- Haskell-Cafe - Haskell.org

Calling a State Monad recursively from within a let-block, via runState?
by David Banas 13 Mar '20

13 Mar '20

Can I call a State Monad recursively from within a let-block, via `runState`, or is that going way out of bounds? -db

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ANNOUNCE: Save the date! Compose Conference 2020 colocated with ICFP
by MightyByte 12 Mar '20

12 Mar '20

We are excited to announce that the Compose Conference will be colocated with ICFP this year. Compose will be Thursday and Friday August 20 and 21 at the NJCU School of Business, a short subway / bus ride from Manhattan. The Compose Unconference will be Saturday and Sunday August 22 and 23 at Microsoft in Times Square. Regarding COVID-19, the Compose Team is closely monitoring the situation and are prepared to make responsible decisions if it comes to that. That being said, the situation will undoubtedly evolve a lot between now and August. We have been very excited about the collaboration between Compose and ICFP and wanted to get an announcement out so that if the conferences do happen as planned everyone is aware. A more detailed announcement will be coming when we have more confirmed details, but if you are already planning to attend ICFP, consider extending your trip by a few days and coming to Compose as well. To get a sense of Compose, you can check out the great talks from past conferences and the Compose Conference website: https://www.youtube.com/channel/UC0pEknZxL7Q1j0Ok8qImWdQ http://www.composeconference.org/ We look forward to seeing you! The Compose Conference Team Sent via Superhuman ( https://sprh.mn/?vip=mightybyte@gmail.com )

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Using GHC option '-optl-static' causes segfault
by Nutr1t07 11 Mar '20

11 Mar '20

Hi, I added '-optl-static' in GHC option to make my program compiled statically. When I compiled the following code using 'stack build': -- Main.hs {-# LANGUAGE OverloadedStrings #-} module Main where import Web.Scotty as Scotty import Network.Wreq as Wreq import Control.Monad.IO.Class main :: IO () main = scotty 8443 $ do Scotty.get (literal "/") $ do _ <- liftIO $ Wreq.get "https://www.google.com/" html "Could not see this" -- Ran the compiled program and accessing "http://localhost:8443" would raise a segmentation fault. Here are what in my 'ghc-option': ghc-options: - -optl-static - -threaded - -rtsopts - -with-rtsopts=-N Then I removed the '-optl-static', compiled it, and the program ran well. It seems that it something has to do with glibc. What can I do with this problem? Regards PS. I'm using GHC 8.8.2, stack 2.1.3

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[ANN] ghc-tag-plugin
by Marcin Szamotulski 09 Mar '20

09 Mar '20

Hi, I wrote a GHC plugin which writes tags files. I've been proof testing it on a large code base where parts of it is using various type extensions, or formats (literate haskell, haskell, hsc files) - it works very well. Here's a blog post about it: https://coot.me/posts/ghc-tags-plugin.html And here's a very fresh hackage version 0.1.3.0: https://hackage.haskell.org/package/ghc-tags-plugin Best regards, Marcin Szamotulski

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WST 2020 - 2nd Call for Papers
by Samir Genaim 05 Mar '20

05 Mar '20

========================================================================== WST 2020 - Call for Papers 17th International Workshop on Termination http://costa.fdi.ucm.es/wst2020 June 29-30, 2020, Paris, France co-located with IJCAR and FSCD 2020. ========================================================================== The Workshop on Termination (WST) traditionally brings together, in an informal setting, researchers interested in all aspects of termination, whether this interest be practical or theoretical, primary or derived. The workshop also provides a ground for cross-fertilization of ideas from the different communities interested in termination (e.g., working on computational mechanisms, programming languages, software engineering, constraint solving, etc.). The friendly atmosphere enables fruitful exchanges leading to joint research and subsequent publications. The workshop is part of "Paris Nord Summer of LoVe 2020", a joint event on LOgic and VErification at Université Paris 13, made of Petri Nets 2020, IJCAR 2020, FSCD 2020, and over 20 satellite events. https://lipn.univ-paris13.fr/summer-of-love-2020/ IMPORTANT DATES: * submission deadline: April 12, 2020 * notification: May 10, 2020 * final version due: May 31, 2020 * workshop: June 29-30, 2020 TOPICS: The 17th International Workshop on Termination welcomes contributions on all aspects of termination. In particular, papers investigating applications of termination (for example in complexity analysis, program analysis and transformation, theorem proving, program correctness, modeling computational systems, etc.) are very welcome. Topics of interest include (but are not limited to): * abstraction methods in termination analysis * certification of termination and complexity proofs * challenging termination problems * comparison and classification of termination methods * complexity analysis in any domain * implementation of termination methods * non-termination analysis and loop detection * normalization and infinitary normalization * operational termination of logic-based systems * ordinal notation and subrecursive hierarchies * SAT, SMT, and constraint solving for (non-)termination analysis * scalability and modularity of termination methods * termination analysis in any domain (lambda calculus, declarative programming, rewriting, transition systems, etc.) * well-founded relations and well-quasi-orders COMPETITION: Since 2003, the catalytic effect of WST to stimulate new research on termination has been enhanced by the celebration of the Termination Competition and its continuously developing problem databases containing thousands of programs as challenges for termination analysis in different categories, see http://termination-portal.org/wiki/Termination_Competition In 2020, the Termination Competition will run shortly before WST and the main venues (IJCAR-FSCD), and the results will be presented at IJCAR or FSCD. PROGRAM COMMITTEE: Martin Avanzini - INRIA Sophia, Antipolis Florian Frohn - Max-Planck-Institut für Informatik, Saarbrücken Carsten Fuhs - Birkbeck, U. of London Samir Genaim (chair) - U. Complutense de Madrid Jürgen Giesl - RWTH Aachen Matthias Heizmann - U. of Freiburg Cynthia Kop - Radboud U. Nijmegen Salvador Lucas - U. Politècnica de València Étienne Payet - U. de La Réunion Albert Rubio - U. Complutense de Madrid René Thiemann - U. of Innsbruck Johannes Waldmann - HTWK Leipzig INVITED SPEAKERS: tba SUBMISSION: Submissions are short papers/extended abstracts which should not exceed 5 pages. There will be no formal reviewing. In particular, we welcome short versions of recently published articles and papers submitted elsewhere. The program committee checks relevance and provides additional feedback for each submission. The accepted papers will be made available electronically before the workshop. Papers should be submitted electronically via the submission page: https://easychair.org/conferences/?conf=wst2020 Please, use LaTeX and the LIPIcs style file http://drops.dagstuhl.de/styles/lipics/lipics-authors.tgz to prepare your submission.

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LF: senior Haskeller to be GSoC mentor
by Jason Chau 03 Mar '20

03 Mar '20

Hi, I am looking for a someone who has a lot of Haskell, OS, networking, and databases experience and knowledge to be a mentor for Google Summer of Code. I need advise on best practises. The project URL is https://github.com/jasonsychau/graphql-w-persistent. Jason Sent from my iPhone

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lib for drawing with mouse
by mechvel＠scico.botik.ru 03 Mar '20

03 Mar '20

Please, does there exist a tool (library) in Haskell that supports doing the following with graphics? (1) To draw a curve by mouse on a screen and save this picture in a file (many different curves to be input this way). (2) To save in data.txt the coordinates of the points of this curve, say, 800 pairs of numbers (floating point or rational ...). (3) Reversely: to draw a curve on a screen by inputting from such data.txt. The main is (1)&(2). Because currently I set a curve by putting many times the '*' character and `space' to a text file, and this takes long. Thanks, ------ Sergei

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ANN: hledger 1.16
by Simon Michael 02 Mar '20

02 Mar '20

I'm pleased to announce hledger 1.17 ! hledger is a robust, cross-platform, plain text accounting tool, with command-line, terminal and web UIs. It is a modern and largely compatible reimplementation of Ledger CLI with many improvements. You can use it to track time, money, investents, cryptocurrencies, inventory and more. See: http://hledger.org http://plaintextaccounting.org hledger 1.17 is released on schedule on 2020-03-01. Thanks to release contributors Aleksandar Dimitrov, Brian Wignall, Stephen Morgan, Jacek Generowicz, Gaith Hallak, Eric Mertens, Jakob Schöttl, Carl Richard Theodor Schneider, David Zhang, Amarandus, Evilham, Mateus Furquim, and Rui Chen. HIGHLIGHTS: CSV single-field matching, easier SSV/TSV conversion, fixed/enhanced close command, undo in add command, more JSON output, org headline support in timedot format, GHC 8.10 support. See all changes at https://hledger.org/release-notes . GETTING STARTED: Many install methods are described at http://hledger.org/download. Here are three ways to build from source: stack update; stack install --resolver=lts hledger-lib-1.17 hledger-1.17 hledger-ui-1.17 hledger-web-1.17 --silent or: cabal v2-update; cabal v2-install hledger-1.17 hledger-web-1.17 hledger-ui-1.17 or: curl -sO https://raw.githubusercontent.com/simonmichael/hledger/master/hledger-insta… less hledger-install.sh bash hledger-install.sh While building, peruse https://hledger.org/start For help, see http://hledger.org#help-feedback and join us on Freenode (#hledger, http://irc.hledger.org) or via Matrix (#freenode_#hledger:matrix.org, http://riot.hledger.org) New and old users, contributors, sponsors, and all feedback are most welcome! Best, -Simon

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Re: [Haskell-cafe] [ANNOUNCE] GHC 8.8.3 is now available
by Ben Gamari 29 Feb '20

29 Feb '20

Ben Gamari <ben(a)well-typed.com> writes: > --text follows this line-- > <#part sign=pgpmime> > > Hello everyone, > > The GHC team is proud to announce the release of GHC 8.8.3. The source > distribution, binary distributions, and documentation are available at > > https://downloads.haskell.org/~ghc/8.8.3 > > Release notes are also available [1]. > Unfortunately there has been a slight mix-up in the binary distributions associated with this release and I will need to do a re-spin. I have pulled down the binary distributions for the time being. They should be back in a few hours. Many apologies for the confusion! Cheers, - Ben

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How to deal with HTML input select option on a form using in a scotty and Text.Blaze.Html5
by Tebogo Sikwane 27 Feb '20

27 Feb '20

I am using scotty and Text.Blaze.Html5 Text.Digestive Text.Digestive.Blaze.Html5 What I want to achieve is a list of options as shown below. I have a Option sum type and will like to restrict the user to those options. data Options = Option1 | Option2 | Option3 | Option4 deriving Show Below is the Register record typeY data Register = Register { regName::Text , regOption::Options } deriving (Show,Eq) My problem is with Text.Digestive.choice. I don't know how to use it with Text.Digestive.Blaze.Html5 and will appreciate your help on the correct way to achieve this. I have tried to use the code below but battle to get it right. registerForm :: Monad m => Form Text m Register registerForm = Register <$> "name" .: text Nothing <*> "options" .: choice options Nothing where options= [(Option1,"Option1"),(Option2,"Option2"), (Option3, "Option3"),Option4,"Option4"] registerView:: View H.Html -> H.Html registerView view = do label "name" view "Name: " inputText "name" view H.br label "options" view "Options: " inputSelect "options" view H.br I get the following error when I compile my code: /root/work/src/Adapter/HTTP/Web/Auth.hs:107:29: error: • Couldn't match type ‘Text’ with ‘Char’ arising from the literal ‘"Option1"’ • In the first argument of ‘pack’, namely ‘"Option1"’ In the expression: pack "Option1" In the expression: (Option1, pack "Option1") | 107 | options= [(Option1,pack "Option1"),(Option2,pack "Option2"),(Option3,pack "Option3"),(Option4,pack "Option4")] Your help will be highly appreciated.

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