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Cybersecurity Posts (2) at the University of Sheffield
by Achim D. Brucker 19 Dec '17

19 Dec '17

(Apologies for duplicates) -- Dr. Achim D. Brucker | Software Assurance & Security | University of Sheffield https://www.brucker.ch | https://logicalhacking.com/blog @adbrucker | @logicalhacking

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coercing D a to D b
by Evan Laforge 19 Dec '17

19 Dec '17

Given: data D a = A a | B Int Char dmapNoCoerce :: (a -> b) -> D a -> D b dmapNoCoerce f (A a) = A (f a) dmapNoCoerce _ (B i c) = B i c I have to reconstruct a B change it from D a to D b. But at the lower level, couldn't this be implemented as a type cast? What prevents such an optimization? I can write this as dmapCoerce :: (a -> b) -> D a -> D b dmapCoerce f (A a) = A (f a) dmapCoerce _ b@(B {}) = Unsafe.Coerce.unsafeCoerce b >From the core, it looks like dmapCoerce indeed has a cast with no allocation, while dmapNoCoerce allocates a new B. It seems to work, but is it safe? Is there a more principled way to do it? I can't convince Data.Coerce to cooperate, presumably because 'a' and 'b' are not coercible themselves, and it doesn't believe me if I try to tell it the type role is phantom.

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error terminated list
by Evan Laforge 18 Dec '17

18 Dec '17

I've been using this lately to represent a process which can fail but still produce data: data UntilFail err a = a :+ UntilFail err a | Done | Fail err I know there's been discussion of this type before, but I don't remember what it was called and I can't find the right search terms to turn it up. Ring any bells? I have some awkward names for it, but maybe someone else thought of something more elegant. I have some ad-hoc functions for it: mapUntilFail :: (a -> Either err b) -> UntilFail err a -> UntilFail err b concatMapUntilFail :: (a -> UntilFail err b) -> UntilFail err a -> UntilFail err b -- | Like 'concatMapUntilFail', but consume a variable number of results. -- -- A more precise type would end with @Done [a]@. processUntilFail :: (a -> [a] -> (UntilFail err b, [a])) -> [a] -> UntilFail err b Maybe someone who has thought more deeply about it has come up with more elegant abstractions.

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Haskell IDE Engine logo poll
by Damien Flament 18 Dec '17

18 Dec '17

Hi ! The final poll is available featuring all logos submitted until last Friday. Please vote for your favourite*s* here: http://freeonlinesurveys.com/p/Cw1FRJ2G?qid=1017541 Thanks. Damien.

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The Definition of Haskell
by Todd Wilson 18 Dec '17

18 Dec '17

Why doesn't Haskell (or at least "core" Haskell) have a formal definition and safety result the way Standard ML does [1], [2]? Is it just that no one has gotten around to producing them, or because there are fundamental difficulties that stand in the way of completing such a project? Todd Wilson [1] Robin Milner, Mads Tofte, Robert Harper, and David MacQueen. The Definition of Standard ML (Revised). MIT Press, 1997. [2] Daniel K. Lee , Karl Crary , Robert Harper, "Mechanizing the Metatheory of Standard ML", http://www.cs.cmu.edu/~dklee/tslf/

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Managing package release workflow
by Clinton Mead 18 Dec '17

18 Dec '17

Hi All I've already got a few packages on hackage <https://hackage.haskell.org/user/clinton>, but I'd like to upload a few more, but I'm finding the workflow management particularly excessive. Here's what I'd like to do roughly: 1. Choose a number of stack snapshots I'd like my package to successfully build and test against. 2. Automatically apply appropriate version bounds to dependencies in my cabal file based on those snapshots. 3. When these changes are pushed to Github, attempt to compile them using Travis CI, against all the stack snapshots chosen. 4. If we do a push to a particular branch or with particular tag, this signifies we're attempting a release. Attempt to compile using Travis CI, perform the tests. If the compile and tests are successful, push a separate commit, adjust the "source-repository" field in github to point to that release commit (not to master) and upload to hackage. I'm currently doing all of this manually but it's increasingly a bit of a pain. Is there tooling to help me automate this? Thanks, Clinton

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Who can send a patche to vim project?
by Takenobu Tani 18 Dec '17

18 Dec '17

Hi cafe, Who can send a patche to vim project? I'd like to update vim syntax file (haskell.vim) to fix numeric literals. I read the vim `CONTRIBUTING.md` file [1]. It instructs me to contact the maintainer of each files. In the header of `haskell.vim`, the maintainor of `haskell.vim` is haskell-cafe@ML. [2] Who is the maintainer of `haskell.vim`? I'd like to make fix on numeric literals extension: [3] * BinaryLiterals * HexFloatLiterals * NumericUnderscores I prepared two kinds of patches. * Exact pattern version [4] * Fast (but approximate) pattern version [5] I visually checked patches with the these files [6][7]. Could you send a patch of [4] or [5] to vim project? P.S. I have already sent patches to two projects. * `language-haskell` for atom and linguist [8] You can already use it on atom. Linghist (which is used from github) will apply it soon. * `pygments` [9] It is pending review. [1]: https://github.com/vim/vim/blob/master/CONTRIBUTING.md#syntax-indent-and-ot… [2]: https://github.com/vim/vim/blob/master/runtime/syntax/haskell.vim#L3 [3]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0009-n… [4]: https://github.com/vim/vim/compare/master...takenobu-hs:syntax-haskell-lite… [5]: https://github.com/vim/vim/compare/master...takenobu-hs:syntax-haskell-lite… [6]: https://github.com/takenobu-hs/ghc/blob/squashed-numeric-underscores/testsu… [7]: https://github.com/takenobu-hs/ghc/blob/squashed-numeric-underscores/testsu… [8]: https://github.com/atom-haskell/language-haskell/commit/f90eb7d8662493536f5… [9]: https://bitbucket.org/birkenfeld/pygments-main/issues/1399/update-haskell-w… Regards, Takenobu

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Is Haskell the best programming language?
by Henning Thielemann 15 Dec '17

15 Dec '17

I just got to know that there is a card game (code quartett) that lets players find out what language is the best: http://codequartett.de/index-en.html :-)

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Announce: Haskell Platform 8.2.2
by Gershom B 14 Dec '17

14 Dec '17

On behalf of the Haskell Platform team, I'm happy to announce the release of Haskell Platform 8.2.2 Now available at https://www.haskell.org/platform/ This includes GHC 8.2.2, cabal-install 2.0.0.1, and stack 1.6.1, all with many bugfixes since the last platform release. A full list of contents is available at https://www.haskell.org/platform/contents.html Thanks to all the contributors to this release, thanks to all the package and tool maintainers and authors, and a big thanks to the GHC team for all their hard work. There are currently no 32 bit Windows builds available. We expect to have those out in short order. A list of new GHC changes is available at: https://ghc.haskell.org/trac/ghc/blog/ghc-8.2.2-released A list of cabal changes is available at: https://hackage.haskell.org/package/cabal-install-2.0.0.1/changelog The cabal documentation page is at: https://www.haskell.org/cabal/users-guide/ A list of stack changes is at: https://docs.haskellstack.org/en/stable/ChangeLog/ The stack documentation page is at: https://docs.haskellstack.org/en/stable/README/ Happy Haskell Hacking all, Gershom

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25th Anniversary of GHC
by Henk-Jan van Tuyl 14 Dec '17

14 Dec '17

L.S., The eleventh of this month was the 25th anniversary of GHC: the first full release of GHC was announced at 1992-12-11; the version number was 0.10 and a Sun 4 workstation was needed to run GHC. The announcement can be read at: http://code.haskell.org/~dons/haskell-1990-2000/msg00960.html Regards, Henk-Jan van Tuyl -- Message from Stanford University: Folding@home What if you could share your unused computer power to help find a cure? In just 5 minutes you can join the world's biggest networked computer and get us closer sooner. Watch the video. http://foldingathome.stanford.edu/ -- http://members.chello.nl/hjgtuyl/tourdemonad.html Haskell programming --

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