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Porting this application to Haskell

Haskell on Reddit - Mon, 01/11/2016 - 2:46pm

I just got hired by a small start-up ( that is creating an interactive web application to for high school and university debaters to flow/record debates. They are considering switching implementations from AngularJs to something more scalable and efficient. Would Yesod be a viable option to suggest?

Does it have good support for interactive web applications and this sort of image manipulation?

Mock up:

submitted by ChavXO
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Categories: Incoming News

Plugin system for an e-commerce/CMS website? (XPOST from /r/haskellquestions)

Haskell on Reddit - Mon, 01/11/2016 - 2:36pm

Note: Recently I posted this question on /r/haskellquestions with no response

I deal a lot with e-commerce, but in interpreted languages. Often they have some type of plugin/module system that you can purchase modules from 3rd parties and plug them into the system. How would you do that in Haskell? Perhaps with Yesod?

It would seem that it would be hard to do while the server is running and would require it to be there during compile time, which is fine.

Perhaps some type of Event-Observer system?

New to Haskell and not sure the best way to achieve this, preferably with as much type safety as possible.



Additional clarification: It seems that in the CMS/E-Commerce field the frameworks/platforms that provide a way for 3rd parties to create plugins/modules succeed as people can customize their installation for what they needTM. I was trying to think of the best way to do that with Haskell so that you have good type safety as well, but I don't have the experience to do this properly.

Mostly this is a curiosity, but on the side I wouldn't mind creating a e-commerce platform and would definitely want to have some type of plugin system.

submitted by sbditto85
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Categories: Incoming News

ANN: true-name released

General haskell list - Mon, 01/11/2016 - 6:40am
It is with some shame that I announce ‘true-name’, a package to assist one in violating those pesky module abstraction boundaries via the magick of Template Haskell. Take ‘Control.Concurrent.Chan’ for example; you can get your grubby mitts on the ‘Chan’ data constructor, despite it not being exported. Here we pattern match on it, and bind ‘chanR’ and ‘chanW’ to the ‘MVar’s containing the read and write ends of the channel respectively: Now, the type of ’chanR’ references the unexported ‘Stream’ and ‘ChItem’ types. We need the ‘ChItem’ data constructor―which is hidden under a few indirections—but that's not a problem: This gives us a rather dodgy ‘peekChan’. This sort of thing is usually a Bad Idea™, but may sometimes be more palatable than the alternatives. Full example: Taking another example, suppose we want the ‘Array’ type constructor hidde
Categories: Incoming News

Eq1, Ord1, Show1: move from eq1, compare1, showsPrec1 to liftEq, liftCompare, liftShowsPrec

libraries list - Sun, 01/10/2016 - 3:08pm
In transformers-0.5:Data.Functor.Classes class methods like eq1 are replaced by liftEq. With transformers-0.4 I could define: data T a = complicated definition ... deriving (Eq, Ord, Show) instance Eq1 T where eq1 = (==) instance Ord1 T where compare1 = compare instance Show1 T where showsPrec1 = showsPrec In transformers-0.5 it seems that I have to implement Eq1, Ord1, Show1 instances manually. Is there some assistance to define eq1 and compare1 for an ADT? What are the use cases where eq1 was not powerful enough and liftEq is needed?
Categories: Offsite Discussion

suppress warning "Defined but not used: type variable ‘x’" in GHC-8.0

glasgow-user - Sun, 01/10/2016 - 12:57am
GHC-8.0 emits several new warnings of this kind: Defined but not used: type variable ‘x’ for declarations like type instance Snd x y = y Enthusiastically, I started to replace unused type function arguments by underscores, only to find out that older GHC versions do not accept that. With what option can I disable this warning? Or can it be removed from -Wall for now?_______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users< at >
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