- Haskell-Cafe - Haskell.org

[ANN] ghc-mod-5.6.0.0: Supporting GHC 8.0 and Cabal 1.24
by Daniel Gröber 01 Aug '16

01 Aug '16

I'm pleased to announce the release of ghc-mod 5.6.0.0! What's new? =========== * Support for GHC 8.0 and Cabal 1.24 Nothing too spectacular to report here, just regular maintenance work. * Type Contexts fixed Thanks to @Lierdakil `ghc-mod type` now finally displays type (class) constraints in most cases. This has been on the TODO list for a very long while now, going back to at least GHC 7.8. GHC's API just doesn't have a nice, simple, way for doing this and we had to resort to manually walking the typechecked AST while collecting constraints in various places. * Various bug fixes and smaller improvements From the change log: * Merge #737, `map-file` caching issues * Merge #767, Add `browse` option to show symbol "parents" * Fix #438, Case splitting not working * Fix #790, Don't try to use 'cabal' or 'stack' when it's not installed What is ghc-mod? ================ ghc-mod is both a back-end program for enhancing editors and other development environments with support for Haskell as well as a library for abstracting the black magic incantations required to use the GHC API in various environments, especially Cabal and Stack projects. The library is used by projects like HaRe[1], and haskell-ide-engine[2] Getting ghc-mod =============== GitHub: https://github.com/DanielG/ghc-mod Hackage: http://hackage.haskell.org/package/ghc-mod Editor frontends: - Emacs (native): https://github.com/DanielG/ghc-mod https://github.com/iquiw/company-ghc - Vim: https://github.com/eagletmt/ghcmod-vim https://github.com/eagletmt/neco-ghc - Atom: https://github.com/atom-haskell/ide-haskell Known issues ============ For issues other than the ones mentioned below visit our issue tracker: https://github.com/DanielG/ghc-mod/issues Frequently reported issues -------------------------- ghc-mod once compiled is bound to one version of GHC since we link against the GHC API library. This used to not be a very big problem but since Stack made it exceedingly easy for users to use more than one version of GHC without even knowing the number of problems in this area has exploded. We are tracing the issue in the following issue: https://github.com/DanielG/ghc-mod/issues/615 (Support switching GHC versions without recompiling ghc-mod) If you do notice any other problems please report them: https://github.com/DanielG/ghc-mod/issues/new ---- [1]: https://github.com/alanz/HaRe [2]: https://github.com/haskell/haskell-ide-engine

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RFC: New version of haskell-src-exts without simplified AST
by Matthew Pickering 31 Jul '16

31 Jul '16

Dear all, For several months I have had a branch of haskell-src-exts which has been updated for all the new features in GHC 8. However, I have not yet released the changes as in this version I also removed the simplified AST. To those unfamiliar, HSE provides two ASTs, one which has source locations and one which doesn't. I have removed the one which doesn't. This simplifies maintenance and I think also makes the library easier to use. I have held back releasing this version as there are some people who use the simplified AST. The changes necessary for the new version are mechanical and easy to make. For example, David Fox updated haskell-names to use my branch [1] with few problems. The question is, are there any users of the library who object to this change? Matt [1]: https://github.com/haskell-suite/haskell-names/pull/73

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Re: [Haskell-cafe] RFC: revisiting the simplified haskell-src-exts AST
by Matthew Pickering 31 Jul '16

31 Jul '16

Hello Bertram, This is a good idea. I also considered this but to provide a proper compatibility layer it is necessary to "bundle" pattern synonyms with suitable type constructors so that when users import the type constructor then they also import the suitable pattern synonyms. This feature was only implemented in GHC 8.0. It is currently not much effort to maintain HSE to support back to at least GHC 7.4 so it didn't seem worth sacrificing this. It would be good to provide this shim in future versions of the library but at the moment the feature isn't mature enough. Message me when you release this to Hackage and I will add a link to the README. Matt On Sat, Jul 30, 2016 at 11:22 PM, Bertram Felgenhauer via Haskell-Cafe < haskell-cafe(a)haskell.org> wrote: > Dear all, > > the latest major release of haskell-src-exts (version 1.18) removed > the annotation free variant of the Haskell AST. It occurred to me that > using ghc's pattern synonyms it is possible to offer a light-weight > simplified view on the annotated AST. For example, > Language.Haskell.Exts.Syntax defines > > data Name l = Ident l String | Symbol l String > > and we can provide a simplified view with all annotations equal to () > by doing > > {-# LANGUAGE PatternSynonyms #-} > import qualified Language.Haskell.Exts.Syntax as H > > type Name = H.Name () > pattern Ident a = H.Ident () a > pattern Symbol a = H.Symbol () a > > Because the type isn't changed, no code has to be reimplemented to > work with this AST. > > A first rough cut at an implementation can be found on github [1]. > Before releasing it on hackage (which requires some more polishing) > I'd appreciate feedback on the approach. Would you consider using > such a package? Is there a better approach? Also any thoughts on > usability (e.g., how to approach documentation) would be welcome. > > Cheers, Bertram > > [1] https://github.com/int-e/haskell-src-exts-simple > > > P.S. This grew out of an effort to update lambdabot to HSE-1.18, > which made me feel awful about all the superfluous and ugly () in > the resulting code. I also have some numbers showing that the > annotation-free view makes updating the code smoother: > > Using the annotation-free view, the update touches 75 lines: > src/Lambdabot/Plugin/Haskell/Eval.hs | 18 +- > src/Lambdabot/Plugin/Haskell/Pointful.hs | 201 +++++++++++++++---------------- > src/Lambdabot/Plugin/Haskell/Pretty.hs | 14 +- > src/Lambdabot/Plugin/Haskell/UnMtl.hs | 62 ++++----- > src/Lambdabot/Plugin/Haskell/Undo.hs | 115 ++++++++--------- > 5 files changed, 72 insertions(+), 75 deletions(-) > > Using the haskell-src-exts 1.18 AST, the update touches 208 lines: > src/Lambdabot/Plugin/Haskell/Pointful.hs | 87 ++++++++++++++----------------- > src/Lambdabot/Plugin/Haskell/Pretty.hs | 12 ++-- > src/Lambdabot/Plugin/Haskell/UnMtl.hs | 10 +-- > src/Lambdabot/Plugin/Haskell/Undo.hs | 34 ++++++------ > 5 files changed, 204 insertions(+), 206 deletions(-) > _______________________________________________ > Haskell-Cafe mailing list > To (un)subscribe, modify options or view archives go to: > http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe > Only members subscribed via the mailman list are allowed to post.

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RFC: revisiting the simplified haskell-src-exts AST
by Bertram Felgenhauer 30 Jul '16

30 Jul '16

Dear all, the latest major release of haskell-src-exts (version 1.18) removed the annotation free variant of the Haskell AST. It occurred to me that using ghc's pattern synonyms it is possible to offer a light-weight simplified view on the annotated AST. For example, Language.Haskell.Exts.Syntax defines data Name l = Ident l String | Symbol l String and we can provide a simplified view with all annotations equal to () by doing {-# LANGUAGE PatternSynonyms #-} import qualified Language.Haskell.Exts.Syntax as H type Name = H.Name () pattern Ident a = H.Ident () a pattern Symbol a = H.Symbol () a Because the type isn't changed, no code has to be reimplemented to work with this AST. A first rough cut at an implementation can be found on github [1]. Before releasing it on hackage (which requires some more polishing) I'd appreciate feedback on the approach. Would you consider using such a package? Is there a better approach? Also any thoughts on usability (e.g., how to approach documentation) would be welcome. Cheers, Bertram [1] https://github.com/int-e/haskell-src-exts-simple P.S. This grew out of an effort to update lambdabot to HSE-1.18, which made me feel awful about all the superfluous and ugly () in the resulting code. I also have some numbers showing that the annotation-free view makes updating the code smoother: Using the annotation-free view, the update touches 75 lines: src/Lambdabot/Plugin/Haskell/Eval.hs | 18 +- src/Lambdabot/Plugin/Haskell/Pointful.hs | 201 +++++++++++++++---------------- src/Lambdabot/Plugin/Haskell/Pretty.hs | 14 +- src/Lambdabot/Plugin/Haskell/UnMtl.hs | 62 ++++----- src/Lambdabot/Plugin/Haskell/Undo.hs | 115 ++++++++--------- 5 files changed, 72 insertions(+), 75 deletions(-) Using the haskell-src-exts 1.18 AST, the update touches 208 lines: src/Lambdabot/Plugin/Haskell/Pointful.hs | 87 ++++++++++++++----------------- src/Lambdabot/Plugin/Haskell/Pretty.hs | 12 ++-- src/Lambdabot/Plugin/Haskell/UnMtl.hs | 10 +-- src/Lambdabot/Plugin/Haskell/Undo.hs | 34 ++++++------ 5 files changed, 204 insertions(+), 206 deletions(-)

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ANN: network-2.6.3.0
by evan＠evan-borden.com 30 Jul '16

30 Jul '16

Good day, I am pleased to announce the release of network 2.6.3.0. This release is primarily focused on stability, but includes a few new APIs. Thank you to the contributors for their continued excellence. https://hackage.haskell.org/package/network-2.6.3.0 Release Notes, Version 2.6.3.0: * New maintainers: Evan Borden (@eborden) and Kazu Yamamoto (@kazu-yamamoto). The maintainer for a long period, Johan Tibell (@tibbe) stepped down. Thank you, Johan, for your hard work for a long time. * New APIs: ntohl, htonl,hostAddressToTuple{,6} and tupleToHostAddress{,6}. [#210](https://github.com/haskell/network/pull/210) * Added a Read instance for PortNumber. [#145]( https://github.com/haskell/network/pull/145) * We only set the IPV6_V6ONLY flag to 0 for stream and datagram socket types, as opposed to all of them. This makes it possible to use ICMPv6. [#180](https://github.com/haskell/network/pull/180) [#181](https://github.com/haskell/network/pull/181) * Work around GHC bug #12020. Socket errors no longer cause segfaults or hangs on Windows. [#192](https://github.com/haskell/network/pull/192) * Various documentation improvements and the deprecated pragmas. [#186](https://github.com/haskell/network/pull/186) [#201](https://github.com/haskell/network/issues/201) [#205](https://github.com/haskell/network/pull/205) [#206](https://github.com/haskell/network/pull/206) [#211](https://github.com/haskell/network/issues/211) * Various internal improvements. [#193](https://github.com/haskell/network/pull/193) [#200](https://github.com/haskell/network/pull/200)

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Re: [Haskell-cafe] Breaking in library, and getting stacktrace
by Carlos D'Agostino 29 Jul '16

29 Jul '16

Without knowing too much about your project setup, and if I'm understanding correctly, see http://haddock.stackage.org/lts-5.1/base-4.8.2.0/Debug-Trace.html#v:traceSt… Keep in mind that you have to build with the corresponding flags in order to get it working correctly. Assuming you're using stack that would be: stack build --enable-profiling --library-profiling --ghc-options="-fprof-auto-rtsopts" Though I'm not sure if that's 100% what you're looking for since it doesn't break as much as that it logs with a stack trace. Hope it helps! > ---------------------------------------------------------------------- > > Message: 1 > Date: Thu, 28 Jul 2016 16:43:03 +0300 > From: Constantine Kharlamov <hi-angel(a)ya.ru> > To: haskell-cafe(a)haskell.org > Subject: [Haskell-cafe] Breaking in library, and getting stacktrace > Message-ID: <147361469713383(a)web5j.yandex.ru> > Content-Type: text/plain; charset="utf-8" > > An HTML attachment was scrubbed... > URL: < > http://mail.haskell.org/pipermail/haskell-cafe/attachments/20160728/b4652af… > > > > ------------------------------ > > Subject: Digest Footer > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe > > > ------------------------------ > > End of Haskell-Cafe Digest, Vol 155, Issue 33 > ********************************************* > -- Carlos D'Agostino.

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Breaking in library, and getting stacktrace
by Constantine Kharlamov 28 Jul '16

28 Jul '16

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Question, re: upgrading Stack manually.
by David Banas 27 Jul '16

27 Jul '16

Hi Stackers, Is this a show stopper, wrt/ upgrading Stack manually, via: - stack unpack stack-1.1.2 - pushed <directory created, above> - stack setup - stack build Warning: /Users/dbanas/Documents/Projects/stack/upgrade_2016-07-27/stack-1.1.2/stack.yaml: Unrecognized field in ProjectAndConfigMonoid: nix ? Thanks, -db

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good choice for random number generator ?
by briand＠aracnet.com 27 Jul '16

27 Jul '16

There's quite a few. Many are very old. I would have like to use vector-random and got this : Data/Vector/Random/Mersenne.hs:33:18: Could not find module ‘Data.Vector.Fusion.Stream’ It is a member of the hidden package ‘vector-0.10.12.3@vecto_1COyUuV1LrA1IjYnWfJnbs’. Perhaps you need to add ‘vector’ to the build-depends in your .cabal file. Use -v to see a list of the files searched for. Data/Vector/Random/Mersenne.hs:35:18: Could not find module ‘Data.Vector.Fusion.Stream.Size’ It is a member of the hidden package ‘vector-0.10.12.3@vecto_1COyUuV1LrA1IjYnWfJnbs’. Perhaps you need to add ‘vector’ to the build-depends in your .cabal file. Use -v to see a list of the files searched for. I wouldn't be opposed to fixing it, but I'm wondering at this point there isn't a better package to use instead. I'm looking for both integer and floating point random numbers, uniform and gaussian. gsl-random looks promising as does mwc-random. any other suggestions ? Thanks, Brian

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How do I debug this RTS segfault?
by Lana Black 26 Jul '16

26 Jul '16

Hello, I have run into this RTS bug recently. In short, when executing multiple consequtive forks, after 500-600 or so the process is terminated by SIGSEGV. I know this kind of thing is totally artificial, but still. The problem I have is that I can't get any meaningful backtrace in gdb. For example, for threaded RTS I get this (gdb) bt #0 0x0000000000560d63 in base_GHCziEventziThread_ensureIOManagerIsRunning1_info () Backtrace stopped: Cannot access memory at address 0x7fffff7fcea0 For non-threaded RTS I get this (gdb) bt #0 0x00000000007138c9 in stg_makeStablePtrzh () Backtrace stopped: Cannot access memory at address 0x7fffff7fc720 Build command: ghc --make -O2 -g -fforce-recomp fork.hs Add threaded if needed. I was able to reproduce this bug with both GHC 7.10.3 and todays HEAD with the code below. >import System.Exit (exitSuccess) >import System.Posix.Process (forkProcess) > >fork_ n | n > 0 = processPid =<< forkProcess (fork_ $! n - 1) > | otherwise = putStrLn "I'm done!" > >processPid pid | pid > 0 = exitSuccess > | pid < 0 = putStrLn "OOOPS, forkProcess failed!" > | otherwise = pure () > >main = fork_ 1000 > With best regards.

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