- Haskell-Cafe - Haskell.org

Cannot install the Haskell Platform on GNU/Linux (possible Cabal issue)
by egarrulo 15 Aug '14

15 Aug '14

Hello guys, I cannot install the Haskell Platform 2014.2.0.0 on my GNU/Linux system: $ ./platform.sh \ > --prefix=/opt/haskell-platform/haskell-platform-2014.2.0.0 \ > ../ghc-7.8.3/ghc-7.8.3-i386-unknown-linux.tar.bz2 Warning: The following packages are likely to be broken by the reinstalls: haskell-platform-2013.2.0.0 Use --force-reinstalls if you want to install anyway. === pre-requisite packages for hptool are not installed run the following: cd hptool ; cabal install --only-dependencies However, the dependencies for *hptool* are already installed: $ cd hptool ; cabal install --only-dependencies Resolving dependencies... All the requested packages are already installed: Use --reinstall if you want to reinstall anyway. The existing Haskell system: - GHC 7.6.3 - Haskell Platform 2013.2.0.0 - cabal-install 1.16.0.2 (using Cabal library 1.16.0) Any help? Thank you.

3 7

How to improve the zipwith's performance
by jun zhang 15 Aug '14

15 Aug '14

Dear All I write a code for Clustering with Data.Clustering.Hierarchical, but it's slow. I use the profiling and change some code, but I don't know why zipwith take so many time? (even I change list to vector) My code is as blow, Any one kindly give me some advices. ====================== main = do .... let cluster = dendrogram SingleLinkage vectorList getVectorDistance .... getExp2 v1 v2 = d*d where d = v1 - v2 getExp v1 v2 | v1 == v2 = 0 | otherwise = getExp2 v1 v2 tfoldl d = DV.foldl1' (+) d changeDataType:: Int -> Double changeDataType d = fromIntegral d getVectorDistance::(a,DV.Vector Int)->(a, DV.Vector Int )->Double getVectorDistance v1 v2 = fromIntegral $ tfoldl dat where l1 = snd v1 l2 = snd v2 dat = DV.zipWith getExp l1 l2 ======================================= build with ghc -prof -fprof-auto -rtsopts -O2 log_cluster.hs run with log_cluster.exe +RTS -p profiling result is log_cluster.exe +RTS -p -RTS total time = 8.43 secs (8433 ticks @ 1000 us, 1 processor) total alloc = 1,614,252,224 bytes (excludes profiling overheads) COST CENTRE MODULE %time %alloc getVectorDistance.dat Main 49.4 37.8 tfoldl Main 5.7 0.0 getExp Main 4.5 0.0 getExp2 Main 0.5 1.5

3 2

HaskellWiki page about SDL
by Henk-Jan van Tuyl 14 Aug '14

14 Aug '14

L.S., Does the problem with SDL on OS X, as mentioned on the HaskellWiki page about SDL[0], still exist? This text is quite old and I would like to remove it. Regards, Henk-Jan van Tuyl [0] https://www.haskell.org/haskellwiki/SDL#Haskell-SDL_with_Mac_OS_X -- Folding@home What if you could share your unused computer power to help find a cure? In just 5 minutes you can join the world's biggest networked computer and get us closer sooner. Watch the video. http://folding.stanford.edu/ http://Van.Tuyl.eu/ http://members.chello.nl/hjgtuyl/tourdemonad.html Haskell programming --

1 0

haskell (and beyond) in education
by Rustom Mody 14 Aug '14

14 Aug '14

I am collecting some data on FP used to introduce programming ie as a first course: http://blog.languager.org/2014/08/universities-starting-functional.html Naturally the haskell link is the first: http://www.haskell.org/haskellwiki/Haskell_in_education I was just wondering if there are more extremal cases of this: eg Are there any univs using Idris/Agda to *introduce* programming/math/proofs etc

5 4

maintainer needed: extensible-effects
by Ben Foppa 14 Aug '14

14 Aug '14

Hey cafe, is there anybody interested in taking over maintainership of the extensible-effects package? I'm rather busy and not keeping a good eye on it.

1 0

Closed Type Family Simplification
by Ian Milligan 14 Aug '14

14 Aug '14

When a closed type family has only one instance it seems like it should never fail to simplify. Yet this doesn't appear to be the case. When I defined (in GHC 7.8.3) the closed type family type family (:.:) f g a where (:.:) f g a = f (g a) I get errors such as 'Could not deduce (Object c3 ((:.:) f g a) ~ Object c3 (f (g a)))' (where Object is a Constraint family), indicating that f (g a) is not being substituted for (:.:) f g a as desired. Any idea why this happens?

3 7

Does the lambda calculus have provisions for I/O? State can be done with free variables.
by KC 14 Aug '14

14 Aug '14

Hi: Does the lambda calculus have provisions for I/O? State can be done with free variables. -- -- Sent from an expensive device which will be obsolete in a few months! :D Casey

2 1

ANNOUNCE: hayland 0.1.0.0
by Auke Booij 14 Aug '14

14 Aug '14

I just pushed the first release of the Haskell bindings to Wayland I've been working on to Hackage. SHAMELESS SPAM ----- I'm looking for a PhD position in (mathematical) type theory (preferably in Europe). Contact me for my (interesting!) background. What is Wayland? ----- For those of you who have been living under a rock, X11 is probably going to be ditched soon (porting work for GNOME, KDE, and E is already well underway), and the graphics stack reworked, in favor of "wayland". There will no longer be a monolithic server between the compositor (aka window manager) and the window clients. In the new design, the compositor *is* the central server. The new architecture allows for proper isolation of clients (a HUGE security improvement over X11), as well as major cleanups of code (enabling embedded use). Why bind to C code? ----- In theory, wayland should only be a protocol specification (which happens to have a reference implementation) which could be implemented in Haskell. However, the current state of the matter is that for EGL implementation reasons, one is forced to bind to this reference implementation. (More precisely, the EGL libraries need to be able to configure wayland - and such code would have to be written for every wayland implementation.) So in practice, one can't write a pure Haskell implementation, and that's why I made bindings for the C library. Where's the code? ----- https://github.com/tulcod/haskell-wayland Wait, why are you even binding to Wayland? ----- Not sure, but it's pretty foundational stuff so I'm sure it'll be of use to someone, somewhere. Maybe someone wants to write a window manager for the new ecosystem (I'm looking at you XMonad)? Wow, I've never seen a module expose this many symbols ----- Yes, if anyone has ideas on how to reorganize and/or clean up the symbols exposed by the various part of the library, I am most interested. The problem here is that I'm generating a lot of code using template haskell, and TH does not give you control over which symbols you want to expose and how. I could write this list to a haskell source file at configure time instead (which might be useful for other reasons as well), but ideally I would like to split up the library into the various "interfaces" wayland offers - but these interfaces are unknown at dev time time, and I don't think there is remotely any mechanism to generate /modules/ at compile time. I'm interested to hear what you guys think about controlling the symbol exposure of TH-generated code. TemplateHaskell /and/ GeneralizedNewtypeDeriving? Are you /trying/ to derive bottom? ----- Well I sacrificed some Safety in favor of exposing nice Haskelly types. Feedback is welcome. Final note ----- By the way, I also wrote bindings to xkbcommon a while ago, although they need some attention. Anyway, my point is that with hayland and xkbcommon in place (both in a semi-usable state), there should be plenty of groundwork ready for you to get started with Wayland on Haskell. (xkbcommon is the de facto standard library to work with keyboard layouts in wayland. It translates keyboard events ("which key did you press") into Unicode symbols ("what letter should appear on the screen"), using the right keyboard layout.)

1 0

Visualising Haskell function execution
by Jan Paul Posma 13 Aug '14

13 Aug '14

Hey all, Last weekend my friend Steve and I did a small project for visualising Haskell function execution in the browser. It's meant to be used in education, and uses a tiny custom parser. I figured it could be of interest for anyone here learning or teaching Haskell: https://stevekrouse.github.io/hs.js/ To see it in action, scroll a bit down to the red bordered box, and click on "map", and then keep clicking on each new line. I hope it can be useful to someone. Cheers, JP

7 7

Openings for brilliant Haskell devs for exciting project "as close to a space station as you can get" @ Swedish spinoff, DSLs/safety-critical/embedded software, and more
by Johan Glimming 13 Aug '14

13 Aug '14

Dear All, I’d like to share this exciting job opportunity (formatted text below), as this forum might be right for the very skilled developers we are looking for here. The LinkedIn posting is on the following webpage, e.g. in case the email does not display correctly: https://www.linkedin.com/today/post/article/20140812174919-547525-openings-… … Best wishes, Johan Glimming @ LinkedIn: http://se.linkedin.com/in/glimming — Openings for brilliant Haskell devs for exciting project "as close to a space station as you can get" @ Swedish spinoff, DSLs/safety-critical/embedded software, and more As we grow our business further we look for extraordinary Haskell developers to further strengthen our exceptionally skilled teams in our spinoff and startup Functor Group AB, Kista/Stockholm, Sweden, with subsidiaries. www.functorgroup.com @functors +FunctorGroups You would have an impressive background in computer science, with industrial experience and first-class academic education including certainly advanced functional programming. Compiler design skills are valued highly. Experience of static code analysis (tools and/or research) and safety-critical software and embedded software development are all relevant to this startup and spinoff. You would be part of a team with extraordinary skills and work with other talented individuals which, for those with the right mindset, is extremely rewarding. It's relevant with skill sets that include AFP, EDSLs, type systems, Martin-Löf type theory, dependent types, formal methods, standard-type static analysis tools (as we offer a new kind that adds dependent types to the abstract interpretation approach), experience from tools form e.g. Coverity, Klocwork, MathWorks,, Spec#, Coq, Agda, Epigram, Twelf or other such tools, LLVM, ANSI / ISO C, MISRA C, software testing, various programming languages and their implementation, domain-specific languages, DDD, language-based programming turned into our emerging method named language-driven development, logical frameworks, meta languages, operational semantics, logic, theorem provers. (Learn more atwww.functor.se.) You should be able to contribute to very demanding, challenging, creative teamwork as it manifests itself in a pioneering high-tech spinoff. This all means great responsibility, important contributions to be made, with multiple and varying roles in our highly dynamic work environment where you would be working with other exceptional talents and contribute with your passion for functional programming. You are assumed to share our enthusiasm for and commitment to the new constructive programming paradigm, and recognise the value and great importance of our research foundation, our core technology, being made available in the industry. You would share and nourish our vision for the future of the software industry with the new constructive programming paradigm based on type theory research and the next level of functional programming with EDSL integrated in programming as never done before. But most important is of course your documented talent and experience in Haskell development at an industrial level as well as great teamwork skills and enthusiasm about relevant technologies, and being aligned with our mission (for which see www.functorgroup.com) Several of our developers have higher academic degrees such as a PhD in computer science, logic or mathematics, including two of our Research Engineers, who are professors. (and two more in our Advisory Board, both with own spinoffs, plus an extensive network to leading researchers that we work closely with now and in the future). Your experience may include software development in segments such as safety-critical software and embedded software, hardware modelling, advanced DSL implementation, compiler design and compiler technologies, GPU applications, implementing software testing tools and tools for formal methods. We do not expect you to have all these listed skills, but we expect you to be exceptionally talented and contribute to the success and further growth of Functor Group and its subsidiaries. We are now in an extremely interesting but demanding phase as a spinoff eg with one extraordinarily high-profile customer. You will be part of that project and other very exciting customer projects where we deploy unmatched new technology that brings a new programming paradigm to the software industry, with customers internationally, and an exciting journey into a future where research progress is finally bring aligned with best-practices also in software engineering in a world where software drives innovation and much of growth, but where our technology opens up for much needed improvements in the way software is being developed, designed and tested. Mail your application with resumé with references etc to jobs(a)functor.se. www.functorgroup.com Posted by Dr Johan Glimming at Functor Group AB and Functor AB —

1 0