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Proposal: Add a strictly accumulating scanl' to Data.List

libraries list - Thu, 07/24/2014 - 9:55pm
Joachim Breitner wrote, in, a strictly accumulating version of scanl, to be named scanl'. I was initially concerned about its safety for fusion, but am now convinced of its correctness and believe it should be added to Data.List. scanl' :: (b -> a -> b) -> b -> [a] -> [b] scanl' f a bs = build $ \c n -> a `seq` a `c` foldr (\b g x -> (let b' = f x b in b' `seq` (b' `c` g b'))) (\b -> b `seq` n) bs a
Categories: Offsite Discussion

callCC inside expression

haskell-cafe - Thu, 07/24/2014 - 7:41pm
Hello all I recently saw a video on call/cc in Scheme, where call/cc was used inside an expression and call/cc faithfully figured out the rest of the computation. I tried the same in haskell, but was bitten badly. Then I looked at the type signature and learned that call/cc only works inside a continuation monad (if I am not mistaken). Is this correct and why is that so? Are scheme's call/cc and haskell's callCC semantically different?
Categories: Offsite Discussion

HOPE 2014 Call for Participation (with Workshop Program)

General haskell list - Thu, 07/24/2014 - 5:48pm
---------------------------------------------------------------------- CALL FOR PARTICIPATION HOPE 2014 The 3rd ACM SIGPLAN Workshop on Higher-Order Programming with Effects August 31, 2014 Gothenburg, Sweden (the day before ICFP 2014) ---------------------------------------------------------------------- HOPE 2014 aims at bringing together researchers interested in the design, semantics, implementation, and verification of higher-order effectful programs. It will be *informal*, consisting of invited talks, contributed talks on work in progress, and open-ended discussion sessions. ------------ Registration ------------ Deadline for early registration: 3 August 2014 Web site: This is the registration site for ICFP 2014 and all the affiliated workshops in
Categories: Incoming News

Are functional languages (or specifically GHC Haskell) bad at GC?

Haskell on Reddit - Thu, 07/24/2014 - 4:55pm

I've been reading the StackOverflow thread on Hackernews and stubmled upon this comment that says, quote

Functional languages are terrible for garbage collection

I'm pretty sure this isn't the first time I'm seeing this, so I wanted to ask if someone who knows a bit how GC in GHC vs something like .NET or Java works, and if this is actually true?

I'm not looking to start a flame war, but rather asking for some hard facts. It's sort of hard to google information of this type.

Here's a link to the parent discussion.

submitted by progfu
[link] [18 comments]
Categories: Incoming News

Call for Talk Proposals: Domain-Specific Language Designand Implementation 2014

General haskell list - Thu, 07/24/2014 - 4:19pm
********************************************************************* CALL FOR TALK PROPOSALS DSLDI 2014 Second Workshop on Domain-Specific Language Design and Implementation October 20/21, 2014 Portland, USA Co-located with SPLASH/OOPSLA ********************************************************************* Deadline for talk proposals: August 27, 2014 If designed and implemented well, domain-specific languages (DSLs) combine the best features of general-purpose programming languages (e.g., performance) with high productivity (e.g., ease of programming). *** Workshop Goal *** The goal of the DSLDI workshop is to bring together researchers and practitioners interested in sharing ideas on how DSLs should be designed, implemented, supported by tools, and applied in realistic application contexts. We are both interested in discovering how already known domains such as graph processing or machine learning can be best supported by DSLs, but also in exploring new dom
Categories: Incoming News

FHPC 2014 (and reminder about ICFP early reg)

General haskell list - Thu, 07/24/2014 - 2:27pm
The programme for the Workshop on Functional High Performance Computing (Sept. 4 immediately after ICFP) is available at It will be a very enjoyable workshop so please consider attending. This is also a reminder that the last day for early registration at ICFP and associated workshops is August 3. Online registration for both ICFP and FHPC starts here: with best wishes Mary Sheeran _______________________________________________ Haskell mailing list Haskell< at >
Categories: Incoming News

Functional Jobs: Senior Haskell Developer at Plow Technologies (Full-time)

Planet Haskell - Thu, 07/24/2014 - 2:07pm

Plow Technologies is looking for an experienced Haskell developer who can lead software design. Deep understanding of the Haskell programming language is preferred. This person would be expected to work at all levels of our platform to optimize performance, reliability, and maintainability of our code base. We want the kind of programmer who makes everyone else better by: (1) designing application programming interfaces and libraries that speed up time of development; and (2) teaching others through direct interaction. The kind of skills that are desired for this position are rare, so remote work would definitely be an option. However, some direct interaction (including travel) should be expected.

Get information on how to apply for this position.

Categories: Offsite Blogs

Papers every haskeller should read

Haskell on Reddit - Thu, 07/24/2014 - 10:11am

What are some papers that every Haskeller should read?

submitted by incompetentacademic
[link] [35 comments]
Categories: Incoming News

determining the origin of imported symbols

haskell-cafe - Thu, 07/24/2014 - 9:29am
Hi everyone, I looking for a way to analyze Haskell source to determine which module each imported symbol comes from. My goal is to transform source code like this: import Data.List ... main = do nums <- fmap (map read . words) getLine :: IO [Int] print $ sort nums to code like this: import qualified Prelude as B import qualified Data.List as A ... main = do nums <- B.fmap ( B.. B.words) B.getLine :: B.IO [B.Int] B.print B.$ A.sort nums That is, I want to qualify all imported symbols with a module alias. Can anyone suggest modules or programs I should look at? Thanks, ER _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe< at >
Categories: Offsite Discussion

Markov Text Generator & Randomness

haskell-cafe - Thu, 07/24/2014 - 3:29am
Hi -cafe, I'm coding a Markov Text Generator (of order 1). Basically, you have a source text, and knowing the frequencies of pairs of consecutive words, you generate a somewhat syntactically correct text from this. Here's the link to my code and to a source text you can use as example. test.txt code The kickers is that this code generates sentences with consecutive words that never appears next to each other in the source text. For example, the code generated "They sat over at because old those the lighted.", but "over at" never occurs in the source text, so it shouldn't occur in a generated sentence. The makeDb function gives is correct, so my problem actually lies in generate and/or in draw. I think there's something about RVar that I messed up, but I don't see the problem. Any ideas? Cheers,
Categories: Offsite Discussion

Haskell on JVM (using LLVM backend)

haskell-cafe - Thu, 07/24/2014 - 3:26am
Hello! I was recently discussing with some frients possibilities of running Haskell programs on JVM. I belive such possibility could be a breakdown for the popularity of Haskell and could be very interesting for new people and new usage-scenarios. I have seen some topics, like these: but are a little old and do NOT mention the LLVM backend. If we've got the LLVM backend in GHC right now, why cannot we just use something like LLJVM to convert the LLVMIR into JVM bytecode? I understand that the LLVM bytecode (optained from GHC) has all the optimizations applied (including tail recursion expansion) so it **could** be possible to just run it on JVM? All the best, Wojciech Daniło _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe< at > http://www.hask
Categories: Offsite Discussion

Locating Modules in Haskell

Haskell on Reddit - Thu, 07/24/2014 - 2:22am

What is the rationale in locating the standard modules in Haskell?

For instance, why Monoid, Functor, etc. are located in Data, while Applicative, Monad, Category, etc. are located in Control?

submitted by BanX
[link] [10 comments]
Categories: Incoming News

GHCi: Behave nicely on `-e`, like `ghc` and other programs

libraries list - Thu, 07/24/2014 - 12:29am
Like many programming language environments, GHC offers a handy `-e` option for evaluating an expression, then returning to the shell. $ ghc -e '2 + 2' 4 One would expect the interpreter, GHCi, to offer a similar flag, but it surprisingly rejects it. ghci -e '2 + 2' ghc: on the commandline: cannot use `--interactive' with `-e' Usage: For basic information, try the `--help' option. I think this behavior is quite unintuitive--when I pass `-e <exp>` to ghci, or pass `--interactive -e <exp>` to ghc, I expect the expression to be evaluated as the leading expression in an interactive interpreter session. Could we please tweak ghc like this to make it slightly more intuitive when these flags are used together?
Categories: Offsite Discussion

Enhancement: Default cabal to `-p` profiling enabled

libraries list - Thu, 07/24/2014 - 12:18am
I love GHC's profiling support, and like to use it to analyze the performance of my Haskell applications. However, profiling an application is difficult when it depends on any third-party libraries, as cabal doesn't include profiling information by default. Fortunately, cabal can reinstall a library with profiling support, with: cabal install --reinstall -p <library> Unfortunately, cabal is a bit of a simpleton, so this will fail unless that libraries dependencies are also installed with profiling enabled: cabal install --reinstall -p <libraryX> <libraryY> <libraryZ> ... For example, a user who wants to profile his die-rolling program must run: $ sudo apt-get install haskell-platform haskell-platform-doc haskell-platform-prof $ sudo cabal install --reinstall -p mwc-random rvar random-fu random-source mersenne-random-pure64 stateref flexible-defaults th-extras MonadPrompt math-functions erf vector-th-unbox monad-loops random-shuffle MonadRandom And that long list of packages must be slowly grown one at
Categories: Offsite Discussion

Retrieving information about type families

haskell-cafe - Wed, 07/23/2014 - 7:48pm
Dear Café, My quest for obtaining information about type families continues. Now I have a simple question: how should I access the information about "type instance"s via the GHC API? My aim is to do so after type checking, that is, to get that information from a TypecheckedModule. However, I haven't yet been able to touch the right buttons to make it work ;( Thanks in advance, Alejandro _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe< at >
Categories: Offsite Discussion