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ANN: network-2.6.3.3
by evan＠evan-borden.com 10 Jan '18

10 Jan '18

Announcing network-2.6.3.3 * Add a function to show the defaultHints without reading their undefined fields [#291](https://github.com/haskell/network/pull/292) * Improve exception error messages for getAddrInfo and getNameInfo [#289](https://github.com/haskell/network/pull/289) * Deprecating SockAddrCan. As always a huge thank you to the network contributors.

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Re: [Haskell-cafe] Getting some funny brackets in Haddock docs
by Johannes Waldmann 10 Jan '18

10 Jan '18

OverloadedLists solves this, in a way? Prelude> :set -XOverloadedLists Prelude> import qualified Data.Map.Strict as M Prelude M> M.size [(2,3)] 1 because of the IsList instance https://hackage.haskell.org/package/containers-0.5.10.2/docs/src/Data.Map.I… Do we want to use this in code examples in the docs? Equivalently, is it recommended to use this notation in actual code? The problem I see is that this (and similar) extensions will be active for all literals in a module - while we only want it for literals of some specific type. I know this is handled in the parser, and we don't know the types at this point. - J

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Getting some funny brackets in Haddock docs
by David Feuer 10 Jan '18

10 Jan '18

The containers Haddock documentation currently represents sequences, sets, and maps via the relevant `fromList` function. For example, Data.Map gives the example findWithDefault 'x' 1 (fromList [(5,'a'), (3,'b')]) == 'x' I find these `fromList` calls exceedingly distracting, and I think they obscure the key ideas. Of course, I *could* just specify at the top that the documentation assumes OverloadedLists, but I think that's likely to be somewhat confusing, especially to beginners. My preference would really be to represent these data structures using funny brackets of some sort. Perhaps ⟦7,34,12⟧ for a sequence, ⦃40,3⦄ for a set, and ⟪(12,"alpha"), (14,"bravo")⟫ for a map. But there are three problems: 1. How can I insert the brackets conveniently? I definitely don't want to fill the module with Unicode. My preference would be to use \{ and \} or \[ and \] and have them get replaced by the left and right brackets appropriate to the module in question. But I don't actually know how to do that. 2. Funny brackets could presumably cause trouble for people who don't have appropriate fonts available. How could I mitigate this? 3. This whole idea could cause trouble for people who want to copy and paste examples from the documentation. Are people likely to want to do that? If so, how might I mitigate that problem? Are there tricks I can play to make copy/paste turn a funny left bracket into `fromList [` and a funny right bracket into `]`, and also not break things for non-HTML backends? Thanks, David

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Re: [Haskell-cafe] Package takeover: re2
by Andrey Sverdlichenko 09 Jan '18

09 Jan '18

Thanks! On Mon, Jan 8, 2018 at 11:20 PM John Millikin <john(a)john-millikin.com> wrote: > Just added you to the maintainer's list. Sorry for the delayed response, > I've been away from reliable internet for a few weeks. > > When you upload the next version, please also update the contact info to > yours. I'll say on my site that you're the new maintainer. > > On Mon, Jan 8, 2018 at 9:54 AM, Andrey Sverdlichenko <blaze(a)ruddy.ru> > wrote: > >> I'd like to take over maintenance of the package re2. It is built >> against old version of re2 library, never updated after 2014 and listed as >> "deprecated" on the author's website. I rather update this one than add >> another package for the same bindings. >> >> I tried to contact owner a week ago, but to no avail. My hackage username >> is blaze. >> > >

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looking for deep learning explanation a la Lämmel's map-reduce paper
by Johannes Waldmann 08 Jan '18

08 Jan '18

Dear Cafe, I like this paper (R. Lämmel in SCP 2008) very much https://userpages.uni-koblenz.de/~laemmel/MapReduce/ both for contents and for style - and I wonder if there's something similar ("Haskell for design recovery", "rigorous description", "executable specification") on deep learning. Mainly for understanding/teaching without all the hype. (But of course, an accelerate-* implementation would be nice.) Yes I know that hyperbole *is* the main thing in this area. Happy New Year - J.

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Package takeover: re2
by Andrey Sverdlichenko 08 Jan '18

08 Jan '18

I'd like to take over maintenance of the package re2. It is built against old version of re2 library, never updated after 2014 and listed as "deprecated" on the author's website. I rather update this one than add another package for the same bindings. I tried to contact owner a week ago, but to no avail. My hackage username is blaze.

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Syntax highlight for numeric literals
by Takenobu Tani 07 Jan '18

07 Jan '18

Dear cafe, I wrote and pushed a bit about the syntax highlights of numeric literals for `BinaryLiterals`, `HexFloatLiterals` and `NumericUnderscores` extensions on editors. https://github.com/takenobu-hs/haskell-numeric-highlight I'm glad if this helps you. Regards, Takenobu

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PSA: `cabal update` command needs manual unsticking
by Gershom B 05 Jan '18

05 Jan '18

Dear Haskellers, A recent update to hackage, which fixed up the 01-index.tar.gz file, revealed a bug in existing versions of cabal-install, when index files are cleaned up. This bug means that the `cabal update` command, which updates the hackage index file, will fail silently and leave the old file in place. It is easy to get things working again, but it requires manual intervention. Here is the most straightforward way to get things working again: On gnu/linux or mac: rm ~/.cabal/packages/hackage.haskell.org/01-index.* On windows: remove the same files, but from %appdata%\cabal\packages\hackage.haskell.org rerun `cabal update` to fetch a new 01-index. Apologies all for the inconvenience and any confusion this may have caused. There is a PR to fix this behavior in the works, but since the problem is on the client side, the fix will only improve the situations for new versions of `cabal`. Happy New Years to all, and cheers to a very functional 2018, Gershom p.s.: since the problem comes in unpacking the 01-index.tar.gz into the 01-index.tar, you can also just untar that file in place manually, or force cabal into doing the same by running `touch ~/.cabal/packages/hackage.haskell.org/01-index.tar`

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How does the RTS pin ByteArray# objects during FFI calls?
by Reiner Pope 03 Jan '18

03 Jan '18

Hi Haskell-Cafe, I understand from https://mail.haskell.org/pipermail/haskell-cafe/2014-June/114763.html that it is safe to pass ByteArray# objects to FFI calls, using the UnliftedFFITypes language extension. As I understand it, the implicit guarantee is that the RTS will pin the ByteArray#'s address in memory for the duration of the FFI call -- even if the ByteArray# wasn't allocated pinned. I'm curious: how does the RTS achieve this "retroactive" pinning? The documentation at https://ghc.haskell.org/trac/ghc/wiki/Commentary/Rts/Storage/GC/Pinned suggests that *all* ByteArrays are allocated pinned to account for the possibility that they will in future be passed to the FFI. Is this really the case? This seems like it forces an unreasonably slow allocator on small (say, ~10-byte) ByteArray allocations where the GC's usual bump-pointer allocator might otherwise be preferable. Regards, Reiner

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ANN: capataz-0.0.0.1 - An OTP-like supervisor library for Haskell
by Román González 02 Jan '18

02 Jan '18

Hello, I'm glad to share the release of a new library for supervising Haskell threads inspired in OTP/Akka called capataz * Hackage: http://hackage.haskell.org/package/capataz * Github: https://github.com/roman/Haskell-capataz * Documentation/Tutorials: https://romanandreg.gitbooks.io/capataz/content/ capataz enhances the reliability of your concurrent applications by offering supervision of threads that run in your application. Advantages over standard libraries: * Links related long-living processes together under a common capataz supervisor, with restart/shutdown order. * Set restart strategies (Permanent, Transient, Temporary) on `IO` sub-routines on a granular level * Set restart strategies on a pool of long-living worker threads (AllForOne, OneForOne) * Complete telemetry on your supervised threads lifecycle (start, error, restarts, shutdown) * Drop-in replacement of forkIO invocations Please feel free to reach out if you are curious and have any ideas/improvements. Cheers. Roman.-

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