Re: [Haskell-cafe] Haskell on the iPhone
Ryan Trinkle wrote: Rick, I know some work has been done on JVM - iirc, Don Stewart did some work back in the day, www.cse.unsw.edu.au/~pls/thesis/dons-thesis.ps.gz, but I'm not sure how comprehensive it is. Is anyone else interested in JVM-based Haskell targets? Hello, certainly I am. I think it would be great if someone might combine Haskell code with what's already written in Java (i.e. all those app servers or development environments). In the past I've given a try to LambdaVM[1][2] and it looked like a sane approach to get there. Unfortunately I'm not so power-haskell user to be able to update this patch forward to more recent GHC. I've also submitted ticket for it[3]. Cheers, Karel [1]: http://wiki.brianweb.net/LambdaVM/LambdaVM [2]: http://www.cs.rit.edu/~bja8464/lambdavm/ [3]: http://hackage.haskell.org/trac/ghc/ticket/2959 Ryan On Mon, Jun 22, 2009 at 20:42, Rick R rick.richard...@gmail.com wrote: This is definitely good news! So... who's doing the Android/JVM target? ;) On Mon, Jun 22, 2009 at 7:37 PM, Daniel Peebles pumpkin...@gmail.comwrote: How exciting! I fully support the creation of a new mailing list about iphone+haskell :) On Mon, Jun 22, 2009 at 6:30 PM, Ryan Trinkleryant5...@gmail.com wrote: Dear Haskellers, Recently, there's been a groundswell of activity in the Haskell community regarding the Haskell's use in developing iPhone games. The iPhone is a powerful, innovative platform (with a great monetization scheme, to boot), and it's not surprising that many of us would want to develop apps for it in our favorite language. I am proud to announce today that my company, iPwn Studios Inc., is currently preparing to release an open source patch to GHC that allows it to output binaries for iPhone OS. The patch will be released under a BSD license as soon as possible and hopefully integrated into the GHC main-line in the near future. As the first (to my knowledge) Haskell-based game studio, iPwn Studios is committed to giving back to the Haskell community through open source - contributing to a rising tide that lifts us all. I would like to take this opportunity to propose the creation of a haskell-iphone mailing list, so that all Haskellers working with the iPhone - whether for profit or for pleasure - can come together to make Haskell a force to be reckoned with in the burgeoning iPhone App marketplace. Best wishes, Ryan Trinkle President, iPwn Studios Inc. P.S.: If you wish to be involved in the preparation of the GHC patch or in the creation of iPwn Studios' first game, don't hesitate to contact me by email (ryant5...@gmail.com), AIM (RyanT5000), or IRC (RyanT5000 on irc.freenode.net). ___ 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 -- The greatest obstacle to discovering the shape of the earth, the continents, and the oceans was not ignorance but the illusion of knowledge. - Daniel J. Boorstin ___ 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 mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Optimizing spelling correction program
Using Bryan O'Sullivan's fantastic BloomFilter I got it down below Python's run time! Now it is 35.56s, 28% of the time is spent on GC, which I think means there is still some room for improvement. One easy way to fix the GC time is to increase the default heap size. ./a.out +RTS -A200M It does make the GC only 1.4% of run time but it increases it overall by 14s. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Optimizing spelling correction program
On Jun 22, 10:12 pm, Bulat Ziganshin bulat.zigans...@gmail.com wrote: Hello Kamil, Tuesday, June 23, 2009, 12:54:49 AM, you wrote: I went back to using Strings instead of ByteStrings and with that hashtable the program finishes in 31.5s! w00t! and GC times are? also, try ByteString+HT, it should be pretty easy to write hashByteString GC time is 10%. I'll try ByteString+HT tonight. It might indeed be faster because BloomFilter+String is slower that BloomFilter +ByteString. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] HaRe (the Haskell Refactorer) in action - short screencast
2009/6/23 Claus Reinke claus.rei...@talk21.com: I've heard that many Haskellers know HaRe only as a rumour. It has been many years since the original project finished, and HaRe hasn't been maintained for quite some time, so just pointing to the sources isn't quite the right answer. The sources are still available, and build with GHC 6.8.3 (I had to fix one lineending issue on windows, iirc, and copy one old bug fix that hadn't made it into the latest release), but there is currently noone with the time or funding for maintenance, fixing bugs, making releases, or ironing out practical issues. If anyone would provide funding, people to do the work could be found, but the effort would probably be better spent on reimplementing the ideas in a GHC / Cabal environment (instead of the Haskell'98 environment targetted by our Refactoring Functional Programs project). If you've got the funding, please get in touch - even a three month run could get something started at least!-) In principle, the project experiences and lessons learned are quite well documented at the project site http://www.cs.kent.ac.uk/projects/refactor-fp/ but that doesn't give anyone an idea of what working with HaRe was like. With the recent interest in screencasts, I thought I'd make a little demo, for archival purposes. Nothing fancy, using only features that were already present in HaRe 0.3 (end of 2004), and not all of those, on a tiny 2-module example (screenspace is a bit crowded to keep the text readable on YouTube). I hope it might give a rough idea of what the papers, slides and reports are talking about, for Haskellers who weren't around at the time: http://www.youtube.com/watch?v=4I7VZV7elnY For the old HaRe team, Claus --- YouTube video description: HaRe - the Haskell Refactorer (a mini demo) [4:10] The Haskell Refactorer HaRe was developed in our EPSRC project Refactoring Functional Programs http://www.cs.kent.ac.uk/projects/refactor-fp/ Building on Programatica's Haskell-in-Haskell frontend and Strafunski's generic programming library, it supported module-aware refactorings over the full Haskell'98 language standard. Interfaces to the refactoring engine were provided for both Vim and Emacs (this demo uses HaRe via GVim on Windows). While HaRe has continued to see occasional contributions by students and researchers, who use its Haskell program transformation API as a platform for their own work, it is not currently maintained. As the Haskell environment marches on, this demo is meant to record a snapshot of what working with HaRe could be like when it still built (here with GHC 6.8.3). The lessons learned (note, eg, the preservation of comments, and the limited use of pretty-printing, to minimize layout changes) are well documented at the project site, and should be taken into account when porting the ideas to the GHC Api, or other Haskell frontends. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe It would be interesting to see if the Yi developers could implement some of this functionality for the Haskell mode, which has become quite nice and is under active development. It already has a dollarification function which converts stuff like hello (there (how (are you))) into hello $ there $ how $ are you (I'm bad at coming up with examples). -- Deniz Dogan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Getting my mind around UArray - STUArray conversion
This is the best I could come up with.
We let the compiler prove that s is irrelevant to the MArray
instance for a particular instance of STUArray, and package up that
knowledge using an existential type. We can then extract the instance
for any type; in particular, the instance for the current state
thread. I think this argues that the class context for MArray is too
constrained.
(I don't really use GADTs here, just pack up the class context, but I
like the GADT syntax for doing this)
-- ryan
{-# LANGUAGE GADTs, RankNTypes, FlexibleContexts, ScopedTypeVariables #-}
module StuTest where
import Control.Monad;
import Control.Monad.ST;
import Data.Array.ST;
import Data.Array.Unboxed;
import Data.Array.MArray;
import Data.Word;
data HasMArray s e where
HasMArray :: MArray (STUArray s) e (ST s) = HasMArray s e
newtype HasUnbox e = HasUnbox (forall s. HasMArray s e)
wombat :: forall s ix e. (IArray UArray e, Ix ix) = HasUnbox e -
UArray ix e - ST s (UArray ix e)
wombat (HasUnbox h) arr = case h of
(HasMArray :: HasMArray s e) -
(unsafeThaw arr :: ST s (STUArray s ix e)) = unsafeFreeze
intHasUnbox :: HasUnbox Int
intHasUnbox = HasUnbox HasMArray
test :: (IArray UArray e, Ix ix) = HasUnbox e - UArray ix e - UArray ix e
test ctxt mem = runST (wombat ctxt mem)
simpleTest :: Ix ix = UArray ix Int - UArray ix Int
simpleTest a = runST (wombat (HasUnbox HasMArray) a)
On Fri, Jun 19, 2009 at 6:43 PM, Scott Michelscooter@gmail.com wrote:
I'm trying to get my mind around how to thaw and then freeze a UArray.
Theoretically, what I've written below should be a no-op, but I keep
getting typing errors that I can't figure out. GHCI 6.10.3 says:
Couldn't match expected type `UArray ix a'
against inferred type `ST s (STUArray s ix1 e)'
In the first argument of `(=)', namely
`(unsafeThaw mem :: ST s (STUArray s ix e))'
In the expression:
(unsafeThaw mem :: ST s (STUArray s ix e))
=
(\ mmem - unsafeFreeze mmem)
In the definition of `wombat':
wombat val idx mem
= (unsafeThaw mem :: ST s (STUArray s ix e))
=
(\ mmem - unsafeFreeze mmem)
I'm figuring that usafeThaw with the type annotation should have given
GHIC enough clue.
Any suggestions?
-scooter
(WOMBAT = Waste Of Money Brains And Time)
import Control.Monad;
import Control.Monad.ST;
import Data.Array.ST;
import Data.Array.Unboxed;
import Data.Array.MArray;
import Data.Word;
wombat :: (IArray UArray e, Ix ix, MArray (STUArray s) e (ST s)) = e
- ix - UArray ix e - UArray ix e
wombat val idx mem = (unsafeThaw mem :: ST s (STUArray s ix e)) =
(\mmem - unsafeFreeze mmem)
___
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] IMO ghc 6.8.2 misleading warning messages
Hi Vasili, IMO the warning messages should be reversed! (parseOptional was never used .. called ... but I would strongly prefer the type signature warning first. Can you motivate why? Any order looks fine to me... Gr. Matthijs signature.asc Description: Digital signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] GHCi infers a type but refuses it as type signature
Simple: the definition of MonadState uses those extensions. Thanks, yes it helps and explains all. :^) I suppose then that if -XFlexibleContexts is indeed required by the standard libraries, it is a safe extension, meaning supported by all compilers? Are many such extensions de-facto standard that anyone can enable by default? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Optimizing spelling correction program
Hello Kamil, Tuesday, June 23, 2009, 11:17:43 AM, you wrote: One easy way to fix the GC time is to increase the default heap size. ./a.out +RTS -A200M It does make the GC only 1.4% of run time but it increases it overall by 14s. not surprising - you lose L2 cache locality. try to use -A size that is equal to your L2 cache size -- Best regards, Bulatmailto:bulat.zigans...@gmail.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Forward compatibility (was Re: [Haskell-cafe] GHCi infers a type but refuses it as type signature)
On Tue, Jun 23, 2009 at 2:20 AM, papa.e...@free.fr wrote: Simple: the definition of MonadState uses those extensions. Thanks, yes it helps and explains all. :^) I suppose then that if -XFlexibleContexts is indeed required by the standard libraries, it is a safe extension, meaning supported by all compilers? Are many such extensions de-facto standard that anyone can enable by default? You should treat all compilers the same way as a universal quantifier in mathematics. It's not just all the compilers you know about, but all possible compilers. In which case the answer to your question is of course no. (Beware: incoming my recurring rant of the month, which I am trying ferociously to cram down the throats of my peers :-p) By measuring your software's portability on this stricter criterion, you contribute to the exponential growth of our field. It means that *every *future compiler can compile your code for 10% less effort*. *A future innovation may rely on one such compiler, which means it can use your code 10% sooner -- which may be the difference between your good code being used and it being badly reimplemented (and future bug fixes in the new code does not benefit yours). And so on, ad infinitum. When you think about potability, think about it from the perspective of twenty years in the future. Fundeps are becoming obsolete now, will your code still work when they are gone? Will it still work when the typeclass resolution algorithm is obsoleted by a superior algorithm (I'm looking at you, Oleg! :-)? When Haskell is obsolete, how hard will it be to port? Of course, there is definitely a place for extensions -- we should be testing them, to help refine the language that will one day obsolete Haskell. A culture of extension users helps us to know that, for example, even though implicit params are cool, nobody cares. I think works on all existing compilers is a fine definition of portable -- let's just realize that there is a level of portability beyond that, a level which gives our whole field a little boost. /rant Luke ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Forward compatibility (was Re: [Haskell-cafe] GHCi infers a type but refuses it as type signature)
Hi Luke, Simple: the definition of MonadState uses those extensions. [Snip question: Is this extension supported by all compilers] You should treat all compilers the same way as a universal quantifier in mathematics. It's not just all the compilers you know about, but all possible compilers. In which case the answer to your question is of course no. I think the reasoninging here is the following: If MonadState is part of the standard library and it needs this extension to work, then all compilers must support this extension. I'm not completely sure how standard the MonadState class is though. Also, it might be that there could be implementations of MonadState that do not use the extension? If the latter is not the case, so MonadState will always require this extension, than it seems that using the extension in your code gives you the same portability as using the MonadState class. Not using the extension to improve your portability only makes sense if you also stop using the MonadState class, right? Gr. Matthijs signature.asc Description: Digital signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] GHCi infers a type but refuses it as type signature
On Tue, Jun 23, 2009 at 2:20 AM, papa.e...@free.fr wrote: Simple: the definition of MonadState uses those extensions. Thanks, yes it helps and explains all. :^) I suppose then that if -XFlexibleContexts is indeed required by the standard libraries, it is a safe extension, meaning supported by all compilers? Are many such extensions de-facto standard that anyone can enable by default? Now to answer your question, with 50% less idealistic ranting! There is definitely a canon of safe extensions in the community. Hierarchical libraries (that's not even an -X flag, it's just on), multiparam typeclasses, fundeps are among them. I can't say whether FlexibleContexts is. However, your question is rather moot here, as you are using the *mtl. *It uses UndecidableInstances, whose blessing into the de facto standard would require as a precondition the batshit-insanity of the de facto community. I personally use *transformers* as my monad library, as it is (as far as I know) the only Haskell 98 monad library on Hackage (you'll hardly notice the more explicit lifts, I promise!). However, looking a bit more optimistically into the future, I'd say *mmtl *is the most likely to succeed, since it solves the combinatorical explosion problem which haunts all the other monad libraries (and at least avoids the extensions which are doomed to failure). Anyway, it is never too early to free yourself of mtl. Look at the monad libraries on hackage and weigh their pros and cons; the only thing special about mtl is its mediocrity. Luke ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] INAP 2009: 2nd Call for Papers
[apologies for cross-posting; please distribute] --- (PLEASE DISTRIBUTE) Second Call for Papers INAP 2009 18th International Conference on Applications of Declarative Programming and Knowledge Management November 5-7, 2009 Evora, Portugal http://www.di.uevora.pt/inap2009/ http://inap.dialogengines.com/ Organized by the Portuguese AI Society (APPIA), the INAP Committee and the Society of Logic Programming (GLP e.V.) == Overview == Declarative Programming is a family of advanced paradigms for the modeling and solving of complex problems. These specification and implementation methods have attracted more and more attention over the past years, e.g. in the domains of databases and natural language processing, for modeling and the processing of combinatorial problems, and for establishing systems for the web. == INAP 2009 == INAP is a communicative and dense forum for intensive discussion of applications of important technologies related to Prolog, Logic and Constraint Programming as well as closely related advanced software. It comprehensively covers the impact of programmable logic solvers in the Internet Society, its underlying technologies, and leading edge applications in industry, commerce, government, and societal services. INAP 2009 continues a tradition of successful workshops cast around the applications of declarative programming, which were held in Kobe (1997), Tokyo (1995, 1996, 1998 - 2001), Potsdam (2004), Fukuoka (2005) and Wuerzburg (2007). We invite the submission of high quality papers on the described topics, especially, but not exclusively, on different aspects of Declarative Programming, Constraint Processing and Knowledge Management as well as their use for Distributed Systems and the Web: - Knowledge Management, e.g. Data Mining, Decision Support, Deductive Databases - Distributed Systems and the Web, e.g. Agents and Concurrent Engineering, Semantic Web - Constraints, e.g. Constraint Systems, Extensions of Constraint (Logic) Programming - Theoretical Foundations, e.g. Deductive Databases, Nonmonotonic Reasoning - Systems and Tools for Academic and Industrial Use - Knowledge-based Web Services - Logic Solvers and Applications == Workshop Format == The technical program of the workshop will include invited presentations (to be announced), regular technical sessions with presentations of the accepted papers, system demonstrations and a panel discussion. == Conference Venue == The conference will be held at the University of Evora, Portugal in November 5-7, 2009. Evora is a nice and quiet historical city located in the south of Portugal that can be reached from Lisbon by train or coach in under 2 hours. It is a small city of 60.000 inhabitants, 120 km inland from Lisbon and classified by Unesco as World Heritage. The University of Evora was established in the 16th Century and is the 2nd oldest Portuguese University. The social program is promising since the region is very rich in historical sites (Stone Age, Roman, Medieval and Renaissance remains) and also offers a very special gastronomy. See http://en.wikipedia.org/wiki/%C3%89vora for more information. == Important Dates == Paper Submission Deadline: June 29, 2009 Notifications to Authors:August 17, 2009 Camera-ready Version Deadline: September 14, 2009 INAP 2009 Workshop: November 5-7, 2009 == Submission Guidelines == Participants should submit a paper (maximum 15 pages, PDF format), describing their work in topics relevant to the workshop. Accepted papers will be presented during the workshop. At least one author of an accepted contribution is expected to register for the workshop, and present the paper. All submissions should include the author's name(s), affiliation, complete mailing address, and email address. Authors are requested to prepare their submissions, following the LNCS/LNAI Springer format. Please see: http://www.springer.de/comp/lncs/authors.html for further details. The submission should be submitted through the electronic submission site: http://www.easychair.org/conferences/?conf=inap2009 The deadline for receipt of submissions is June 29, 2009. Papers received after this date will not be reviewed. Eligible papers will be peer-reviewed by at least three members of the Program Committee. Authors will be notified via email of the results by August 17, 2009. Authors of accepted papers are expected to improve their paper based on reviewers' comments and to
[Haskell-cafe] Ann: Emping-0.6 and Tests/Examples
Hello All, Version 0.6 of Emping is now, imo, at the level of a working prototype. It is available on Hackage (but won't build there because it uses Gtk2Hs. It did build with Cabal on FC8 with GhC 6.8 and Gtk2Hs 0.9.13). The package includes a user guide, but see the update on my web site about two UI corner case bugs (program hangs). My site http://www.muitovar.com discusses three examples of possible use, with tests using SQLite, OO Calc and dotty. There's also a .zip archive of all sources (two data sets from the UCI machine learning repository) and .csv and .dot files with the results. All comments most welcome... Emping is a (prototype) interactive tool for the discovery and analysis of (universal, not statistical) predictive rules in tables of nominal data. Best Regards, Hans van Thiel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: ANN: haskell-src-exts-1.0.0
Hi Maurício, How far is Unicode from beeing parsed? It doesn't seem to be a huge step (from my ill-informed viewpoint), and it would not let behind those who are happy to be able to declare names in their own native language. (Oh, and sorry for resorting to politically correct blackmail...) Unicode in identifiers and symbols actually already works, assuming you don't use the non-Unicode-aware parseFile, parseFileWithExts or parseFileWithMode (which all use Prelude.readLine). What doesn't work is to use the Unicode versions of special symbols like -, = etc. I'm waiting for a stable and blessed unicode-aware text package to replace utf8-string, before we have one of those then my support would only be half-hearted at best. But in the mean time you can use the readLine provided by utf8-string, and then parseFileContents on that, which should give you the politically correct names. ;-) Cheers, /Niklas ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Generate Fortran 77 parser from a yacc grammar using Happy
I have stumbled upon the following F77 yacc grammar: http://yaxx.cvs.sourceforge.net/viewvc/yaxx/yaxx/fortran/fortran.y?revision=1.3view=markup . How can I make a Fortran 77 parser out of this file using Happyhttp://www.haskell.org/happy/ ? Why is there some C?/C++? code in that .y file? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell on the iPhone
I have strong interest in Haskell on the JVM. Not for Android, however. Seems like every time this topic comes up, the consensus is that it's not easy to support new targets with GHC, but that work is underway to make such developments easier. Regards, John A. De Goes N-Brain, Inc. The Evolution of Collaboration http://www.n-brain.net|877-376-2724 x 101 On Jun 22, 2009, at 11:23 PM, Ryan Trinkle wrote: Rick, I know some work has been done on JVM - iirc, Don Stewart did some work back in the day, www.cse.unsw.edu.au/~pls/thesis/dons-thesis.ps.gz , but I'm not sure how comprehensive it is. Is anyone else interested in JVM-based Haskell targets? Ryan On Mon, Jun 22, 2009 at 20:42, Rick R rick.richard...@gmail.com wrote: This is definitely good news! So... who's doing the Android/JVM target? ;) On Mon, Jun 22, 2009 at 7:37 PM, Daniel Peebles pumpkin...@gmail.com wrote: How exciting! I fully support the creation of a new mailing list about iphone+haskell :) On Mon, Jun 22, 2009 at 6:30 PM, Ryan Trinkleryant5...@gmail.com wrote: Dear Haskellers, Recently, there's been a groundswell of activity in the Haskell community regarding the Haskell's use in developing iPhone games. The iPhone is a powerful, innovative platform (with a great monetization scheme, to boot), and it's not surprising that many of us would want to develop apps for it in our favorite language. I am proud to announce today that my company, iPwn Studios Inc., is currently preparing to release an open source patch to GHC that allows it to output binaries for iPhone OS. The patch will be released under a BSD license as soon as possible and hopefully integrated into the GHC main-line in the near future. As the first (to my knowledge) Haskell-based game studio, iPwn Studios is committed to giving back to the Haskell community through open source - contributing to a rising tide that lifts us all. I would like to take this opportunity to propose the creation of a haskell-iphone mailing list, so that all Haskellers working with the iPhone - whether for profit or for pleasure - can come together to make Haskell a force to be reckoned with in the burgeoning iPhone App marketplace. Best wishes, Ryan Trinkle President, iPwn Studios Inc. P.S.: If you wish to be involved in the preparation of the GHC patch or in the creation of iPwn Studios' first game, don't hesitate to contact me by email (ryant5...@gmail.com), AIM (RyanT5000), or IRC (RyanT5000 on irc.freenode.net). ___ 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 -- The greatest obstacle to discovering the shape of the earth, the continents, and the oceans was not ignorance but the illusion of knowledge. - Daniel J. Boorstin ___ 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 mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell on the iPhone
This is great news! I'd love to be able to write our cellphone automated vehicle location clients in Haskell. -- Jeff On Mon, Jun 22, 2009 at 6:38 PM, Don Stewartd...@galois.com wrote: If you're doing it in Haskell, please feel free to keep plugging. A new market for Haskell apps is highly welcome. ryant5000: Jason, iPwn is currently in pre-production for its first title, which will be an action-RPG reminiscent of Diablo and Fallout. I'll try to keep the shameless plugging on Haskell-cafe to a minimum, but I make no promises :P I will definitely let people know when our website is put together in some useful way. Ryan On Mon, Jun 22, 2009 at 18:34, Jason Dagit da...@codersbase.com wrote: On Mon, Jun 22, 2009 at 3:30 PM, Ryan Trinkle ryant5...@gmail.com wrote: Dear Haskellers, Recently, there's been a groundswell of activity in the Haskell community regarding the Haskell's use in developing iPhone games. The iPhone is a powerful, innovative platform (with a great monetization scheme, to boot), and it's not surprising that many of us would want to develop apps for it in our favorite language. I am proud to announce today that my company, iPwn Studios Inc., is currently preparing to release an open source patch to GHC that allows it to output binaries for iPhone OS. The patch will be released under a BSD license as soon as possible and hopefully integrated into the GHC main-line in the near future. As the first (to my knowledge) Haskell-based game studio, iPwn Studios is committed to giving back to the Haskell community through open source - contributing to a rising tide that lifts us all. Hi Ryan, This is great news! Thanks! Does iPwn have any up coming titles? Perhaps a blog where we could read about them so the advertising doesn't hit the list. I would like to take this opportunity to propose the creation of a haskell-iphone mailing list, so that all Haskellers working with the iPhone - whether for profit or for pleasure - can come together to make Haskell a force to be reckoned with in the burgeoning iPhone App marketplace. Sounds good to me. Please post back here if it gets created. Jason ___ 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 mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] memoization using unsafePerformIO
Hi,
I have tried to implement a memo function using stable names and weak
pointers like it is presented in the paper stretching the storage
manager. There is an abstract datatype SNMap a b which implements a
map that maps values of type StableName a to values of type b. The map
is located in an IORef.
{-# NOINLINE memo #-}
memo :: (a - b) - a - b
memo f =
unsafePerformIO (do
tref - newSNMap
return (applyWeak f tref))
{-# NOINLINE applyWeak #-}
applyWeak :: (a - b) - SNMap a (Weak b) - a - b
applyWeak f tbl arg =
unsafePerformIO (do
sn - makeStableName arg
lkp - lookupSNMap tbl sn
case lkp of
Nothing - not_found sn
Just weak - do
val - deRefWeak weak
case val of
Just result - return result
Nothing - not_found sn)
where
not_found sn = do
let res = f arg
weak - mkWeak arg res Nothing
insertSNMap tbl sn weak
return res
Using this memo function I have implemented a fibonacci function like
it is defined in the paper.
fib :: Int - Int
fib = memo ufib
ufib :: Int - Int
ufib 0 = 1
ufib 1 = 1
ufib n = fib (n-1) + fib (n-2)
When I compile this program with 6.10.3 fib yields the correct results
up to 18 but for 19 it detects a loop.
Can anybody give me a hint how I can avoid this behaviour (and still
use unsafePerformIO ; ) )?
Cheers, Jan
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to determine if a FilePath is a directory name or regular file?
On Jun 22, 2009, at 07:37 , Duncan Coutts wrote: One explanation is that isBlah asks is this thing a blah, but we're not asking that because there is an indirection via the filepath. We're asking does this filepath refer to a directory not is this filename a directory. The latter could be a function: isDirectory :: FileInfo - Bool along with a hypothetical getFileInfo :: FilePath - IO FileInfo Hypothetical? import System.Posix.Files (getFileStatus, isDirectory) -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell on the iPhone
There seems to be quite a bit more interest now in supporting platforms other than win/*nix on x86 these days*. Maybe now there will be sufficient motivation to make the fundamental changes required. Caveat: I have absolutely no idea of the scope or complexity of said changes. I will look through the LambdaVM code (and iPwn when available) to get an idea. Perhaps we can devote a section of Haskell Wiki to generalizing Haskell for multiple targets? The industry has been clamoring for a unified solution to all of the mobile platforms out there. If Haskell can provide that, it would be a huge win for its popularity. * Thanks primarily to the iPhone and Android systems. I think currently iPhone is swaying the most votes but Android is due to be on a dozen phones and possibly even a netbook. (I have heard two announcements and one cancellation with regards to the netbooks). On Tue, Jun 23, 2009 at 8:34 AM, John A. De Goes j...@n-brain.net wrote: I have strong interest in Haskell on the JVM. Not for Android, however. Seems like every time this topic comes up, the consensus is that it's not easy to support new targets with GHC, but that work is underway to make such developments easier. Regards, John A. De Goes N-Brain, Inc. The Evolution of Collaboration http://www.n-brain.net|877-376-2724 x 101 On Jun 22, 2009, at 11:23 PM, Ryan Trinkle wrote: Rick, I know some work has been done on JVM - iirc, Don Stewart did some work back in the day, www.cse.unsw.edu.au/~pls/thesis/dons-thesis.ps.gzhttp://www.cse.unsw.edu.au/%7Epls/thesis/dons-thesis.ps.gz, but I'm not sure how comprehensive it is. Is anyone else interested in JVM-based Haskell targets? Ryan On Mon, Jun 22, 2009 at 20:42, Rick R rick.richard...@gmail.com wrote: This is definitely good news! So... who's doing the Android/JVM target? ;) On Mon, Jun 22, 2009 at 7:37 PM, Daniel Peebles pumpkin...@gmail.comwrote: How exciting! I fully support the creation of a new mailing list about iphone+haskell :) On Mon, Jun 22, 2009 at 6:30 PM, Ryan Trinkleryant5...@gmail.com wrote: Dear Haskellers, Recently, there's been a groundswell of activity in the Haskell community regarding the Haskell's use in developing iPhone games. The iPhone is a powerful, innovative platform (with a great monetization scheme, to boot), and it's not surprising that many of us would want to develop apps for it in our favorite language. I am proud to announce today that my company, iPwn Studios Inc., is currently preparing to release an open source patch to GHC that allows it to output binaries for iPhone OS. The patch will be released under a BSD license as soon as possible and hopefully integrated into the GHC main-line in the near future. As the first (to my knowledge) Haskell-based game studio, iPwn Studios is committed to giving back to the Haskell community through open source - contributing to a rising tide that lifts us all. I would like to take this opportunity to propose the creation of a haskell-iphone mailing list, so that all Haskellers working with the iPhone - whether for profit or for pleasure - can come together to make Haskell a force to be reckoned with in the burgeoning iPhone App marketplace. Best wishes, Ryan Trinkle President, iPwn Studios Inc. P.S.: If you wish to be involved in the preparation of the GHC patch or in the creation of iPwn Studios' first game, don't hesitate to contact me by email (ryant5...@gmail.com), AIM (RyanT5000), or IRC (RyanT5000 on irc.freenode.net). ___ 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 -- The greatest obstacle to discovering the shape of the earth, the continents, and the oceans was not ignorance but the illusion of knowledge. - Daniel J. Boorstin ___ 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 mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- The greatest obstacle to discovering the shape of the earth, the continents, and the oceans was not ignorance but the illusion of knowledge. - Daniel J. Boorstin ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] Haskell on the iPhone
Good news about the iPhone port! There seems to be quite a bit more interest now in supporting platforms other than win/*nix on x86 these days*. Maybe now there will be sufficient motivation to make the fundamental changes required. Caveat: I have absolutely no idea of the scope or complexity of said changes. I will look through the LambdaVM code (and iPwn when available) to get an idea. There is definitely an opportunity here for someone to make an impact. There is no reason in principle why Haskell can't run on a JVM or .net or other platform. But it's not just a simple matter of absorbing some patch or other. Here's a summary I wrote a little while ago: http://haskell.org/haskellwiki/GHC:FAQ#Why_isn.27t_GHC_available_for_.NET_or_on_the_JVM.3F The short summary is: * There is interesting design work to do; and then interesting engineering work to make it a reality. * We (at GHC HQ) would love to see that happen, but are not likely to drive it. * If someone, or a small group, wanted to take up the cudgels and work on it, we'd be happy to advise. * We'd certainly consider folding the results into the HEAD, provided the author(s) are willing to maintain it, and we feel that the result is comprehensible and maintainable. * But another viable route might well be to use the GHC API, which means that the result wouldn't be part of GHC at all, just a client of the API. That would make it much easier to distribute upgrades etc, just as a Cabal package. Simon From: haskell-cafe-boun...@haskell.org [mailto:haskell-cafe-boun...@haskell.org] On Behalf Of Rick R Sent: 23 June 2009 14:53 To: Haskell Cafe Subject: Re: [Haskell-cafe] Haskell on the iPhone There seems to be quite a bit more interest now in supporting platforms other than win/*nix on x86 these days*. Maybe now there will be sufficient motivation to make the fundamental changes required. Caveat: I have absolutely no idea of the scope or complexity of said changes. I will look through the LambdaVM code (and iPwn when available) to get an idea. Perhaps we can devote a section of Haskell Wiki to generalizing Haskell for multiple targets? The industry has been clamoring for a unified solution to all of the mobile platforms out there. If Haskell can provide that, it would be a huge win for its popularity. * Thanks primarily to the iPhone and Android systems. I think currently iPhone is swaying the most votes but Android is due to be on a dozen phones and possibly even a netbook. (I have heard two announcements and one cancellation with regards to the netbooks). On Tue, Jun 23, 2009 at 8:34 AM, John A. De Goes j...@n-brain.netmailto:j...@n-brain.net wrote: I have strong interest in Haskell on the JVM. Not for Android, however. Seems like every time this topic comes up, the consensus is that it's not easy to support new targets with GHC, but that work is underway to make such developments easier. Regards, John A. De Goes N-Brain, Inc. The Evolution of Collaboration http://www.n-brain.net|877-376-2724 x 101 On Jun 22, 2009, at 11:23 PM, Ryan Trinkle wrote: Rick, I know some work has been done on JVM - iirc, Don Stewart did some work back in the day, www.cse.unsw.edu.au/~pls/thesis/dons-thesis.ps.gzhttp://www.cse.unsw.edu.au/%7Epls/thesis/dons-thesis.ps.gz, but I'm not sure how comprehensive it is. Is anyone else interested in JVM-based Haskell targets? Ryan On Mon, Jun 22, 2009 at 20:42, Rick R rick.richard...@gmail.commailto:rick.richard...@gmail.com wrote: This is definitely good news! So... who's doing the Android/JVM target? ;) On Mon, Jun 22, 2009 at 7:37 PM, Daniel Peebles pumpkin...@gmail.commailto:pumpkin...@gmail.com wrote: How exciting! I fully support the creation of a new mailing list about iphone+haskell :) On Mon, Jun 22, 2009 at 6:30 PM, Ryan Trinkleryant5...@gmail.commailto:ryant5...@gmail.com wrote: Dear Haskellers, Recently, there's been a groundswell of activity in the Haskell community regarding the Haskell's use in developing iPhone games. The iPhone is a powerful, innovative platform (with a great monetization scheme, to boot), and it's not surprising that many of us would want to develop apps for it in our favorite language. I am proud to announce today that my company, iPwn Studios Inc., is currently preparing to release an open source patch to GHC that allows it to output binaries for iPhone OS. The patch will be released under a BSD license as soon as possible and hopefully integrated into the GHC main-line in the near future. As the first (to my knowledge) Haskell-based game studio, iPwn Studios is committed to giving back to the Haskell community through open source - contributing to a rising tide that lifts us all. I would like to take this opportunity to propose the creation of a haskell-iphone mailing list, so that all Haskellers working with the iPhone - whether for profit or for
Re: [Haskell-cafe] Haskell on the iPhone
How about setting up some sort of Summer of Code-type project, where companies can pledge dollars toward a certain goal, which will cover the cost of the work? Is there someone at GHC HQ who could provide guidance to a sponsored developer working on getting additional targets into HEAD? Regards, John A. De Goes N-Brain, Inc. The Evolution of Collaboration http://www.n-brain.net|877-376-2724 x 101 On Jun 23, 2009, at 8:16 AM, Simon Peyton-Jones wrote: Good news about the iPhone port! There seems to be quite a bit more interest now in supporting platforms other than win/*nix on x86 these days*. Maybe now there will be sufficient motivation to make the fundamental changes required. Caveat: I have absolutely no idea of the scope or complexity of said changes. I will look through the LambdaVM code (and iPwn when available) to get an idea. There is definitely an opportunity here for someone to make an impact. There is no reason in principle why Haskell can’t run on a JVM or .net or other platform. But it’s not just a simple matter of absorbing some patch or other. Here’s a summary I wrote a little while ago: http://haskell.org/haskellwiki/GHC:FAQ#Why_isn.27t_GHC_available_for_.NET_or_on_the_JVM.3F The short summary is: · There is interesting design work to do; and then interesting engineering work to make it a reality. · We (at GHC HQ) would love to see that happen, but are not likely to drive it. · If someone, or a small group, wanted to take up the cudgels and work on it, we’d be happy to advise. · We’d certainly consider folding the results into the HEAD, provided the author(s) are willing to maintain it, and we feel that the result is comprehensible and maintainable. · But another viable route might well be to use the GHC API, which means that the result wouldn’t be part of GHC at all, just a client of the API. That would make it much easier to distribute upgrades etc, just as a Cabal package. Simon From: haskell-cafe-boun...@haskell.org [mailto:haskell-cafe-boun...@haskell.org ] On Behalf Of Rick R Sent: 23 June 2009 14:53 To: Haskell Cafe Subject: Re: [Haskell-cafe] Haskell on the iPhone There seems to be quite a bit more interest now in supporting platforms other than win/*nix on x86 these days*. Maybe now there will be sufficient motivation to make the fundamental changes required. Caveat: I have absolutely no idea of the scope or complexity of said changes. I will look through the LambdaVM code (and iPwn when available) to get an idea. Perhaps we can devote a section of Haskell Wiki to generalizing Haskell for multiple targets? The industry has been clamoring for a unified solution to all of the mobile platforms out there. If Haskell can provide that, it would be a huge win for its popularity. * Thanks primarily to the iPhone and Android systems. I think currently iPhone is swaying the most votes but Android is due to be on a dozen phones and possibly even a netbook. (I have heard two announcements and one cancellation with regards to the netbooks). On Tue, Jun 23, 2009 at 8:34 AM, John A. De Goes j...@n-brain.net wrote: I have strong interest in Haskell on the JVM. Not for Android, however. Seems like every time this topic comes up, the consensus is that it's not easy to support new targets with GHC, but that work is underway to make such developments easier. Regards, John A. De Goes N-Brain, Inc. The Evolution of Collaboration http://www.n-brain.net|877-376-2724 x 101 On Jun 22, 2009, at 11:23 PM, Ryan Trinkle wrote: Rick, I know some work has been done on JVM - iirc, Don Stewart did some work back in the day, www.cse.unsw.edu.au/~pls/thesis/dons-thesis.ps.gz , but I'm not sure how comprehensive it is. Is anyone else interested in JVM-based Haskell targets? Ryan On Mon, Jun 22, 2009 at 20:42, Rick R rick.richard...@gmail.com wrote: This is definitely good news! So... who's doing the Android/JVM target? ;) On Mon, Jun 22, 2009 at 7:37 PM, Daniel Peebles pumpkin...@gmail.com wrote: How exciting! I fully support the creation of a new mailing list about iphone+haskell :) On Mon, Jun 22, 2009 at 6:30 PM, Ryan Trinkleryant5...@gmail.com wrote: Dear Haskellers, Recently, there's been a groundswell of activity in the Haskell community regarding the Haskell's use in developing iPhone games. The iPhone is a powerful, innovative platform (with a great monetization scheme, to boot), and it's not surprising that many of us would want to develop apps for it in our favorite language. I am proud to announce today that my company, iPwn Studios Inc., is currently preparing to release an open source patch to GHC that allows it to output binaries for iPhone OS. The patch will be released under a BSD license as soon as possible and hopefully integrated into the GHC main-line in the near
Re: [Haskell-cafe] How to determine if a FilePath is a directory name or regular file?
On Tue, 2009-06-23 at 09:31 -0400, Brandon S. Allbery KF8NH wrote: On Jun 22, 2009, at 07:37 , Duncan Coutts wrote: One explanation is that isBlah asks is this thing a blah, but we're not asking that because there is an indirection via the filepath. We're asking does this filepath refer to a directory not is this filename a directory. The latter could be a function: isDirectory :: FileInfo - Bool along with a hypothetical getFileInfo :: FilePath - IO FileInfo Hypothetical? import System.Posix.Files (getFileStatus, isDirectory) Yeah, if we could make a standard portable variant of this, that'd be great. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re[2]: [Haskell-cafe] How to determine if a FilePath is a directory name or regular file?
Hello Duncan, Tuesday, June 23, 2009, 6:34:17 PM, you wrote: import System.Posix.Files (getFileStatus, isDirectory) Yeah, if we could make a standard portable variant of this, that'd be great. isdir - withFileStatus isdir? filename isDirectory module System.Directory withFileStatus :: String - FilePath - (Ptr CStat - IO a) - IO a isDirectory :: Ptr CStat - IO Bool -- 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] rewrite rules
| I have a rewrite rule as follows:
|
| {-# RULES
| transform/transform forall (f::forall m. Monoid m = (a - m) - (b -
| m))
| (g::forall m. Monoid m = (b - m) - (c
| - m))
| (l::FMList c). transform f (transform g
| l) = transform (g.f) l
|#-}
|
| It fires on this code:
|
|print $ transform (. (*2)) (transform (. (+1)) (upto 10))
|
| But it doesn't fire on this code:
|
|print $ map (*2) (map (+1) (upto 10)))
That's odd. It works for me.
Specifically, I compiled the attached code with GHC 6.10, and I get two firings
of transform/transform.
Does that not happen for you?
Simon
Rules.hs
Description: Rules.hs
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: [Haskell] ANN: Reusable Corecursive Queues via Continuations
On Mon, Jun 22, 2009 at 10:31:34PM -0400, Leon Smith wrote: Also, a substantially revised draft of the associated paper, Lloyd Allison's Corecursive Queues: Why Continuations Matter is now available. [3] This paper will appear in the upcoming Monad Reader issue 14, and comments would be most appreciated. As per [1], it seems n+k patterns will be removed from Haskell', so you may want to remove them from the paper as well. [1] http://hackage.haskell.org/trac/haskell-prime/wiki/Status -- Felipe. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ICFP contest
Hi, The good folks here are really quiet about the ICFP Contest. Is anyone participating this year? As in the previous four years, I will probably download the problem, take a look, and try for a while... Having a family don't allow me to go much further, especially when teaming up with myself! Best regards, Rafael Gustavo da Cunha Pereira Pinto ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ICFP contest
Well, I can make a bit more concrete prediction. I'll download the problem, take a look, try for a while, discover, that it's too hard to be cracked at once, and lose interest. That sounds like a reason why I'm not participating. On 23 Jun 2009, at 22:49, Rafael Gustavo da Cunha Pereira Pinto wrote: Hi, The good folks here are really quiet about the ICFP Contest. Is anyone participating this year? As in the previous four years, I will probably download the problem, take a look, and try for a while... Having a family don't allow me to go much further, especially when teaming up with myself! Best regards, Rafael Gustavo da Cunha Pereira Pinto ___ 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] Type system trickery
Ross Mellgren wrote:
This works for me:
{-# LANGUAGE EmptyDataDecls, GADTs #-}
module Main where
data NoZoo
data Zoo
newtype X = X Int deriving (Show)
newtype Y = Y Char deriving (Show)
data Foobar a where
Foo :: X - Y - Foobar NoZoo
Bar :: X - Y - Foobar NoZoo
Zoo :: Foobar NoZoo - Foobar Zoo
foobar :: Foobar a - X
foobar f = case f of
Foo x _ - x
Zoo g - foobar g
main :: IO ()
main = putStrLn . show $ foobar (Zoo $ Foo (X 1) (Y 'a'))
Could you post a test case?
Thinking about this more carefully, I started out with
data Foobar a where
Foo :: X - Y - Foobar a
Zoo :: Foobar a - Foobar Zoo
which is no good, because Zoo can be nested arbitrarily deep. So I tried
to change it to
data Foobar a where
Foo :: X - Y - Foobar NoZoo
Zoo :: Foobar NoZoo - Foobar Zoo
But *actually*, changing the second type signature only is sufficient.
Indeed, it turns out I don't *want* to change the first one. I want to
use the type system to track whether Zoo may or may not be present,
not whether it is or is not present. In other words, I want Foobar
Zoo to mean that there *might* be a Zoo in there, but there isn't
guaranteed to be one. But I want Foobar NoZoo to be guaranteed not to
contain Zoo.
So anyway... my program now uses GADTs, I've spent ages chasing down all
the typechecker errors (and, inevitably, in some places clarifying what
the code is actually supposed to do), and my program now typechecks and
does what it did before, except with slightly more type safety. (In
particular, I've deleted several calls to error now, because those
case alternatives can never occur).
Thanks to all the people for your help! :-D
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
AW: [Haskell-cafe] ICFP contest
Last year the problem was not too bad, but I failed because I didn't have a working linux installation and the live cd started on my notebook in the first day, but in the second no more (you had to deliver a linux binary). Two years ago there was no need to deliver a binary, but I did not have any idea how to start. This year I'll try again (in Haskell, of course), but you're right, alone it can be very hard. Nicu Ionita -Ursprüngliche Nachricht- Von: haskell-cafe-boun...@haskell.org [mailto:haskell-cafe-boun...@haskell.org] Im Auftrag von Miguel Mitrofanov Gesendet: Dienstag, 23. Juni 2009 21:27 An: Rafael Gustavo da Cunha Pereira Pinto Cc: Haskell Café Betreff: Re: [Haskell-cafe] ICFP contest Well, I can make a bit more concrete prediction. I'll download the problem, take a look, try for a while, discover, that it's too hard to be cracked at once, and lose interest. That sounds like a reason why I'm not participating. On 23 Jun 2009, at 22:49, Rafael Gustavo da Cunha Pereira Pinto wrote: Hi, The good folks here are really quiet about the ICFP Contest. Is anyone participating this year? As in the previous four years, I will probably download the problem, take a look, and try for a while... Having a family don't allow me to go much further, especially when teaming up with myself! Best regards, Rafael Gustavo da Cunha Pereira Pinto ___ 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 mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANN: New release of ZeroTH
This announcement will only be of interest to Haskell programmers using, or thinking of using, Template Haskell. I am very pleased to announce a new release (2009.6.23.3) of ZeroTH (also known as zeroth), a tool for preprocessing Haskell code to run splices and remove Template Haskell dependencies: http://hackage.haskell.org/package/zeroth For example, you could use it to reduce the size of your Haskell program binaries, if you use Template Haskell. (zeroth now actually uses itself on itself, for this very purpose, and you can use the Distribution.ZeroTH module for that in your own cabal projects.) It's still very much a hack - in that it would probably be more efficient and clean to implement it as an option to GHC - but hopefully now at least it's a slightly *better* hack. Lemmih has kindly agreed to hand over the job of being maintainer of ZeroTH to me. So please send any patches or complaints my way. The new darcs repository for the project, which is a darcs 2 repository, is at: http://patch-tag.com/publicrepos/zerothDarcs2 For this release, the cabal command-line tool is the only officially supported means of installation. So you should do something like: cabal update cabal install zeroth to install it. To get a summary of command-line options, type: zeroth --help Major changes from previous releases: * Much more Haskell code is now supported. This is partly because the code has been updated to work with the just-released haskell-src-exts 1.0.0; and partly because it supports a wider variety of Template Haskell code, including code which refers to definitions declared in the same source file. * It is now compulsory to specify any Haskell language extensions you are using in the input file, with a LANGUAGE pragma. (For debugging purposes, zeroth prints to stderr the result of parsing the LANGUAGE pragma, if any. If haskell-src-exts doesn't understand the LANGUAGE pragma, this will be Nothing. But that shouldn't happen.) * Template Haskell imports are now *automatically* stripped by default by zeroth, and so cpphs doesn't need to be run if you aren't otherwise using CPP. * New command-line options have been added (see zeroth --help). * Error messages are now more informative. * Librification! Almost anything can benefit from being made into a library, and zeroth is no exception. Of course, the executable is still there. * You can still use it on certain code which doesn't compile in GHC (yes, really, I've tested this!) but you now have to use the --only-splices option if you want to do this. Obviously, the splices themselves have to compile. --only-splices also makes zeroth faster. It is very lightly tested, so it might not work for your code out of the box. Please let me know if you have any problems with it, no matter how small. Happy hacking, -- Robin ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Could FFI support pass-by-value of structs?
On Tue, Jun 16, 2009 at 10:48:19AM -0300, Maurício wrote:
It's not usual, but it is allowed to have values of
structs passed between functions directly instead of
using pointers:
/*/
struct ex {
int x;
int y;
int z;
};
ex example_functions (ex p)
{
(...)
}
/*/
Would it be possible to allow that in Haskell FFI
by, say, allowing any instance of Storable to be
used in a 'foreign' declaration? Like:
There are a couple problems with this. First, the storage layout for a
given C struct may be radically different depending on the back end,
even sometimes depending on the operating system. So you can't write a
portable Storable instance.
The other problem is that the storage layout isn't enough to use structs
as arguments as the calling conventions also come into play. Some
calling conventions want structs expanded and places on the stack,
others want a pointer to some stack allocated data, returning a struct
may or may not create a hidden first argument. Now, Haskell compilers
already have to tackle calling conventions for basic types, so it is
entirely plausable to solve this, the question is, is it worth the
effort? anything you write will end up not being portable anyway because
it depends on the structure layout.
The end result being, structure passing is complicated, so if you need
to interface to a library that has pre-defined structeres, use hsc2hs to
manually peek and poke into the correct offsets, it will make things
easier and be more portable.
John
--
John Meacham - ⑆repetae.net⑆john⑈ - http://notanumber.net/
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Could FFI support pass-by-value of structs?
On Tue, Jun 16, 2009 at 10:48:19AM -0300, Maurício wrote:
/*/
struct ex {
int x;
int y;
int z;
};
ex example_functions (ex p)
{
(...)
}
/*/
You may adopt the approach I used with Hipmunk[1] where there is
a wrapper library written in C. For your example you could do
something like
void wr_example_functions(ex *p) {
*p = example_functions(*p);
}
and in you Haskell code you write something like
foreign import ccall unsafe wrapper.h
wr_example_functions :: Ptr Ex - IO ()
exampleFunctions :: Ex - IO Ex
exampleFunctions input =
with input $ \ptr - do
wr_example_functions ptr
peek ptr
The structure is allocated on the stack, so the drawbacks are
only another function call and two structure copies, and probably
that shouldn't hurt a lot. Note that depending on the C compiler
those costs may even get somewhat optimized (e.g. by inlining).
[1] http://hackage.haskell.org/package/Hipmunk
--
Felipe.
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Type system trickery
On Jun 22, 2009, at 14:43 , Andrew Coppin wrote: data Foobar a where Foo :: X - Y - Foobar NoZoo Bar :: X - Y - Foobar NoZoo Zoo :: Foobar NoZoo - Foobar Zoo For some reason, if I do this I get endless type check errors. I have to change the top two back to Foobar a before it will work. *sigh* That's probably because ghc can't fix a type for Foobar a if you never actually use a anywhere. Functional dependencies could solve that, but giving ghc a way to infer a type for it by using it where it doesn't affect anything important is easier and doesn't risk possible(?) weird interactions between FDs and GADTs. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] GHCi infers a type but refuses it as type signature
Thanks for your answers. I still have a question, though... I think the reasoninging here is the following: If MonadState is part of the standard library and it needs this extension to work, then all compilers must support this extension. Yes, exactly, that was my point. I'm not completely sure how standard the MonadState class is though. Also, it might be that there could be implementations of MonadState that do not use the extension? And indeed, I understand from the next (Luke Palmer's) answer that the community does not fully agree on what should be standard: However, your question is rather moot here, as you are using the *mtl. *It uses UndecidableInstances, whose blessing into the de facto standard would require as a precondition the batshit-insanity of the de facto community. I personally use *transformers* as my monad library, as it is (as far as I know) the only Haskell 98 monad library on Hackage (you'll hardly notice the more explicit lifts, I promise!). I just looked through Transformers and it does not define MonadState, indeed. Well... I am a beginner in haskell. I have detailed in the first post the very simplistic example I was trying to set up, the level of a beginner's tutorial. As anyone discovering a new language, I certainly did not intend to look so soon at compiler extensions. Now, trying to avoid duplicate code at this very level of simplicity seems to require compiler extensions! Here it is: - The MonadState type seems required to reuse the same code for State s a and StateT s IO a. - MonadState needs compiler extensions and is implemented using the mtl library which seems to have drawbacks. So 1) How can I use transformers instead of the mtl? This is in no tutorial, and searchinf for mtl on the haskell wiki yields no result at all. 2) What should be the Haskell98-compatible type signature for my play2 function, instead of (MonadState [a] m, Eq a) = a - m Bool ? Thanks again. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] GHCi infers a type but refuses it as type signature
On Tue, Jun 23, 2009 at 6:05 PM, Eric Dedieu papa.e...@free.fr wrote: So 1) How can I use transformers instead of the mtl? This is in no tutorial, and searchinf for mtl on the haskell wiki yields no result at all. cabal install transformers (you need cabal-install to do this... consult #haskell if confused) perhaps: ghc-pkg hide mtl (I think mtl and transformers fight over the Control.Monad module) Then import Control.Monad.Trans.State instead of Control.Monad.State. All else should be well, if I am not forgetting something. 2) What should be the Haskell98-compatible type signature for my play2 function, instead of (MonadState [a] m, Eq a) = a - m Bool ? That depends on the monad library. In transformers it would be: (Monad m, Eq a) = a - StateT [a] m Bool State s is just a type synonym for StateT s Identity, so this works for State as well. Luke ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] GHCi infers a type but refuses it as type signature
On Jun 22, 2009, at 20:02 , Eric wrote: Non type-variable argument in the constraint: MonadState [a] m (Use -XFlexibleContexts to permit this) In the type signature for `play3': play3 :: (MonadState [a] m, Eq a) = a - m Bool So how is it possible that GHCi can infer (and use) a type that you cannot use as signature? This is an infelicity in the GHC type checker: if a library uses an extension, inferred types involving things in the library will silently use the extension even though you haven't declared it --- but if you try to specify the type manually, you have to explicitly declare the extension. I think there's a bug report open on it, because it's poor form (not to mention confusing). http://hackage.haskell.org/trac/ghc/ticket/1897 I think this is the right bug. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] GHCi infers a type but refuses it as type signature
On Tue, Jun 23, 2009 at 6:05 PM, Eric Dedieu papa.e...@free.fr wrote: Now, trying to avoid duplicate code at this very level of simplicity seems to require compiler extensions! Here it is: On a higher level, in case you are interested, here's a description of how I would model your problem. Take this with a grain of salt: we are already in the area where different haskell vets will model this in different ways. This is one of many approaches... Instead of possibly tying the game to its side effects inside a monad, I would model the game as a pure data structure, and then have different interfaces just talk about the pure structure. Note: In the real world, things would be more polymorphic, but I'll keep it concrete for expository purposes: For example: newtype Game = MkGame [Char] empty :: Game empty = MkGame [] play :: Char - Game - (Bool, Game) play x (MkGame mvs) = (x `elem` moves, MkGame (x:mvs)) moves :: Game - [Char] moves (MkGame mvs) = mvs These constitute the only interface you have to Game; it is immoral to use MkGame from here on out. If you were being rigorous, these would go into a module with export list (Game, empty, play, moves). Everything else is straightforward from here. The code you wished to reuse is in play, hidden behind an abstraction barrier so the compiler may ensure that it is reused (because there is no other way to play a Game). State monads don't even enter the picture at this level. (The return type of Play is Game - (Bool, Game), which is State Game Bool... but I would just choose not to notice that; the state structure isn't important enough here to formalize). Luke ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Type system trickery
I'm no expert, but it seems like those constructors should return
Foobar NoZoo, unless you're nesting so there could be a Zoo, in which
case the type variable a should transit, for example:
data Foobar a where
Foo :: X - Y - Foobar NoZoo
Bar :: X - Y - Foobar NoZoo
Baz :: Foobar a - Foobar a
Zoo :: Foobar NoZoo - Foobar Zoo
value = Zoo $ Foo (X 1) (Y 'a')
value2 = Zoo $ Baz $ Foo (X 1) (Y 'a')
-- value3 = Zoo $ Baz $ Zoo $ Foo (X 1) (Y 'a')
--Couldn't match expected type `NoZoo' against inferred type `Zoo'
-- Expected type: Foobar NoZoo
-- Inferred type: Foobar Zoo
--In the second argument of `($)', namely
--`Baz $ Zoo $ Foo (X 1) (Y 'a')'
--In the expression: Zoo $ Baz $ Zoo $ Foo (X 1) (Y 'a')
That is, if you construct a Baz with something else that doesn't have
a Zoo (e.g. NoZoo) then the resultant type is also NoZoo. The converse
is true.
Why would you want it to generate a polymorphic Foobar when it
definitely is NoZoo?
-Ross
(p.s. the example names in this thread are a bit ridiculous ;-) )
On Jun 23, 2009, at 4:01 PM, Andrew Coppin wrote:
Ross Mellgren wrote:
This works for me:
{-# LANGUAGE EmptyDataDecls, GADTs #-}
module Main where
data NoZoo
data Zoo
newtype X = X Int deriving (Show)
newtype Y = Y Char deriving (Show)
data Foobar a where
Foo :: X - Y - Foobar NoZoo
Bar :: X - Y - Foobar NoZoo
Zoo :: Foobar NoZoo - Foobar Zoo
foobar :: Foobar a - X
foobar f = case f of
Foo x _ - x
Zoo g - foobar g
main :: IO ()
main = putStrLn . show $ foobar (Zoo $ Foo (X 1) (Y 'a'))
Could you post a test case?
Thinking about this more carefully, I started out with
data Foobar a where
Foo :: X - Y - Foobar a
Zoo :: Foobar a - Foobar Zoo
which is no good, because Zoo can be nested arbitrarily deep. So I
tried to change it to
data Foobar a where
Foo :: X - Y - Foobar NoZoo
Zoo :: Foobar NoZoo - Foobar Zoo
But *actually*, changing the second type signature only is
sufficient. Indeed, it turns out I don't *want* to change the first
one. I want to use the type system to track whether Zoo may or
may not be present, not whether it is or is not present. In
other words, I want Foobar Zoo to mean that there *might* be a Zoo
in there, but there isn't guaranteed to be one. But I want Foobar
NoZoo to be guaranteed not to contain Zoo.
So anyway... my program now uses GADTs, I've spent ages chasing down
all the typechecker errors (and, inevitably, in some places
clarifying what the code is actually supposed to do), and my program
now typechecks and does what it did before, except with slightly
more type safety. (In particular, I've deleted several calls to
error now, because those case alternatives can never occur).
Thanks to all the people for your help! :-D
___
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] HaRe (the Haskell Refactorer) in action - short screencast
On Tue, 2009-06-23 at 00:02 +0100, Claus Reinke wrote: [...] With the recent interest in screencasts, I thought I'd make a little demo, for archival purposes. [...] Impressive! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Generate Fortran 77 parser from a yacc grammar using Happy
On Jun 23, 2009, at 07:57 , Cetin Sert wrote:
Why is there some C?/C++? code in that .y file?
It has the look of a production grammar with the reduction actions
stripped out (but whatever they used didn't strip the %{ initializer
block). I would say that, for starters, you want to strip or modify
the %{ block, and possibly remove/replace the empty { } actions in the
grammar. More I can't say; I know yacc, not happy.
--
brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com
system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu
electrical and computer engineering, carnegie mellon universityKF8NH
PGP.sig
Description: This is a digitally signed message part
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to determine if a FilePath is a directory name or regular file?
On Jun 23, 2009, at 10:34 , Duncan Coutts wrote: On Tue, 2009-06-23 at 09:31 -0400, Brandon S. Allbery KF8NH wrote: Hypothetical? import System.Posix.Files (getFileStatus, isDirectory) Yeah, if we could make a standard portable variant of this, that'd be great. I've wanted to do that ever since I tripped over it implementing the original filetests in pugs; I know it can be done with some genericness but don't know enough win32 to do it. One question is what to do with the non-generic stuff. For example, Win32 doesn't have symbolic links, but does have reparse points which are sort of similar if you squint; they're a superset of symlink functionality. (The closest thing Unix (not POSIX) has is mountpoints, but those are userspace aside from . and .. being the same inode. POSIX doesn't touch this space, IIRC, because there are POSIX implementations for Win32 (no mountpoints, some implementations may use reparse points to simulate them) and OpenVMS (no mountpoints).) -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Forward compatibility (was Re: [Haskell-cafe] GHCi infers a type but refuses it as type signature)
On Jun 23, 2009, at 05:20 , Luke Palmer wrote: obsolete now, will your code still work when they are gone? Will it still work when the typeclass resolution algorithm is obsoleted by a superior algorithm (I'm looking at you, Oleg! :-)? When Haskell is obsolete, how hard will it be to port? This is the point at which 99% of programmers throw up their hands at the futility of trying to guess what lies 20 years in the future, and just writes the fscking code. I mean, you've just ruled out both Haskell98 *and* Haskell-with-extensions. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Re[2]: Re: (fwd) Haskell logo fail
On Thu, 18 Jun 2009 12:13:09 +0400, Bulat Ziganshin bulat.zigans...@gmail.com wrote: Hello minh, Thursday, June 18, 2009, 11:17:07 AM, you wrote: Why don't we have a picture of a cool dinosaur instead? Something cool because the last heat of life went out of it 65 million years ago? made with secret dinosaur technology made with dinosaur technology :))) Let's see how far we can take this idea: Haskell. Avoid success at all costs. Made with dinosaur technology. Wow, we Haskellites must really be going out to lunch ;-). Speaking of lunch, it's almost 12:00. Now I must be going out to lunch, too. ;- -- Benjamin L. Russell -- Benjamin L. Russell / DekuDekuplex at Yahoo dot com http://dekudekuplex.wordpress.com/ Translator/Interpreter / Mobile: +011 81 80-3603-6725 Haskell. Avoid success at all costs. Made with dinosaur technology. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Type system trickery
On Tue, Jun 23, 2009 at 9:25 PM, Ross Mellgrenrmm-hask...@z.odi.ac wrote: I'm no expert, but it seems like those constructors should return Foobar NoZoo, unless you're nesting so there could be a Zoo, in which case the type variable a should transit, for example: data Foobar a where Foo :: X - Y - Foobar NoZoo Bar :: X - Y - Foobar NoZoo Baz :: Foobar a - Foobar a Zoo :: Foobar NoZoo - Foobar Zoo value = Zoo $ Foo (X 1) (Y 'a') value2 = Zoo $ Baz $ Foo (X 1) (Y 'a') -- value3 = Zoo $ Baz $ Zoo $ Foo (X 1) (Y 'a') -- Couldn't match expected type `NoZoo' against inferred type `Zoo' -- Expected type: Foobar NoZoo -- Inferred type: Foobar Zoo -- In the second argument of `($)', namely -- `Baz $ Zoo $ Foo (X 1) (Y 'a')' -- In the expression: Zoo $ Baz $ Zoo $ Foo (X 1) (Y 'a') That is, if you construct a Baz with something else that doesn't have a Zoo (e.g. NoZoo) then the resultant type is also NoZoo. The converse is true. Why would you want it to generate a polymorphic Foobar when it definitely is NoZoo? You might have a higher-arity constructor and want to construct things like, Qux (Foo X Y) (Zoo (Bar X Y)) What's the type of Qux? If Foobar Zoo means might contain a Zoo, then you can just declare data Foobar a where Foo :: X - Y - Foobar a Bar :: X - Y - Foobar a Zoo :: Foobar NoZoo - Foobar Zoo Qux :: Foobar a - Foobar a - Foobar a and everything is fine. On the other hand, if Foobar Zoo means definitely contains a Zoo, then you need type families to express the type of Qux. Qux :: Foobar a - Foobar b - Foobar (EitherZoo a b) type family EitherZoo a b :: * type instance EitherZoo Zoo Zoo = Zoo type instance EitherZoo NoZoo Zoo = Zoo type instance EitherZoo Zoo NoZoo = Zoo type instance EitherZoo NoZoo NoZoo = NoZoo -- Dave Menendez d...@zednenem.com http://www.eyrie.org/~zednenem/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
