Re: [Haskell-cafe] (no subject)
Jake McArthur wrote: staafmeister wrote: Yes I know but there are a lot of problems requiring O(1) array updates so then you are stuck with IO again Or use ST. Or use IntMap (which is O(log n), but n is going to max out on the integer size for your architecture, so it's really just O(32) or O(64), which is really just constant time). Actually, IntMap is O(min(n,W)) where W is the number of bits in an Int. Yes, IntMaps are linear time in the worst case (until they become constant-time). In practice this is competitive with all those O(log n) structures though. Whereas Data.Map is O(log n) for the usual balanced tree approach. -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] (no subject)
There are also the judy arrays http://hackage.haskell.org/package/HsJudy http://hackage.haskell.org/package/judy dons recently advertised the latter as being 2x faster than IntMap, but I don't know in what respect these two packages differ and why Don decided to create 'judy' despite the existence of HsJudy. 2009/10/15 wren ng thornton w...@freegeek.org: Jake McArthur wrote: staafmeister wrote: Yes I know but there are a lot of problems requiring O(1) array updates so then you are stuck with IO again Or use ST. Or use IntMap (which is O(log n), but n is going to max out on the integer size for your architecture, so it's really just O(32) or O(64), which is really just constant time). Actually, IntMap is O(min(n,W)) where W is the number of bits in an Int. Yes, IntMaps are linear time in the worst case (until they become constant-time). In practice this is competitive with all those O(log n) structures though. Whereas Data.Map is O(log n) for the usual balanced tree approach. -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Eugene Kirpichov Web IR developer, market.yandex.ru ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] is proof by testing possible?
Joe Fredette wrote: I fiddled with my previous idea -- the NatTrans class -- a bit, the results are here[1], I don't know enough really to know if I got the NT law right, or even if the class defn is right. Any thoughts? Am I doing this right/wrong/inbetween? Is there any use for a class like this? I listed a couple ideas of use-cases in the paste, but I have no idea of the applicability of either of them. /Joe http://hpaste.org/fastcgi/hpaste.fcgi/view?id=10679#a10679 A few problems there: (1) The |a| should be natural, i.e. universally qualified in the class methods, not an argument of the typeclass. (2) Just because there's a natural transformation from F to G does not mean there's a related natural transformation back. The law you want is, forall (X :: *) (Y :: *) (f :: X - Y). eta_Y . fmap_F f == fmap_G f . eta_X (3) There can be more than one natural transformation between two functors. Which means a type class is the wrong way to go about things since there can only be one for the set of type parameters. Consider for instance: type F a = [a] type G a = [a] identity :: F a - G a identity [] = [] identity (x:xs) = (x:xs) reverse :: F a - G a reverse = go [] where go ys [] = ys go ys (x:xs) = go (x:ys) xs nil :: F a - G a nil = const [] ... -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Re[2]: [Haskell-cafe] GHC devs
On Wed, Oct 14, 2009 at 11:06 PM, Bulat Ziganshin bulat.zigans...@gmail.com wrote: Hello Andrew, Thursday, October 15, 2009, 12:54:37 AM, you wrote: Does anybody actually get paid to develop GHC? Or is this all people SPJ, SM and Ian are paid by MS Research. Other people involved in core development are mainly scientists (afaik) Taking the opportunity to thank very much both Simons and Ian for the work they do and the enthusiasm they show. You guys rock. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Parsec bug, or...?
Uwe Hollerbach wrote: Yes, I've looked at that and am thinking about it. I'm not quite certain it's needed in my real program... I seem to have convinced myself that if I actually specify a proper set of unique prefixes, ie, set the required lengths for both frito and fromage to 3 in the test program, I won't get into this situation. Assuming I haven't committed another brain-fart there, that would be sufficient; presumably, in a real program one would want to actually specify the unique prefix, rather than a non-unique pre-prefix. It seems to work fine in my real program, anyway. Another approach ---assuming you're not wedded to Parsec--- would be to construct a trie, e.g. with bytestring-trie[1]. Then use Data.Trie.submap to look up the query. If the result is unique then you go with it, if not then list the submap's keys in your error message. The big benefit of this approach is that you needn't maintain a list of lengths for disambiguating the keys, the trie does that for you. [1] http://hackage.haskell.org/cgi-bin/hackage-scripts/package/bytestring-trie -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] Monotype error
It's a poor error message, but GHC's entire handling of impredicative
polymorphism is poor at the moment. Indeed, I'm seriously considering removing
it altogether until we can come up with a more robust story. (So don't rely on
it!)
The error happens because you are trying to use the type (forall a. a) in a
context that requires a monotype (one with no foralls). I have not stared at
the typing rules (in our papers) to convince myself that your program does
transgress them; indeed, I regard the necessity to do so as evidence that the
approach is not robust.
Simon
| -Original Message-
| From: haskell-cafe-boun...@haskell.org
[mailto:haskell-cafe-boun...@haskell.org] On
| Behalf Of Martijn van Steenbergen
| Sent: 14 October 2009 19:35
| To: Haskell Cafe
| Subject: [Haskell-cafe] Monotype error
|
| Dear café,
|
| {-# LANGUAGE Rank2Types #-}
| {-# LANGUAGE ImpredicativeTypes #-}
|
| type Void = forall a. a
|
| newtype Mono a = Mono { runMono :: [Void] }
|
| beep :: Mono a - Mono a
| beep (Mono vs) = Mono (map undefined vs)
|
| Compiling this with GHC results in:
|
| Monotype.hs:9:28:
| Cannot match a monotype with `Void'
|Expected type: Void
|Inferred type: a
|
| What does this error mean and why does the code not compile?
|
| Thanks!
|
| Martijn.
| ___
| Haskell-Cafe mailing list
| Haskell-Cafe@haskell.org
| http://www.haskell.org/mailman/listinfo/haskell-cafe
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Re: [Haskell-cafe] Monotype error
See our previous discussion on this topic here:
http://www.nabble.com/Fwd:-Unification-for-rank-N-types-td23942179.html
Thanks,
Vladimir
On Wed, Oct 14, 2009 at 10:35 PM, Martijn van Steenbergen
mart...@van.steenbergen.nl wrote:
Dear café,
{-# LANGUAGE Rank2Types #-}
{-# LANGUAGE ImpredicativeTypes #-}
type Void = forall a. a
newtype Mono a = Mono { runMono :: [Void] }
beep :: Mono a - Mono a
beep (Mono vs) = Mono (map undefined vs)
Compiling this with GHC results in:
Monotype.hs:9:28:
Cannot match a monotype with `Void'
Expected type: Void
Inferred type: a
What does this error mean and why does the code not compile?
Thanks!
Martijn.
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Re: [Haskell-cafe] (no subject)
At Thu, 15 Oct 2009 10:15:46 +0400, Eugene Kirpichov wrote: but I don't know in what respect these two packages differ and why Don decided to create 'judy' despite the existence of HsJudy. HsJudy doesn't compile against the latest judy library (as Don knew) - presumably he had a good reason to start a new package instead of patching the old one. There should be a way to mark packages as deprecated on hackage, and at the same time direct people to a more suitable alternative. Aside from uploading a dummy new version (ugh!), I don't see a way to do that currently. -- Robin ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Examples/docs for simulated annealing bindings
I found the HsASA library [1] on Hackage, but there's no documentation and it's not particularly intuitive. I can't see any obvious way of choosing initial config or generating new configurations. Google reveals no one using it. Does anyone have ideas? [1]: http://hackage.haskell.org/package/HsASA-0.1 Cheers, D -- Dougal Stanton dou...@dougalstanton.net // http://www.dougalstanton.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Relational Algebra
Hi all, has anybody already developed an EDSL for relational algebra? HaskellDB does that, but its current implementation only allows for generating SQL, are there other implementations? Günther ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Examples/docs for simulated annealing bindings
2009/10/15 Dougal Stanton dou...@dougalstanton.net: I found the HsASA library [1] on Hackage, but there's no documentation and it's not particularly intuitive. I can't see any obvious way of choosing initial config or generating new configurations. Google reveals no one using it. Does anyone have ideas? [1]: http://hackage.haskell.org/package/HsASA-0.1 If the wrapping is not too involved, the original documentation [*] should help... Cheers, Thu [*] http://www.ingber.com/ASA-README.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANNOUNCE: hs-ffmpeg 0.3.2 - Bindings to FFMpeg library
Hello, I am glad to announce next release of hs-ffmpeg library. Now you could download it from the Hackage along with the ffmpeg-tutorials, which show capabilities of this library. The installation process is a bit tricky now, so welcome to my blog post http://progandprog.blogspot.com/2009/10/video-processing-on-haskell-easy.html, where I am describing how to build and install library. Best regards, Vasyl Pasternak ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Parsec bug, or...?
Hi, all, thanks for the further inputs, all good stuff to think about... although it's going to be a little while before I can appreciate the inner beauty of Doaitse's version! :-) I had considered the approach of doing a post-parsec verification, but decided I wanted to keep it all inside the parser, hence the desire to match prefixes there (and lack of desire to write 'string p | string pr | string pre ...'. By way of background, the actual stuff I'm wanting to match is not food names, but some commands for a small ledger program I'm working on. I needed something like that and was tired of losing data to quicken every so often. I realize of course that there are other excellent ledger-type programs out there, but hey, I also needed another hacking project. I'll put this onto hackage in a while, once it does most of the basics of what I need. No doubt the main differentiator between mine and those other excellent ledger programs out there will be that mine has fewer features and more bugs... thanks again, all! Uwe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Finally tagless - stuck with implementation of lam
(sorry for the slow reply on this topic...) Robert Atkey and Oleg presented some very interesting code in response to your query. But some of you might (and should!) be asking why on earth did Jacques use unsafePerformIO?, especially when neither Robert nor Oleg did. Simply put: I answered your question exactly as asked, while they answered the question you *should* have asked. At the exact 'type' involved in your question, there is no good answer; if you want an instance of lam at a monadic type 'directly', you need to 'extract' from the monad. But the point is that that isn't really the right question. Rather than requiring complete parametric polymorphism in the answer-type, if you allow a little non-uniformity through a simple type family, the shift in types is sufficient to no longer require a monadic 'extract' at all. But even once you've gotten to that point, that's not enough, because at that point you still have the issue of what calling convention (by value, name or need) to use. And figuring that out is rather fun, so you got detailed answer from Robert and Oleg explaining that part in detail. Robert carefully used IntT and :- to label the different types, and Oleg's code (http://okmij.org/ftp/tagless-final/CB.hs) showed how these were really just 'labels', which are useful mnemonics for humans, but not essential. If you dig into our JFP paper describing finally tagless in all its gory details, you'll see that we use a poor man's version of type families there too (see section 4.3). Jacques ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Relational Algebra
has anybody already developed an EDSL for relational algebra? HaskellDB does that, but its current implementation only allows for generating SQL, are there other implementations? Hello Günther, Ganesh did something called squiggle a while ago: http://code.haskell.org/squiggle/unstable/ I've done something similar but it's not published or hosted anywhere, so no link. Can upload it to code.haskell.org if you're interested. Both of our projects just generate SQL though, AFAIK. Was there something else you wanted to generate? Alistair ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Relational Algebra
Hi Alistair, Both of our projects just generate SQL though, AFAIK. Was there something else you wanted to generate? I wish I could provide a clear answer to that myself, truth is I'm not certain myself at the moment. All this is related to a rl problem I have, it concerns the business logic of the app I wrote. I hindsight it occurred to me that the algorithm can be abstractly expressed in terms of relational algebra for which I need an EDSL. One concrete implementation could then be an interpreter / compiler to SQL, if I choose to use a database backend, and another implementation could be a interpretor to in-memory data structures (maps, whathaveyou), or a debugger to see if I have got the abstract algorithm right. I had made very good experience with HaskellDB, it was a great help, but the DSL of HaskellDB immediately translates to SQL, it's hardwired to do so. With the newer techniques for designing EDSLs (finally tagless in particular), I'm considering to roll one myself, and I suppose I'll also need HList to do so too. Quite a number of people on this list also use Haskell for rl applications, so I reason that someone must already have tried something similar. Günther ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Finally tagless - stuck with implementation of lam
Hi Jacques, thank you again for your post, better late than never :)! Let me first apologize to you, I did not immediately recognize you as one of the authors of the Finally Tagless paper. After 2 years now of using haskell at a mere layman's level and nevertheless writing better and more concise code than in the 10 years before using other languages I was ready to move a step further. I must admit that things like type arithmetic, monads, functors and whathaveyou can be quite intimidating, but the other day I wrote my first monad, and it really wasn't that hard at all. Anyway, so I had managed to improve my code slightly by introducing an abstraction, a tiny, trivial, naive DSL. That certainly was an eye-opener. When you gave me your solution, I realized that while it was correct, that just couldn't be the last word on it. Something from Oleg that contains a bug? Can't be, I must have a mistake in my thinking here. So I didn't give up on Finally Tagless but read everything I could get my hands on, plus the responses to my posts were also quite enlightening. One minor problem with your paper, and other work from Oleg, well to me that is, I don't ML. Also Oleg is such an insider sometimes he forgets tiny hints for the rest of us. The initial post (not from me) was about An issue with finally tagless ... and in Olegs response to that he eliminates the problem with ease (I know, typically Oleg). Well as soon as I tried that nothing worked until I put the NoImplicitPrelude in there, duh. So at least now I know what to do next: Design an EDSL taglessly for relational algebra (using HList too) write one or 2 interpreters / compilers for SQL and in-memory Dump the code I have written so far and pretend I never had. Best wishes Günther Am 15.10.2009, 17:05 Uhr, schrieb Jacques Carette care...@mcmaster.ca: (sorry for the slow reply on this topic...) Robert Atkey and Oleg presented some very interesting code in response to your query. But some of you might (and should!) be asking why on earth did Jacques use unsafePerformIO?, especially when neither Robert nor Oleg did. Simply put: I answered your question exactly as asked, while they answered the question you *should* have asked. At the exact 'type' involved in your question, there is no good answer; if you want an instance of lam at a monadic type 'directly', you need to 'extract' from the monad. But the point is that that isn't really the right question. Rather than requiring complete parametric polymorphism in the answer-type, if you allow a little non-uniformity through a simple type family, the shift in types is sufficient to no longer require a monadic 'extract' at all. But even once you've gotten to that point, that's not enough, because at that point you still have the issue of what calling convention (by value, name or need) to use. And figuring that out is rather fun, so you got detailed answer from Robert and Oleg explaining that part in detail. Robert carefully used IntT and :- to label the different types, and Oleg's code (http://okmij.org/ftp/tagless-final/CB.hs) showed how these were really just 'labels', which are useful mnemonics for humans, but not essential. If you dig into our JFP paper describing finally tagless in all its gory details, you'll see that we use a poor man's version of type families there too (see section 4.3). Jacques ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] CBN, CBV, Lazy in the same final tagless framework
Just a short note to show how the 3 evaluation orders can be written in a very symmetric manner: o...@okmij.org wrote these as: In call-by-name, we have lam f = S . return $ (unS . f . S) In call-by-value, we have lam f = S . return $ (\x - x = unS . f . S . return) In call-by-need, we have lam f = S . return $ (\x - share x = unS . f . S) These can be rewritten as call-by-name (eta-expanded and application made visible): lam f = S . return $ (\x - unS . f . S $ x) call-by-value (flip) lam f = S . return $ (\x - unS . f . S . return = x) call-by-need (flip) lam f = S . return $ (\x - unS . f . S = share x ) This pushes us to write two helper functions: execS :: (IO a - IO b) - IO a - IO b execS g x = g = share x execM :: Monad m = (m a - m b) - m a - m b execM g x = g . return = x And now, with the magic of slices, we can truly display those 3 in highly symmetric fashion: call-by-name: lam f = S . return $ ((unS . f . S) $) call-by-value (flip) lam f = S . return $ ((unS . f . S) `execM`) call-by-need (flip) lam f = S . return $ ((unS . f . S ) `execS`) (the redundant $ is left in to make the symmetry explicit) And now we see the pattern: lam f = wrap . lift $ ((unwrap . f . wrap) `apply`) where the names above are meant to be suggestive rather than 'actual' names. Jacques ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Need help with ghc static compile for cgi using mysql
For now, I've given up on cheap hosting (via statically compiled CGI). I've created a GHC 6.10.4, cabal-install, Ubuntu 9.04 ec2 instance + MySQL and it works well. Running this plus EBS and Elastic IP will run a little over $60 a month. Ouch. The work going into Haskell Platform is amazing, but... Haskell needs a better commodity hosting story, to allow for casual, fun web hacking. For the record, I tried nearlyfreespeech.net and dreamhost. I wasn't able to install ghc and cabal due to: * FreeBSD GHC support (old version) * FreeBSD library support (no HDBC) * Linux - Missing 'dev' libraries like zlib and not having root access ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Need help with ghc static compile for cgi using mysql
I've run Haskell stuff on VPS hosts like Linode or SliceHost. $20/month is a lot better than $60. On Thu, Oct 15, 2009 at 12:32 PM, Austin King sh...@ozten.com wrote: For now, I've given up on cheap hosting (via statically compiled CGI). I've created a GHC 6.10.4, cabal-install, Ubuntu 9.04 ec2 instance + MySQL and it works well. Running this plus EBS and Elastic IP will run a little over $60 a month. Ouch. The work going into Haskell Platform is amazing, but... Haskell needs a better commodity hosting story, to allow for casual, fun web hacking. For the record, I tried nearlyfreespeech.net and dreamhost. I wasn't able to install ghc and cabal due to: * FreeBSD GHC support (old version) * FreeBSD library support (no HDBC) * Linux - Missing 'dev' libraries like zlib and not having root access ___ 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] Need help with ghc static compile for cgi using mysql
On Thu, Oct 15, 2009 at 10:11 AM, John Van Enk vane...@gmail.com wrote: I've run Haskell stuff on VPS hosts like Linode or SliceHost. $20/month is a lot better than $60. lambdabot is currently hosted on the lowest end linode. The biggest hurdle I hit was that gnu ld is a memory pig when GHC is compiled with split obj. I had to build my own ghc (after disabling split obj, not hard but not adequately documented either) and things seem to be fine now. Before I built GHC without split obj I wasn't even able to link Setup.hs to start building anything. I would go so far as to recommend GHC HQ do something about the split obj issue. I think ideally we need someone to improve gnu ld. RAM is expensive on the linode so you need to make sure the code you want to run is memory efficient (swap is prohibitively slow). Having root and and nice web control panel is a huge win. I'm reasonably happy considering the relative cost. Jason ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] GHC devs
Don Stewart wrote: bulat.ziganshin: Hello Andrew, Thursday, October 15, 2009, 12:54:37 AM, you wrote: Does anybody actually get paid to develop GHC? Or is this all people SPJ, SM and Ian are paid by MS Research. Other people involved in core development are mainly scientists (afaik) Perhaps these are the three people the speaker was referring to then. Seems like there are plenty of other people involved though... Besides MSR and the university groups, the IHG funds Well-Typed to do development, as well. ...not least of all these. ;-) But still, it seems the total GHC manpower effort is significantly smaller than I imagined. (Which just makes it more impressive that GHC is so good...) Ah, MSR, the only known Haskell-related enterprise based in the UK. Sometimes I have these delusions that I should go ever there and see if they'll hire me... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] GHC devs
Well-Typed is in the UK too :) On Thu, Oct 15, 2009 at 1:52 PM, Andrew Coppin andrewcop...@btinternet.com wrote: Don Stewart wrote: bulat.ziganshin: Hello Andrew, Thursday, October 15, 2009, 12:54:37 AM, you wrote: Does anybody actually get paid to develop GHC? Or is this all people SPJ, SM and Ian are paid by MS Research. Other people involved in core development are mainly scientists (afaik) Perhaps these are the three people the speaker was referring to then. Seems like there are plenty of other people involved though... Besides MSR and the university groups, the IHG funds Well-Typed to do development, as well. ...not least of all these. ;-) But still, it seems the total GHC manpower effort is significantly smaller than I imagined. (Which just makes it more impressive that GHC is so good...) Ah, MSR, the only known Haskell-related enterprise based in the UK. Sometimes I have these delusions that I should go ever there and see if they'll hire me... ___ 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] GHC devs
Daniel Peebles wrote: Well-Typed is in the UK too :) Really? Cool! I wonder where... Oh, Oxford. So also not far from me. However, given that I can't even construct a simple sentence correctly... On Thu, Oct 15, 2009 at 1:52 PM, Andrew Coppin andrewcop...@btinternet.com wrote: Sometimes I have these delusions that I should go ever there and see if they'll hire me... ...I think we can safely conclude that nobody is going to be interested in hiring me. :-/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Need help with ghc static compile for cgi using mysql
lambdabot is currently hosted on the lowest end linode. The biggest hurdle I [...] +1. I use linode for (most of) my Haskell work. John ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANN: Reverse Dependencies in Hackage (demo)
Hello, I have implemented reverse dependencies in Hackage. You can play with the demo here: http://bifunctor.homelinux.net/~roel/hackage I already send a message to Haskell-Cafe, but I made a few changes and would like some feedback. You can sort the tables of reverse dependencies by clicking on the column headers. Large tables (base or the total overview) might take some time. Sorting is done client-side with a bit of JavaScript. I added a link to an overview of the reverse dependencies of every package in hackage. It is sorted by the total number of rev. deps by default, so the most dependent-on packages (within hackage) are at the top. In the future such a list might be expanded with other information, like the download count. Things I would like feedback on: - Rev. deps overview for all packages; is it useful? - If you look at the reverse dependencies for a package like digest you'll see a list of packages that depend on digest. Next to the names of the packages that depend on digest are their respective reverse dependencies. The idea is that you can see which are the most important (for some value of important) packages that depend on digest. Is that useful? - Is this the best way to present the information? Currently I am working on a patch for the new hackage-server. Regards, Roel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: Reverse Dependencies in Hackage (demo)
Hi, This is really neat. 2009/10/15 Roel van Dijk vandijk.r...@gmail.com: Things I would like feedback on: - Rev. deps overview for all packages; is it useful? Yes. - If you look at the reverse dependencies for a package like digest you'll see a list of packages that depend on digest. Next to the names of the packages that depend on digest are their respective reverse dependencies. The idea is that you can see which are the most important (for some value of important) packages that depend on digest. Is that useful? Yes, I think so. - Is this the best way to present the information? Are the packages with all zeroes in the columns still reverse dependencies (that don't have any dependencies in turn)? -- Johan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: Reverse Dependencies in Hackage (demo)
2009/10/15 Johan Tibell johan.tib...@gmail.com: - Is this the best way to present the information? Are the packages with all zeroes in the columns still reverse dependencies (that don't have any dependencies in turn)? Yes. They are reverse dependencies which have no reverse dependencies of their own. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Very evil
{-# LANGUAGE EmptyDataDecls #-}
module Main (main) where
import Unsafe.Coerce
data Anything
newtype Key x = Key Int deriving Eq
type Dict = [(Key Anything, Anything)]
put :: Key x - x - Dict - Dict
put k' v' = raw (unsafeCoerce k') (unsafeCoerce v')
where
raw k0 v0 [] = [(k0,v0)]
raw k0 v0 ((k,v):zs)
| k == k0 = (k0 ,v0) : zs
| otherwise = (k ,v ) : raw k0 v0 zs
get :: Key x - Dict - Maybe x
get k' zs = unsafeCoerce (raw (unsafeCoerce k') zs)
where
raw k0 [] = Nothing
raw k0 ((k,v):zs)
| k == k0 = Just v
| otherwise = raw k0 zs
main = do
let k1 = Key 1 :: Key Int
let k2 = Key 2 :: Key Double
let k3 = Key 3 :: Key String
let k4 = Key 4 :: Key Bool
let d0 = []
let d1 = put k1 123 d0
let d2 = put k2 123 d1
let d3 = put k3 123 d2
let d4 = put k4 True d3
print (get k1 d4)
print (get k2 d4)
print (get k3 d4)
print (get k4 d4)
Unsafe coerce, anyone?
This particular example appears to run without incident, but the GHC
docs suggest that this is very... well, unsafe. (In particular, the docs
claim this will fall over on function types.)
I presume there's some less-evil way of doing this?
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Re: [Haskell-cafe] more improvable randomness
On Thu, 8 Oct 2009, Michael Mossey wrote:
I wrote some code to model the keystroke-to-keystroke delay in a person
typing, with pseudorandomness. There are two kinds of delays.. one is a
very small delay as the person reaches for a new key (call this 'reach'
delays), the other is a larger delay that represents a pause to think or
to take a break (call this 'break' delays).
Has this to do with your PortMidi problems?
breakSeries :: Int - Int - StdGen - [Float]
breakSeries lowerB upperB gen =
let (n,gen1) = randomR (lowerB,upperB) gen
(gen2,gen3) = split gen1
delay = generate 1 gen2 breakM
in replicate n 0 ++ [delay] ++ breakSeries lowerB upperB gen3
breakM :: Gen Float
breakM = frequency [ (10, choose( 1::Float , 2))
, (10, choose( 4::Float , 6)) ]
test = (print . take 100 . breakSeries 2 4 ) = newStdGen
Gen is from QuickCheck package, isn't it? That can't be mixed with Random
from 'random' package. You could wrap 'randomR' in a State monad
('transformers' package), write your own 'frequency' function for that,
and run that with the seed from 'newStdGen'.
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Re: [Haskell-cafe] Very evil
It looks like you may want
http://www.haskell.org/ghc/docs/latest/html/libraries/base/Data-Dynamic.html
. It does more or less what you're talking about behind the scenes,
but probably uses the magical Any type to not encounter issues with
functions, and gives you a Nothing if you attempt to coerce it to the
wrong type.
On Thu, Oct 15, 2009 at 5:10 PM, Andrew Coppin
andrewcop...@btinternet.com wrote:
{-# LANGUAGE EmptyDataDecls #-}
module Main (main) where
import Unsafe.Coerce
data Anything
newtype Key x = Key Int deriving Eq
type Dict = [(Key Anything, Anything)]
put :: Key x - x - Dict - Dict
put k' v' = raw (unsafeCoerce k') (unsafeCoerce v')
where
raw k0 v0 [] = [(k0,v0)]
raw k0 v0 ((k,v):zs)
| k == k0 = (k0 ,v0) : zs
| otherwise = (k ,v ) : raw k0 v0 zs
get :: Key x - Dict - Maybe x
get k' zs = unsafeCoerce (raw (unsafeCoerce k') zs)
where
raw k0 [] = Nothing
raw k0 ((k,v):zs)
| k == k0 = Just v
| otherwise = raw k0 zs
main = do
let k1 = Key 1 :: Key Int
let k2 = Key 2 :: Key Double
let k3 = Key 3 :: Key String
let k4 = Key 4 :: Key Bool
let d0 = []
let d1 = put k1 123 d0
let d2 = put k2 123 d1
let d3 = put k3 123 d2
let d4 = put k4 True d3
print (get k1 d4)
print (get k2 d4)
print (get k3 d4)
print (get k4 d4)
Unsafe coerce, anyone?
This particular example appears to run without incident, but the GHC docs
suggest that this is very... well, unsafe. (In particular, the docs claim
this will fall over on function types.)
I presume there's some less-evil way of doing this?
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Re: [Haskell-cafe] Parsec bug, or...?
On 15 okt 2009, at 16:58, Uwe Hollerbach wrote: Hi, all, thanks for the further inputs, all good stuff to think about... although it's going to be a little while before I can appreciate the inner beauty of Doaitse's version! :-) The nice thing is that you do not have to understand the inner workings ;-} I basically builds a greedy parser for each word to be recognised which can stop and assume the rest is there if it can no longer proceed (the `opt` is greedy in its left alternative) . Hence it recognises the longest possible prefix. Since my parsers pursue all alternatives in parallel you automatically get what you want, without having to indicate prefix lengths, calls to try, etc. The amb combinator has type amb :: Parser a - Parser [a] and collects the result from all alternatives its argument parser is constructed from; you might say it convert an ambiguous parser to a parser with a list as result, hence preventing the rest of the input being parsed over and over again. I am currently working on bringing back more abstract interpretation in the implementation (i.e. what we have had for almost 10 years in the uulib library), but I do not expect you to see a lot of that from the outside. If you want to work with left-recursive parsers (which does not seem to be the case), you may revert to more complicated solutions such as found in the christmastree (Changing Haskell's Read Implementation Such That by Manipulationg Abstract Syntax Trees Read Evaluates Efficiently) package if you need to generate parsers online, or to happy-based solutions in case your grammar is fixed. If you have any questions do not hesitate to ask, Doaitse I had considered the approach of doing a post-parsec verification, but decided I wanted to keep it all inside the parser, hence the desire to match prefixes there (and lack of desire to write 'string p | string pr | string pre ...'. By way of background, the actual stuff I'm wanting to match is not food names, but some commands for a small ledger program I'm working on. I needed something like that and was tired of losing data to quicken every so often. I realize of course that there are other excellent ledger-type programs out there, but hey, I also needed another hacking project. I'll put this onto hackage in a while, once it does most of the basics of what I need. No doubt the main differentiator between mine and those other excellent ledger programs out there will be that mine has fewer features and more bugs... thanks again, all! Uwe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: ANN: Reverse Dependencies in Hackage (demo)
You can sort the tables of reverse dependencies by clicking on the column headers. I wouldn't have thought about clicking in the columns headers. Maybe you could show the order arrow already in the beggining, before any clicks, this would give a hint. - Rev. deps overview for all packages; is it useful? Sure! Do you think it could be complemented with a graph view? I liked this, from graphviz page: http://graphviz.org/Gallery/undirected/softmaint.html - Is this the best way to present the information? Just cosmetics: in the individual package rev. dependencies, what do you think of using two columns, one for direct dependencies table and other for indirect dependencies? This would remove the need for navigation links in the main table. Also, here, if it's feasible, I think a graph with just the central package and 1fst and 2nd order dependencies could be usefull. Best, Maurício ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Best Editor In Windows
Nathan P. Campos wrote: Hello, I'm very new at Haskell, i'm reading a book and starting, but i want to know which is the best editor for development under Windows, because now i'm using Notepad++(That i use to develop in C++). Thanks, Nathan Paullino Campos If you use emacs, check out http://www.haskell.org/haskell-mode/ -- View this message in context: http://www.nabble.com/Best-Editor-In-Windows-tp25908187p25917670.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Best Editor In Windows
I'm very new at Haskell, i'm reading a book and starting, but i want to know which is the best editor for development under Windows, because now i'm using Notepad++(That i use to develop in C++). The best editor for development is Emacs, of course. http://www.gnu.org/software/emacs Stefan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Best Editor In Windows
Hello! On Thu, Oct 15, 2009 at 8:10 PM, Stefan Monnier monn...@iro.umontreal.ca wrote: I'm very new at Haskell, i'm reading a book and starting, but i want to know which is the best editor for development under Windows, because now i'm using Notepad++(That i use to develop in C++). The best editor for development is Emacs, of course. http://www.gnu.org/software/emacs Stefan I've been using Emacs with haskell-mode that Stefan Monnier created and maintains, and I have to say, it's fantastic! On Linux or Windows, it just works(TM). Thank you, Stefan! The only thing I haven't figured out is how to do tab-completion of words in the ghci buffer. Do I need to use a different key combination? I couldn't find that in the documentation. Paulo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Best Editor In Windows
In my humble opinion, one of the best editors for development of all time is Leo: http://webpages.charter.net/edreamleo/front.html Leo takes the idea of code folding and gives you complete control over it. That is, unlike other editors which only let you fold the code inside if/while/for/etc. statements and which only show you an outline consisting of a level for files and a level for function, Leo lets you structure the levels of your outline arbitrarily so that you can fold arbitrary chunks of code and do things like grouping together functions and files with a similar purpose or implementation. By structuring your code as an outline, you make it easier for others and yourself both to navigate through the code and also to see at a glance the high-level structure. Anyway, just wanted to use this opportunity to plug my favorite tool. :-) The downside about it is that the implementation sometimes feels a bit slow and clunky, so part of me really hopes that at the very least people will learn enough about this tool to take its ideas and steal them for other editors! Cheers, Greg On Oct 15, 2009, at 6:10 PM, Stefan Monnier wrote: I'm very new at Haskell, i'm reading a book and starting, but i want to know which is the best editor for development under Windows, because now i'm using Notepad++(That i use to develop in C++). The best editor for development is Emacs, of course. http://www.gnu.org/software/emacs Stefan ___ 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: Best Editor In Windows
The only thing I haven't figured out is how to do tab-completion of words in the ghci buffer. Do I need to use a different key combination? I couldn't find that in the documentation. I think it's just a missing feature. Stefan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Fwd: [BostonHaskell] Next meeting: October 21st at MIT (32G-882)
-- Forwarded message -- From: Ravi Nanavati rav...@alum.mit.edu Date: Thu, Oct 15, 2009 at 11:07 PM Subject: [BostonHaskell] Next meeting: October 21st at MIT (32G-882) To: bostonhask...@googlegroups.com I'm pleased to announce the October meeting of the Boston Area Haskell Users' Group. Based on the feedback from the meeting polls and the constraints of our speakers, the October meeting has been scheduled for Wednesday, October 21st from 7pm - 9pm. Like the past three meetings, it will be held in the MIT CSAIL Reading Room (32-G882, i.e. a room on the 8th floor of the Gates Tower of the MIT's Stata Center at 32 Vassar St in Cambridge, MA). Based on the topic poll (and because he volunteered), our first speaker will be Brian Sniffen with an introduction to Parsec. Following his presentation will be our traditional break (with the now-traditional baked goods). Our second speaker will be Edward Kmett, who will be picking up the part of his monoids and parsing presentation that we didn't get to in August or September (third time's the charm!): A Parallel Parsing Trifecta: Iteratees, Parsec, and Monoids. Edward's slides from August are here: http://comonad.com/reader/wp-content/uploads/2009/08/IntroductionToMonoids.pdf I'd recommend looking at them if you weren't at the August meeting (or want a refresher on the material) since the two parts of his presentation were designed to go concurrently. There's also a preview of the presentation as part of this post on Edward's blog: http://comonad.com/reader/2009/iteratees-parsec-and-monoid/ The October attendance poll is at: http://doodle.com/u7762nfxpghsrn2r As always, responding to this poll will help with two things: 1. Getting an idea of what fraction of the Boston-area Haskell community can and can't attend this meeting (to help with future scheduling). 2. Giving me an estimated count of attendees, since I have talked my wife into baking some more goodies and bringing drinks again. Helping with BostonHaskell (besides volunteering to speak at future meetings): 1. Sponsorship of refreshments is still being eagerly solicited. 2. Please let me know if you're willing to arrive early (6:30pm) to help me move refreshments from my car. Based on past experience, I could use 3-4 volunteers. 3. Please let me know if you're willing to arrive early (6:30pm) to stand by the door and let people into the 8th floor. I'm guessing 1 or 2 volunteers is enough here. 4. If someone is willing to edit the HaskellWiki page, post to reddit or otherwise publicize the meeting please just go ahead and do that (especially as I'm sending this out a bit later than intended). 5. I'm also still having trouble embedding this poll in a page on our Google Group, so if anyone has any ideas about that, please feel free to try (any group member can edit pages) and/or offer other suggestions. If you have any questions about the meeting please send them to the BostonHaskell mailing list: bostonhask...@googlegroups.com or contact me directly. I look forward to seeing many Boston-area Haskellers at the October meeting! Thank you, - Ravi Nanavati --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups BostonHaskell group. To post to this group, send email to bostonhask...@googlegroups.com To unsubscribe from this group, send email to bostonhaskell+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/bostonhaskell?hl=en -~--~~~~--~~--~--~--- ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] GHC devs
It is pretty amazing what such a small coterie of devs has accomplished in GHC. Compare this to the thousands that work on GCC/ javac/csc and vis studio etc. So, once again, kudos. max On Oct 16, 2009, at 2:30 AM, Andrew Coppin wrote: Daniel Peebles wrote: Well-Typed is in the UK too :) Really? Cool! I wonder where... Oh, Oxford. So also not far from me. However, given that I can't even construct a simple sentence correctly... On Thu, Oct 15, 2009 at 1:52 PM, Andrew Coppin andrewcop...@btinternet.com wrote: Sometimes I have these delusions that I should go ever there and see if they'll hire me... ...I think we can safely conclude that nobody is going to be interested in hiring me. :-/ ___ 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] Very evil
Maybe you would like the hetero-map package. Its purpose is to do
precisely what you are doing, but in a typesafe way.
On Thu, Oct 15, 2009 at 3:10 PM, Andrew Coppin
andrewcop...@btinternet.com wrote:
{-# LANGUAGE EmptyDataDecls #-}
module Main (main) where
import Unsafe.Coerce
data Anything
newtype Key x = Key Int deriving Eq
type Dict = [(Key Anything, Anything)]
put :: Key x - x - Dict - Dict
put k' v' = raw (unsafeCoerce k') (unsafeCoerce v')
where
raw k0 v0 [] = [(k0,v0)]
raw k0 v0 ((k,v):zs)
| k == k0 = (k0 ,v0) : zs
| otherwise = (k ,v ) : raw k0 v0 zs
get :: Key x - Dict - Maybe x
get k' zs = unsafeCoerce (raw (unsafeCoerce k') zs)
where
raw k0 [] = Nothing
raw k0 ((k,v):zs)
| k == k0 = Just v
| otherwise = raw k0 zs
main = do
let k1 = Key 1 :: Key Int
let k2 = Key 2 :: Key Double
let k3 = Key 3 :: Key String
let k4 = Key 4 :: Key Bool
let d0 = []
let d1 = put k1 123 d0
let d2 = put k2 123 d1
let d3 = put k3 123 d2
let d4 = put k4 True d3
print (get k1 d4)
print (get k2 d4)
print (get k3 d4)
print (get k4 d4)
Unsafe coerce, anyone?
This particular example appears to run without incident, but the GHC docs
suggest that this is very... well, unsafe. (In particular, the docs claim
this will fall over on function types.)
I presume there's some less-evil way of doing this?
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