- Haskell-Cafe - Haskell.org

Parsec combinator like Prolog's cut operator?
by Erik de Castro Lopo 03 Jul '10

03 Jul '10

Hi all, I'm reading John Hughes' paper "Generalizing Monads to Arrows" and found the statement regarding parser combinators: "... depend on the programmer using an additional combinator similar to Prolog's 'cut' operator do declare that a parser need never backtrack beyond a certain point." Does something like this already exist in Parsec? If not is there a way to write it? Having this would really help with a parsing problem I have. Cheers, Erik -- ---------------------------------------------------------------------- Erik de Castro Lopo http://www.mega-nerd.com/

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a very pedestrian question about maillists
by Vasili I. Galchin 03 Jul '10

03 Jul '10

Hello, Suppose I have the following fragment of a posting: Message: 3 Date: Fri, 2 Jul 2010 12:32:43 -0500 From: aditya siram <aditya.siram(a)gmail.com> Subject: Re: [Haskell-cafe] How easy is it to hire Haskell programmers To: Andrew Coppin <andrewcoppin(a)btinternet.com> Cc: haskell-cafe(a)haskell.org Message-ID: <AANLkTil-p8qMNkPdqEwDSciqw2RjASzbRL2-sPyf079u(a)mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1 On another posting I tried counter-posting using the "Message-ID" but the counter-post bounced back to me as non-deliverable. How do I post on a "thread" like "How easy is it to hire Haskell programmers"? Thanks, Vasili

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Status of status on freenode
by Walt Rorie-Baety 03 Jul '10

03 Jul '10

My work environment is what I'd call typical US corporate - IRC nodes are blocked, but I can use a web-based client to access it. A couple of days ago, someone had the poor taste to throw a pack of rabid spam bots into the #haskell channel, forcing the short-term solution of shutting down all web-based users. I noticed today that I can now access #haskell again, but have no voice. I'm wondering: is there any way to modify access to allow registered users to speak? I've tried using other web-based clients, but none of then connect to the freenode server. At home, I can (and do) use mIRC, so I'm not totally cut off - and now I can read, but not communicate back to, the #haskell channel. BTW, please direct me to another list, if this issue does not belong on it. Walt "BMeph" Rorie-Baety "A mountain that eats people? I want one!." - Richard, of LFGComic.com

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ANNOUNCE: hs-cryptohash 0.4
by Vincent Hanquez 03 Jul '10

03 Jul '10

Hi Haskell-cafe, I'ld like to announce the existence of hs-cryptohash [1] which provides most common digests (sha1, sha2 family, md[245], ripemd160) in a incremental and one-pass api. It's also much faster than pure haskell implementation i've played with, since the underlaying algorithms are all fairly optimized in C. The API remains pure with the use of unsafePerformIO, which after reading everything i could about it and some testing, seems to be safe in this context. The main reason for this library is the lack of incremental api exposed by current digest libraries, and filling the void about some missing digest algorithms; Also the speed comes as a nice bonus. I'm looking forward to hear any comments, [1] http://github.com/vincenthz/hs-cryptohash -- Vincent Hanquez

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MState: A consistent State monad for concurrent applications
by Nils Schweinsberg 03 Jul '10

03 Jul '10

Hi, I have been trying to use the State monad for concurrent applications and came up with a little library.[1] My "MState" uses an IORef to maintain the state between different threads. The library also offers a simple way to fork off new threads using its own "forkM" function. This function will asure that every thread in an "evalMState"/"execMState" call will be finished before the final result is returned. The library is also on github.com.[2] Please let me know what you think of it and whether or not I should put it on hackage. Cheers, Nils Schweinsberg [1] http://n-sch.de/hdocs/mstate/Control-Concurrent-MState.html [2] http://github.com/mcmaniac/mstate

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Re: [Haskell-cafe] ANN: Haskell-mode 2.8.0
by Ivan Lazar Miljenovic 02 Jul '10

02 Jul '10

Deniz Dogan <deniz.a.m.dogan(a)gmail.com> writes: > Doing so would only mean that haskell-mode will most likely never be a > part of Emacs, meaning that anyone looking for programming Haskell in > Emacs would have to download an external library, be it through > package.el or not. And what's so bad about that? I suppose it might be possible to have a cut-down haskell-mode in Emacs for casual hacking, the way there's python-mode and pymacs. > To put it short, there are no pros in making the new Haskell indenter > a strict part of haskell-mode. There are if it brings in a lot of cool features. -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com

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Re: [Haskell-cafe] ANN: Haskell-mode 2.8.0
by Svein Ove Aas 02 Jul '10

02 Jul '10

On Sat, Jul 3, 2010 at 1:07 AM, Deniz Dogan <deniz.a.m.dogan(a)gmail.com> wrote: > > Since there is no reason what so ever to integrate this external > Haskell indenter tightly into haskell-mode, I don't see any reason to > do so. Doing so would only mean that haskell-mode will most likely > never be a part of Emacs, meaning that anyone looking for programming > Haskell in Emacs would have to download an external library, be it > through package.el or not. > > To put it short, there are no pros in making the new Haskell indenter > a strict part of haskell-mode. > Sure there is. I expect there to be quite a lot of shared code. It's not solely an indenter; the same interface and capabilities will be used for a debugger, refactoring, and type signature info. Haskell-mode should still work without it, to about the same degree as today, but actually doing so would be a *major* degradation compared to the state of the art once I'm done with it. In any case, I expect the actual installation to be via cabal-install. -- Svein Ove Aas

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Re: [Haskell-cafe] ANN: Haskell-mode 2.8.0
by Ivan Lazar Miljenovic 02 Jul '10

02 Jul '10

Deniz Dogan <deniz.a.m.dogan(a)gmail.com> writes: > Why should it not become part of Emacs? > > I would like it if this Haskell indenter was external to haskell-mode > itself instead of making haskell-mode external to Emacs. Why should it? Look at all the effort that the Haskell community went through to _unbundle_ libraries from GHC, and now Emacs is bundling more and more with it, which means it's harder to use a newer version of a package than the bundled one. -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com

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Looking for GUI (WX) example code
by Günther Schmidt 02 Jul '10

02 Jul '10

Hi all, I'd be interested in studying GUI (wxhaskell) code. Does anyone have links to good gui code? Best regards Günther

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GHCi and State
by corentin.dupont＠ext.mpsa.com 02 Jul '10

02 Jul '10

Another couple of reflexions (sorry for monopolizing): 1. Since i am making a Nomic game, players will have to submit rules. These rules will be written in a sub-set of haskell. Instead of writing my own reader/interpreter, i'd like to use GHC to compil them on the fly, and then add them to the current "legislation". What would you suggest me to do that? Any pointers? 2. For now, the game is more or less playable in GHCi. But my concern is: When you use GHCi, you are in the IO monad, right? How to had state to this monad? I would like that the player can compose his rule in GHCi, and when he is done, he can submit it in GHCi with something like: *Nomic> submitRule <myrule> And then the game takes the rule, possibly modify the current legislation, and give the hand back to GHCi. So the "current legislation" has to be a state of the GHCi's loop. Is this possible at all? submitRule would have a type more or less like that (GameState contains the legislation): submitRule :: Rule -> StateT GameState IO () Thanks for your attention! I know this is a bit confused! Best, Corentin

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