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[ANNOUNCE] GHC 8.0.1 release candidate 4 available
by Ben Gamari 29 Apr '16

29 Apr '16

Hello Haskellers, The GHC team is happy to announce the availability of fourth release candidate of the Glasgow Haskell Compiler's 8.0.1 release. Source and binary distributions can be found at, http://downloads.haskell.org/~ghc/8.0.1-rc4/ This is the last of four candidates leading up to the 8.0.1 release, addressing nearly all of the known issues of the previous candidates. These include, * A type-checker panic triggered by use of Typeable on a kind-polymorphic type constructor (#11334) * A type-checker explosion where -XTypeInType would gobble up massive amounts of memory when used in a data instance (#11407) * A variety of other typechecker issues (#11811, #11797, #11813, #11814) * A build issue seen on OS X (#11828) * Template Haskell can now produce instances with OVERLAPP{ING,ABLE,ED} pragmas * Autoconf has improved version checks for libdw (#11820) * Typeable and hs-boot files now interact nicely (#11824) * The build system now checks for the broken Apple `nm` utility (#11823, #11744) * Various issues involving unexpected laziness resulting in exception handlers not being invoked (#11555) * GHC now fails more gracefully when used with an older cabal-install release (#11558) * TypeInType now has proper documentation in the users guide (#11614) * The story surrounding type `RuntimeRep`s (formerly known as `Levity`) is now far better developed, closing several doors to unsafe behavior that TypeInType previously opened (#11473, #11723) * A long-standing bug in the constant-folding rules for `mod` for the `Word` type has been resolved (#11702) * Various issues introduced by OverloadedRecordFields have been fixed (#11662, #11401) * A regression in the typechecker resulting in the rejection of code in the `free` and `microlens` packages has been fixed (#11608) * A bug in the LLVM code generator which caused some programs to emit unbuildable LLVM IR has been fixed (#11649) * A bug where pattern synonyms defined in terms of a pattern match on a record would be rejected if the fields weren't written in the same order as they were defined has been resolved (#11633) * A bug in the runtime system's treatment of weak references which could result in segmentation faults in some cases has been fixed (#11108) * a variety of optimizations improving compiler performance have been merged * and many others Mac OS X users should be aware that the recent XCode 7.3 release ships with a broken `nm` utility which breaks the GHC build (#11744, #11823). The build system will check for this condition and request that the tree is configured to use the `nm-classic` utility if found. OS X users running XCode 7.3 are encouraged to open a ticket with Apple so that this issue may be fixed in future XCode releases. If no major issues pop up we expect that this will be the last release candidate before the final release, which we hope to push out in the coming weeks. Thanks to everyone who has contributed code, testing, builds, and bug reports thusfar! Cheers and happy testing, - Ben

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Fw: Bikeshedding request for GHCi's :type
by Takenobu Tani 29 Apr '16

29 Apr '16

Dear cafe, I'm forwarding mail from ghc-devs ML [1]. I think `:type` command is very important for beginners and middle users. Please feedback your opinion to them ;) [1]: https://mail.haskell.org/pipermail/ghc-devs/2016-April/011933.html > 2016-04-26 22:08 GMT+09:00 Richard Eisenberg <eir(a)cis.upenn.edu>: > Hi devs, > > Over the weekend, I was pondering the Haskell course I will be teaching next year and shuddered at having to teach Foldable at the same time as `length`. So I implemented feature request #10963 ( https://ghc.haskell.org/trac/ghc/ticket/10963) which allows for a way for a user to request a specialization of a type. It all works wonderfully, but there is a real user-facing design issue here around the default behavior of :type and whether or not to add new :type-y like commands. I have outlined the situation here: https://ghc.haskell.org/trac/ghc/wiki/Design/GHCi/Type > > I'd love some broad input on this issue. If you've got a stake in how this all works, please skim that wiki page and comment on #10963. > > Thanks! > Richard Cheers, Takenobu

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Re: [Haskell-cafe] Fw: Bikeshedding request for GHCi's :type
by Anton Felix Lorenzen 28 Apr '16

28 Apr '16

As a middle user, I often depend on `:type` when learning a library. I don't have strong preferences over one proposal or the other, but I would like to add, that there should always be `:type` in its current form (renamed or not). I wouldn't like getting lots of for me irrelevant information, like examples, when I only want a one-line type signature. That said, I like the general idea, although I don't know, whether a beginner would like having to learn the type signatures again, when getting to a more advanced level. - Anton Lorenzen

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ANN: Haskell Prime 2020 committee has formed
by Herbert Valerio Riedel 28 Apr '16

28 Apr '16

Dear Haskell Community! Some time ago I asked for nominations to reboot the Haskell Prime process[1], and now I'm pleased to finally announce the formation of the new Haskell Language 2020 Committee! The goal of the Haskell Language committee together with the Core Libraries Committee is to work towards a new Haskell 2020 Language Report. I'd like to remind everyone that the Haskell Prime Process[4] relies on *everyone* in the community to help by contributing proposals which the committee will then evaluate and if suitable help formalise for inclusion. Everyone interested in participating is also invited to join the haskell-prime mailing list. Four years (or rather ~3.5 years) from now may seem like a long time. However, given the magnitude of the task at hand, to discuss, formalise, and implement proposed extensions (taking into account the recently enacted three-release-policy[3]) to the Haskell Report, the process shouldn't be rushed. Consequently, this may even turn out to be a tight schedule after all. However, it's not excluded there may be an interim revision of the Haskell Report before 2020. Based on this schedule, GHC 8.8 (likely to be released early 2020) would be the first GHC release to feature Haskell 2020 compliance. Prior GHC releases may be able to provide varying degree of conformance to drafts of the upcoming Haskell 2020 Report. The Haskell Language 2020 committee starts out with 20 members which contribute a diversified skill-set. These initial members also represent the Haskell community from the perspective of practitioners, implementers, educators, and researchers. - Andres Löh - Antonio Nikishaev - Austin Seipp - Carlos Camarao de Figueiredo - Carter Schonwald - David Luposchainsky - Henk-Jan van Tuyl - Henrik Nilsson - Herbert Valerio Riedel - Iavor Diatchki - John Wiegley - José Manuel Calderón Trilla - Jurriaan Hage - Lennart Augustsson - M Farkas-Dyck - Mario Blažević - Nicolas Wu - Richard Eisenberg - Vitaly Bragilevsky - Wren Romano The Haskell 2020 committee is a language committee; it will focus its efforts on specifying the Haskell language itself. Responsibility for the libraries laid out in the Report is left to the Core Libraries Committee (CLC)[5]. Incidentally, the CLC still has an available seat[2]; if you would like to contribute to the Haskell 2020 Core Libraries you are encouraged to apply for this opening. As this is a general announcement broadcasted to multiple mailing lists, a separate email discussing the next steps of the new committee will be sent to the haskell-prime mailing list shortly. [1]: https://mail.haskell.org/pipermail/haskell-prime/2015-September/003936.html [2]: https://mail.haskell.org/pipermail/libraries/2015-November/026497.html [3]: https://prime.haskell.org/wiki/Libraries/3-Release-Policy [4]: https://prime.haskell.org/wiki/Process [5]: https://prime.haskell.org/wiki/Libraries -- hvr

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Sending email
by David Escobar 28 Apr '16

28 Apr '16

Hi everyone, I'm trying to use the *Network.Mail.SMTP* library to send email: *{-# LANGUAGE OverloadedStrings #-}* *module Main where* *import Control.Exception* *import qualified Data.Text as T* *import qualified Data.Text.Lazy as LT* *import Network.Mail.SMTP* *main :: IO ()* *main = do* * sendEmail (“Person sender”, “sender@somewhere.com <sender(a)somewhere.com>”)* * [(“Person recipient“, “recipient@somewhere.com <recipient(a)somewhere.com>”)]* * "Test email"* * "Some message goes here."* *sendEmail :: (T.Text, T.Text) -> [(T.Text, T.Text)] -> T.Text -> T.Text -> IO ()* *sendEmail (fromName, fromEmail) toAddresses subject' body' = do* * let toNameAddrs = map (\(toName, toEmail) -> Address (Just toName) toEmail) toAddresses* * msg = simpleMail (Address (Just fromName) fromEmail)* * toNameAddrs* * []* * []* * subject'* * [ plainTextPart $ LT.fromStrict body' ]* * result <- try $ sendMailWithLogin' "smtp.gmail.com <http://smtp.gmail.com>"* * 465 -- SSL port* * “sender_login”* * “sender_password”* * msg :: IO (Either SomeException ())* * case result of* * Left e -> putStrLn $ "Exception caught: " ++ (displayException e)* * Right _ -> putStrLn "Sent email successfully."* The program compiles, but when I run it, I get: *Exception caught: <socket: 49>: Data.ByteString.hGetLine: end of file* I tried using the TLS port of 587, but then I just get an authentication failure. Am I using the wrong library or is it just the wrong configuration. Thanks.

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Summer of Haskell - Now Accepting Applications!
by Gershom B 28 Apr '16

28 Apr '16

(Note: I am posting this on behalf of Edward Kmett who has spotty availability at the moment) We've posted an official Summer of Haskell website: https://summer.haskell.org/ It contains the full timeline for the program this summer, and most importantly, a form for submitting student applications, also linked here: https://docs.google.com/forms/d/1JLIa58u7AcWN31bH_LcCBujN9uzAwfd3HxrT32qz9_… The student application period ends next Friday, May 6. Last year we had a very successful project brainstorming thread. This led to our largest and most successful Summer of Code, ever. There is a thread on reddit now devoted to the purpose of further brainstorming for this year: https://www.reddit.com/r/haskell/comments/4gh1tu/summer_of_haskell_now_acce… If you have a proposal that you think a student could make a good dent in over the course of a summer, especially one with broad impact on the community, please feel free to discuss it there. If you are a potential student, please feel free to skim the proposals for ideas, or put forth ones of your own! If you are a potential mentor, please feel free to comment on proposals that interest you, put forth ideas looking for students and express your interest, to help us pair up potential students with potential mentors. Ultimately, the project proposals that are submitted get written by students, but if we can give a good sense of direction for what the community wants out of the summer, we can improve the quality of proposals, and we can recruit good mentors to work with good students on good projects. Resources: We have a wiki on https://ghc.haskell.org/trac/summer-of-code/ It is, of course, a Wiki, so if you see something out of order, take a whack at fixing it. We have an active #haskell-gsoc channel on irc.freenode.net that we run throughout the summer. Potential mentors and students alike are welcome. We have a Trac full of suggested Google Summer of Code proposals both current and from years past, but it could use a whole lot of eyeballs and an infusion of fresh ideas: https://ghc.haskell.org/trac/summer-of-code/report/1 Many of our best proposals in years have come from lists of project suggestions that others have blogged about. Many of our best students decided to join the summer of code based on these posts. The Trac isn't the only source of information on interesting projects, and I'd encourage folks to continue posting their ideas. If you or your employer would be interested in helping to fund additional students, please feel free to reach out to me. Thank you, -Edward Kmett

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Hackage package index download failure
by Sean Leather 28 Apr '16

28 Apr '16

I'm unable to download the package index file used by cabal: $ cabal update Downloading the latest package list from hackage.haskell.org cabal: Failed to download http://hackage.haskell.org/packages/archive/00-index.tar.gz : ErrorMisc "Error HTTP code: 502" A few hours ago the error was a 503. Anybody know what's going on? Regards, Sean

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Interactive ASCII graphics
by Jeffrey Brown 27 Apr '16

27 Apr '16

Gary Fixler recently gave a talk, to the Santa Monica Haskell Users Group at Brainium, in which he creates an interactive explorer for (among other images) the Mandelbrot set, using nothing but text. No complex libraries for graphics or reactivity are involved -- the only foreign import statements are to Data.Monoid, Data.Function, Data.Complex, and System.IO. The code is here: https://github.com/gfixler/continou This gif demonstrates it: http://www.garyfixler.com/2016-04-18-012037_3840x1024_scrot.gif The video is here: https://vimeo.com/163287967/99e0595942 -- Jeffrey Benjamin Brown

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When using Cereal, what is the right way to write `get` for multi-constructor type?
by Magicloud Magiclouds 27 Apr '16

27 Apr '16

Hi, Say I have code already like: data STH = A | B | C instance Serialize STH where put A = putWord8 1 put B = putWord8 66 put C = putWord8 111 Then what is the better way to do `get`? Is following the only one? get = do i <- getWord8 case i of 1 -> return A 66 -> return B 111 -> return C Thanks.

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Dropping support for NHC98 and old GHC from containers
by David Feuer 26 Apr '16

26 Apr '16

The containers package currently includes CPP and Cabal directives intended to support NHC98 and versions of GHC before 7.0. However, our TravisCI script tests only GHC versions 7.0 and above. It is therefore likely that the compatibility code is bit-rotted to some extent. Wren Romano and I are strongly inclined to immediately remove all code intended to support NHC98 or pre-7.0 GHC. If anyone uses any such implementations with the current version of containers, please speak now or forever hold your peace. Thanks, David Feuer

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