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Recommended way to install, use and maintain haskell tools on OS X
by Nicola Gigante 20 Oct '14

20 Oct '14

Hi I know this question might be a little old, but I happen to have a from scratch installation of OS X (yosemite) on my machine and I want to install the haskell tools in the currently best way. So I summarize the options that I understand are available: 1) A non-option first: the Homebrew formula for haskell-platform is no longer available, but… 2) There are formulas for GHC (7.8.x) and cabal, so I can install those and install the other packages with the homebrew cabal. 3) I can install the binary distribution of the Haskell Platform for OS X directly from the website, and then install any needed package with cabal. 4) I’ve heard of Nix, what is this all about? 5) Installing manually the binary distributions of ghc and cabal. No thanks. That said, what is the recommended way to manage packages once I have cabal and ghc? 1) Installing everything locally into ~/Library/Haskell, which afaik is the default behavior of cabal. That also means having ~/Library/Haskell/bin in the PATH. But do I have to also have ~/.cabal/bin in the PATH? Why having two different local bin directories? What happens to the packages installed by haskell platform system-wide? They are left there, shadowed by the local ones, and never again touched nor updated? 2) Installing everything globally, changing the cabal configuration to make it the default. Afaik bad idea, but then I don’t have obsoleted packages installed system-wide. 3) Installing nothing, and relying on sandboxes to install exactly what is needed for any single package I need. This option is still a bit mysterious to me. 3a) If I need to install a package I need for development, I do cabal sandbox init in my source tree and then if I install something from inside it, cabal installs it in the sandbox. Am I correct? 3a) If I need to install a package I need to _use_, instead, what to do? Sorry for the confusion and thanks for the clarification. Bye, Nicola

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ANN: Haskell plugin for IntelliJ
by Rik van der Kleij 20 Oct '14

20 Oct '14

Hi everyone, I'm glad to announce initial version of Haskell plugin for IntelliJ. It's available in the plugin repository. This plugin is written mainly in Scala and is not mentioned to support GHC/Cabal directly. This plugin support sandbox projects and expects that the Cabal init/install/build is done on command-line. Features - Syntax highlighting (which can be customised); - Error/warning highlighting; - Find Usages of identifiers; - Resolving references of identifiers (also to library code if library source code is added to project and resolves inside import declaration); - Code completion by resolving references; - Renaming variables (which first shows preview so refactoring scope can be adjusted); - View type info from (selected) expression; - View expression info; - View quick documentation; - View quick definition; - Structure view; - Navigate to declaration (called `Class` in IntelliJ menu); - Navigate to identifier (called `Symbol` in IntelliJ menu); - Code completion by looking to import declarations; - Simple form of code formatting; A lot of features are with the help of ghc-mod and ghc-modi. Documentation is provided by haskell-docs. See for more information and getting started: https://github.com/rikvdkleij/intellij-haskell Any feedback is welcome! Regards, Rik

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Eval forgotten unless type specified?
by Jeffrey Brown 19 Oct '14

19 Oct '14

In this passage, after the seq call, :sprint reveals x and y to be evaluated: let x = 1 + 2 :: Int let y = x + 1 :sprint x :sprint y seq y () :sprint x :sprint y The above is a verbatim quote of Marlow's Concurrency book, chapter 2. In the below, however, :sprint shows them unevaluated both before and after the seq call. let x = 1 + 2 let y = x + 1 :sprint x :sprint y seq y () :sprint x :sprint y Why?

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Profiling with an interpreter
by Corentin Dupont 18 Oct '14

18 Oct '14

Hi, I'm trying to profile my game (Nomyx) but I get: "You can't call hscCompileCoreExpr in a profiled compiler". I figured out it's because I'm embbeding an intrepreter. Is there a way to avoid that and profile anyway? Maybe ignoring the calls to the interpreter or something... Cheers Corentin

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What happened to hugs?
by Thorsten Rangwich 18 Oct '14

18 Oct '14

Hi, I suppose this question is not new, but neither google nor a manual search file be file through the archives brought enlightement. www.haskell.org/hugs still exists, but none of the links there does work. Documentation and source point to cvs.haskell.org ("server does not exist") and development points to http://hackage.haskell.org/trac/hugs ("page does not exist"). Was it migrated to somewhere else or is it dead - in latter case the page would not make sense any more. "Raskell" (iPad app) provided a development environment usinh hugs, so I would at least like to install hugs on my Mac as well... Thank you very much in advance. Thorsten. Sent from my mobile phone

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Best way to Introduce FP into a dev team with many C, C++ and Java developers?
by Birmjin In 18 Oct '14

18 Oct '14

Hi, Recently our development team had decided to attempt using Haskell or Scala as one of our programming language. (We had hoped some of our problem will be addressed through taking advantage of some element of FP, like immutability and Rx) Most of our team members have fairly good knowledge of C, C++ and Java. And few of them, including myself, have been self-studying a FP language like Haskell and Scala since last year. Besides some early starters, functional programming is quite new to us. When we held a lecture on FP, we found many of our developers were struggling in grasping some idea of FP. They fumbled with writing functional programming style code. We kept on lecturing several times, but still not quite successful. It seems more difficult than it looks - thinking in functional programming way for the long time C, C++ and Java developers. Does anyone had an experience with initiating FP adoption into a large dev team without pain? Our development team has around 300+ people. Thanks.

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beginnners book
by Roelof Wobben 17 Oct '14

17 Oct '14

Hello, What is a good book to learn Haskell with a lot of exercises so I can check if I understand everything right ? Roelof

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2^770000 triggers Bus Error?
by Erik Rantapaa 17 Oct '14

17 Oct '14

Running ghci under OSX I am seeing the following behavior: Prelude> 2^750000 {... lots of digits...} Prelude> 2^760000 Segmentation Fault: 11 Prelude> 2^770000 Bus Error: 10 and I'm curious why this happens. More details: $ ghci --version The Glorious Glasgow Haskell Compilation System, version 7.8.3 I'm using the 64-bit version of the Haskell Platform (x86_64-darwin-7.8.3).

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Haskell software engineering master thesis
by Jon Kristensen 17 Oct '14

17 Oct '14

Hi, everyone! I'm about to write a software engineering/management master thesis at the IT University of Gothenburg, and I'm considering to do research into the Haskell world. It should probably be in one of the following five fields: empirical software engineering, requirements engineering, software architecture, model-driven engineering or quality management. The focus should probably be more towards an empirical study, rather than something more computer science-related. It should also add to general body of knowledge, and not be too tied to, for example, a specific implementation. Does anyone have any suggestions of relevant topics that I could write about, or perhaps some related papers that I could read? Thanks! Warm regards, Jon Kristensen

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Splicing type signature in TH
by Hugo Pacheco 17 Oct '14

17 Oct '14

Hi list, I am 99.9% sure that this is currently not possible, but I might as well ask: - Is there a way to lift type variables into Template Haskell type splices? What I had in mind would be something like this (erroneous) code: liftT :: a -> Q Type liftT (_::a) = [t| $a |] I have no idea how hard it would be to implement such a feature, or if it is remotely doable. Naively, it seems to me that TH would have to delay evaluating the splice until the type variable is fully expanded, but all the necessary information would still be available at some point during compilation. Cheers, hugo -- www.cs.cornell.edu/~hpacheco

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