Re: [Haskell-cafe] ghc 7.2.1 Generics problem
Hi. I do not know why, my ghc 7.2.1 does not seem to support DeriveRepresentable. I compiled the ghc 7.2.1 myself by ghc 7.0.4. All options default. $ ghc Types/TopTalkerRecord.hs Types/TopTalkerRecord.hs:2:14: Unsupported extension: DeriveRepresentable There's no extension of that name in 7.2.1. Do you mean DeriveGeneric? Cheers, Andres ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ghc 7.2.1 Generics problem
On 1 November 2011 16:07, Magicloud Magiclouds magicloud.magiclo...@gmail.com wrote: Hi, I do not know why, my ghc 7.2.1 does not seem to support DeriveRepresentable. I compiled the ghc 7.2.1 myself by ghc 7.0.4. All options default. $ ghc Types/TopTalkerRecord.hs Types/TopTalkerRecord.hs:2:14: Unsupported extension: DeriveRepresentable $ ghc --version The Glorious Glasgow Haskell Compilation System, version 7.2.1 All I can find about DeriveRepresentable is a patch submitted in April [1]. However, it seems [2] that it has been renamed to DeriveGenerics [1]: http://www.haskell.org/pipermail/cvs-ghc/2011-April/061666.html [2]: http://code.galois.com/cgi-bin/gitweb?p=type-naturals/base.git;a=commitdiff;h=792a8b86185d4cc74bb3d0d31b481ff0de4cf0d6 -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] blog software in Haskell?
On Mon, Oct 31, 2011 at 2:14 AM, Ketil Malde ke...@malde.org wrote: Hi, I just upgraded my server, and set up everything again. Except wordpress, as 1) I'm not too fond of its user interface, and 2) it's a big pile of PHP, difficult to keep updated, and basically a disaster waiting to happen (and in fact, it was hacked at one point). Before I enable it again, is there any alternatives I should consider? Preferably written in Haskell, of course, but other suggestions welcome as well. Not in Haskell, but it looks really promising (and it's driven by version control), I give you Octopress: http://octopress.org/ It's basically jekyll + github. Who knows, maybe you can use Hakyll instead of jekyll. Since you didn't ask for it, I'll include my $0.02 :) I don't worry about my blog being written in Haskell because I don't actually want to spend any time shaving yaks related to running my blog. I use blogspot. It's not great but I pay $0/year and someone else deals with the issues of keeping it secure, keeping it backed up, etc. If you find a cool solution, let us know. Jason ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Amazon AWS storage best to use with Haskell?
On Tue, Nov 1, 2011 at 5:03 AM, Ryan Newton rrnew...@gmail.com wrote: Any example code of using hscassandra package would really help! I'll ask my student. We may have some simple examples. Also, I have no idea as to their quality but I was pleasantly surprised to find three different amazon related packages on Hackage (simply by searching for the word Amazon in the package list). http://hackage.haskell.org/package/hS3 http://hackage.haskell.org/package/hSimpleDB http://hackage.haskell.org/package/aws It would be great to know if these work. Thinking about how to implement Data.Map on top of hscassandra or any other key-value storage ... For example creating new map with fromList will require to store *all* (key, value) list elements in external storage at once. How to deal with laziness in this case? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Amazon AWS storage best to use with Haskell?
We use all three (in various ways as they have arrived on the scene over time) in production systems. On 1 Nov 2011, at 02:03, Ryan Newton wrote: Any example code of using hscassandra package would really help! I'll ask my student. We may have some simple examples. Also, I have no idea as to their quality but I was pleasantly surprised to find three different amazon related packages on Hackage (simply by searching for the word Amazon in the package list). http://hackage.haskell.org/package/hS3 http://hackage.haskell.org/package/hSimpleDB http://hackage.haskell.org/package/aws It would be great to know if these work. -Ryan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Amazon AWS storage best to use with Haskell?
Word of caution Understand the semantics (and cost profile) of the AWS services first - you can't just open a HTTP connection and dribble data out over several days and hope for things to work. It is not a system that has that sort of laziness at its heart. AWS doesn't supply a traditional remote file store semantics - is queuing, simple database and object store have all been designed for large scale systems being offered as a service to a (potentially hostile) large set of users - you can see that in the way that things are designed. There are all sorts of (sensible from their point of view) performance related limits and retries. The challenge in designing nice clean layers on top of AWS is how/when to hide the transient/load related failures. Neil On 1 Nov 2011, at 06:21, dokondr wrote: On Tue, Nov 1, 2011 at 5:03 AM, Ryan Newton rrnew...@gmail.com wrote: Any example code of using hscassandra package would really help! I'll ask my student. We may have some simple examples. Also, I have no idea as to their quality but I was pleasantly surprised to find three different amazon related packages on Hackage (simply by searching for the word Amazon in the package list). http://hackage.haskell.org/package/hS3 http://hackage.haskell.org/package/hSimpleDB http://hackage.haskell.org/package/aws It would be great to know if these work. Thinking about how to implement Data.Map on top of hscassandra or any other key-value storage ... For example creating new map with fromList will require to store *all* (key, value) list elements in external storage at once. How to deal with laziness in this case? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Organizing big repository
Hi On Thu, Oct 27, 2011 at 08:02:58PM +0300, Konstantin Litvinenko wrote: Having program 'foo' depends on lib 'bar' I want to edit some files in 'bar' than build 'foo' and get 'bar' rebuilt and 'foo' rebuilt/relink. How can I do this? I use cabal-dev [1] along with the react tool [2]. The former does the dependencies-configure-build-install and the latter is a command-line wrapper around inotify. With this combo you can rebuild your project whenever any Haskell source file changes: react -p *.hs src/ cabal-dev install For my workflow, I have an additional wrapper script for cabal-dev that generates a quickfix file for Vim [3]. Then the workflow goes like: safe file - wait for build to complete (OSD/libnotify) - press F5 to jump to the location of the first compiler error or warning. Together with NERDTree [4] this is almost like an IDE ;-) Greetings Alex [1] https://github.com/creswick/cabal-dev [2] https://github.com/copton/react [3] http://vimdoc.sourceforge.net/htmldoc/quickfix.html [4] http://www.vim.org/scripts/script.php?script_id=1658 signature.asc Description: Digital signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] LDTA 2012: Call for Papers
LDTA 2012 Call for Papers 12th International Workshop on Language Descriptions, Tools, and Applications www.ldta.info Tallinn, Estonia March 31 April 1, 2012 an ETAPS workshop LDTA is an application and tool-oriented workshop focused on grammarware - software based on grammars in some form. Grammarware applications are typically language processing applications and traditional examples include parsers, program analyzers, optimizers and translators. A primary focus of LDTA is grammarware that is generated from high-level grammar-centric specifications and thus submissions on parser generation, attribute grammar systems, term/graph rewriting systems, and other grammar-related meta-programming tools, techniques, and formalisms are encouraged. LDTA is also a forum in which theory is put to the test, in many cases on real-world software engineering challenges. Thus, LDTA also solicits papers on the application of grammarware to areas including, but not limited to, the following: - program analysis, transformation, generation, and verification, - implementation of Domain-Specific Languages, - reverse engineering and re-engineering, - refactoring and other source-to-source transformations, - language definition and language prototyping, and - debugging, profiling, IDE support, and testing. Note that LDTA is a well-established workshop similar to other conferences on (programming) language engineering topics such as SLE and GPCE, but is solely focused on grammarware. Paper Submission LDTA solicits papers in the following categories. - research papers: original research results within the scope of LDTA with a clear motivation, description, analysis, and evaluation. - short research papers: new innovative ideas that have not been completely fleshed out. As a workshop, LDTA strongly encourages these types of submissions. - experience report papers: description of the use of a grammarware tool or technique to solve a non-trivial applied problem with an emphasis on the advantages and disadvantages of the chosen approach to the problem. - tool demo papers: discussion of a tool or technique that explains the contributions of the tool and what specifically will be demonstrated. Each submission must clearly state in which of these categories it falls, and must not be published or submitted elsewhere. Papers are to use the standard LaTeX article style and the authblk style for affiliations; a sample of which is provided at www.ldta.info. Research and experience papers are limited to 15 pages, tool demonstration papers are limited to 10 pages, and short papers are limited to 6 pages. The final version of the accepted papers will, pending approval, be published in the ACM Digital Library and will also be made available during the workshop. Please submit your abstract and paper using EasyChair at http://www.easychair.org/conferences/?conf=ldta2012. The authors of each submission are required to give a presentation at LDTA 2011 and tool demonstration paper presentations are intended to include a significant live, interactive demonstration. The authors of the best papers will be invited to write a journal version of their paper which will be separately reviewed and, assuming acceptance, be published in journal form. As in past years this will be done in a special issue of the journal Science of Computer Programming (Elsevier Science). Invited Speaker --- To be announced Important Dates --- Abstract submission: Nov. 28, 2011 Full paper submission: Dec. 5, 2011 Author notification: Jan. 20, 2012 Camera-ready papers: Feb. 05, 2012 LDTA Workshop: Mar. 31 - Apr. 1, 2012 LDTA Tool Challenge --- The 2011 Workshop pioneered the LDTA Tool Challenge where tool developers were invited to develop solutions to a range of language processing tasks over a simple but evolving set of imperative programming languages. We expect a challenge to form part of LDTA every two years. The 2012 workshop will feature presentations devoted to a de-brief of the 2011 challenge, based on the paper currently being prepared by challenge participants. Program Committee - Suzana Andova, Eindhoven University of Technology, The Netherlands (co-chair) Anya Helene Bagge, University of Bergen, Norway Kyung-Goo Doh, Hanyang University, Ansan, South Korea Jeff Gray, University of Alabama, USA Görel Hedin, Lund Institute of Technology, Sweden Zoltán Horváth, Eötvös Loránd University, Budapest, Hungary Zhenjiang Hu, National Institute of Informatics, Japan Roberto Ierusalimschy, Pontifícia Universidade Católica do Rio de Janeiro, Brazil Ivan Kurtev, University of Twente, The Netherlands Marjan Mernik, University of Maribor, Slovenia Nate Nystrom, University of Lugano, Switzerland João Saraiva,
Re: [Haskell-cafe] Amazon AWS storage best to use with Haskell?
On Tue, Nov 1, 2011 at 10:53 AM, Neil Davies semanticphilosop...@gmail.comwrote: Word of caution Understand the semantics (and cost profile) of the AWS services first - you can't just open a HTTP connection and dribble data out over several days and hope for things to work. It is not a system that has that sort of laziness at its heart. AWS doesn't supply a traditional remote file store semantics - is queuing, simple database and object store have all been designed for large scale systems being offered as a service to a (potentially hostile) large set of users - you can see that in the way that things are designed. There are all sorts of (sensible from their point of view) performance related limits and retries. The challenge in designing nice clean layers on top of AWS is how/when to hide the transient/load related failures. As a straw-man approach I would go first to NData.Map backed by Data.Map with addition of flush function to write Data.Map to external key-value store / NoSQL DB. Another requirement for NData.Map is concurrent consistency, so different clients could modify its state preserving happen-before relationship. For this I would add to NData.Map a reftresh function, that updates local copy from external key-value store. As for hSimpleDB package, it looks like it doesn't build on ghc7: http://hackage.haskell.org/package/hSimpleDB The hSimpleDB package Interface to Amazon's SimpleDB service. PropertiesVersions0.1 http://hackage.haskell.org/package/hSimpleDB-0.1, 0.2 http://hackage.haskell.org/package/hSimpleDB-0.2, *0.3*Dependencies base http://hackage.haskell.org/package/base-3.0.3.2 (≥3 ≤4), bytestring http://hackage.haskell.org/package/bytestring-0.9.2.0, Cryptohttp://hackage.haskell.org/package/Crypto-4.2.4, dataenc http://hackage.haskell.org/package/dataenc-0.14.0.2, HTTPhttp://hackage.haskell.org/package/HTTP-4000.1.2, hxt http://hackage.haskell.org/package/hxt-9.1.4, networkhttp://hackage.haskell.org/package/network-2.3.0.7, old-locale http://hackage.haskell.org/package/old-locale-1.0.0.3, old-time http://hackage.haskell.org/package/old-time-1.0.0.7, utf8-string http://hackage.haskell.org/package/utf8-string-0.3.7License BSD3AuthorDavid Himmelstrup 2009, Greg Heartsfield 2007MaintainerDavid Himmelstrup lem...@gmail.comCategoryDatabasehttp://hackage.haskell.org/packages/archive/pkg-list.html#cat:database, Web http://hackage.haskell.org/packages/archive/pkg-list.html#cat:web, Networkhttp://hackage.haskell.org/packages/archive/pkg-list.html#cat:networkUpload dateThu Sep 17 17:09:26 UTC 2009Uploaded byDavidHimmelstrupBuilt onghc-6.10, ghc-6.12Build failureghc-7.0 (loghttp://hackage.haskell.org/packages/archive/hSimpleDB/0.3/logs/failure/ghc-7.0 ) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hackage feature request: E-mail author when a package breaks
Yitzchak Gale g...@sefer.org writes: Gregory Crosswhite wrote: could [Hackage] have a feature where when a working package breaks with a new version of GHC the author is automatically e-mailed? This would be nice. However, there would have to be a way for it to be turned on and off by the author. (Spam is not nice.) This is where it stranded the last time, IIRC. That sentiment makes me a bit uneasy; so you are the official maintainer of a package on Hackage, but you do not want to hear about it when it fails to compile? To me, this raises the question whether you should take on the responsibility as maintainer at all. Ideally, I think Hackage should avoid being a dumping ground for non-working code, and I think the key to high quality software is having active maintainers for each package. If the author of a package is unwilling to accept failure reports, I suggest she could leave the Maintainer field blank, or fill it with a dummy value (e.g. unmaintained). -k -- If I haven't seen further, it is by standing in the footprints of giants ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ghc 7.2.1 Generics problem
On Tue, Nov 1, 2011 at 1:59 PM, Andres Löh andres.l...@googlemail.com wrote: Hi. I do not know why, my ghc 7.2.1 does not seem to support DeriveRepresentable. I compiled the ghc 7.2.1 myself by ghc 7.0.4. All options default. $ ghc Types/TopTalkerRecord.hs Types/TopTalkerRecord.hs:2:14: Unsupported extension: DeriveRepresentable There's no extension of that name in 7.2.1. Do you mean DeriveGeneric? Cheers, Andres I do not know. I will try that. I got the name from http://www.haskell.org/haskellwiki/Generics. -- 竹密岂妨流水过 山高哪阻野云飞 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ghc 7.2.1 Generics problem
Oh, right, I see that some things on that page need updating; I'll do so. Thanks, Pedro On Tue, Nov 1, 2011 at 09:33, Magicloud Magiclouds magicloud.magiclo...@gmail.com wrote: On Tue, Nov 1, 2011 at 1:59 PM, Andres Löh andres.l...@googlemail.com wrote: Hi. I do not know why, my ghc 7.2.1 does not seem to support DeriveRepresentable. I compiled the ghc 7.2.1 myself by ghc 7.0.4. All options default. $ ghc Types/TopTalkerRecord.hs Types/TopTalkerRecord.hs:2:14: Unsupported extension: DeriveRepresentable There's no extension of that name in 7.2.1. Do you mean DeriveGeneric? Cheers, Andres I do not know. I will try that. I got the name from http://www.haskell.org/haskellwiki/Generics. -- 竹密岂妨流水过 山高哪阻野云飞 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Problem with TemplateHaskell
Hi,
I have code as following, to make a toDocument function (using
Data.Bsin.=:) for a data structure.
bson :: DecsQ - DecsQ
bson decsq = do
decs - decsq
let datad = head decs
DataD _ _ _ cons _ = datad
to = mkName toDocument
from = mkName fromDocument
fund - mapM (\con -
case con of
RecC n types - do
let nvs = map (\(nv, _, _) -
nv
) types
funD to [clause [conP n $ map varP nvs]
(normalB $ listE $ map (\nv -
infixE (Just $
litE $ stringL $ show nv)
(varE $
mkName =:)
$ Just $
appE (varE $ mkName val)
$ varE nv
) nvs) []]
) cons
return (datad : fund)
Testing code is as:
data T = T { a :: Int
, b :: Char }
*TH runQ (bson [d|data T = T {a :: Int, b :: Char}|])
[DataD [] T_0 [] [RecC T_1 [(a_2,NotStrict,ConT
GHC.Types.Int),(b_3,NotStrict,ConT GHC.Types.Char)]] [],FunD
toDocument [Clause [ConP T_1 [VarP a_2,VarP b_3]] (NormalB (ListE
[InfixE (Just (LitE (StringL a_2))) (VarE =:) (Just (AppE (VarE val)
(VarE a_2))),InfixE (Just (LitE (StringL b_3))) (VarE =:) (Just
(AppE (VarE val) (VarE b_3)))])) []]]
So you see that, it changed the name from T/a/b to T_0/T_1/a_2/b_3.
Why is that? I did not have code to modify original data declaration.
--
竹密岂妨流水过
山高哪阻野云飞
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Re: [Haskell-cafe] Hackage feature request: E-mail author when a package breaks
On 1 November 2011 03:43, Alexander Kjeldaas alexander.kjeld...@gmail.com wrote: On 31 October 2011 17:22, Yitzchak Gale g...@sefer.org wrote: Gregory Crosswhite wrote: could [Hackage] have a feature where when a working package breaks with a new version of GHC the author is automatically e-mailed? This would be nice. However, there would have to be a way for it to be turned on and off by the author. (Spam is not nice.) How about sending an email to haskell-package-packate-name@haskell.org, and then people can join that mailing list if they are interested in that sort of stuff? Mailman is good at doing subscribe and unsubscribe. +1 I like this because it is opt-in for the maintainer, and also allows anyone else who is interested in the package to track it. Per-package RSS updates of build failures would also be useful. Conrad. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hackage feature request: E-mail author when a package breaks
On 1 November 2011 09:00, Ketil Malde ke...@malde.org wrote: This is where it stranded the last time, IIRC. That sentiment makes me a bit uneasy; so you are the official maintainer of a package on Hackage, but you do not want to hear about it when it fails to compile? Don't forget that some packages fail to compile on Hackage even though they work fine, because e.g. they depend on a third-party C library that is not installed, or depend on some other package that Hackage cannot build. Max ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hackage feature request: E-mail author when a package breaks
On Tue, Nov 1, 2011 at 09:43, Conrad Parker con...@metadecks.org wrote: On 1 November 2011 03:43, Alexander Kjeldaas alexander.kjeld...@gmail.com wrote: On 31 October 2011 17:22, Yitzchak Gale g...@sefer.org wrote: Gregory Crosswhite wrote: could [Hackage] have a feature where when a working package breaks with a new version of GHC the author is automatically e-mailed? This would be nice. However, there would have to be a way for it to be turned on and off by the author. (Spam is not nice.) How about sending an email to haskell-package-packate-name@haskell.org , and then people can join that mailing list if they are interested in that sort of stuff? Mailman is good at doing subscribe and unsubscribe. +1 I like this because it is opt-in for the maintainer, and also allows anyone else who is interested in the package to track it. Per-package RSS updates of build failures would also be useful. +1 Pedro Conrad. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hackage feature request: E-mail author when a package breaks
I wrote: This would be nice. However, there would have to be a way for it to be turned on and off by the author. (Spam is not nice.) Ketil Malde wrote: This is where it stranded the last time, IIRC. That sentiment makes me a bit uneasy; so you are the official maintainer of a package on Hackage, but you do not want to hear about it when it fails to compile? You are absolutely right about this. In fact, besides build failures, it probably would be a good idea for each maintainer to get, say, one automated email per month with a summary of all the packages that person is officially maintaining, even when there are no build failures. So I'm changing my vote to +1. But let's think about why the instinctive reaction is to be hesitant about this. First of all, an automated system like a build bot can go wrong. What guarantee is there that I won't be flooded with emails when that happens, if I can't shut it off myself? Second, let's say someone decides they don't want to be maintainer anymore. Are they married for life? There is currently no way to remove a package. I guess they would have to upload a new version with no maintainer. I am just a little worried that if uploading to Hackage requires agreeing to unlimited uncontrollable spamming by a bot, it may cause some good packages not to be uploaded by people who are hesitant to agree to that. Thanks, Yitz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hackage feature request: E-mail author when a package breaks
Max Bolingbroke batterseapo...@hotmail.com writes: This is where it stranded the last time, IIRC. That sentiment makes me a bit uneasy; so you are the official maintainer of a package on Hackage, but you do not want to hear about it when it fails to compile? Don't forget that some packages fail to compile on Hackage even though they work fine, because e.g. they depend on a third-party C library that is not installed, or depend on some other package that Hackage cannot build. True, in that case, it's harder to avoid getting one email every time you upload a new version. We should still strive to have stuff build on Hackage (e.g. installing C libs or fixing the ohter packages); if the build fails for one of these reasons, you never know if it fails for other reasons as well. So, I'd *love* to get an email when my packages fail to build, but I will accept that other people have a more sensitive relationship with their inbox. (I assume that the people who raise this objection - Max and Yitzchak - belong in this category? It's not entirely clear from your comments, and I do hope we're not avoiding useful functionality based on a purely *hypothetical* problem.) Conrad suggested creating a mailing list per package, another option could be to automatically post to a single maintainers list, highlighting the package (and preferably also maintainer) name in the Subject. A decent MUA could then up-score the more relevant messages. I'd really like to see Hackage move to a continuous integration type of system, where everything is automatically built and tests are run on every submission. If somebody works out the software infrastructure, I'll volunteer CPU cycles. Next hackathon? -k -- If I haven't seen further, it is by standing in the footprints of giants ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hackage feature request: E-mail author when a package breaks
On 1 November 2011 10:14, Ketil Malde ke...@malde.org wrote: So, I'd *love* to get an email when my packages fail to build, but I will accept that other people have a more sensitive relationship with their inbox. (I assume that the people who raise this objection - Max and Yitzchak - belong in this category? Don't get me wrong, I personally would like such a notification service. I'm just making a case for making it somehow opt-out, perhaps at a per-package granularity. I already use the packdeps service to find out when I should relax my package's version bounds. Packdeps delivers this information to me via RSS, which I think this is a great solution - I don't feel under any pressure to read it but the information is there if I want to have a look. So ideally what I would like from Hackage 2.0 is a RSS feed that includes build failure messages, packdeps-like information and perhaps other stuff -- notification of automated testsuite failures, milestones reached (Your edit-distance package has been downloaded 1000 times! Congratulations! :-)) and new reviews/comments on my packages (if Hackage ever gets that feature). Max ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hackage feature request: E-mail author when a package breaks
On Tue, Nov 1, 2011 at 06:14, Ketil Malde ke...@malde.org wrote: Max Bolingbroke batterseapo...@hotmail.com writes: This is where it stranded the last time, IIRC. That sentiment makes me a bit uneasy; so you are the official maintainer of a package on Hackage, but you do not want to hear about it when it fails to compile? Don't forget that some packages fail to compile on Hackage even though they work fine, because e.g. they depend on a third-party C library that is not installed, or depend on some other package that Hackage cannot build. True, in that case, it's harder to avoid getting one email every time you upload a new version. We should still strive to have stuff build on Hackage (e.g. installing C libs or fixing the ohter packages); if the build fails for one of these reasons, you never know if it fails for other reasons as well. Instead of immediately sending mail, a daily process should pull up the most recent status for each package, grouped by maintainer, and send all the failures in a single daily message. Perhaps monthly this could be expanded to also report for the successful packages. -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hackage feature request: E-mail author when a package breaks
Yitzchak Gale g...@sefer.org writes: I am just a little worried that if uploading to Hackage requires agreeing to unlimited uncontrollable spamming by a bot, The bot would, of course, be implemented in Haskell. Anybody who still worries about bugs, is free to implement a better one in Agda. :-) it may cause some good packages not to be uploaded by people who are hesitant to agree to that. One solution could be to have a Maintainer field contain a name, but no email address? So I could do: Maintainer: Ketil Malde ke...@malde.org -- send email to me or Maintainer: Ketil Malde -- don't send email, Google me if you are -- human and it's that important or even Maintainer: Ketil Malde ketil at malde dot org -- email me if you are human Or of course Maintainer: -- empty field means unmaintained, caveat emptor! Generalizing from my sample of one, I think most people would stick with the first option, but at least this policy would leave things open for those preferring alternatives. -k -- If I haven't seen further, it is by standing in the footprints of giants ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] arr considered harmful
2011/11/1 Ryan Ingram ryani.s...@gmail.com: For example, I would love to be able to use the arrow syntax to define objects of this type: data Circuit a b where Const :: Bool - Circuit () Bool Wire :: Circuit a a Delay :: Circuit a a And :: Circuit (Bool,Bool) Bool Or :: Circuit (Bool,Bool) Bool Not :: Circuit Bool Bool Then :: Circuit a b - Circuit b c - Circuit a c Pair :: Circuit a c - Circuit b d - Circuit (a,b) (c,d) First :: Circuit a b - Circuit (a,c) (b,c) Swap :: Circuit (a,b) (b,a) AssocL :: Circuit ((a,b),c) (a,(b,c)) AssocR :: Circuit (a,(b,c)) ((a,b),c) Loop :: Circuit (a,b) (a,c) - Circuit b c etc. Would you mind give me some examples on how you desribe real circuits with that abstraction and, especially, an Arrow instance (even imaginary one)? I am interested because I thought about an approach like that and found it not easy to use one. So I stuck with monadic netlists. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hackage feature request: E-mail author when a package breaks
On 1 November 2011 21:35, Ketil Malde ke...@malde.org wrote: or even Maintainer: Ketil Malde ketil at malde dot org -- email me if you are human Though unless the hackage email bot is smart enough, this will result in a lot of unsendable emails... -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hackage feature request: E-mail author when a package breaks
On 1 November 2011 21:35, Ketil Malde ke...@malde.org wrote: or even Maintainer: Ketil Malde ketil at malde dot org -- email me if you are human Though unless the hackage email bot is smart enough, this will result in a lot of unsendable emails... But the bot is not a human, so that's what ketil wanted after all. That said, I agree with Ketil that a maintainer should care about its package being broken, and the least would be to accept to be noticed. If the build process fails because of some reasons other than broken package (missing deps, wrong platform ...), then fix the build process. It should not be too hard to skip packages with unmet dependencies, or to get them installed on hackage servers, or even for the maintainer to bundle them within the package, like for example this package : http://hackage.haskell.org/package/yaml-0.4.1.1 Regarding unsolicited mail, when a maintainer fill its email adress in the project.cabal, and send it to hackage, his adress will appear in clear text on the hackage page and rapidly be scrapped, invariably leading to tons of spam (in the proper sens of SPAM). So I guess these maintainers have some way to filter their mail inbox anyway, and should be able, if they really want, to filter hackage build-failure email :) -- Paul ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hackage feature request: E-mail author when a package breaks
How about to a new optional Cabal field like mail-report? (don't bother about this name, I chose it randomly) If a build failure happens, or there is some relevant information about your package, Hackage will send a mail to the direction specified in that field. A field which content will NOT appear in the package page, so internet bots can't record so easily your mail direction to send you real spam. This is the reason because I write my direction in the name at domine dot com form (since a while ago), in spite of I would really like to receive mails about fails in those packages I maintain. Furthermore, since the field would be optional, you still can avoid to receive these mails. -- Daniel Díaz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hackage feature request: E-mail author when a package breaks
On 2011-11-01 12:59 +0100, Daniel Díaz Casanueva wrote: How about to a new optional Cabal field like mail-report? (don't bother about this name, I chose it randomly) If a build failure happens, or there is some relevant information about your package, Hackage will send a mail to the direction specified in that field. A field which content will NOT appear in the package page, so internet bots can't record so easily your mail direction to send you real spam. This is the reason because I write my direction in the name at domine dot com form (since a while ago), in spite of I would really like to receive mails about fails in those packages I maintain. Furthermore, since the field would be optional, you still can avoid to receive these mails. Doing anything like this in the .cabal file is a mistake, since there is no way to change it after uploading. If your mail address changes, or if you don't want to maintain a package any more, or if you simply change your mind about receiving status updates by email, then if this gets hardcoded in the .cabal file you have no recourse. Cheers, -- Nick Bowler, Elliptic Technologies (http://www.elliptictech.com/) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hackage feature request: E-mail author when a package breaks
On Tue, Nov 1, 2011 at 08:24, Nick Bowler nbow...@elliptictech.com wrote: On 2011-11-01 12:59 +0100, Daniel Díaz Casanueva wrote: How about to a new optional Cabal field like mail-report? (don't bother about this name, I chose it randomly) Doing anything like this in the .cabal file is a mistake, since there is no way to change it after uploading. If your mail address changes, or if you don't want to maintain a package any more, or if you simply change your mind about receiving status updates by email, then if this gets hardcoded in the .cabal file you have no recourse. Additionally, if you maintain a lot of packages, you don't really want to have to change it everywhere; this kind of setting is really per maintainer, not necessarily per package. (It is also arguably not of much interest to someone downloading the package. Users' questions and bug reports would generally be expected to go to the main contact address, not the buildbot automated report address.) -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hackage feature request: E-mail author when a package breaks
Then, the mailing list seems to be an option. But then I will receive mails for every package, and there is a lot of packages! Is not a lot of mails this? There is another work around? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hackage feature request: E-mail author when a package breaks
Daniel Díaz Casanueva writes: How about to a new optional Cabal field like mail-report? (don't bother about this name, I chose it randomly) If a build failure happens, or there is some relevant information about your package, Hackage will send a mail to the direction specified in that field. A field which content will NOT appear in the package page, so internet bots can't record so easily your mail direction to send you real spam. This is the reason because I write my direction in the name at domine dot com form (since a while ago), in spite of I would really like to receive mails about fails in those packages I maintain. A field in the .cabal file is just as available to bots as a field on the package page. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hackage feature request: E-mail author when a package breaks
On Nov 1, 2011 8:45 PM, Daniel Díaz Casanueva dhelta.d...@gmail.com wrote: Then, the mailing list seems to be an option. But then I will receive mails for every package, and there is a lot of packages! Is not a lot of mails this? There is another work around? Nobody would read every build error for thousands of packages; such a list is useless as-is, and requires any recipient to customize filters to be of any use. Per-package removes the need for filters: just subscribe to the packages you care about. An rss feed would be perfect: it's easy to ignore old reports. Also, implementing rss is just a matter of generating one more web page per package: no mailserver or list config required. Conrad. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] arr considered harmful
On Mon, Oct 31, 2011 at 5:33 PM, Ryan Ingram ryani.s...@gmail.com wrote: For example, I would love to be able to use the arrow syntax to define objects of this type: data Circuit a b where Const :: Bool - Circuit () Bool Wire :: Circuit a a Delay :: Circuit a a And :: Circuit (Bool,Bool) Bool Or :: Circuit (Bool,Bool) Bool Not :: Circuit Bool Bool Then :: Circuit a b - Circuit b c - Circuit a c Pair :: Circuit a c - Circuit b d - Circuit (a,b) (c,d) First :: Circuit a b - Circuit (a,c) (b,c) Swap :: Circuit (a,b) (b,a) AssocL :: Circuit ((a,b),c) (a,(b,c)) AssocR :: Circuit (a,(b,c)) ((a,b),c) Loop :: Circuit (a,b) (a,c) - Circuit b c etc. Then we can have code that examines this concrete data representation, converts it to VHDL, optimizes it, etc. As mentioned by others, Adam Megacz's generalized arrow (and its syntax) could accomplish this. But if all you want is VHDL and the like, consider Conal Elliott's work on Vertigo, Pan, Compiling Embedded Languages [1], and the similar work on the Haskell GPipe package. [1] http://conal.net/papers/jfp-saig/ Regards, Dave However, due to the presence of the opaque 'arr', there's no way to make this type an arrow without adding an 'escape hatch' Arr :: (a - b) - Circuit a b which breaks the abstraction: circuit is supposed to represent an actual boolean circuit; (Arr not) is not a valid circuit because we've lost the information about the existence of a 'Not' gate. The arrow syntax translation uses arr to do plumbing of variables. I think a promising project would be to figure out exactly what plumbing is needed, and add those functions to a sort of 'PrimitiveArrow' class. All of these plumbing functions are trivially implemented in terms of 'arr', when it exists, but if it doesn't, it should be possible to use the arrow syntax regardless. -- ryan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to implement digital filters using Arrows
On Mon, Oct 31, 2011 at 3:19 PM, John Lask jvl...@hotmail.com wrote: On 1/11/2011 1:35 AM, Captain Freako wrote: you need to study ArrowLoop and understand that. Thanks, John. I'm working my way through Hughes' suggested exercise in `Programming with Arrows', to wit: The reader who finds this argument difficult should work out the sequence of approximations in the call `runSF (loop (arr swap)) [1,2,3]' I think I understand how wrapping `cs' in `stream' provides the needed delay of evaluation, in order to avoid a self propagating `undefined'. However, it's not clear to me exactly what finally triggers the evaluation of c0. So, for instance, I think the `sequence of approximations' looks like this: 1) let (bs, cs) = unzip (map swap (zip as (_:_:_:...))) in bs : bs = [c0, (_:_:...)] cs = [1,2,3] At this point, `c0' is equal to 1, but what triggers the evaluation of c0? Is it simply the binding of it to `b0'? If so, then why aren't `c1' and `c2' also evaluated, which would yield undefined values? Thanks, -db ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] happstack file serving
Hello all, I want to have a web application using one 'index.html' file with ajax requests and a happstack web server which response to server requests. For that purpose I need to use some javascript libraries in my directory tree. I tried: main = simpleHTTP nullConf $ msum [ serveFile (asContentType text/html) index.html , serveFile (asContentType text/javascript) javascript/js.js ] The js.js - file will never be found in this way because after finding the index.html, the msum function stops (as described in the happstack crash course). If I change the order, I can see the source of js.js. I also tried leaving it. In every case, inside index.html a function defined in js.js cannot be called. (naturally, I sourced the file inside index.html) Is it possible to obtain the effect of beeing able to call a function in an external file without jmacro? I also tried: main = simpleHTTP nullConf $ msum [ dir ok $ ok jeah! , serveFile (asContentType text/html) index.html Couldn't match expected type `[Char]' with actual type `Response' Expected type: ServerPartT IO [Char] Actual type: ServerPartT IO Response In the return type of a call of `serveFile' In the expression: serveFile (asContentType text/html) index.html The webserver should take requests, and if there is none (no dir, personal convention), it should provide index.html. The error is because msum needs the same input types. Is it possible to transform one of these types to the other? It seems that my approach to the problem is not the right one, the one the authors thought about while programming. I wanted to have a clear seperation from logic (haskell) and interface (javascript). Is it right that using a running haskell webserver with the web application 'in it' is in general a faster solution than using for example apache with the fcgi module? Which approach would you prefer to realize such an ajax application? Greets Gary ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] happstack file serving
Hi Gary, A convention I use in my top-level handler is: simpleHTTP nullConf $ msum [ dynamic content handler , serveDirectory DisableBrowsing [] static , 404 handler ] where 'serveDirectory' is a function that ships with happstack-server and serves up the contents of a directory which it is pointed at. I then keep all of my static CSS and Javascript files in the static directory. The second argument to 'serveDirectory' is used to specify the index-files to look for in a folder if the user browses to a static folder, so here you could specify index.html to have 'serveDirectory' look for files named index.html and serve them up when a top-level folder is requested. Antoine On Tue, Nov 1, 2011 at 9:48 AM, Gary Klindt gary.kli...@googlemail.com wrote: Hello all, I want to have a web application using one 'index.html' file with ajax requests and a happstack web server which response to server requests. For that purpose I need to use some javascript libraries in my directory tree. I tried: main = simpleHTTP nullConf $ msum [ serveFile (asContentType text/html) index.html , serveFile (asContentType text/javascript) javascript/js.js ] The js.js - file will never be found in this way because after finding the index.html, the msum function stops (as described in the happstack crash course). If I change the order, I can see the source of js.js. I also tried leaving it. In every case, inside index.html a function defined in js.js cannot be called. (naturally, I sourced the file inside index.html) Is it possible to obtain the effect of beeing able to call a function in an external file without jmacro? I also tried: main = simpleHTTP nullConf $ msum [ dir ok $ ok jeah! , serveFile (asContentType text/html) index.html Couldn't match expected type `[Char]' with actual type `Response' Expected type: ServerPartT IO [Char] Actual type: ServerPartT IO Response In the return type of a call of `serveFile' In the expression: serveFile (asContentType text/html) index.html The webserver should take requests, and if there is none (no dir, personal convention), it should provide index.html. The error is because msum needs the same input types. Is it possible to transform one of these types to the other? It seems that my approach to the problem is not the right one, the one the authors thought about while programming. I wanted to have a clear seperation from logic (haskell) and interface (javascript). Is it right that using a running haskell webserver with the web application 'in it' is in general a faster solution than using for example apache with the fcgi module? Which approach would you prefer to realize such an ajax application? Greets Gary ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] happstack file serving
Hey Antoine, thank you for answering. Your strategy is quite similar to the one I prefer. I misunderstood the behaviour of serveDirectory. The problem with external javascript files is solved. The other problem I had, was, that the argument 'msum' is a list, which has elements with the same type, so I needed a conversion from m [Char] to m Response. In Happstack.Server.Response there is a function, which actually does that: flatten: module Main where import Happstack.Server import Control.Monad main :: IO () main = simpleHTTP nullConf $ msum [ flatten $ dir ok $ ok jeahh! , serveDirectory DisableBrowsing [index.html] static ] Cheers On 11/01/2011 03:58 PM, Antoine Latter wrote: Hi Gary, A convention I use in my top-level handler is: simpleHTTP nullConf $ msum [dynamic content handler , serveDirectory DisableBrowsing [] static ,404 handler ] where 'serveDirectory' is a function that ships with happstack-server and serves up the contents of a directory which it is pointed at. I then keep all of my static CSS and Javascript files in the static directory. The second argument to 'serveDirectory' is used to specify the index-files to look for in a folder if the user browses to a static folder, so here you could specify index.html to have 'serveDirectory' look for files named index.html and serve them up when a top-level folder is requested. Antoine On Tue, Nov 1, 2011 at 9:48 AM, Gary Klindtgary.kli...@googlemail.com wrote: Hello all, I want to have a web application using one 'index.html' file with ajax requests and a happstack web server which response to server requests. For that purpose I need to use some javascript libraries in my directory tree. I tried: main = simpleHTTP nullConf $ msum [ serveFile (asContentType text/html) index.html , serveFile (asContentType text/javascript) javascript/js.js ] The js.js - file will never be found in this way because after finding the index.html, the msum function stops (as described in the happstack crash course). If I change the order, I can see the source of js.js. I also tried leaving it. In every case, inside index.html a function defined in js.js cannot be called. (naturally, I sourced the file inside index.html) Is it possible to obtain the effect of beeing able to call a function in an external file without jmacro? I also tried: main = simpleHTTP nullConf $ msum [ dir ok $ ok jeah! , serveFile (asContentType text/html) index.html Couldn't match expected type `[Char]' with actual type `Response' Expected type: ServerPartT IO [Char] Actual type: ServerPartT IO Response In the return type of a call of `serveFile' In the expression: serveFile (asContentType text/html) index.html The webserver should take requests, and if there is none (no dir, personal convention), it should provide index.html. The error is because msum needs the same input types. Is it possible to transform one of these types to the other? It seems that my approach to the problem is not the right one, the one the authors thought about while programming. I wanted to have a clear seperation from logic (haskell) and interface (javascript). Is it right that using a running haskell webserver with the web application 'in it' is in general a faster solution than using for example apache with the fcgi module? Which approach would you prefer to realize such an ajax application? Greets Gary ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] HDBC SQLite error
Hi all,
I have recently switched one of my web applications to SQLite via HDBC. I use
it to store some user credentials and data. Initially it seemed to work fine,
until I tried logging in from two different browsers. That's when I got the
following error when trying to log in:
SqlError {seState = , seNativeError = 5, seErrorMsg = step: database is
locked}
My application only uses two functions (query and query', see [1]) directly,
and the authentication code[2] uses HDBC directly. I'm not sure why I'm getting
this error, because as far as I can see, I'm not keeping any transactions open
longer than I have to in the auth code. Does anyone have an idea what might be
wrong and how to fix it?
Cheers,
Jurriën
[1]
https://github.com/norm2782/snaplet-hdbc/blob/master/src/Snap/Snaplet/Hdbc.hs#L155
[2]
https://github.com/norm2782/snaplet-hdbc/blob/master/src/Snap/Snaplet/Auth/Backends/Hdbc.hs
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[Haskell-cafe] happstack file serving
Including list. -- Forwarded message -- From: Antoine Latter aslat...@gmail.com Date: Tue, Nov 1, 2011 at 11:33 AM Subject: Re: [Haskell-cafe] happstack file serving To: Gary Klindt gary.kli...@googlemail.com On Tue, Nov 1, 2011 at 11:24 AM, Gary Klindt gary.kli...@googlemail.com wrote: Hey Antoine, thank you for answering. Your strategy is quite similar to the one I prefer. I misunderstood the behaviour of serveDirectory. The problem with external javascript files is solved. The other problem I had, was, that the argument 'msum' is a list, which has elements with the same type, so I needed a conversion from m [Char] to m Response. In Happstack.Server.Response there is a function, which actually does that: flatten: module Main where import Happstack.Server import Control.Monad main :: IO () main = simpleHTTP nullConf $ msum [ flatten $ dir ok $ ok jeahh! , serveDirectory DisableBrowsing [index.html] static ] I would likely write that particular example: dir ok $ ok $ toResponse jeahh! I find it convenient to convert to a 'Response' as close to the 'bottom' of the stack as possible. Antoine ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hackage feature request: E-mail author when a package breaks
On Tue, Nov 1, 2011 at 2:45 AM, Max Bolingbroke batterseapo...@hotmail.com wrote: On 1 November 2011 09:00, Ketil Malde ke...@malde.org wrote: This is where it stranded the last time, IIRC. That sentiment makes me a bit uneasy; so you are the official maintainer of a package on Hackage, but you do not want to hear about it when it fails to compile? Don't forget that some packages fail to compile on Hackage even though they work fine, because e.g. they depend on a third-party C library that is not installed, or depend on some other package that Hackage cannot build. Exactly. Building on hackage only means that it builds on hackage. It doesn't actually mean the code works or fails to build on the actual machines people use. If we had a community run build farm with appropriate sandboxing and people could test their builds there that would be amazing, but that's not the same as checking the build on the hackage machine. Jason ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] HDBC SQLite error
01.11.2011 20:30, Jurriën Stutterheim пишет:
Hi all,
I have recently switched one of my web applications to SQLite via HDBC. I use
it to store some user credentials and data. Initially it seemed to work fine,
until I tried logging in from two different browsers. That's when I got the
following error when trying to log in:
SqlError {seState = , seNativeError = 5, seErrorMsg = step: database is
locked}
My application only uses two functions (query and query', see [1]) directly,
and the authentication code[2] uses HDBC directly. I'm not sure why I'm getting
this error, because as far as I can see, I'm not keeping any transactions open
longer than I have to in the auth code. Does anyone have an idea what might be
wrong and how to fix it?
Cheers,
This is a problem of hdbc-sqlite package, author think, than it can't work correctly without open
transaction, so just commit after open database or modify hdbc-sqlite like this:
--- a/Database/HDBC/Sqlite3/Connection.hs
+++ b/Database/HDBC/Sqlite3/Connection.hs
@@ -75,7 +75,7 @@ genericConnect strAsCStrFunc fp =
mkConn :: FilePath - Sqlite3 - IO Impl.Connection
mkConn fp obj =
do children - newMVar []
- begin_transaction obj children
+-- begin_transaction obj children
ver - (sqlite3_libversion = peekCString)
return $ Impl.Connection {
Impl.disconnect = fdisconnect obj children,
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Re: [Haskell-cafe] Hackage feature request: E-mail author when a package breaks
Ross A field in the .cabal file is just as available to bots as Ross a field on the package page. Yes, absolutly. There are at least one easy solution for this problem : having a server-side user model that is related to packages, or to packages versions, indicating wich user is the maintainer of which package. User would be able to provide its mail address, as well as some preferencies. I think it is planned on hackage 2.0 already. A .cabal based solution would need hackage to use asymetric encryption and to provide a public key that maintainer would use to encode its email address. But I'm not sure its worth the trouble. -- Paul ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to implement digital filters using Arrows
Hi John, I'm trying to use the GHCI debugger on this code: 20 instance ArrowLoop SF where 21 loop (SF f) = SF $ \as - 22 let (bs, cs) = unzip (f (zip as (stream cs))) in bs 23 where stream ~(x:xs) = x : stream xs 24 25 swap :: (a,b) - (b,a) 26 swap (x,y) = (y,x) in order to watch the recursion of the `loop' function unfold. However, when I single step through the code, I never stop on line 22 (where I could, presumably, peek in at `bs' and `cs', in order to see them develop): *SF :break swap Breakpoint 1 activated at SF.hs:26:1-18 *SF runSF (loop (arr swap)) [1,2,3] Stopped at SF.hs:26:1-18 _result :: (b, a) = _ [SF.hs:26:1-18] *SF :step Stopped at SF.hs:26:14-18 _result :: (b, a) = _ x :: a = _ y :: b = _ [SF.hs:26:14-18] *SF : [1Stopped at SF.hs:23:34-42 _result :: [a] = _ xs :: [a] = _ [SF.hs:23:34-42] *SF : Stopped at SF.hs:23:13-42 _result :: [a] = _ [SF.hs:23:13-42] *SF : Stopped at SF.hs:23:30-42 _result :: [a] = _ x :: a = _ xs :: [a] = _ [SF.hs:23:30-42] *SF : (Pattern repeats.) Do you have any advice? Thanks, -db On Mon, Oct 31, 2011 at 3:19 PM, John Lask jvl...@hotmail.com wrote: On 1/11/2011 1:35 AM, Captain Freako wrote: you need to study ArrowLoop and understand that. In the code ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] blog software in Haskell?
Did someone mention hakyll already ? For the record, this is a nice recent blog built with it: http://www.skybluetrades.net/posts/2011/10/21/hakyll-setup.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] arr considered harmful
On Tue, Nov 1, 2011 at 3:36 AM, Serguey Zefirov sergu...@gmail.com wrote: 2011/11/1 Ryan Ingram ryani.s...@gmail.com: Would you mind give me some examples on how you desribe real circuits with that abstraction and, especially, an Arrow instance (even imaginary one)? Sure, here's a simple SR latch: nor :: Circuit (Bool,Bool) Bool nor = Or `Then` Not rs :: Circuit (Bool,Bool) (Bool,Bool) rs = proc (r,s) - do rec q - nor - (r, q') q' - nor - (s, q) id - (q,q') instance Category Circuit where id = Wire (.) = flip Then instance GArrow Circuit where ga_first = First -- Circuit a b - Circuit (a,c) (b,c) ga_second = Second -- Circuit a b - Circuit(c,a) (c,b) ga_cancelr = Cancel -- Circuit (a,()) a ga_cancell = Swap `Then` Cancel -- Circuit ((),a) a ga_uncancelr = Uncancel -- Circuit a (a, ()) ga_uncancell = Uncancel `Then` Swap -- Circuit a ((),a) ga_assoc = AssocL -- Circuit ((a,b),c)) (a,(b,c)) ga_unassoc = AssocR -- Circuit (a,(b,c)) ((a,b),c) instance GArrowDrop Circuit where ga_drop = Ground -- Circuit a () instance GArrowCopy Circuit where ga_copy = Split -- Circuit a (a,a) instance GArrowSwap Circuit where ga_swap = Swap -- Circuit (a,b) (b,a) instance GArrowLoop Circuit where ga_loop = Loop -- Circuit (a,c) (b,c) - Circuit a b which would turn into something like rs = -- (r,s) Loop ( -- Input plumbing -- ((r,s),(q_in,q'_in)) AssocL `Then` -- (r, (s, (q_in,q'_in)) Second ( -- (s, (q_in,q'_in)) Second swap `Then` -- (s, (q'_in,q_in)) AssocR `Then` First Swap `Then` AssocL -- (q'_in, (s,q_in)) ) `Then` -- (r, (q'_in, (s,q_in))) AssocR `Then` -- ((r,q'_in), (s,q_in)) -- Computation! First (Or `Then` Not) `Then` -- from nor -- (q, (s,q_in)) Second (Or `Then` Not) `Then` -- from nor -- (q, q') -- Output plumbing Split -- ((q,q'), (q,q')) ) `Then` -- (q,q') Wire -- from id I am interested because I thought about an approach like that and found it not easy to use one. So I stuck with monadic netlists. When I did some circuit generation for the ICFP contest last year, I also went with monadic netlists. But I had problems coming up with compile-time-enforcable guarantees like 'this wire is only used once' And really, this description is for more than circuit generation; it applies to any sort of computation that you might want to create with arrows. I was looking at arrowized FRP earlier this year and was frustrated by how impossible it was to optimize the resulting dataflow networks. I was continually plagued by the appearance of 'arr' in my networks, in situations where I didn't think it belonged, and with no good way to see what that 'arr' was actually doing. -- ryan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] arr considered harmful
On Mon, Oct 31, 2011 at 6:52 PM, Paterson, Ross r.pater...@city.ac.ukwrote: If you require the circuit to be parametric in the value types, you can limit the types of function you can pass to arr to simple plumbing. See the netlist example at the end of my Fun of Programming slides ( http://www.soi.city.ac.uk/~ross/papers/fop.html). That's a neat trick, Ross! It seems really similar to using parametricity to recover the insides of lambdas in PHOAS metaprogramming: -- HOAS expression language data Expr (v :: * - *) a where Ap :: Expr v (a - b) - Expr v a - Expr v b Var :: v a - Expr v a Lam :: (v a - Expr v b) - Expr v (a - b) -- some expressions that are paremetric in the variable type ex_id :: Expr v (a - a) ex_id = Lam $ \x - Var x ex_const :: Expr v (a - b - a) ex_const = Lam $ \x - Lam $ \y - Var x -- a print function that relies on parametricity to expose the insides of the functions inside Lam printExpr :: (forall v. Expr v a) - String printExpr e = pe_helper vars 0 e where vars = map (:[]) ['a' .. 'z'] ++ map (\n - t ++ show n) [1..] prec_lam = 1 prec_ap = 2 newtype VarName a = VarName String pe_helper :: [String] - Expr VarName a - Int - ShowS pe_helper fv prec (Var (VarName s)) = showString s pe_helper fv prec (Ap x y) = showParen (prec prec_ap) (pe_helper fv prec_ap x . showString . pe_helper fv (prec_ap+1) y) pe_helper (v:fv) prec (Lam k) = showParen (prec prec_lam) (showString \ . showString v . showString - . pe_helper fv prec_lam e) where e = k (VarName v) -- some test cases test1 = printExpr ex_const -- \a - \b - a test2 = printExpr (ex_id `Ap` ex_const) -- (\a - a) (\a - \b - a) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Persistent Concurrent Data Structures
Hi, Please comment on the idea and advise on steps to implement it. Real world applications need persistent data, that can be accessed and modified concurrently by several clients, in a way that preserves happen-before relationship. Idea: Design and implement Persistent Concurrent Data Types in Haskell. These data types should mirror existing Data.List , Data.Map and similar types but provide persistency and support consistent concurrent access and modification (or simply - concurrency). Persistency and concurrency should be configurable through these type interfaces. Configuration should include: 1) Media to persist data, such as file, DBMS, external key-value store (for example Amazon SimpleDB, CouchDB, MongoDB, Redis, etc) 2) Caching policy - when (on what events) and how much data to read/write from/to persistent media. Media reads / writes can be done asynchronously in separate threads. 3) Concurrency configuration: optimistic or pessimistic data locking. One may ask why encapsulate persistency and concurrency in the data type instead of using native storage API, such as for example key-value / row-column API that NoSQL databases provide? The answer is simple: APIs that your code use greatly influence the code itself. Using low-level storage API directly in your code results in bloated obscure code, or you need to encapsulate this low-level API in clear and powerful abstractions. So why not to do this encapsulation once and for all for such powerful types as Data.Map, for example, and forget all Cassandra and SimpleDB low-level access method details? When the right time comes and you will need to move your application to the next new shiny_super_cloud, you will just write the implementation of NData.Map backed by Data.Map in terms of low-level API of this super-cloud. (Side note: I really need such a NData.Map type. I was requested to move my code that heavily uses Data.Map and simple text file persistence into Amazon AWS cloud. Looking at SimpleDB API, I realized that I will have to rewrite 90% of code. This rewrite will greatly bloat my code and will make it very unreadable. In case I had NData.Map I would just switch implementation from 'file' to SimpleDB persistency inside my NData.Map type.) Implementation: To start playing with this idea, NData.Map persisted in a regular file will do, no concurrency yet. Next step - NData.Map persisted in SimpleDB or Cassandra or Redis, with concurrent access supported. So it looks like NData.Map should be a monad ... Any ideas on implementation and similar work? Thanks! Dmitri --- http://sites.google.com/site/dokondr/welcome ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to implement digital filters using Arrows
Try swap p = (snd p, fst p) or, equivalently swap ~(x,y) = (y,x) -- ryan On Tue, Nov 1, 2011 at 1:30 PM, Captain Freako capn.fre...@gmail.comwrote: Hi John, I'm trying to use the GHCI debugger on this code: 20 instance ArrowLoop SF where 21 loop (SF f) = SF $ \as - 22 let (bs, cs) = unzip (f (zip as (stream cs))) in bs 23 where stream ~(x:xs) = x : stream xs 24 25 swap :: (a,b) - (b,a) 26 swap (x,y) = (y,x) in order to watch the recursion of the `loop' function unfold. However, when I single step through the code, I never stop on line 22 (where I could, presumably, peek in at `bs' and `cs', in order to see them develop): *SF :break swap Breakpoint 1 activated at SF.hs:26:1-18 *SF runSF (loop (arr swap)) [1,2,3] Stopped at SF.hs:26:1-18 _result :: (b, a) = _ [SF.hs:26:1-18] *SF :step Stopped at SF.hs:26:14-18 _result :: (b, a) = _ x :: a = _ y :: b = _ [SF.hs:26:14-18] *SF : [1Stopped at SF.hs:23:34-42 _result :: [a] = _ xs :: [a] = _ [SF.hs:23:34-42] *SF : Stopped at SF.hs:23:13-42 _result :: [a] = _ [SF.hs:23:13-42] *SF : Stopped at SF.hs:23:30-42 _result :: [a] = _ x :: a = _ xs :: [a] = _ [SF.hs:23:30-42] *SF : (Pattern repeats.) Do you have any advice? Thanks, -db On Mon, Oct 31, 2011 at 3:19 PM, John Lask jvl...@hotmail.com wrote: On 1/11/2011 1:35 AM, Captain Freako wrote: you need to study ArrowLoop and understand that. In the code ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to implement digital filters using Arrows
Never mind, I misread the code, 'zip' and the lazy definition of stream should add the necessary laziness. -- ryan On Tue, Nov 1, 2011 at 3:36 PM, Ryan Ingram ryani.s...@gmail.com wrote: Try swap p = (snd p, fst p) or, equivalently swap ~(x,y) = (y,x) -- ryan On Tue, Nov 1, 2011 at 1:30 PM, Captain Freako capn.fre...@gmail.comwrote: Hi John, I'm trying to use the GHCI debugger on this code: 20 instance ArrowLoop SF where 21 loop (SF f) = SF $ \as - 22 let (bs, cs) = unzip (f (zip as (stream cs))) in bs 23 where stream ~(x:xs) = x : stream xs 24 25 swap :: (a,b) - (b,a) 26 swap (x,y) = (y,x) in order to watch the recursion of the `loop' function unfold. However, when I single step through the code, I never stop on line 22 (where I could, presumably, peek in at `bs' and `cs', in order to see them develop): *SF :break swap Breakpoint 1 activated at SF.hs:26:1-18 *SF runSF (loop (arr swap)) [1,2,3] Stopped at SF.hs:26:1-18 _result :: (b, a) = _ [SF.hs:26:1-18] *SF :step Stopped at SF.hs:26:14-18 _result :: (b, a) = _ x :: a = _ y :: b = _ [SF.hs:26:14-18] *SF : [1Stopped at SF.hs:23:34-42 _result :: [a] = _ xs :: [a] = _ [SF.hs:23:34-42] *SF : Stopped at SF.hs:23:13-42 _result :: [a] = _ [SF.hs:23:13-42] *SF : Stopped at SF.hs:23:30-42 _result :: [a] = _ x :: a = _ xs :: [a] = _ [SF.hs:23:30-42] *SF : (Pattern repeats.) Do you have any advice? Thanks, -db On Mon, Oct 31, 2011 at 3:19 PM, John Lask jvl...@hotmail.com wrote: On 1/11/2011 1:35 AM, Captain Freako wrote: you need to study ArrowLoop and understand that. In the code ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to implement digital filters using Arrows
I can't comment on using ghci debugger to observe evaluation. I have in the past used hood (http://hackage.haskell.org/package/hood) and found it both convenient and useful when trying to observe evaluation order. On 2/11/2011 7:00 AM, Captain Freako wrote: Hi John, I'm trying to use the GHCI debugger on this code: 20 instance ArrowLoop SF where 21 loop (SF f) = SF $ \as - 22 let (bs, cs) = unzip (f (zip as (stream cs))) in bs 23 where stream ~(x:xs) = x : stream xs 24 25 swap :: (a,b) - (b,a) 26 swap (x,y) = (y,x) in order to watch the recursion of the `loop' function unfold. However, when I single step through the code, I never stop on line 22 (where I could, presumably, peek in at `bs' and `cs', in order to see them develop): ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to implement digital filters using Arrows
First, let's lay out our definitions: unzip [] = ([], []) unzip ((x,y):xys) = (x:xs, y:ys) where (xs,ys) = unzip xys zip [] _ = [] zip _ [] = [] zip (x:xs) (y:ys) = (x,y) : zip xs ys map _ [] = [] map f (x:xs) = f x : map f xs stream ~(a:as) = a : stream as -- equivalently stream xs = head xs : stream (tail xs) Now we want to evaluate this: runSF (loop (arr swap)) [1,2,3] Lets simplify some of the insides a bit: arr swap = SF $ map swap = SF $ map (\(x,y)-(y,x)) loop (arr swap) = SF $ \as - let (bs,cs) = unzip (map swap (zip as (stream cs))) in bs runSF (loop (arr swap)) [1,2,3] = runSF (SF $ ...) [1,2,3] = (\as - let (bs,cs) = unzip (map swap (zip as (stream cs))) in bs) [1,2,3] Here is our heap at this point; we are trying to evaluate bs: p = unzip (map swap (zip as (stream cs))) as = [1,2,3] bs = fst p cs = snd p snd p forces p, unzip forces its argument, map forces its second argument, and zip forces both its arguments. So now we have: p = unzip retmap retmap = map swap retzip retzip = zip as retstream retstream = stream cs as = [1,2,3] bs = fst p cs = snd p Evaluating further: retstream = head cs : retstream2 retstream2 = stream (tail cs) retzip = (1, head cs) : retzip2 retzip2 = zip [2,3] (stream (tail cs)) retmap = (head cs, 1) : retmap2 retmap2 = map swap retzip2 p = (head cs : xs1, 1 : ys1) (xs1,ys1) = unzip retmap2 bs = head cs : xs1 cs = 1 : ys1 bs = 1 : xs1 and we can now return the first cons cell of bs. This repeats until we get [1,2,3] back out; note that each value goes through both sides of the swap before coming out the 'front' again. -- ryan On Tue, Nov 1, 2011 at 1:30 PM, Captain Freako capn.fre...@gmail.comwrote: Hi John, I'm trying to use the GHCI debugger on this code: 20 instance ArrowLoop SF where 21 loop (SF f) = SF $ \as - 22 let (bs, cs) = unzip (f (zip as (stream cs))) in bs 23 where stream ~(x:xs) = x : stream xs 24 25 swap :: (a,b) - (b,a) 26 swap (x,y) = (y,x) in order to watch the recursion of the `loop' function unfold. However, when I single step through the code, I never stop on line 22 (where I could, presumably, peek in at `bs' and `cs', in order to see them develop): *SF :break swap Breakpoint 1 activated at SF.hs:26:1-18 *SF runSF (loop (arr swap)) [1,2,3] Stopped at SF.hs:26:1-18 _result :: (b, a) = _ [SF.hs:26:1-18] *SF :step Stopped at SF.hs:26:14-18 _result :: (b, a) = _ x :: a = _ y :: b = _ [SF.hs:26:14-18] *SF : [1Stopped at SF.hs:23:34-42 _result :: [a] = _ xs :: [a] = _ [SF.hs:23:34-42] *SF : Stopped at SF.hs:23:13-42 _result :: [a] = _ [SF.hs:23:13-42] *SF : Stopped at SF.hs:23:30-42 _result :: [a] = _ x :: a = _ xs :: [a] = _ [SF.hs:23:30-42] *SF : (Pattern repeats.) Do you have any advice? Thanks, -db On Mon, Oct 31, 2011 at 3:19 PM, John Lask jvl...@hotmail.com wrote: On 1/11/2011 1:35 AM, Captain Freako wrote: you need to study ArrowLoop and understand that. In the code ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Persistent Concurrent Data Structures
If I have a list [a], and I want to make that persistence, then I have to have some way to serialize values of type 'a'. If I then modify my type, then the serialized structure will be out of sync with the new version of the type -- so I will need some sort of migration feature. safecopy addresses both the issues of serializing the data and migrating it when the datastructure changes: http://hackage.haskell.org/package/safecopy You should definitely consider using that. When it comes to concurrency.. my big question is how do you plan to deal with transaction boundaries / atomicness. For example, if each function (like, filter, map, etc) is atomic. That doesn't mean you have something atomic when you do: filter pred = map f l something could sneak in between the 'map' and the 'filter'. An obviously solution would be to do something like: transaction $ filter pred = map f l Which could mean that the datastore would have to be locked until that entire operation is done? Also.. what does it mean to have a 'persistent list'. In that example, is map destructive? Does it modify the list ? Or does it produce a new list? A somewhat related system is, of course, acid-state (formerly happstack-state). The solution there is pretty simple, and somewhat more flexible. To write code you basically just use the State monad. You can store just about any types you want and use just about any functions you want. To get and update the state you just use get/set. simpleTransaction do l - get let l' = filter pred (map f l) put l' return l' That updates the list and returns the modified list as well. To make that into a transaction we use a bit of template-haskell to mark it is a transaction $(makeAcidic ''MyDatabase ['simpleTransaction]) The appeal of this solution is that you are not limited to just a List or Map or whatever types people have bother to import into the system. If you decide you want to use Data.Tree you need only do: $(deriveSafeCopy 1 'base ''Tree) And now you can use it persistently and concurrently as well. You do not have to recreate every function in Data.Tree. Still, I can see the appeal of just being able to import NData.Map, deriving a serialize instance for your data, and start writing very normal looking code. There is something very nice about just being able to use a function like 'transaction' to mark the boundaries of a transaction rather than having to give the transaction and name and call some template haskell function. Using acid-state, it would be very easy to implement a persistent version of Data.Map where each function is atomic. However, there is currently no way to group multiple events into a single transaction. Though I think I can imagine how to add such a feature. Of course, the idea of having a big lock blocking everything is not very appealing. But as an experimental fork it could be interesting.. But, first I would like to hear more about how you imagined transactions would actually work in the first place.. The big issue I see is that transactions can be a real performance problem. If I write code for a Map-like persistent structure: transaction $ do v - lookup key pmap v' - doSomethingExpensive v insert v pmap That is going to really lock things up, since nothing else can happen while that transaction is running? Still, it sounds interesting.. just not easy :) I would definitely encourage you to consider safecopy at the very least. It is completely independent of acid-state. It is simply a fast versioned data serialization library. - jeremy On Tue, Nov 1, 2011 at 5:31 PM, dokondr doko...@gmail.com wrote: Hi, Please comment on the idea and advise on steps to implement it. Real world applications need persistent data, that can be accessed and modified concurrently by several clients, in a way that preserves happen-before relationship. Idea: Design and implement Persistent Concurrent Data Types in Haskell. These data types should mirror existing Data.List , Data.Map and similar types but provide persistency and support consistent concurrent access and modification (or simply - concurrency). Persistency and concurrency should be configurable through these type interfaces. Configuration should include: 1) Media to persist data, such as file, DBMS, external key-value store (for example Amazon SimpleDB, CouchDB, MongoDB, Redis, etc) 2) Caching policy - when (on what events) and how much data to read/write from/to persistent media. Media reads / writes can be done asynchronously in separate threads. 3) Concurrency configuration: optimistic or pessimistic data locking. One may ask why encapsulate persistency and concurrency in the data type instead of using native storage API, such as for example key-value / row-column API that NoSQL databases provide? The answer is simple: APIs that your code use greatly influence the code itself. Using low-level storage API
Re: [Haskell-cafe] Persistent Concurrent Data Structures
So I guess you're talking about imperative mutated data structures (which is btw the opposite of what persistence usually means in haskell). It seems like switching data storage would be as easy or hard as you've been able to abstract it, e.g. if you can put everything through 'get' and 'put' then it's easy, just change those two functions. But if you can't, then maybe it's because you're relying on features specific to some data store, and then some generic interface won't help you. So I guess I'm skeptical that generic auto-serialized types would be able to help. Why not write to an interface that expresses exactly what your app requires instead? Anyway, unless I'm misunderstanding your question, this just an imperative style design thing, and no different in haskell than python or java, except of course haskell will encourage you to not write in this style in the first place :) But maybe you can factor out the IO by e.g. 'data - readData; writeData (diff data (transform data))' where data is a plain persistent (in the haskell sense) data structure. That way interaction with the storage is in one place. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Persistent Concurrent Data Structures
Several of the Haskell web server frameworks (Yesod, HAppS, etc.) come with persistence support. I believe you're taking the wrong approach here, with respect to `modified concurrently` and the like. What does it mean for a Data.List to be 'modified concurrently'? If you need concurrency, first find a good abstraction for a concurrent collection - one that already covers such details as ordered or collaborative updates. The result might not look much like Data.List. On Tue, Nov 1, 2011 at 3:31 PM, dokondr doko...@gmail.com wrote: Hi, Please comment on the idea and advise on steps to implement it. Real world applications need persistent data, that can be accessed and modified concurrently by several clients, in a way that preserves happen-before relationship. Idea: Design and implement Persistent Concurrent Data Types in Haskell. These data types should mirror existing Data.List , Data.Map and similar types but provide persistency and support consistent concurrent access and modification (or simply - concurrency). Persistency and concurrency should be configurable through these type interfaces. Configuration should include: 1) Media to persist data, such as file, DBMS, external key-value store (for example Amazon SimpleDB, CouchDB, MongoDB, Redis, etc) 2) Caching policy - when (on what events) and how much data to read/write from/to persistent media. Media reads / writes can be done asynchronously in separate threads. 3) Concurrency configuration: optimistic or pessimistic data locking. One may ask why encapsulate persistency and concurrency in the data type instead of using native storage API, such as for example key-value / row-column API that NoSQL databases provide? The answer is simple: APIs that your code use greatly influence the code itself. Using low-level storage API directly in your code results in bloated obscure code, or you need to encapsulate this low-level API in clear and powerful abstractions. So why not to do this encapsulation once and for all for such powerful types as Data.Map, for example, and forget all Cassandra and SimpleDB low-level access method details? When the right time comes and you will need to move your application to the next new shiny_super_cloud, you will just write the implementation of NData.Map backed by Data.Map in terms of low-level API of this super-cloud. (Side note: I really need such a NData.Map type. I was requested to move my code that heavily uses Data.Map and simple text file persistence into Amazon AWS cloud. Looking at SimpleDB API, I realized that I will have to rewrite 90% of code. This rewrite will greatly bloat my code and will make it very unreadable. In case I had NData.Map I would just switch implementation from 'file' to SimpleDB persistency inside my NData.Map type.) Implementation: To start playing with this idea, NData.Map persisted in a regular file will do, no concurrency yet. Next step - NData.Map persisted in SimpleDB or Cassandra or Redis, with concurrent access supported. So it looks like NData.Map should be a monad ... Any ideas on implementation and similar work? Thanks! Dmitri --- http://sites.google.com/site/dokondr/welcome ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Persistent Concurrent Data Structures
hi Dimitri Take a look at TCache. It is a transactional cache with configurable persistence. http://hackage.haskell.org/package/TCache It defines persistent TVars (DBRef`s) with similar primitives. Persistence can be defined by the user for each datatype by an instance declaration. There is a default persistence in files. Cache size, synchronization with the database and caching policies are also defined by the user. Using this package is easy to define persistent concurrent data structures. An example are the persistent Queues defined in the package Workflow: http://hackage.haskell.org/package/Workflow 2011/11/1 dokondr doko...@gmail.com: Hi, Please comment on the idea and advise on steps to implement it. Real world applications need persistent data, that can be accessed and modified concurrently by several clients, in a way that preserves happen-before relationship. Idea: Design and implement Persistent Concurrent Data Types in Haskell. These data types should mirror existing Data.List , Data.Map and similar types but provide persistency and support consistent concurrent access and modification (or simply - concurrency). Persistency and concurrency should be configurable through these type interfaces. Configuration should include: 1) Media to persist data, such as file, DBMS, external key-value store (for example Amazon SimpleDB, CouchDB, MongoDB, Redis, etc) 2) Caching policy - when (on what events) and how much data to read/write from/to persistent media. Media reads / writes can be done asynchronously in separate threads. 3) Concurrency configuration: optimistic or pessimistic data locking. One may ask why encapsulate persistency and concurrency in the data type instead of using native storage API, such as for example key-value / row-column API that NoSQL databases provide? The answer is simple: APIs that your code use greatly influence the code itself. Using low-level storage API directly in your code results in bloated obscure code, or you need to encapsulate this low-level API in clear and powerful abstractions. So why not to do this encapsulation once and for all for such powerful types as Data.Map, for example, and forget all Cassandra and SimpleDB low-level access method details? When the right time comes and you will need to move your application to the next new shiny_super_cloud, you will just write the implementation of NData.Map backed by Data.Map in terms of low-level API of this super-cloud. (Side note: I really need such a NData.Map type. I was requested to move my code that heavily uses Data.Map and simple text file persistence into Amazon AWS cloud. Looking at SimpleDB API, I realized that I will have to rewrite 90% of code. This rewrite will greatly bloat my code and will make it very unreadable. In case I had NData.Map I would just switch implementation from 'file' to SimpleDB persistency inside my NData.Map type.) Implementation: To start playing with this idea, NData.Map persisted in a regular file will do, no concurrency yet. Next step - NData.Map persisted in SimpleDB or Cassandra or Redis, with concurrent access supported. So it looks like NData.Map should be a monad ... Any ideas on implementation and similar work? Thanks! Dmitri --- http://sites.google.com/site/dokondr/welcome ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Persistent Concurrent Data Structures
Thanks everybody for advice! I'll try to clarify what I mean by persistence and concurrent access that preserves happens-before relationship. 1) Persistence - imagine Haskell run-time executing in infinite physical memory. My idea is to implement really huge, almost infinite memory in the cloud of one or another type. Nothing more nothing less, nothing imperative, exactly the same environment that GHC runtime works today, but extended to huge virtual memory in the cloud. 2) Concurrent access that preserves happens-before relationship. Before talking about transactions, I would use locking data structures in two different ways: - Optimistic lock - everybody can read and write / delete simultaneously, system ensures only happens-before relationship. In other words Best Effort Modification - you can try to modify data, but there is no guarantee that your modification will work. - Pessimistic lock - when you get lock - structure is all yours as long as you held the lock - everybody else can only read, happens-before relationship is ensured at all times. About happens-before relationship: http://en.wikipedia.org/wiki/Happened-before ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Persistent Concurrent Data Structures
On Wed, Nov 2, 2011 at 3:12 AM, dokondr doko...@gmail.com wrote: Thanks everybody for advice! I'll try to clarify what I mean by persistence and concurrent access that preserves happens-before relationship. 1) Persistence - imagine Haskell run-time executing in infinite physical memory. My idea is to implement really huge, almost infinite memory in the cloud of one or another type. Nothing more nothing less, nothing imperative, exactly the same environment that GHC runtime works today, but extended to huge virtual memory in the cloud. I am afraid I am confused everybody, didn't mean it, sorry. I understand that infinite physical memory is not quite the same that implementing NData.* on top of some cloud framework. Yet NData.* may be the first step in this direction. Infinite memory will require support in Haskell run-time, run-time distributed across many physical instances. Yet, it looks like physical memory will eventually will be very huge virtual memory persistent in the cloud for some period of time. IMHO this will simplify programming model considerably. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hackage feature request: E-mail author when a package breaks
The perl community has something really interesting for quite long time: http://wiki.cpantesters.org/wiki/HomePage Or more specifically: http://matrix.cpantesters.org/?dist=DBI The idea is simple: there are many different platforms that would be to expensive for one to support. So they ask the community for help, and then distribute the load amongst the perl community. It servers for testing modules and also perl distribution itself. It may work better for this purpose than relying on a single centralized platform, namely Hackage. ~dsouza At Mon, 31 Oct 2011 17:08:22 +1000, Gregory Crosswhite wrote: [1 multipart/alternative (7bit)] [1.1 text/plain; us-ascii (quoted-printable)] Hey everyone, I have uploaded a number of small packages to Hackage that I no longer actively use so that I don't find out immediately when a new version of GHC has broken them. Since Hackage is going to the trouble of finding out when a package no longer builds anyway, could it have a feature where when a working package breaks with a new version of GHC the author is automatically e-mailed? This would make me (and probably others) a lot more likely to notice and proactively fix broken packages. (Heck, I wouldn't even necessarily mind being nagged about it from time to time. :-) ) Cheers, Greg [1.2 text/html; us-ascii (7bit)] [2 text/plain; us-ascii (7bit)] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
