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[OS X] Quick Question on Leskah Setup

Haskell on Reddit - Fri, 10/10/2014 - 7:00pm

The first time Leskah is launched, it presents a dialog box wherein the user can specify the "[p]aths under which Haskell sources for packages may be found":

http://i.imgur.com/OrNVefW.png

Which path(s) should a user using Haskell Platform 2014.2.0.0 on OS X select?

edit: Apologies, s/Leskah/Leksah/g

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

cabal sandbox using absolute path on symlinked dir

haskell-cafe - Fri, 10/10/2014 - 3:14pm
Hello Cafe, On Ubuntu, after creating a sandboxed project in a symlinked directory, cabal.sandbox.config contains absolute (canonical) paths of the directory, and not the symlinked paths. Is this a bug, and is there a way to correct that behavior? There is no way to move the project to a different place without recreating the whole sandbox. Best regards, vlatko
Categories: Offsite Discussion

Chaining a map over lists with lenses

haskell-cafe - Fri, 10/10/2014 - 2:51pm
Hi! I’m sure the answer to this question is under my eyes but I can’t understand it only from the docs. Suppose a data type like this: data Type1 = Type1 { _myField :: [Type2] } makeLenses ‘’Type1 data Type2 = Type2 { _otherField :: String } Then with t^.myField I get access to the [Type2] list. Now, i would like to go through each element of the list, apply the otherField lens to each element, and get the list of the results. Of course this means: map (view otherField) (t^.myField) but I’m sure there’s some combinator to do the same thing by chaining lenses/prisms/traversals/whatever, right? E.g. something like t^.myField.something.otherField I’m still trying to understand the full picture about lenses, but afaik what I need is a prism, because a list is a sum type, right? Thank you for your help, Nicola
Categories: Offsite Discussion

Mathematics of Program Construction (MPC 2015): firstcall for papers

General haskell list - Fri, 10/10/2014 - 1:59pm
Apologies for multiple copies. FIRST CALL FOR PAPERS 12th International Conference on Mathematics of Program Construction (MPC 2015) Königswinter, Germany, 29 June - 1 July 2015 http://www.cs.ox.ac.uk/conferences/MPC2015/ BACKGROUND The MPC conferences aim to promote the development of mathematical principles and techniques that are demonstrably practical and effective in the process of constructing computer programs, broadly interpreted. The 2015 MPC conference will be held in Königswinter, Germany, from 29th June to 1st July 2015. The previous conferences were held in Twente, The Netherlands (1989), Oxford, UK (1992), Kloster Irsee, Germany (1995), Marstrand, Sweden (1998), Ponte de Lima, Portugal (2000), Dagstuhl, Germany (2002), Stirling, UK (2004, colocated with AMAST), Kuressaare, Estonia (2006, colocated with AMAST), Marseille, France (2008), Québec City, Canada (2010, colocated with AMAST), and Madrid, Spain (2012). TOPICS Papers are solicited on mathematical methods and tools put to use
Categories: Incoming News

Skills Matter

del.icio.us/haskell - Fri, 10/10/2014 - 12:55pm
Categories: Offsite Blogs

Skills Matter

del.icio.us/haskell - Fri, 10/10/2014 - 10:06am
Categories: Offsite Blogs

Skills Matter

del.icio.us/haskell - Fri, 10/10/2014 - 10:06am
Categories: Offsite Blogs

Need help testing hGetContents modification

haskell-cafe - Fri, 10/10/2014 - 8:43am
I uploaded a change to hGetContents as D327 on Phabricator to address TRAC #9236. In particular, this generates an error when attempting to read from a closed handle instead of silently returning an empty string. I would love to get some help testing this against code that uses lazy I/O heavily, *especially* with pipes, sockets, and other such weirdness, if such things exist in the wild. I don't usually read haskell-cafe, so please send responses to my address as well as the list. Thanks a lot, David Feuer _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe< at >haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Categories: Offsite Discussion

Stackage Server

del.icio.us/haskell - Fri, 10/10/2014 - 7:03am
Categories: Offsite Blogs

Stackage Server

del.icio.us/haskell - Fri, 10/10/2014 - 7:03am
Categories: Offsite Blogs

Skills Matter

del.icio.us/haskell - Fri, 10/10/2014 - 6:28am
Categories: Offsite Blogs

Current state-of-the-art in getting a dev env set up(windows 8)

haskell-cafe - Fri, 10/10/2014 - 2:15am
What is the current advice for getting a haskell dev env set up on windows? There's a lot of options, and it can be hard to quickly determine which are current and which are deprecated/bit-rotted. For example, apparently cabal sandbox is preferred over cabal-dev these days. I've read: http://onoffswitch.net/started-haskell/ http://stackoverflow.com/questions/304614/haskell-on-windows-setup http://coldwa.st/e/blog/2013-08-20-Cabal-sandbox.html http://bob.ippoli.to/archives/2013/01/11/getting-started-with-haskell/ I've installed the latest haskell platform (2014.2), and am using Sublime Text 2 as my editor. SublimeHaskell is installed, but apparently it needs aeson, haskell-src-ext, and haddock. cabal install aeson indicates that it will break unordered-containers-0.2.4.0 and case-insensitive-1.1.0.3, so I must use --force-reinstalls to get it. I'm doing this in a sandbox, in case it is a terrible idea. https://github.com/SublimeHaskell/SublimeHaskell Not yet sure how I'm going to get the sandbox install
Categories: Offsite Discussion

ICFP 2015 Call for Workshop and Co-located EventProposals

haskell-cafe - Thu, 10/09/2014 - 11:32pm
CALL FOR WORKSHOP AND CO-LOCATED EVENT PROPOSALS ICFP 2015 20th ACM SIGPLAN International Conference on Functional Programming August 30 - September 5, 2015 Vancouver, Canada http://icfpconference.org/icfp2015/ The 120th ACM SIGPLAN International Conference on Functional Programming will be held in Vancouver, British Columbia, Canada on August 30-September 5, 2015. ICFP provides a forum for researchers and developers to hear about the latest work on the design, implementations, principles, and uses of functional programming. Proposals are invited for workshops (and other co-located events, such as tutorials) to be affiliated with ICFP 2015 and sponsored by SIGPLAN. These events should be less formal and more focused than ICFP itself, include sessions that enable interaction among the attendees, and foster the exchange of new ideas. The preference is for one-day events, but other schedules can also be considered
Categories: Offsite Discussion

ICFP 2015 Call for Workshop and Co-located Event Proposals

General haskell list - Thu, 10/09/2014 - 11:32pm
CALL FOR WORKSHOP AND CO-LOCATED EVENT PROPOSALS ICFP 2015 20th ACM SIGPLAN International Conference on Functional Programming August 30 - September 5, 2015 Vancouver, Canada http://icfpconference.org/icfp2015/ The 120th ACM SIGPLAN International Conference on Functional Programming will be held in Vancouver, British Columbia, Canada on August 30-September 5, 2015. ICFP provides a forum for researchers and developers to hear about the latest work on the design, implementations, principles, and uses of functional programming. Proposals are invited for workshops (and other co-located events, such as tutorials) to be affiliated with ICFP 2015 and sponsored by SIGPLAN. These events should be less formal and more focused than ICFP itself, include sessions that enable interaction among the attendees, and foster the exchange of new ideas. The preference is for one-day events, but other schedules can also be considered
Categories: Incoming News

Combine type family return value

haskell-cafe - Thu, 10/09/2014 - 6:12pm
Hello! Following code is my attempt to comprehend type families and data kinds. I want to annotate boolean formula with variables it contains, so I get function `value` checked at compile time. `value` should return Bool, if no variables are present in formula, list of variables otherwise. Of course, `value` can just return Either [Var] Bool, but I want to get Type-level programming-fu. {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE StandaloneDeriving #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE UndecidableInstances #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE DataKinds #-} data Nat = Zero | Succ Nat type family Plus (x :: Nat) (y :: Nat) :: Nat type instance Plus Zero x = x type instance Plus (Succ x) y = Plus x (Succ y) type family Multi (x :: Nat) (y :: Nat) :: Nat type instance Multi Zero x = Zero type instance Multi (Succ x) y = Plus y (Multi x y) type One = Succ Zero type Two = Succ One type Three = Succ Two type Power2 a = Power Two a type family Power (n :: Nat) (k :: Nat) :: Nat type insta
Categories: Offsite Discussion

Haskell Weekly News: Issue 309

General haskell list - Thu, 10/09/2014 - 5:07am
Welcome to issue 309 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers from September 28 to October 4, 2014 Quotes of the Week * Uh... I'ma have to read the IRC logs... No good quotes < at >remember'd Top Reddit Stories * Announcing needle: ASCII-fied arrow notation Domain: scrambledeggsontoast.github.io, Score: 103, Comments: 119 Original: [1] http://goo.gl/wCPh8K On Reddit: [2] http://goo.gl/UwTJSt * How we might abolish Cabal Hell, part 1 Domain: well-typed.com, Score: 95, Comments: 69 Original: [3] http://goo.gl/N19hPq On Reddit: [4] http://goo.gl/CQQRF0 * After some failed attempts to learn Parsec I came across this incredibly patient tutorial and now I'm writing parsers! Domain: github.com, Score: 79, Comments: 17 Original: [5] http://goo.gl/msqtkb On Reddit: [6] http://goo.gl/p3EgqQ * Neil Mitchell's Haskell Blog: Why Traversable/Foldable should not be in the Prelu
Categories: Incoming News

Proposal: Make a very slight change to the semantics of Data.List.isSuffixOf

libraries list - Wed, 10/08/2014 - 9:15am
Currently, isSuffixOf is defined like this: xs `isSuffixOf` ys = reverse xs `isPrefixOf` reverse ys If ys is much longer than xs, this is not so wonderful, because we have to reverse the whole spine of ys. It also will fail whenever either xs *or* ys is infinite. The following implementation seems a lot saner (although longer): isSuffixOf :: forall a . (Eq a) => [a] -> [a] -> Bool [] `isSuffixOf` _ = True needle `isSuffixOf` hay = maybe False (\fp -> needle `eq` getEndChunk hay fp) (getFrontPointer needle hay) where eq :: [a] -> [a] -> [a] (x:xs) `eq` (y:ys) = x==y && (xs `eq` ys) getEndChunk :: [a] -> [a] -> [a] getEndChunk (_:hy) (_:fp) = getEndChunk hy fp getEndChunk hy _ = hy getFrontPointer :: [a] -> [a] -> Maybe [a] getFrontPointer [] hy = Just hy getFrontPointer _ [] = Nothing getFrontPointer (_:nd) (_:hy) = getFrontPointer nd hy This doesn't do any of that crazy stuff, and it will w
Categories: Offsite Discussion

PLT Redex: The Summer School, Call for Participation

General haskell list - Tue, 10/07/2014 - 2:04pm
PLT REDEX: THE SUMMER SCHOOL CALL for PARTICIPATION Matthias Felleisen, Robert Bruce Findler, Matthew Flatt LOCATION: University of Utah, Salt Lake City DATES: July 27 - July 31, 2015 http://www.cs.utah.edu/~mflatt/plt-redex/ PLT Redex is a lightweight, embedded DSL for modeling programming languages, their reduction semantics, and their type systems. It comes with an IDE and a toolbox for exploring, testing, debugging, and type-setting language models. The PLT research group has successfully used Redex to model and analyze a wide spectrum of published models. The summer school will introduce students to the underlying theory of reduction semantics, programming in the Redex language, and using its tool suite effectively. The course is intended for PhD students and researchers in programming languages. Enrollment is limited to 25 attendees. While the workshop itself is free, attendees must pay for travel, room, and board. We expect room and board to be around $500, assuming an arrival in the evening of
Categories: Incoming News

New gtk2hs 0.12.4 release

gtk2hs - Wed, 11/21/2012 - 12:56pm

Thanks to John Lato and Duncan Coutts for the latest bugfix release! The latest packages should be buildable on GHC 7.6, and the cairo package should behave a bit nicer in ghci on Windows. Thanks to all!

~d

Categories: Incoming News