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2nd CfP: Haskell in Leipzig (Germany) 2015

haskell-cafe - Thu, 10/29/2015 - 1:10pm
HaL-10 Haskell in Leipzig (December 4/5) We are proud to present Joachim Breitner (nomeata) as our invited speaker. The submission deadline (November 2) is approaching! See you - Johannes Waldmann (PC chair)
Categories: Offsite Discussion

2nd CfP: Haskell in Leipzig (Germany) 2015

General haskell list - Thu, 10/29/2015 - 1:08pm
HaL-10 Haskell in Leipzig (December 4/5) We are proud to present Joachim Breitner (nomeata) as our invited speaker. The submission deadline (November 2) is approaching! See you - Johannes Waldmann (PC chair)
Categories: Incoming News

Why does this Haskell run 400 times slower than the equivalent OCaml?

Haskell on Reddit - Thu, 10/29/2015 - 10:12am

UPDATE: due to the changes suggested here the program is now...slower! Execution time has gone from 640 seconds to 880.

UPDATE 2: Actually, if I remove the -threaded option the performance has improved from 640 to 620 seconds.

UPDATE 3: It looks like there is a chunk of code missing in the haskell version, and this is causing the problem. I will fix and upload.

FINAL UPDATE: new code checked in, GHC version now runs in about 0.7 seconds vs. Ocaml's 2.5.

This repo contains part of John Harrison's automatic theorem prover code from his book "Handbook of Practical Logic and Automated Reasoning", along with a literal translation of some of that code (specifically, the MESON prover) into 500 lines of Haskell (thanks to Ruben Zilibowitz for this code.) Unfortunately, the Haskell version runs about 400 times more slowly than the ocaml version, and I'm trying to find out why.

% cd ocaml % apt-get install camlp5 % ocaml # #use "";; # meson wishnu;; Searching with depth limit 0 Searching with depth limit 1 Searching with depth limit 2 Searching with depth limit 3 [counts to 16 twice.] Searching with depth limit 14 Searching with depth limit 15 Searching with depth limit 16 - : int list = [16; 16] #

To run the Haskell version:

% cd haskell % ghc -O2 Main.hs -o test % ./test Searching with depth limit 0 Searching with depth limit 1 Searching with depth limit 2 Searching with depth limit 3 [... fifteen minutes later ...] Searching with depth limit 16 [16,16]

My question is, what the heck?

submitted by dsfox
[link] [65 comments]
Categories: Incoming News

Find a point inside (x,y,z) -> Bool

haskell-cafe - Thu, 10/29/2015 - 10:01am
Hello all, I hope this is not a too silly question. It goes like this: Suppose I have a shape defined as (x,y,z) -> Bool how can I find a Point inside this shape? Obviously I could iterate through all possible x,y and z, but this appears very expensive. There may be no point at all at x=0. With brute force iteration I would have no clue that the False I am receiving with (0,1,1) is caused by x=0 and I may nedlessly try all combinations of y and z without ever receiving a True. Are there any alternative ways of finding points inside a shape?
Categories: Offsite Discussion

Stripe-Haskell Updates !

haskell-cafe - Thu, 10/29/2015 - 9:25am
*stripe-haskell 2.0* has been released on hackage. *The 2.0 release will entail the following:* - All types will now live in their own repository 'stripe-core' (for better use w/ ghcjs projects). - 'stripe-http-streams' is a specific http client backend for 'stripe-haskell' - Other backends (wreq, conduit, etc.) can be added. As always, pull requests welcome. - 'stripe-haskell' is now a virtual package that wraps 'stripe-http-streams' and 'stripe-core'. - We have a 'gitter' chat for our repo, to promote collaboration. - We now have a multi-ghc travis build that uses stack. - Jeremy Shaw has implemented a novel approach to the optional parameters problem using typeclasses. The docs will contain more information. - For existing stripe-haskell users version 2.0 is a breaking change, but it features a nicer interface due to Jeremy Shaw's changes. *Other notes:* - Existing 1.4 users will not be neglected. We can continue to submit patches up to 2.0. *Future goals:* - Migrate to servant-cl
Categories: Offsite Discussion

A very unfortunate error message

Haskell on Reddit - Thu, 10/29/2015 - 8:12am

So this just killed 30 minutes of my life.


minimumBy compare [] *** Exception: Prelude.foldr1: empty list

I'm fine with FTP but this is really a bummer. There wasn't a single foldr1 in my code, yet this was the exception. Is there any kind of magic that could be done to keep the generality but provide a decent error message?

Edit: It's not because of FTP.

submitted by Darwin226
[link] [43 comments]
Categories: Incoming News

Manuel M T Chakravarty: Video of Functional Programming in a Stateful World

Planet Haskell - Thu, 10/29/2015 - 6:36am

Earlier this year, at YOW! Lambda Jam (in Brisbane), I gave a talk about developing a Mac app in Swift. More precisely, I described my take on how to best apply functional programming principles when writing Cocoa (Touch) apps in Swift. The video for the talk “Functional Programming in a Stateful World” is now online (and the slides are on Speaker Deck).

Categories: Offsite Blogs

There isn't call stack in Haskell, but a graph?

Haskell on Reddit - Thu, 10/29/2015 - 6:34am

Could someone elaborate more on the comment at 34th minute of this lecture:

submitted by varosi
[link] [2 comments]
Categories: Incoming News

Maintainership of cassava

libraries list - Thu, 10/29/2015 - 5:14am
It wasn't listed in Johan's personal libraries he'd like to investigate personally and it's not part of CLC. Only uploader for the cassava package on Hackage at the moment is him. I pinged a week ago via email, no reply. Pinged on Twitter, no reply. Seems to be online (tweeted earlier today), but hasn't replied to any queries about the status of the library. Cheers, Chris Allen _______________________________________________ Libraries mailing list Libraries< at >
Categories: Offsite Discussion

Faculty Position in Secure and Trustworthy Cyberspace

General haskell list - Thu, 10/29/2015 - 1:42am
The Computer Science Department at Portland State University (PSU) is seeking to hire faculty to work in the broad area of secure and trustworthy cyberspace—including researchers who are applying formal methods, theorem proving, or programming languages to security problems. We invite applications for multiple tenure-track assistant professor faculty positions to begin Fall 2016. Exceptional applicants at other ranks will also be considered. Other specific areas of computer science under consideration are: artificial intelligence; machine learning; data mining; data-intensive systems; and networks and systems of connected things. Our department currently has 24 tenure-track faculty members and offers BS, MS, and PhD degrees. Portland State is Oregon’s largest university, and is located in downtown Portland, Oregon, offering proximity to world-class restaurants, cultural venues, exceptional outdoor activities, and collaborations with Portland’s burgeoning software industry. For more information a
Categories: Incoming News

installing GSL packages on Windows

haskell-cafe - Wed, 10/28/2015 - 11:41pm
I'm currently trying to install the gsl packages (in particular hmatrix-gsl) for a Windows 7/32 system. I've been using a fairly stripped down version of the GHC for a while, but now that I'm trying to install packages like this, I'm running into problems. Anyway, I have installed pkg-config, etc. and I believe I've got the various bits of gsl installed. However cabal is still failing at attaching this to the appropriate haskell modules, at what looks to be very near the end, and suggstions for what I can try to get things to finish would be welcome. Below is the output as generated by cabal (this is the result of several iterations and systematic googling, but google seems to have run out on me). All suggestions, advice, etc. very welcome, Sean Matthews Software\gsl-1.15-dev-win32\include" --extra-lib-dirs="C:\Users\sematthews\My Software\gsl-1.15-dev-win32\lib" Software\gsl-1.15-dev-win32\include" --extra-lib-dirs="C:\Users\sematthews\My Software\gsl-1.15-dev-win32\lib" C:\Users\sematthews\Ap
Categories: Offsite Discussion

Call for Contributions: BOB 2016 - Berlin, Feb 19, 2016

General haskell list - Wed, 10/28/2015 - 8:43pm
NOTE: Deadline is THIS Friday (October 30, 2015) BOB Conference 2016 "What happens when we use what's best for a change?" Berlin, February 19 Call for Contributions Deadline: October 30, 2015 You drive advanced software engineering methods, implement ambitious architectures and are open to cutting-edge innovation? Attend this conference, meet people that share your goals, and get to know the best software tools and technologies available today. We strive to offer a day full of new experiences and impressions that you can use to immediately improve your daily life as a software developer. If you share our vision and want to contribute, submit a proposal for a talk or tutorial! Topics ------ We are looking for talks about best-of-breed software technology, e.g.: - functional programming - reactive programming - persistent data structures and databases - types - formal methods for correctness and robustness - ... everything r
Categories: Incoming News

GHC can't find DLL dependencies on Windows

haskell-cafe - Wed, 10/28/2015 - 8:25pm
I recently decided to try out a simple diagrams-cairo project on Windows 8 (x86_64) to discover that GHC (7.10.2, to be specific) acts rather bizarrely when dealing with external DLL dependencies. To start, I downloaded MSYS2 [1], installed the libraries needed for cairo and pango to work [2], installed diagrams-cairo [3], and tried running a simple diagrams program: module Main (main) where import Diagrams.Prelude import Diagrams.Backend.Cairo.CmdLine main :: IO () main = mainWith (circle 1 :: Diagram B) like so from MSYS2: runghc Cairo.hs -o circle.svg -w 400 And it worked. Hooray! Now, I normally use cmd.exe/PowerShell for most of my Windows command-line tasks, so later I tried invoking the above command on PowerShell, only to be greeted with an error message: $ runghc.exe .\Cairo.hs -o circle.svg -w 400 Cairo.hs: warning: _tzset from msvcrt is linked instead of __imp__tzset Cairo.hs: libcairo-2: The specified procedure could not be found. Cairo.hs: <command
Categories: Offsite Discussion