October 2017 - Haskell-Cafe

Why is Haskell so slow (comparing to Java/Scala)?
by Станислав Черничкин 23 Oct '17

23 Oct '17

I've wrote simple Haskell benchmark program, which populated primitive vector from vector package: import Data.Vector.Primitive.Mutable as P vectorBench :: Benchmark vectorBench = bgroup "vector" [ primitive ] where primitive = bgroup "primitive" [ write1M ] where write1M = bench "write1M" $ nfIO $ do v <- P.unsafeNew 1000000 void $ for [0..1000000 - 1] $ flip (P.unsafeWrite v) (1 :: Int) return () I use `unsafeNew` to skip memory initialization and `unsafeWrite` to skip boundary checks, I guess it's fastest possible way to write something to vector. My result was about 40 ms. I wrote similar program in Scala: for (_ <- 1 to 5) { val start = System.currentTimeMillis() val a = new Array[Long](1000000) for (i <- 0 until 1000000) { a(i) = 1L } val end = System.currentTimeMillis() println(s"${end - start} ms") } I skip neither boundary checks nor memory initialization, I also used generic array here (suitable for any types of objects, not just for primitive types), so I expected longer run time. But what I got was shocking: 7 ms 3 ms 2 ms 1 ms 2 ms This program runs 20-40 times faster than Haskell after warm-up. 20-40 times, Carl! Why is Haskell soo slooooow? How can it be? -- Sincerely, Stanislav Chernichkin.

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[ANN] Haskell ITA meetup in Rome, Italy (2017-11-18)
by Francesco Ariis 23 Oct '17

23 Oct '17

Dear -cafe, the Italian Haskell Community (http://haskell-ita.it/) is happy to announce its autumn Haskell meetup! The event is going to be hosted in Rome, on November 18th. The meeting will be in Italian; we are going to form small groups/projects, to see Haskell in action and to share knowledge and opinions on functional programming. Everyone, experienced or not, is welcome, just make sure to have a laptop and a working Haskell environment! For a more detailed description of the event and to register, check: https://www.eventbrite.it/e/biglietti-haskell-day-roma-aperitech-38962491862

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[ANN] The Disciplined Disciple Compiler (DDC) v0.5.1
by Ben Lippmeier 23 Oct '17

23 Oct '17

# The Disciplined Disciple Compiler (DDC) v.0.5.1 The Disciple language is an experimental dialect of Haskell which investigates static typing and program transformation in the presence of computational effects. Version 0.5.1 is “working alpha” quality, meaning there is a complete system that can be hacked around with, but it’s not yet industrial strength. Homepage: http://disciple.ouroborus.net/ <http://disciple.ouroborus.net/> Github: https://github.com/DDCSF/ddc <https://github.com/DDCSF/ddc> ## Features: * Haskell-like source language, so Haskell-like programs should work with minor modifications. * Modal region and effect system using ‘box’ and ‘run’ to suspend and force computations. * Higher rank polymorphism with bidirectional type inference. * Simple two space copying garbage collection. * Default call-by-value evaluation. * Typed external core language. ## New in This Release: * Copying garbage collection. We now do simple two space Cheney-scan garbage collection, and grow the heap as needed. We use LLVM shadow stack support to retrieve the GC roots. * Implicit parameters. We now support Agda-style implicit parameters, where arguments are construct at use-sites using whatever bindings are currently in scope. For example, we can perform Haskell-style ad-hoc overloading using implicit dictionaries: elem {Eq a} (k: a) (xx: List a): Bool = case xx of Nil -> False Cons x xs | x == k -> True | otherwise -> elem k xs * Floating point primitives. The addition of floating point primitives combined with proper storage management now lets us write more realistic example programs, like the ray tracer demo, which was also described on the blog [1]. * Travis continuous integration. Every push to the GitHub repo now gets tested by the Travis buildbot [2]. Branches can also be tested individually before being merged. * Support for LLVM versions 3.1 - 5.0 We query the version of the installed LLVM compiler and generate LLVM code with the required syntax. This process now works for versions 3.1 through to 5.0, which is the latest at the time of this release. * New home page with the start of a language specification. The home page now consists of the user manual generated from Sphinx / Restructured Text source. The manual includes grammars for source and core lanuages, as well as previous release notes. The bug tracker is still accessible via the development wiki. * Bug fixes for offside rule, compilation of nested pattern matching, string escapes, unsolved meta variables. Now with more bake. [1] http://disciple-devel.blogspot.com.au/2017/07/ray-tracer-demo.html <http://disciple-devel.blogspot.com.au/2017/07/ray-tracer-demo.html> [2] https://travis-ci.org/DDCSF/ddc <https://travis-ci.org/DDCSF/ddc> [3] http://disciple.ouroborus.net/ <http://disciple.ouroborus.net/> ## Work In Progress We are moving to a new indexed binary format for interface files, as re-parsing interface files is currently a bottleneck. The file format is to be provided by the Shimmer project [4], which has been split out into a separate repository. [4] https://github.com/DDCSF/shimmer <https://github.com/DDCSF/shimmer> ## People The following people contributed to DDC since the last release: * Chris Hall - Travis continuous integration. * Amos Robinson - Build system fixes, start on machine fusion transform. * Ben Sinclair - Build system fixes. * Jacob Stanley - Copying garbage collection. * Ben Lippmeier - Copying garbage collection, implicit parameters, floating point, new home page. ## Previous Releases * 2016/09 DDC 0.4.3: Nested patterns and guards, simple type synonyms. * 2016/04 DDC 0.4.2: Compilation of higher order functions, run and box casts. * 2014/03 DDC 0.4.1: Added bi-directional type inference and region extension. * 2013/07 DDC 0.3.2: Added Tetra and Flow language fragments. ## More Information Home Page: http://disciple.ouroborus.net <http://disciple.ouroborus.net/> The GitHub site: http://github.com/DDCSF/ddc <http://github.com/DDCSF/ddc> Development Wiki: http://trac.ouroborus.net/ddc <http://trac.ouroborus.net/ddc> Development Blog: http://disciple-devel.blogspot.com.au/ <http://disciple-devel.blogspot.com.au/> Mailing List: http://groups.google.com/group/disciple-cafe <http://groups.google.com/group/disciple-cafe>

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Failing Travis CI Build
by Steven Leiva 22 Oct '17

22 Oct '17

Hi Everyone, I am trying to contribute to a smallHaskell project in order to break out of structured learning via books into some real-world code. Unfortunately, the pull request that I made (linked above) is failing the continuous integration check. You can see a partial log before. The entire logs can be found here. I thought that this would work because: 1. We are using the 8.20 resolver in our project. 2. The 8.20 resolver includes QuickCheck, hspec, and quickcheck-instances. 3. The dependencies are listed in the cabal file. Am I missing something obvious? Is the above not the way it works? Thank you for any help. Logs Reading available packages...Choosing modular solver.Resolving dependencies...Could not resolve dependencies:trying: twilio-0.2.0.0 (user goal)rejecting: twilio-0.2.0.0:!test (global constraint requires opposite flagselection)trying: twilio-0.2.0.0:*testnext goal: quickcheck-instances (dependency of twilio-0.2.0.0:*test)fail (unknown package: quickcheck-instances)Dependency tree exhaustively searched.Configuring twilio-0.2.0.0...cabal: At least the following dependencies are missing:QuickCheck ==2.*, hspec ==2.*, quickcheck-instances -any Not using Mixmax yet? Steven Leiva 305.528.6038 leiva.steven(a)gmail.com http://www.linkedin.com/in/stevenleiva

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Stackage Haddocks extremely slow
by aditya siram 19 Oct '17

19 Oct '17

Hi all, I've noticed that lately Stackage's Haddock searches have been extremely slow; for example https://www.stackage.org/haddock/lts-9.9/base-4.9.1.0/Prelude.html#v:foldl took almost 8 seconds to pull up on my machine. Is anyone else seeing this? Thanks! -deech

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Re: [Haskell-cafe] [Haskell] Hack “Importify” by Serokell During #Hacktoberfest!
by Henning Thielemann 18 Oct '17

18 Oct '17

On Wed, 18 Oct 2017, Gints Dreimanis wrote: > All of us love to read explicit import lists (especially in an unknown > module), but we all hate to write and maintain them. You won't have many explicit import lists if you design the function names for qualified imports.

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Unused type-classes triggering a recompilation?
by Saurabh Nanda 18 Oct '17

18 Oct '17

Hi, We're trying to optimise the way lenses are built and imported in our project (there are 500+ of them!) . In the simplified version that I have presented below, whenever a new HasX class is added to the LensClasses module, both User & Main end up getting recompiled even though they have nothing to do with the newly added type-class. I've read and re-read "Recompilation Avoidance" [1], but haven't been able to figure out why this would be happening. PS: To work-around this issue we've had to give each HasX class an independent module of its own. We specifically import only those which are required (all of this is done via a code-gen tool). This has resulted in an explosion of modules and is probably causing slow-down of our build process [2] *LensClasses.hs:* {-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, FlexibleInstances #-} module LensClasses where import Control.Lens class HasName s a | s -> a where name :: Lens' s a class HasEmail s a | s -> a where email :: Lens' s a class HasAge s a | s -> a where age :: Lens' s a *User.hs (which defines a few lenses for the User record):* {-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, TypeSynonymInstances, FlexibleInstances #-} module User ( module User , HasName(..) , HasEmail(..)) where import LensClasses(HasName(..), HasEmail(..), HasVariantName(..)) data User = User { _userName :: String , _userEmail :: String } deriving (Eq, Show) instance HasName User String where {-# INLINE name #-} name fctor (User name_ email_) = fmap (\dragon -> User dragon email_) (fctor name_) instance HasEmail User String where {-# INLINE email #-} email fctor (User name_ email_) = fmap (\dragon -> User name_ dragon) (fctor email_) *Main.hs (the final call site/s):* module Main where import Control.Lens import User main :: IO () main = do let u = User "saurabh" "saurabhnanda(a)gmail.com" putStrLn $ u ^. name [1] https://ghc.haskell.org/trac/ghc/wiki/Commentary/Compiler/RecompilationAvoi… [2] https://www.reddit.com/r/haskell/comments/76zljl/hotswapping_haskell_at_fac…

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NYC Haskell Developer Position
by Christopher Lewis 18 Oct '17

18 Oct '17

Karamaan Group, is an investment firm based in Manhattan. We are looking for an outstanding software developer to develop tools for financial analysis and knowledge management. Since we are investors and not traders, our focus is not on building trading systems, but on business and data analysis. We strongly value people who take pride in their work and have a craftsman’s dedication to building bespoke products. Our ideal candidate is an experienced software developer with a penchant for abstraction and analysis, a solid sense of organization, and an ability to communicate and persuade. While we are looking for a candidate who demonstrates an intense focus on quality, she also needs a master engineer’s intuition on how to make trade offs that are a necessary part of day-to-day software development. Candidates should have some formal training in a quantitative field and a keen interest in building robust and elegant software. This is a high-impact, high-visibility position where successful candidates will be entrusted with a lot of responsibility for products that have a direct effect on the P&L of the firm and influence on our workflow. The ideal candidate will have production experience with Haskell or another functional language, relational databases and relational data modeling, Python, and Java. Additionally, as this is a startup environment, the ideal candidate will be comfortable filling many different technology roles, and contributing to the success of the firm wherever they can, not just in agreement with their job description. Remote work is not an option for this position. Karamaan Group is an investment adviser and manager catering to family offices and institutional investors. We value innovative thinking, encourage an entrepreneurial atmosphere, and enjoy spirited discussions. Please send your CV and cover letter to recruitment at karamaan dot com. Please do not reply to the original poster.

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ANN: New Full Platform Build of Haskell Platform 8.2.1 for Mac
by Gershom B 18 Oct '17

18 Oct '17

Thanks to some intrepid sleuthing by Albert Y. C. Lai, we realized there was a serious problem in the full (not core) builds of HP for Mac and Linux (not Windows). If you've seen lots of "unusable due to shadowed dependencies" errors on packages that came with full 8.2.1 platform installs on those systems, this is likely why. We should have tested better and caught this, and I'm sorry for the trouble it has caused. I've released a new build of the full mac installer, and updated the hash on the site. A new generic-linux build should follow soon. Regards, Gershom P.s. For those interested, the technical details are at https://github.com/haskell/haskell-platform/issues/285 -- in brief, the platform had done builds using inplace conf files but deployed using proper target package-conf files. This worked just fine until the new abi-depends machinery was introduced for better computing dependency mismatches (https://phabricator.haskell.org/D2846 is one place to start reading about that). That new machinery then recognized that different abis were generated for the inplace conf than the target conf, and things went screwy. But the problem here isn't with those changes -- it's with our inadequate testing that should have caught when things went wrong and alerted us that we needed to step back and fix things earlier, and the responsibility for that is all on me.

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Re: [Haskell-cafe] [Call for Contributions] Haskell Communities and Activities Report, November 2017 edition (33rd edition)
by Karim Salah 17 Oct '17

17 Oct '17

Asteroids Name: Kareem salah (FCIH) status: stable, actively developed participants: mostafa hazem, khaled hesham, belal ibrahim Asteroids is Haskell version of the known asteroids game which was developed with many programing languages as startup project the main aim of the game is to score the highest score by shooting the coming asteroids while avoiding them (just remember u have only three spaceships) the game is simulating the space physics so don't think it is so easy. the game following up the original game rules beside that we added a multi-player system to invite your friends to join your campaign. our team found it a good opportunity to develop a version using Haskell and by using the lazy programming techniques in our favor we were able to provide a stable fps a stable version of the game was released and it's free to download and play we are looking forward for active contributions in order to add versus system, rewarding system and progression system so, forward contributions related to code refinement or adding features is welcomed url : https://github.com/kareem2048/Asteroids

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