July 2015 - Haskell-Cafe

wiki username request: Eric
by Eric O'Connor 16 Jul '15

16 Jul '15

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ANN: repa-linear-algebra = HMatrix + REPA
by Marcin Mrotek 16 Jul '15

16 Jul '15

Hello, Given that apparently HMatrix uses the same underlying representation as F arrays in REPA, I've wrote some utilities to convert to and from these types, and ported HMatrix functions to work with REPA arrays. http://hackage.haskell.org/package/repa-linear-algebra-0.0.0.0 All functions return F arrays. In general, unqualified functions take F array(s), and the postfixed functions take D array(s), allocating them before feeding to HMatrix: * -S functions allocate sequentially (using computeS) * -SIO functions allocate sequentially inside the IO monad (using computeIntoS) * -P functions allocate in parallel (using computeP) * -PIO functions allocate in parallel inside the IO monad (using computeIntoP) Writing all that boilerplate was quite mind-numbing, so sorry if there are any mistakes or inconsistencies (I wish this was a way to automate it, but it's not always straightforwards, for example I've decided that arguments that will be often supplied unchanged to multiple calls (like the kernel of convolution) shouldn't be changed to take D arrays in the preallocating functions). Please have in mind that the module is HIGHLY experimental, as it does just plain rude casts under the hood. Before you use it for anything serious first check if it works as you expect it to. Best regards, Marcin Mrotek

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Re: [Haskell-cafe] Haskell & Java/Scala interoperbility?
by Vasili I. Galchin 15 Jul '15

15 Jul '15

I am looking to suppprt Haskell (OCaml ??) for apache.spark.org. Currently there is support for programming language "R" which has functional features (not as rich as Haskell, OCaml, et. al.) and does lazy evaluation. I am going to drop back and look at the R->Scala/Java implementation BUT I will also read your link. Any more.suggestions are gratefully welcome. Kind thx, Vasili On Tuesday, July 14, 2015, Jason Dagit <dagitj(a)gmail.com> wrote: > Did you look at java bridge? > * https://hackage.haskell.org/package/java-bridge > > Perhaps counter-intuitively, you're probably better off defining a > protocol and using that for interop. Something like zeromq could simplify > the communication. > > The main hassle with a full interop is the difference between the notions > of types in the two languages. For instance, subtyping on the Java side > doesn't really map well to the Haskell side. > > I would say that it forces attempts at a general interop to go with a > least common denominator approach. In the extreme, this degenerates back to > having the code on each side pretend like it's talking to C. > > Whereas designing a message protocol for your task allows you to > incorporate domain specific knowledge and thus avoid a general solution and > also leave out things you will never use. > > On Tue, Jul 14, 2015 at 7:14 PM, Vasili I. Galchin <vigalchin(a)gmail.com > <javascript:_e(%7B%7D,'cvml','vigalchin(a)gmail.com');>> wrote: > >> Hello, >> >> I have been looking at Hackage for a package/library that >> supports Haskell interoperability with Java/Scala. Didn't see any such >> support. If true, is there any project in the works? >> >> Thanks, >> >> Vasili >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> <javascript:_e(%7B%7D,'cvml','Haskell-Cafe(a)haskell.org');> >> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe >> > >

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Haskell & Java/Scala interoperbility?
by Vasili I. Galchin 15 Jul '15

15 Jul '15

Hello, I have been looking at Hackage for a package/library that supports Haskell interoperability with Java/Scala. Didn't see any such support. If true, is there any project in the works? Thanks, Vasili

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ANN: hledger 0.26
by Simon Michael 14 Jul '15

14 Jul '15

I'm pleased to announce hledger and hledger-web 0.26! This release restores non-regular-expression account aliases as the default, and brings miscellaneous bugfixes and cleanups and some performance work. Also the website and documentation have been improved, and now include many more examples. Full release notes: http://hledger.org/release-notes#hledger-0.26 . Release contributors: Simon Michael, Imuli, Carlos Lopez-Camey, Kyle Marek-Spartz, Rick Lupton, Simon Hengel. About: hledger (http://hledger.org) is a command-line tool and haskell library for tracking financial transactions, which are stored in a human-readable plain text format. It can also read CSV or timelog files, and output CSV. It provides useful reports, and can also help you record new transactions interactively. Add-on commands include hledger-web (a web interface), hledger-irr (for calculating internal rate of return) and hledger-interest (for generating interest transactions). hledger is inspired by and largely compatible with Ledger, and can be used with some Ledger files. Installation: $ cabal update [$ cabal sandbox init] $ cabal install hledger[-web]-0.26 or: install stack (https://github.com/commercialhaskell/stack/wiki/Downloads <https://github.com/commercialhaskell/stack/wiki/Downloads>) $ stack --resolver nightly-2015-07-13 install hledger [hledger-web] or: $ git clone https://github.com/simonmichael/hledger.git $ cd hledger $ git checkout hledger-0.26 $ stack install or see http://hledger.org/download for more options. Best! -Simon

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In " returnIO x = IO $ \ s -> (# s, x #)" what are the # symbols?
by Jeffrey Brown 14 Jul '15

14 Jul '15

That appears here: http://hackage.haskell.org/package/base-4.8.0.0/docs/src/GHC-Base.html#line…

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On Windows after I install the new cabal-install then when I do a cabal update it says there is a new ...
by KC 13 Jul '15

13 Jul '15

On Windows after I install the new cabal-install then when I do a cabal update it says there is a new cabal-install available. Yet cabal-install installed without any errors. Why do I get this message? -- -- Sent from an expensive device which will be obsolete in a few months! :D Casey

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Best way to return Bool based on a successful pattern match?
by Nikolay Amiantov 13 Jul '15

13 Jul '15

Hi Cafe, Every now and then I'm in a need to check if a value satisfies pattern with a Bool result. So far I know several ways to do this: 1. Use lens: `has _Left` 2. Make a function: `isLeft (Left _) = True; isLeft _ = False` 3. (When you need a lambda) Use LambdaCase: `\case Left _ -> True; _ -> False` Usually I go for (1) because I use lens extensively anyway, but for one-time usage all the extra machinery seems too much. I don't like (2) when I don't have a library defining that for me, and also (3) -- they seem inelegant. Is there any syntactic trick that I'm missing that makes it look nicer? -- Nikolay.

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To all users of FGL
by Ivan Lazar Miljenovic 13 Jul '15

13 Jul '15

As you may now, for the past few months I've been (finally!) cleaning up FGL, adding tests, etc. One of the issues that has arisen with this is that the behaviour of the delLEdge [1] function is not well specified when dealing with multiple edges. Specifically, the documentation states that the purpose is to "Remove *an* LEdge from the Graph." (emphasis added)... but the behaviour when dealing with multiple edges is to remove *all* such edges from the graph. The current version on GitHub is to instead just delete a single such labelled edge, with a new function "delAllLEdge" that replicates the current behaviour. Before releasing this change, however, I wanted to make sure that I wouldn't break people's code if they rely upon this functionality; I did try and search through GitHub to see who - if anyone - is using this function, but primarily found various copies of fgl embedded into other people's repositories. As such, please check your code and let me know if this change in behaviour might affect you (if this is the case, I might let delLEdge keep the current behaviour and have a new function delete just one edge). [1]: http://hackage.haskell.org/package/fgl-5.5.1.0/docs/Data-Graph-Inductive-Gr… -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com http://IvanMiljenovic.wordpress.com

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Re: [Haskell-cafe] Announcing libravatar @ hackage
by fr33domlover 12 Jul '15

12 Jul '15

Forgot the link, just in case: http://hackage.haskell.org/package/libravatar On 2015-07-12 fr33domlover <fr33domlover(a)riseup.net> wrote: > Hello! > > Libravatar - http://libravatar.org - is a free-as-in-freedom and decentralized > avatar (profile image delivery service, a replacement of the centralized and > proprietary grava7ar. > > There has been a Haskell library for grava7ar for some time, but not for > Libravatar. I just finished writing one, and did a bit of testing which had > good results. > > More testing and feedback etc. very very welcome! I also enourage you all to > *integrate libravatar into your desktop/web applications and websites*! > Support openness, decentralization and freedom by using Libravatar. > > > > --- > fr33domlover <http://www.rel4tion.org/people/fr33domlover> > GPG key ID: 63E5E57D (size: 4096) > GPG key fingerprint: 6FEE C222 7323 EF85 A49D 5487 5252 C5C8 63E5 E57D --- fr33domlover <http://www.rel4tion.org/people/fr33domlover> GPG key ID: 63E5E57D (size: 4096) GPG key fingerprint: 6FEE C222 7323 EF85 A49D 5487 5252 C5C8 63E5 E57D

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