# News aggregator

### How many elements a list/sequence/vector can contain?

Hello,

Can anyone tell me the maximum number of elements that a list/sequence/vector can contain, and what is the maximum size in KBytes of a list/sequence/vector?

submitted by notooth1[link] [7 comments]

### Introducing Haskell Mode in CodeWorld

### Best engine/library for a VR game?

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

### pattern matching v. type checking

### Help with pcre-heavy

I have this code:

{-# LANGUAGE QuasiQuotes #-} import Text.Regex.PCRE.Heavy (gsub, re) ignore_comments :: String -> String ignore_comments text = gsub [re|\/\*[^\*]\*\/|] "" text main = do print $ ignore_comments "/*test commentary*/ other test"He is cut simple commentary from string. But he doesn't work on test string(prints all string, without changes). I understand this is due to the initial slash in regexp. Maybe exist advanced option or escape rule for this? What's my mistake?

submitted by xolcman[link] [13 comments]

### EndoApplicatives, anything similar?

I've got this typeclass here (EDIT: It's a MonoApplicative, not an EndoApplicative):

class Functor f => MonoApplicative f where pureM :: a -> f a (<#>) :: f (a -> a) -> f a -> f aIt's exactly like Applicative, but restricting <*> to a single type. I tried to find something similar in the ecosystem, is there something out there?

submitted by AisRauli[link] [31 comments]

### Promotion of field accessors using DataKinds

### Recent Spam

Most of you have probably seen some intermittent spam, I just finished overhauling automod to *hopefully* curtail it more quickly than it has been. Please -- if you continue to see this spam -- report it and send me a modmail. Reporting it as 'spam' helps train the reddit spam filter, afaik, and modmailing us helps surface things we might miss.

All of reddit is currently getting pelted by some spam ring, hopefully it lets up soon.

EDIT: (because I forgot) -- part of this will automatically remove posts from users that are less than a few days old. If you are new, I understand this may be inconvenient, but it is necessary for the overall health of the community. If you have something you want to post and can't, wait a day. If you can't wait, send a modmail and we'll see what we can do.

submitted by jfredett[link] [5 comments]

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

### Adding writer transformer to list monad.

Hello, As an exercise, I was trying to write a function that calculates all combinations of given list. So when I call the function like this

combinations [1,2,3]

It would return following value:

[[],[3],[2],[2,3],[1],[1,3],[1,2],[1,2,3]]

So, first I implemented a classic recursive version of the function. Than I implemented another one that is using list monads.

After I have 2 versions of the same function, I wanted to add writer monad to them to log function calls.

I was able to add writer monad to plain version, but I could not do the same thing for the one that uses list monad.

In short, I could not use writer monad transformer. Can somebody go over my function and tell me how to add writer monad transformer to that function?

Here is the all the functions I implemented:

submitted by yilmazhuseyin[link] [7 comments]

### How to make industry quality software with Haskell?

I have only used Haskell in academia where I just run my files using ghc and show my professors the output. Although, now I am looking to start a project with Haskell and I was wondering what are some tools I should be using when developing my project? In conjunction with that I am concerned about directory architecture and I am not sure what the best practice is for Haskell projects, perhaps there is a guide out there.

submitted by lilred181[link] [34 comments]

### Regarding Developing my skills with haskell!

### Douglas M. Auclair (geophf): December 2015 1HaskellADay Problems and Solutions

**December 2015**

- December 30th, 2015: For today's #haskell problem we convert valid airport IATA codes to ints and back http://lpaste.net/9126537884587786240 And a Happy New Year solution: http://lpaste.net/2748656525433110528 Safe travels should you be Haskelling by air!
- December 28th, 2015: So, remember ADVENT? What happens when your INV becomes full? Today's #haskell problem looks at that http://lpaste.net/5153847668711096320
- December 23rd, 2015: Warm and fuzzy December, so we have a warm and fuzzy #haskell problem for today http://lpaste.net/6855091060834566144
- December 21st, 2015: For today's #haskell problem we are to deduce stock splits using LOGIC and SCIENCE http://lpaste.net/7920293407518359552
- December 18th, 2015: Today's #haskell problem... 'may' be thematic with that 'Star ...' what was the name of that movie? http://lpaste.net/7186856307830292480 Gosh! Star ... something! eh, whatevs: just let the Wookie win (always the best policy) http://lpaste.net/4229765238565634048
- December 17th, 2015: For today's #haskell problem we look at reporting out periodically on an investment and, BONUS! charting it! http://lpaste.net/638111979885559808 And we've charted our AAPL investment growth, too! http://lpaste.net/5472780506909114368
- December 16th, 2015: For (coming onto) today's #haskell problem we demask the masked data to unmaskify it, yo! http://lpaste.net/3793517022239784960 And then the solution unmasked that masked data! (that's convenient.) http://lpaste.net/5286190256939335680
- December 15th, 2015: So yesterday we masked some rows, but what happened to the masking dictionary? Today's #haskell problem we save it http://lpaste.net/7703498271758483456 Ah! So that's where that cipher went! http://lpaste.net/2548817005729808384
- December 14th, 2015: We look at a way of masking data for today's #haskell problem http://lpaste.net/4428582328419221504 And the solution gives us some lovely masked rows http://lpaste.net/7169250386480463872
- December 11th, 2015: Today's #haskell problem asks: WHAT DOES THE TRANSFORMED JSON SAY! http://lpaste.net/5253460432890363904 (okay, that was weaksauce)
- December 10th, 2015: For today's #Haskell problem we try to find relevancy in our daily lives http://lpaste.net/4994238781251911680 ...well, in #JSON, which is the same thing.
- December 9th, 2015: Today's #haskell problem asks you to read in some rows of #JSON http://lpaste.net/3949063995918385152 We'll be looking into this data set through the week "Watcha readin'?" "JSON." "Cool! ... No, ... wait." http://lpaste.net/218583096285462528
- December 8th, 2015: My main man, magic Mike (m^5 to his friends) said: "You're doing it wrong."Do it right for today's #haskell problem http://lpaste.net/6186236014281883648 A first stab at the solution, not taking into account splits, is posted at http://lpaste.net/6854975053767901184 And the split-adjusted solution here: http://lpaste.net/2656933684896071680 ~3700%-gain. It's time for me to sing the "You're the Top"-song to @MacNN_Mike
- December 7th, 2015: In today's #haskell problem we cry «On y va!» and have at it! http://lpaste.net/5243343693259210752 En garde, you pesky investment problem, you! The solution shows Dr. Evil does NOT get ONE MILLION DOLLARS! http://lpaste.net/177540921380831232 Nor piranhas with laser beams on their heads, either.
- December 4th, 2015: We write a web-proxy to help out poor, little Ajax go cross domain for today's #haskell problem http://lpaste.net/5120963316033781760
- December 3rd, 2015: We meet the Ip-man for today's #haskell problem. Hiya! http://lpaste.net/8926203451507998720 Today's solution shares a little-known fact http://lpaste.net/5525895581479731200 AND ALSO uses <$> as well! Is there a weekly limit on these thingies?
- December 2nd, 2015: Synthetic data generation for today's #haskell problem http://lpaste.net/4208367754446635008 NOT ONLY did we write a Synthetic data generator in a day http://lpaste.net/6059310371951345664 but we learned all 50 states AND used <$> and <*> – BONUS!
- December 1st, 2015: In today's #haskell problem, we see @geophf lose his cool. http://lpaste.net/6645397898311761920 No... wait... That's not news now, is it. (RID analysis). Unwordin' down-low on the arrr-eye-dee, LIKE A GANGSTA! http://lpaste.net/7371239202307964928

### CfP: Workshop on Program Transformation for Programmability in Heterogeneous Architectures (Co-located with CGO16); Deadline Jan 15

### async docs not on hackage for some reason?

### New gtk2hs 0.12.4 release

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!

~d