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ICFP 2016 Call for Workshop and Co-located Event Proposals

General haskell list - Sat, 10/24/2015 - 12:31am
         CALL FOR WORKSHOP AND CO-LOCATED EVENT PROPOSALS                             ICFP 2016  21st ACM SIGPLAN International Conference on Functional Programming                      September 18-24, 2016                           Nara, Japan       The 21st ACM SIGPLAN International Conference on Functional Programming will be held in Nara, Japan on September 18-24, 2016. 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 2016 and sponsored by SIGPLAN. These events should
Categories: Incoming News

wxHaskell on Windows compilation problems

haskell-cafe - Fri, 10/23/2015 - 4:29pm
I’m trying to compile an established wxHaskell application (Ubuntu) on Windows 7 and after a day of frustration, I wanted to see if anyone had some clues. The problem is getting wxc to compile against wxWidgets, where wxWidgets was compiled with MinGHC (GHC 7.8.4). Following are my steps up to trouble: - On 64 bit Win 7, install MinGHC, which ends up in the AppData path. - Grab wxWidgets with git and using MSYS shell compile like: mingw32-make -f makefile.gcc SHARED=1 UNICODE=1 BUILD=release clean mingw32-make -f makefile.gcc SHARED=1 UNICODE=1 BUILD=release with the goal of compiler compatibility. - Setup some environment variables like: C_INCLUDE_PATH == C:\PCRE\include CPLUS_INCLUDE_PATH == C:\Libs\wxWidgets\3.0.2\include LIBRARY_PATH == C:\PCRE\lib;C:\Libs\wxHaskell\3.0.2\\lib\gcc_lib MSYSTEM == MINGW64 WXCFG == gcc_dll\mswu WXWIN == C:\Libs\wxWidgets\3.0.2 PATH = C:\Users\michaeljones\AppData\Local\Programs\minghc-7
Categories: Offsite Discussion

The fastest way to generate 2d data stucture

Haskell on Reddit - Fri, 10/23/2015 - 4:03pm

Im solving a problem which requires two dimensional data structure.

Im using Matrix from Data.Matrix and fromLists to generate a structure.

However, I need 1000 x 1000 Matrix and the creation process takes too long.

Is there a better / faster way to do that ? Using Data.Matrix is not necessary

submitted by raw909
[link] [2 comments]
Categories: Incoming News

Records with different fields for its constructors can cause a run-time error.

Haskell on Reddit - Fri, 10/23/2015 - 4:02pm

I was just bitten by this behavior.

Here is an example program:

module Main where data ExecResult = ExecFail { exitcode :: Int , stdout :: String , stderr :: String } | ExecSucc { stdout :: String , stderr :: String } deriving (Eq, Show) main :: IO () main = do let failure = ExecFail 1 "fail stdout" "fail stderr" let success = ExecSucc "succ stdout" "succ stderr" putStrLn "failure:" print $ stdout failure print $ stderr failure print $ exitcode failure putStrLn "success:" print $ stdout success print $ stderr success print $ exitcode success putStrLn "done!"

Here is the result:

$ runhaskell -Wall -Werror main.hs failure: "fail stdout" "fail stderr" 1 success: "succ stdout" "succ stderr" main.hs: No match in record selector exitcode

I was surprised by this. I always assumed that this was the kind of run-time error that Haskell should be able to prevent.

I'm also surprised that there isn't a warning about creating such a data-type, since it has the potential to cause run-time errors.

submitted by joehillen
[link] [47 comments]
Categories: Incoming News

'Associative' order of calling

haskell-cafe - Fri, 10/23/2015 - 3:26pm
Is there a name for a fold that promises to call a function such that only an associative function will always return the same result. Or in other words, it has the property that it promises to call a function "associatively" on a set of data? Thanks! Charlie _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe< at >
Categories: Offsite Discussion

fixed-length list library that uses Nat?

Haskell on Reddit - Fri, 10/23/2015 - 2:17pm

Is there a library in Stackage for fixed-length lists that uses the Nat kind for lengths, rather than hand-written Z/S types? The list type constructor should kind "Nat -> * -> *".

submitted by AshleyYakeley
[link] [19 comments]
Categories: Incoming News

Using cabal to build in subdirectories?

Haskell on Reddit - Fri, 10/23/2015 - 1:56pm


I use haskell to to Project Euler problems, so my "project" directory looks like p1,p2, p3 ... pn for each different problem that I'm working on. inside each subdirectory there's a Main.hs and any other supporting .hs files.

I'm wondering if there's a way to use cabal with unix wildcards or regexes to build everything without needing an explicit executable section for each problem in the .cabal file.

submitted by cptwolf
[link] [7 comments]
Categories: Incoming News

[ANN] haskell-ide project

haskell-cafe - Thu, 10/22/2015 - 8:06pm
The ongoing effort to save us as a community from separately implementing the same functionality over and over around IDEs[1] has found a home in the haskell-ide project on github [2]. This mail serves as a call to collaborate for all parties interested in this space. It is still at a very early stage, but the intent is to pool resources so that we can have really good support for IDEs that can extend through the entire tool chain from changes to GHC to better support tooling through the build environment and community information management. This should mean that people who are familiar with a particular part of the chain can focus their efforts there, knowing that the other parts will be covered too. This is a deliberately broad and vague scope, the reality is likely to be much more limited initially, but the sooner we can get started the sooner we will have something concrete to criticise and improve. For those wishing to get involved the following resources currently exist * the haskell-ide maili
Categories: Offsite Discussion

Breaking Changes and Long Term Support Haskell

libraries list - Wed, 10/21/2015 - 10:33am
There seems to be a fair amount of friction between those who want to introduce new features or fix significant historical warts in the base libraries - even if this requires breaking changes - and those who insist on no significant breaking changes in new releases, regardless of the reason or how much warning was given. The rest of the industry has already solved this with long-term/extended support releases. Some version of the platform is blessed with long-term support, and will continue to receive bug fixes and security patches for a number of years, but no other changes. This solution exists for Haskell as well, in the form of Long-Term Support Haskell ( by FP Complete. Not only GHC but an entire ecosystem of libraries are frozen when a new LTS version is released and only bug/security fixes are allowed going forward. Users requiring long-term stability over new features could use LTS Haskell, while those who accept some fixing up of old code
Categories: Offsite Discussion

3 release policy

libraries list - Tue, 10/20/2015 - 8:55pm
A "3 release policy" has been recently mentioned several times, whereby it should always be possible to write code that compiles with the last three releases of GHC, without generating any -Wall warnings. The no warning requirement seems excessively harsh. Will early warnings of impending breakage really cause so much trouble that accepted proposals have to be dragged out over several years to avoid them? If so, would a flag to suppress the warnings suffice? I should note that GHC has traditionally had no qualms about introducing new warnings, on by default. -- View this message in context: Sent from the Haskell - Libraries mailing list archive at
Categories: Offsite Discussion

Default definition for fromRational

libraries list - Thu, 10/15/2015 - 11:51pm
A suitable default definition for fromRational could be the following: fromRational n = fromInteger (numerator n) / fromInteger (denominator n) Changing the MINIMUM pragma to just {-# MINIMAL recip | (/) #-} - Joe
Categories: Offsite Discussion

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!


Categories: Incoming News