[Haskell-cafe] REMINDER: Haskell Communities and Activities Report
Dear all, It is not yet too late to contribute to the 18th edition of HCAR. If you haven't already, please write an entry for your new project or update your old entry, and send to me this weekend or early next week. More information about format etc. can be found in the original call: http://www.haskell.org/pipermail/haskell/2010-April/022012.html I am looking forward to receiving your contributions, Janis (current editor) -- Jun.-Prof. Dr. Janis Voigtländer http://www.iai.uni-bonn.de/~jv/ mailto:j...@iai.uni-bonn.de ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] are forkIO threads event-driven?
Hello Aran, Friday, April 30, 2010, 2:26:20 AM, you wrote: In GHC, if a thread spawned by forkIO blocks on some network or disk IO, is the threading system smart enough not to wake the thread afaik, yes. it's controlled by special i/o thread that multiplexes all i/o done via stdlibs. but ghc i/o manager can't use epoll/kqueue so it's appropriate only for small (or medium?) servers read Writing High-Performance Server Applications in Haskell, Case Study: A Haskell Web Server http://www.haskell.org/~simonmar/papers/web-server.ps.gz -- Best regards, Bulatmailto:bulat.zigans...@gmail.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] are forkIO threads event-driven?
bulat.ziganshin: Hello Aran, Friday, April 30, 2010, 2:26:20 AM, you wrote: In GHC, if a thread spawned by forkIO blocks on some network or disk IO, is the threading system smart enough not to wake the thread afaik, yes. it's controlled by special i/o thread that multiplexes all i/o done via stdlibs. but ghc i/o manager can't use epoll/kqueue so it's appropriate only for small (or medium?) servers Look at the recent work on the event library and replacing the IO manager. http://www.serpentine.com/blog/2010/01/22/new-ghc-io-manager-first-benchmark-numbers/ There's much more background on the new code here, http://www.serpentine.com/blog/2009/12/17/making-ghcs-io-manager-more-scalable/ and some nice benchmarks http://blog.johantibell.com/2010/01/scalable-timeout-support-for-ghcs-io.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] maling-list manager in haskell?
Hi, I've just uploaded mhailist, a mailing list manager a friend and I started working on a while ago, to hackage [1]. It's very much experimental and an alpha release, but it does the job for some mailing lists we have. We're also looking for people who'd like to join us developing it; if you're interested then by all means let me know. Thanks, Lars [1] http://hackage.haskell.org/package/Mhailist ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Using the Clipboard under Windows
On Fri, 30 Apr 2010 08:21:11 +0300, Jason Dagit da...@codersbase.com wrote: As far as I can tell from google wxwidgets does have clipboard support. Perhaps wxHaskell can do it or needs to be extended? Jason I searched with Hayoo for clipboard wx and found Graphics.UI.WXCore.Controls.execClipBoardData [1]; following links, I found a set of clipboard functions [2]. Regards, Henk-Jan van Tuyl [1] http://hackage.haskell.org/packages/archive/wxcore/latest/doc/html/Graphics-UI-WXCore-Controls.html#v:execClipBoardData [2] http://hackage.haskell.org/packages/archive/wxcore/latest/doc/html/Graphics-UI-WXCore-WxcClassesAL.html#28 -- http://Van.Tuyl.eu/ http://members.chello.nl/hjgtuyl/tourdemonad.html -- ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Haskell XML Parsers
Dear all, I have been looking at using XML for a little program I have been writing. The file I am currently trying to load is about 9MB, and I have now tried to use HaXml and HST. Without any of my own code, just a simple call to the basic parsers, they both use huge amount of memory. HST is the worst and about 7GB and climbing. HaXml uses 1.3Gb. The code I am using is HST xml - readFile file_name_here;k-runX (parseXmlDocument True) xml;print k and for HaXml x-readFile file_name_here let (Document _ _ e _) = xmlParse t x let t = myFilter $ CElem e print $ length t I have seen on previous posts to the cafe that other people have run into this problem with HST. Is this a general problem with XML in Haskell (I know that XML parsing is a slow and bulky process but this seems excessive)? Is there a known solution? Does anyone have any advice? Cheers RS ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell XML Parsers
I have been looking at using XML for a little program I have been writing. The file I am currently trying to load is about 9MB, and I have now tried to use HaXml and HST. Without any of my own code, just a simple call to the basic parsers, they both use huge amount of memory. HST is the worst and about 7GB and climbing. HaXml uses 1.3Gb. Are you using Text.XML.HaXml.ParseLazy, or Text.XML.HaXml.Parse? The lazy version should show much better space usage, provided your subsequent usage of the document is roughly a single-pass traversal. Regards, Malcolm ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Using the Clipboard under Windows
Hello all, the application from which I wish to copy (text) data to the clipboard is not a GUI app, it's more of a simple test-script. So I'd like to do it without having to install wxHaskell. I guess I'll just have to bite my way through the Win32 API. Right now I'm dumping the text output to a file and copy paste from there. Günther Am 30.04.10 11:19, schrieb Henk-Jan van Tuyl: On Fri, 30 Apr 2010 08:21:11 +0300, Jason Dagit da...@codersbase.com wrote: As far as I can tell from google wxwidgets does have clipboard support. Perhaps wxHaskell can do it or needs to be extended? Jason I searched with Hayoo for clipboard wx and found Graphics.UI.WXCore.Controls.execClipBoardData [1]; following links, I found a set of clipboard functions [2]. Regards, Henk-Jan van Tuyl [1] http://hackage.haskell.org/packages/archive/wxcore/latest/doc/html/Graphics-UI-WXCore-Controls.html#v:execClipBoardData [2] http://hackage.haskell.org/packages/archive/wxcore/latest/doc/html/Graphics-UI-WXCore-WxcClassesAL.html#28 -- http://Van.Tuyl.eu/ http://members.chello.nl/hjgtuyl/tourdemonad.html -- ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to make way into a hadoop infrastructure
I think you'll want to look at the Hadoop Streaming or Hadoop Pipes API. Further down the line, I think somebody will want to implement a Haskell library to deal with the Avro serialization protocol when it becomes possible to write non-JVM mappers and reducers directly. This JIRA issue covers the RPC part of the Avro-Hadoop integration work: https://issues.apache.org/jira/browse/HADOOP-6659 Looks like folks have already implemented support for Thrift and Protocol Buffers, so implementing a library for Avro would likely be pretty similar. -md begin C K Kashyap quotation: Dear Haskellers, A big part of my new job requires tuning app's on Hadoop. I was wondering if there is a way to push some Haskell code in the mix. I did some googling on Hadoop/Haskell and came across Holumbus - but looks like that is parallel to Hadoop. I was thinking in the lines of doing a Haskell implementation that could run in a Hadoop cluster - has anyone tried anything like that? -- Regards, Kashyap ___ 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] Re: FRP for game programming / artifical life simulation
On Fri, Apr 30, 2010 at 3:37 AM, Daniel Fischer daniel.is.fisc...@web.de wrote: Am Donnerstag 29 April 2010 20:08:00 schrieb Ben: A technical question: it seems like the instance of ArrowLoop is too strict (this is something I've wondered about in Liu's paper too.) Shouldn't it be instance ArrowLoop SFAuto where loop (SFAuto s f) = SFAuto s f' where f' (b, s1) = let (~(c, d), s2) = f ((b, d), s1) in (c, s2) Let-bindings are already lazy, so the '~' makes no difference here. Apart from the readability, both are the same as where f' (b,s1) = let x = f ((b, snd $ fst x),s1) in (fst $ fst x, snd x) Ben's version is slightly lazier - even though the let binding is lazy, pattern matching is strict. so (let ((x,y).z) = (undefined, hello) in z) will exception out, but (let (~(x,y),z) = (undefined, hello) in z) will not. I don't know if you need that level of laziness, though. Antoine ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Downloading Haskell repos from GitHub
Along the lines of http://blog.patch-tag.com/2010/03/13/mirroring-patch-tag/ for downloading all patch-tag.com repositories, I've begun to wonder how to download all Github repositories since more and more people seem to be using it. Nothing in http://develop.github.com/ seems especially useful for grabbing the git:// URLs of all repos by language - just by user. The only real list of repos by language seems to be gotten at via http://github.com/languages/Haskell/updated or http://github.com/languages/Haskell/created . (You might think http://github.com/languages/Haskell would be good, but no, it's just a few random repos by interest and not a full listing.) I looked at the HTML, and it looks possible to use tagsoup to get all 98 pages and then parse the entries to get the HTTP URLs of the repos, and then turn *that* into git:// URLs suitable for shelling out to 'git clone', but I can't help but wonder if maybe there's a better approach someone more familiar with Github would know. -- gwern ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: FRP for game programming / artifical life simulation
Am Freitag 30 April 2010 17:23:19 schrieb Antoine Latter: On Fri, Apr 30, 2010 at 3:37 AM, Daniel Fischer daniel.is.fisc...@web.de wrote: Am Donnerstag 29 April 2010 20:08:00 schrieb Ben: A technical question: it seems like the instance of ArrowLoop is too strict (this is something I've wondered about in Liu's paper too.) Shouldn't it be instance ArrowLoop SFAuto where loop (SFAuto s f) = SFAuto s f' where f' (b, s1) = let (~(c, d), s2) = f ((b, d), s1) in (c, s2) Let-bindings are already lazy, so the '~' makes no difference here. Apart from the readability, both are the same as where f' (b,s1) = let x = f ((b, snd $ fst x),s1) in (fst $ fst x, snd x) Ben's version is slightly lazier - even though the let binding is lazy, pattern matching is strict. so (let ((x,y).z) = (undefined, hello) in z) will exception out, but (let (~(x,y),z) = (undefined, hello) in z) will not. I don't know if you need that level of laziness, though. Probably not. Although, you're right, if only s2 is ever looked at and not c, Ben's version can give a result where the library instance throws an exception. Was fooled by the use of c in the result. Antoine ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Downloading Haskell repos from GitHub
On Fri, Apr 30, 2010 at 5:38 PM, Gwern Branwen gwe...@gmail.com wrote: Nothing in http://develop.github.com/ seems especially useful for grabbing the git:// URLs of all repos by language - just by user. The only real list of repos by language seems to be gotten at via http://github.com/languages/Haskell/updated or http://github.com/languages/Haskell/created . (You might think http://github.com/languages/Haskell would be good, but no, it's just a few random repos by interest and not a full listing.) Github has a REST API for accessing data. Unfortunately it can't give you the wanted breakdown, but I would ask them for it. It is much simpler for you, and it does not put an extra strain on their servers due to the scraping. Usually, the github guys are helpful when you have a question. -- J. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Downloading Haskell repos from GitHub
On Fri, Apr 30, 2010 at 11:51 AM, Jesper Louis Andersen jesper.louis.ander...@gmail.com wrote: On Fri, Apr 30, 2010 at 5:38 PM, Gwern Branwen gwe...@gmail.com wrote: Nothing in http://develop.github.com/ seems especially useful for grabbing the git:// URLs of all repos by language - just by user. The only real list of repos by language seems to be gotten at via http://github.com/languages/Haskell/updated or http://github.com/languages/Haskell/created . (You might think http://github.com/languages/Haskell would be good, but no, it's just a few random repos by interest and not a full listing.) Github has a REST API for accessing data. Unfortunately it can't give you the wanted breakdown, but I would ask them for it. It is much simpler for you, You mean ask for a new feature? (Just a one-time list is no good since I intend to repeat it regularly to pick up new repos, just like with patch-tag.) and it does not put an extra strain on their servers due to the scraping. Well, it'd only be about 2000 HTTP hits. (98 + (20 * 98)). The downloading of the repos would probably reduce that demand to insignificance, especially the first time around when most of the repos would need to be downloaded. Usually, the github guys are helpful when you have a question. Any suggested method besides the obvious http://github.com/contact ? -- gwern ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Downloading Haskell repos from GitHub
On Fri, Apr 30, 2010 at 6:02 PM, Gwern Branwen gwe...@gmail.com wrote: Github has a REST API for accessing data. Unfortunately it can't give you the wanted breakdown, but I would ask them for it. It is much simpler for you, You mean ask for a new feature? (Just a one-time list is no good since I intend to repeat it regularly to pick up new repos, just like with patch-tag.) Yes. Any suggested method besides the obvious http://github.com/contact ? No. -- J. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANN: Combinatorrent v0.3.0
We are pleased to announce Combinatorrent v0.3.0 Combinatorrent is a bittorrent client, written in Haskell and with an emphasis on concurrency. This version has the following changes from v0.2.0: - Numerous space leak fixes. The client doesn't leak memory anymore for typical runs. - A number of performance optimizations. In particular the number of CPU seconds per downloaded megabyte went down considerably compared to earlier versions. - Lowered allocation rate of the client so the garbage collector has less work to do. - Support BEP 0027 implicitly. - Add support for compiling with GHC HEAD (6.13.mmdd series). - Change the parser in the incoming direction to attoparsec and use its incremental features to simplify the receiver loop. Outgoing direction still uses cereal. - Claim BEP 0006 support by implementing the Fast-extension. - Add (untested) BEP 0007 support: Handle IPv6 addresses as well as IPv4 addresses. - Fix a bug where interest updates were not considered correctly. Also lower the amount of interest communication to peers to save bandwidth. Looking ahead, the goal is to support at least the extended messaging protocol. The EMP is a dependency prerequisite for many of the other extensions, hence it is an important building block for further work. As always, the source code and issue tracker is at github: http://github.com/jlouis/combinatorrent -- J. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] 64-bit code on OSX?
Hey everyone, Just out of curiosity, does anyone know the story on what is holding up the ability of GHC to generate 64-bit code on OSX? Cheers, Greg ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] are forkIO threads event-driven?
Thanks for the excellent links, that's exactly what I wanted. It's interesting that they've chosen not to base the new work on libevent. As an aside, I really don't think that the case study should be given any more linkjuice as a response to GHC/Haskell IO concurrency questions. While it's a wonderful tutorial on the programming technique side, it's a decade old and was written at a time when serving 4000 requests was a reasonable benchmark. These days modern web servers are moving more and more toward handling tens of thousands of concurrent held-open *connections*---a different metric and a different scale. Cheers, Aran On Fri, Apr 30, 2010 at 2:51 AM, Don Stewart d...@galois.com wrote: bulat.ziganshin: Hello Aran, Friday, April 30, 2010, 2:26:20 AM, you wrote: In GHC, if a thread spawned by forkIO blocks on some network or disk IO, is the threading system smart enough not to wake the thread afaik, yes. it's controlled by special i/o thread that multiplexes all i/o done via stdlibs. but ghc i/o manager can't use epoll/kqueue so it's appropriate only for small (or medium?) servers Look at the recent work on the event library and replacing the IO manager. http://www.serpentine.com/blog/2010/01/22/new-ghc-io-manager-first-benchmark-numbers/ There's much more background on the new code here, http://www.serpentine.com/blog/2009/12/17/making-ghcs-io-manager-more-scalable/ and some nice benchmarks http://blog.johantibell.com/2010/01/scalable-timeout-support-for-ghcs-io.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Benchmarks game updated to ghc 6.12.2
ketil: Don Stewart d...@galois.com writes: http://shootout.alioth.debian.org/u64q/haskell.php Observations: Although we're mostly beaten on speed, and about the same on code size, we're using a lot less memory than Java. Prior to the upgrade we weren't mostly beaten on speed, so I think a bit of tuning (ghc -server :) should help. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] why does Data.Text.Lazy.IO.readFile return the internal type Data.Text.Lazy.Internal.Text, when Data.Text.IO.readFile returns plain IO Data.Text.Text?
*Main :t Data.Text.IO.readFile Data.Text.IO.readFile :: FilePath - IO T.Text but *Main :t Data.Text.Lazy.IO.readFile Data.Text.Lazy.IO.readFile :: FilePath - IO text-0.7.1.0:Data.Text.Lazy.Internal.Text why does the lazy version use the internal type, whereas the strict version of Text IO just using plain Data.Text type? and how can I get from internal type to regular type when using Data.Text? also the internal type doesn't appear to be reflected in the haddock: http://hackage.haskell.org/packages/archive/text/0.7.1.0/doc/html/Data-Text-Lazy-IO.html ghc-pkg list | grep -i text text-0.7.1.0 thanks for any help! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] why does Data.Text.Lazy.IO.readFile return the internal type Data.Text.Lazy.Internal.Text, when Data.Text.IO.readFile returns plain IO Data.Text.Text?
Data.Text.Lazy.Internal.Text = Data.Text.Lazy.Text Data.Text.Internal.Text = Data.Text.Text You can use fromChunks/toChunks from Data.Text.Lazy to break it up into strict Text fragments. The lazy version returns a Lazy Text value, which is isomorphic to [Data.Text.Text]. The strict version just returns a single strict Text value. On Fri, Apr 30, 2010 at 4:37 PM, Thomas Hartman tphya...@gmail.com wrote: *Main :t Data.Text.IO.readFile Data.Text.IO.readFile :: FilePath - IO T.Text but *Main :t Data.Text.Lazy.IO.readFile Data.Text.Lazy.IO.readFile :: FilePath - IO text-0.7.1.0:Data.Text.Lazy.Internal.Text why does the lazy version use the internal type, whereas the strict version of Text IO just using plain Data.Text type? and how can I get from internal type to regular type when using Data.Text? also the internal type doesn't appear to be reflected in the haddock: http://hackage.haskell.org/packages/archive/text/0.7.1.0/doc/html/Data-Text-Lazy-IO.html ghc-pkg list | grep -i text text-0.7.1.0 thanks for any help! ___ 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] why does Data.Text.Lazy.IO.readFile return the internal type Data.Text.Lazy.Internal.Text, when Data.Text.IO.readFile returns plain IO Data.Text.Text?
Am Freitag 30 April 2010 22:37:38 schrieb Thomas Hartman: *Main :t Data.Text.IO.readFile Data.Text.IO.readFile :: FilePath - IO T.Text but *Main :t Data.Text.Lazy.IO.readFile Data.Text.Lazy.IO.readFile :: FilePath - IO text-0.7.1.0:Data.Text.Lazy.Internal.Text Hmm, Prelude :t Data.Text.Lazy.IO.readFile Data.Text.Lazy.IO.readFile :: FilePath - IO text-0.7.1.0:Data.Text.Lazy.Internal.Text Prelude :t Data.Text.IO.readFile Data.Text.IO.readFile :: FilePath - IO text-0.7.1.0:Data.Text.Internal.Text why does the lazy version use the internal type, whereas the strict version of Text IO just using plain Data.Text type? Both are using the type from the corresponding .Internal, because that's where the type is defined (note that, as with ByteStrings, the strict and lazy types are different, lazy is basically a list of strict). Now, the interesting question is, why is the one displayed as T.Text? It must be what you import to your Main, but I don't know how to produce that effect. and how can I get from internal type to regular type when using Data.Text? Use id :: a - a ;) also the internal type doesn't appear to be reflected in the haddock: http://hackage.haskell.org/packages/archive/text/0.7.1.0/doc/html/Data-T ext-Lazy-IO.html Follow the 'Source' link at Data.Text.Lazy.Text, that sends you to http://hackage.haskell.org/packages/archive/text/0.7.1.0/doc/html/src/Data- Text-Lazy-Internal.html#Text ghc-pkg list | grep -i text text-0.7.1.0 thanks for any help! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: FRP for game programming / artifical life simulation
FYI i got the lazy pattern match from Patterson's Programming with Arrows, so I'm assuming it makes a difference. (I'll work out a real example later.) B On Fri, Apr 30, 2010 at 8:45 AM, Daniel Fischer daniel.is.fisc...@web.de wrote: Am Freitag 30 April 2010 17:23:19 schrieb Antoine Latter: On Fri, Apr 30, 2010 at 3:37 AM, Daniel Fischer daniel.is.fisc...@web.de wrote: Am Donnerstag 29 April 2010 20:08:00 schrieb Ben: A technical question: it seems like the instance of ArrowLoop is too strict (this is something I've wondered about in Liu's paper too.) Shouldn't it be instance ArrowLoop SFAuto where loop (SFAuto s f) = SFAuto s f' where f' (b, s1) = let (~(c, d), s2) = f ((b, d), s1) in (c, s2) Let-bindings are already lazy, so the '~' makes no difference here. Apart from the readability, both are the same as where f' (b,s1) = let x = f ((b, snd $ fst x),s1) in (fst $ fst x, snd x) Ben's version is slightly lazier - even though the let binding is lazy, pattern matching is strict. so (let ((x,y).z) = (undefined, hello) in z) will exception out, but (let (~(x,y),z) = (undefined, hello) in z) will not. I don't know if you need that level of laziness, though. Probably not. Although, you're right, if only s2 is ever looked at and not c, Ben's version can give a result where the library instance throws an exception. Was fooled by the use of c in the result. Antoine ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] why does Data.Text.Lazy.IO.readFile return the internal type Data.Text.Lazy.Internal.Text, when Data.Text.IO.readFile returns plain IO Data.Text.Text?
On Fri, Apr 30, 2010 at 5:09 PM, Daniel Fischer daniel.is.fisc...@web.dewrote: and how can I get from internal type to regular type when using Data.Text? Use id :: a - a ;) Not quite, there is still a distinction between Data.Text(.Internal).Text and Data.Text.Lazy(.Internal).Text. but the machinery to work with the results he gets back are found in Data.Text.Lazy including the functions to turn it into a list of strict Text fragments. also the internal type doesn't appear to be reflected in the haddock: http://hackage.haskell.org/packages/archive/text/0.7.1.0/doc/html/Data-T ext-Lazy-IO.html Follow the 'Source' link at Data.Text.Lazy.Text, that sends you to http://hackage.haskell.org/packages/archive/text/0.7.1.0/doc/html/src/Data- Text-Lazy-Internal.html#Text ghc-pkg list | grep -i text text-0.7.1.0 thanks for any help! ___ 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] why does Data.Text.Lazy.IO.readFile return the internal type Data.Text.Lazy.Internal.Text, when Data.Text.IO.readFile returns plain IO Data.Text.Text?
Am Freitag 30 April 2010 23:20:59 schrieb Edward Kmett: On Fri, Apr 30, 2010 at 5:09 PM, Daniel Fischer daniel.is.fisc...@web.dewrote: and how can I get from internal type to regular type when using Data.Text? Use id :: a - a ;) Not quite, there is still a distinction between Data.Text(.Internal).Text and Data.Text.Lazy(.Internal).Text. Yes, I understood it so that he wanted to convert from Data.Text.Lazy.Internal.Text to Data.Text.Lazy.Text. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] why does Data.Text.Lazy.IO.readFile return the internal type Data.Text.Lazy.Internal.Text, when Data.Text.IO.readFile returns plain IO Data.Text.Text?
On Fri, Apr 30, 2010 at 3:14 PM, Daniel Fischer daniel.is.fisc...@web.dewrote: Yes, I understood it so that he wanted to convert from Data.Text.Lazy.Internal.Text to Data.Text.Lazy.Text. It's the same type. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] why does Data.Text.Lazy.IO.readFile return the internal type Data.Text.Lazy.Internal.Text, when Data.Text.IO.readFile returns plain IO Data.Text.Text?
Am Samstag 01 Mai 2010 00:26:26 schrieb Bryan O'Sullivan: On Fri, Apr 30, 2010 at 3:14 PM, Daniel Fischer daniel.is.fisc...@web.dewrote: Yes, I understood it so that he wanted to convert from Data.Text.Lazy.Internal.Text to Data.Text.Lazy.Text. It's the same type. That's why I suggested id. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] why does Data.Text.Lazy.IO.readFile return the internal type Data.Text.Lazy.Internal.Text, when Data.Text.IO.readFile returns plain IO Data.Text.Text?
On Fri, Apr 30, 2010 at 11:09:05PM +0200, Daniel Fischer wrote: Hmm, Prelude :t Data.Text.Lazy.IO.readFile Data.Text.Lazy.IO.readFile :: FilePath - IO text-0.7.1.0:Data.Text.Lazy.Internal.Text Prelude :t Data.Text.IO.readFile Data.Text.IO.readFile :: FilePath - IO text-0.7.1.0:Data.Text.Internal.Text It depends on what is on your scope: Prelude :t Data.Text.Lazy.IO.readFile Data.Text.Lazy.IO.readFile :: FilePath - IO text-0.7.1.0:Data.Text.Lazy.Internal.Text Prelude :m Data.Text.Lazy Prelude Data.Text.Lazy :t Data.Text.Lazy.IO.readFile Data.Text.Lazy.IO.readFile :: FilePath - IO Text HTH, -- Felipe. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] why does Data.Text.Lazy.IO.readFile return the internal type Data.Text.Lazy.Internal.Text, when Data.Text.IO.readFile returns plain IO Data.Text.Text?
Am Samstag 01 Mai 2010 00:58:23 schrieb Felipe Lessa: It depends on what is on your scope: Prelude :t Data.Text.Lazy.IO.readFile Data.Text.Lazy.IO.readFile :: FilePath - IO text-0.7.1.0:Data.Text.Lazy.Internal.Text Prelude :m Data.Text.Lazy Prelude Data.Text.Lazy :t Data.Text.Lazy.IO.readFile Data.Text.Lazy.IO.readFile :: FilePath - IO Text HTH, Indirectly. From the original post: *Main :t Data.Text.IO.readFile Data.Text.IO.readFile :: FilePath - IO T.Text So the scope is the top level of the Main module. I didn't immediately figure out why it was displayed as T.Text. I couldn't reproduce that with a couple of different imports, but I only tried import [qualified] Data.Text.IO as T. When I saw Prelude :m Data.Text.Lazy it became clear, he had import qualified Data.Text as T in Main, thanks :) -- Felipe. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Functional Dependencies Help
On Apr 29, 7:47 am, John Creighton johns2...@gmail.com wrote:
I've been trying to apply some stuff I learned about functional
dependencies, but I run into one of two problems. I either end up with
inconsistent dependencies (OverlappingInstances doesn't seem to
apply) or I end up with infinite recursion. I want to be able to do
simple things like if a is a subset of b and b is a subset of c then a
is a subset of c. If a is a is a subset of b and b is a c then a is a
c.
Before I added the equality functions I had infinite recursion. Once I
put them them in then I have trouble with overlapping instances.
I've been doing some reading and I think the following is an
improvement but I end up hanging the compiler so I can't tell what the
errors are. I'll see if their are any trace options that might be
helpfully for GHC.
{-# LANGUAGE EmptyDataDecls,
MultiParamTypeClasses,
ScopedTypeVariables,
FunctionalDependencies,
FlexibleInstances #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE UndecidableInstances #-} --10
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE FlexibleContexts #-}
data Noun = Noun deriving (Show) --15
data Verb = Verb deriving (Show) --
data Adjactive = Adjactive deriving (Show)
data Animal=Animal deriving (Show)
data Feline=Feline deriving (Show) --20
data Cat = Cat deriving (Show)
data Taby_Cat=Taby_Cat deriving (Show)
data T=T deriving (Show)
data F=F deriving (Show) --25
--data Z=Z
--data S i = S i
--type One = S Z
--type Zero = Z
class Isa a b c | a b-c where isa::a-b-c --30
instance Isa Animal Noun T where isa a b = T --
class Parrent a b| a-b where -- Specific Cases
parrent :: a-b --
instance Parrent Cat Feline where --
parrent a = Feline --40
instance Parrent Feline Animal where --
parrent a= Animal --
class TypeOr a b c|a b-c where
typeOr :: a-b-c
instance TypeOr T T T where
typeOr a b = T --50
instance TypeOr T F T where
typeOr a b = T
instance TypeOr F T T where
typeOr a b = T
instance TypeOr F F T where
typeOr a b = T
class TypeEq' () x y b = TypeEq x y b | x y - b
instance TypeEq' () x y b = TypeEq x y b
class TypeEq' q x y b | q x y - b --60
class TypeEq'' q x y b | q x y - b
instance TypeCast b T = TypeEq' () x x b
instance TypeEq'' q x y b = TypeEq' q x y b
instance TypeEq'' () x y F
-- see http://okmij.org/ftp/Haskell/typecast.html
class TypeCast a b | a - b, b-a where typeCast :: a - b
class TypeCast' t a b | t a - b, t b - a where typeCast' :: t-a-
b
class TypeCast'' t a b | t a - b, t b - a where typeCast'' :: t-a-
b --70
instance TypeCast' () a b = TypeCast a b where typeCast x =
typeCast' () x
instance TypeCast'' t a b = TypeCast' t a b where typeCast' =
typeCast''
instance TypeCast'' () a a where typeCast'' _ x = x
-- overlapping instances are used only for ShowPred
class EqPred a flag | a-flag where {}
-- Used only if the other
-- instances don't apply -- 80
class IsSuperSet a b c | a b-c where -- General Definition
isSuperSet :: a-b-c
--instance (TypeEq b Animal T,TypeEq c F T)=IsSuperSet a b c where
--85
-- isSuperSet a b = F --
u=undefined
instance (
TypeEq a b iseq, --90
TypeEq Animal b isaninmal,
IsSuperSet' isaninmal iseq a b c3 --
) =
IsSuperSet a b c3 where --
isSuperSet a b=(isSuperSet' (u::isaninmal) (u::iseq) (a::a)
(b::b))::c3
class IsSuperSet' isanimal iseq a b c| isanimal iseq a b-c where
isSuperSet' :: a-b-c
instance IsSuperSet' isanimal T a b T where
isSuperSet' a b = T
instance (Parrent b d, IsSuperSet a b c)=IsSuperSet' F F a b c where
isSuperSet' a b = (isSuperSet a ((parrent (b::b)::d)))::c
instance IsSuperSet' T F a b F where
isSuperSet' a b = F
class ToBool a where
toBool :: a-Bool
instance ToBool T where
toBool a = True
instance ToBool F where
toBool a = False
myCat=Cat
bla=isSuperSet Animal Cat
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[Haskell-cafe] FGL instance constraint
I need help understanding how to express the following: data (Cls a) = B a = B [a] data GrB a b = GrB (B a) instance Graph GrB where ... In the methods for the instance specification, I need to perform Cls a operations on a. * As shown, the compiler complains that it cannot deduce (Cls a) from the context () on those methods. * I can't redefine the Graph methods to introduce the (Cls a) constraint [reasonable] * If I try to express the constraint as part of the Graph instance: instance (Cls a) = Graph GrB where ... then it says it's an ambiguous constraint because 'a' isn't mentioned. * I've tried specifying a functional constraint: instance (Cls a) = Graph GrB | GrB - a where ... but that's not valid for an instance declaration. * I can't include a in the GrB instance: instance (Cls a) = Graph (GrB a b) where ... because that's a kind conflict. Suggestions/solutions are appreciated. Thanks! -- -KQ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
