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Programs for Cheap! (pdf)

Haskell on Reddit - Mon, 01/19/2015 - 8:55am
Categories: Incoming News

Announcing a solution to the records problem

libraries list - Mon, 01/19/2015 - 6:54am
This thing seems to be going viral on social networks already, nonetheless here's a link for those of you, who aren't yet informed: _______________________________________________ Libraries mailing list Libraries< at >
Categories: Offsite Discussion

Reading papers and other resources

Haskell on Reddit - Mon, 01/19/2015 - 4:52am

My background is in computer engineering and I have been doing some stuff in haskell the last year and really liking it. I have also looked at Idris and other languages and coming from a background with imperative languages, it's really exciting.

Since I have mostly used books and google to learn and find help and information, I would like to find some other sources for more information, since my knowledge hub is quite sparse at the moment, about these things anyways.

New, experimental topics being studied right now about languages, techniques, functional programming, the future of it and so forth. Anything exciting, really. A place where these things are published, discussed and exposed, is what I am looking for. The format I had in mind is papers, but I will also read articles and books gladly.

Where are haskell/functional programming/new language research being published to? Where do you guys find these papers and articles? I would like to know about any resource where I can be exposed to great material.

Feel free to recommend me older papers on the topics also. I haven't read any about this yet, so most anything should be knew to me.

Go at it, thanks!

submitted by sirhcreffot
[link] [16 comments]
Categories: Incoming News

Philip Wadler: My email is a monster

Planet Haskell - Mon, 01/19/2015 - 3:40am

My New Year's resolution is to look at my e-mail at most once a day. If you need a response in less than a day or two, please arrange it with me in advance or use a different medium. Cartoon courtesy of Oatmeal.
Categories: Offsite Blogs

This code produces an infinite output... why? it's abug in ghc?

haskell-cafe - Mon, 01/19/2015 - 2:45am
This code produces an infinite output... why? it's a bug in ghc? UTCTime (fromGregorian 2015 1 1) (timeOfDayToTime $ TimeOfDay 0 0 0)
Categories: Offsite Discussion

Tooling for equational reasoning in Haskell

haskell-cafe - Mon, 01/19/2015 - 1:46am
Hi I quite enjoy doing equational reasoning to prove that my functions satisfy some laws, I like to type out each substitution step until I get back what I started with. The only trouble is that it's rather manual and possibly error prone. Is there any tooling anywhere out there that can take in a Haskell expression and reduce it by one step? I only know of stepeval: But it's just a prototype and works on a teeny weeny subset of Haskell. As much as I like doing tooling, my bandwidth for this area is already full. It seems quite hard to implement such a tool with existing tooling. Real compilers and interpreters tend to be distinctly far away from a simple substitution model or retaining the original source code and being able to print valid source back out. If such a tool existed, though, it'd be super handy and you could probably include it as another check for your build process like your type checking, yo
Categories: Offsite Discussion

Haskell and Math, Math and Haskell...

Haskell on Reddit - Sun, 01/18/2015 - 11:08pm

I've heard it said over and over that Haskell is very mathematical, math-oriented, etc. I've been reading through this subreddit and reading lots of "should I learn haskell?" posts with a lot of people giving qualified yeses on the condition that the learner is interested in and good at math.

Well, I might be somewhat novel then: I've done a bit of programming in python, and I'm teaching myself C, but I'm curious about FP. Also, I'm not really terribly good at math. The last serious math class I passed was intermediate college algebra (the class you take before trigonometry).

Flash forward a few years, and I have a much different relationship to learning math: I'm curious about it, and I want to understand it more than just get correct answers. But I've still got a ways to go :)

Here's the question (aka, tl;dr): If knowing math can help you understand Haskell, does learning Haskell help you to better understand math? Will learning Haskell have benefits outside of, well, programming in Haskell?

submitted by tunabee
[link] [17 comments]
Categories: Incoming News

Hackage is flooded with old package versions reuploads

libraries list - Sun, 01/18/2015 - 7:56pm
Hi, guys, It looks old (and even ancient) versions of many packages gets uploaded to hackage over and over again in ever increasing amounts. The username of uploader for vast majority of these uploads is HerbertValerioRiedel. While this is harmless I wonder what idea stands behind this? Cheers, Kyra
Categories: Offsite Discussion

Haskell Programming Challenges

Haskell on Reddit - Sun, 01/18/2015 - 7:38pm

I created a subreddit called HardyCoding and am hoping I have the same success as I did founding The University of Reddit. I'm reaching out to the Haskell community as I see functional programming as one of the purest forms of programming and would love for their help. The reason for this post is to 1. Describe the point of the subreddit and 2. to explain why I'm reaching out to this subreddit specifically.

  1. I have an idea to build a user submitted programming challenge subreddit. What makes this different from the rest of them? The difference is posts are able to place restrictions on the way that an answer can be accepted. I have a problem with traditional learning and education where you learn something where there is already an established answer. I want people to ask questions that have never been asked.

  2. Haskell is one of my favorite languages and I believe this platform will benefit Haskell developers wanting to share their language with other people by Haskell users submitting coding challenges with restrictions on functional programming and specific languages (Ocaml, Haskell, F#).

I'll be posting to a few more subreddits tonight to get a nice mix of people. Suggestions of where to look for good users are appreciated.

Let me know what everyone thinks.


I'm just starting the sub and looking to grow slower than The University of Reddit did.

submitted by eawesome3
[link] [5 comments]
Categories: Incoming News

Similarities between Universal Properties and Parametricity?

Haskell on Reddit - Sun, 01/18/2015 - 3:06pm

Hi there,
It seems to me that there is a lot in common between UMPs in Category Theory and Parametricity/Free Theorems in FP. Pull me up where I run off the tracks: (I suspect my terminology and descriptive language will betray some confusion)


In Category Theory, Universal Mapping Properties are this really useful device that shines light on structures through:
* An arrow that is being "tested" (ie one that generates free structure)
* Universal quantification (forall) of another generated "target" and a second arrow to the "target", which proves that the first arrow isn't deriving input from anywhere else.
* Uniqueness (up to isomorphism) of the arrow from the original generated object to the "forall" object, which proves that the generated structures don't contain extraneous information.


Now, compare to the idea of parametricity and Free Theorems that we know and love in FP:


Parametricity is a really useful device that gives us more information (free theories) about an implementation/proof through universally quantified (forall) type variables, that proves that the types carry no more information than is required.


Or something like that. In both cases, universal quantification is preventing unnecessary specificity, which allows us to know a lot more about the whole structure.


Is that the extent of the similarity between the two concepts? Is the use of uniqueness in UMPs mirrored in some way? Are there some deeper parallels that I'm missing?


Thanks for your time, Ken

submitted by kenbot_
[link] [3 comments]
Categories: Incoming News

StateT and ContT

haskell-cafe - Sun, 01/18/2015 - 12:56pm
In the transformers library, there are two implementations for callCC for use with StateT (both lazy and strict) [1,2], the second of which is documented to not satisfy the laws of a monad transformer. [1]: [2]: However, in mtl the MonadCont class [3] uses the second definition for the StateT instance. Is there a good reason for this, or just to match the behaviour of pre-transformers mtl [4] ? [3]: [4]: (I did raise an issue for this on mtl's Github issue tracker, but it hasn't had any responses for two months.)
Categories: Offsite Discussion

Canoo RIA Blog - Sun, 01/18/2015 - 4:28am
Categories: Offsite Blogs

enable-executable-profiling failing with cabal 1.22

haskell-cafe - Sun, 01/18/2015 - 3:17am
Using cabal 1.22 for some reason does not like —enable-executable-profiling. I am working on a rebuilt machine that had 1.18 from the distribution, with 1.22 installed afterwards. I found a little info on people having this problem, but I failed to fix the problem. Note than the library profiling option is accepted. Only the executable fails. Is there any know way to start with platform 2014 with GHC 7.8.3 and install cabal 1.22 and can use this option?
Categories: Offsite Discussion