainer? Me, or cafe?) Regards, -- Tomáš Janoušek, a.k.a. Liskni_si, http://work.lisk.in/

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libraries [was GUI haters]
by gladstein＠gladstein.com 08 Apr '10

08 Apr '10

As a working engineer, one of my greatest frustrations is my inability to use Haskell in the workplace. The unfortunate fact is that my media industry clients use mostly Windows, some Macs, and no linux except for servers. The core system works everywhere, but many contributed libraries don't. GUIs are the big showstopper. One of the reasons Java won out over Common Lisp is that it had huge libraries. Franz's libraries were superb but few in number. One diehard Lisp user converted his lab to Java because "Java gives you everything you want, for free." That languages are distinct from their libraries escapes a lot of people; they see each language as a package. I met a COBOL programmer recently (I'm not making this up) that was looking into Java. He didn't see how people could use it, he said, because it had "thousands of commands". I'll stop whining now.

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Metaprogramming in Haskell vs. Ocaml
by aditya siram 08 Apr '10

08 Apr '10

Hi all, I would like to learn a little bit more about metaprogramming in Haskell. And I'm also wondering why metaprogramming is used much more in Ocaml than in Haskell. Camlp4 (Ocaml's metaprogramming facility) doesn't seem to much more powerful that Template Haskell. The former is celebrated in its community as a killer feature of the language and its use is encouraged by numerous accessible tutorials. The latter however is down-played and not as well documented. Seeing that the languages are parallel in many ways is there some reason for this? Is metaprogramming less useful in Haskell? Is it worth learning? thanks ... -deech

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Established names for a couple of list functionals?
by Stephen Tetley 08 Apr '10

08 Apr '10

Hello all Having traversals with special behaviour for the first or last element is useful for my current work: -- first element special -- anacrusisMap :: (a -> b) -> (a -> b) -> [a] -> [b] anacrusisMap _ _ [] = [] anacrusisMap f g (a:as) = f a : map g as -- last element special -- cabooseMap :: (a -> b) -> (a -> b) -> [a] -> [b] cabooseMap _ _ [] = [] cabooseMap f g (a:as) = step a as where step x [] = [g x] step x (y:ys) = f x : step y ys *Overlay1> anacrusisMap (+1) id [1..10] [2,2,3,4,5,6,7,8,9,10] *Overlay1> cabooseMap id (+1) [1..10] [1,2,3,4,5,6,7,8,9,11] My question (trivial, but still...) - is there any prior art naming these functions? For the record, my name derivation is: + anacrusis - musical term, the pickup notes before the first bar in a score. + caboose - there was discussion on Haskell-Cafe a couple of months ago about a list data type with a distinguished terminal type. Caboose is the name I remember. Thanks Stephen

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