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Haskell IDE on Windows (source editing; project preparation and compiling/building)

Haskell on Reddit - Sun, 04/12/2015 - 12:39pm

I'm learning C++ at college ATM and using Visual Studio. Needless to say, it's a breeze; I only ever have to worry about the code and the dependencies between files. Everything else just works.

So I've become quite interested, very recently, in Haskell. In FP in general. Started out with messing with F# a bit and it intrigued me. Read around, went ahead and installed the Haskell Platform, and now I'm supremely stuck.

I can load/run separate .hs files through GHCi/runhaskell but otherwise, nothing works. Tried setting up several plugins, the last being several IntelliJ ones, but I can't for the life of me figure out how project handling works. Some sources speak of GHC and Cabal different build environments, of manually written make files and stuff like that...

I've yet to find a tutorial speaking a language I can understand. Using cabal init fails on the 3rd step with "Error: cabal: git: no source" or something like that.

Thanks a lot.

submitted by Enamex
[link] [44 comments]
Categories: Incoming News

Why there isn't a Pure typeclass ?

Haskell on Reddit - Sun, 04/12/2015 - 11:50am

An Applicative is a Functor with 2 functions, one to create an instance from a value (pure) and one to zip them (through <*>). However, I'm sure they are functors for which pure makes sense, but <*> doesn't. As now Applicative is a superclass of Monad, it would have make sense to also introduce a Pure class just defining pure?.

submitted by maxigit
[link] [78 comments]
Categories: Incoming News

Dealing with GHC 7.10 prelude imports

haskell-cafe - Sun, 04/12/2015 - 8:55am
Hi, I've run into a couple of cases when attempting to support multiple GHC versions in my libraries (7.6.3 -> 7.10) where I've repeatedly made mistakes due to being warned about unused imports for various modules that are now part of the Prelude such as Data.Monoid, Data.Foldable, etc. which I subsequently remove either manually or via editor automation sufficiently indistinguishable from magic. This then results in successful compilation on 7.10 and failure on earlier versions of GHC due to missing imports (ie. Data.Monoid (mappend, mempty)), which prior to my current workflow of manually building on multiple versions of GHC before releasing a new version, manifested once or twice only after uploading to Hackage. Now this is all user/workflow error on my part, but I wondered if others have some kind of trick up their sleeve for avoiding these kind of issues? I could attempt to tailor the compiler's warning flags appropriately, but it bodes ill for spotting genuinely unused imports. Cheers, Brendan ____
Categories: Offsite Discussion


glasgow-user - Sat, 04/11/2015 - 5:44pm
What’s the story with this? I tried to follow the instructions here: <> but I get Dominic Steinitz dominic< at > _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users< at >
Categories: Offsite Discussion

Proposal for a generic showIntAtBase

libraries list - Sun, 04/05/2015 - 5:46pm
Hi, The current implementation of showIntAtBase in Numeric is limited to Chars currently. *showIntAtBase* * :: (Integral a, Show a) => a -> (Int -> Char) -> a -> ShowS* The 2 reasons for this constraint is: a) We only accept functions of the form (Int -> Char) b) An implicit concatenation using (:) I'd like to propose a new function showIntAtBaseGeneric that removes the (Int -> Char) function constraint and takes an additional function to replace the implicit (:) operator. *showIntAtBaseGeneric* * :: (Integral a1, Num b, Show a1) =>* * a1 -> (b -> a) -> (a -> s -> s) -> a1 -> s -> s* Now showIntAtBase may be implemented as: *showIntAtBase :: (Integral a, Show a) => a -> (Int -> Char) -> a -> ShowS* *showIntAtBase base toChr n0 r0 = showIntAtBaseGeneric base toChr (:) n0 r0* The API and behavior of showIntAtBase remains unchanged while allowing for generic conversions not limited to Chars alone. *Example: * *λ> showIntAtBaseGeneric 26 id (:) 500 [] -- convert 500 to base26 and provid
Categories: Offsite Discussion

A Random Strawman

libraries list - Sat, 04/04/2015 - 6:57pm
Hello All, Having skimmed the literature, run some tests and benchmarks: The current System.Random is broken: Furthermore, this is recorded in at least two published papers: and The tf-random package does not have this breakage and is based on good theoretical foundations. In my tests tf-random performs better than System.Random. As a result of which, I am very much inclined to suggest we replace the code in System.Random with tf-random. Before doing any more work on this, I’d like to understand what the next steps should be. How much review should be carried out? I have no reason to doubt the implementors have done a great job but should someone (who?) review the code more formally. If so what would the process / tools be? Tests in packages / applications may now fail as the (pseudo) random numbers will be different w
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