Re: [Haskell-cafe] [Haskell] ANN: Haskell bindings for the igraph C library
Am 16.12.2012 20:24, schrieb Jason Dagit: How does this compare with fgl? http://hackage.haskell.org/package/fgl FGL is a pure Haskell library while our haskell-igraph package uses the foreign function interface to run all graph-related calculations in C the C library igraph (I haven't implemented any graph algorithms). The runtime performance with our igraph library should be the same as if you'd be using the native C library (if you ignore the small Haskell-C-Haskell overhead). It is also seems to be more of a higher level library. As user you don't have to worry about node-IDs/labels or whether your graph is static or not (in the FGL context). Using features like GADTs and type families/associated types it is possible to keep track of informations like whether or not your graph is directed/weighted or not, while in FGL all graphs are by default directed and unweighted. Consider for example edges :: Graph d a - [Edge d a] -- directed, unweighted graph g :: Graph D a -- undirected, weighted graph w :: Graph (Weighted U) a which leads to edges g :: [Edge D a] edges w :: [Edge (Weighted U) a] or even functions like toUndirected :: (IsDirected d, E (ToUndirected d) a) = Graph d a - Graph (ToUndirected d) a toDirected :: (IsUndirected u, E (ToDirected u) a) = Graph u a - Graph (ToDirected u) a which evaluate to toUndirected g :: Graph U a toDirected w :: Graph (Weighted D) a This is even revertable, and `toDirected . toUndirected == id` while the FGL function `undir` simply adds all missing edges and loses track of what the original/directed graph looked like. Maybe George has more details on why he wanted to use igraph instead of FGL. - Nils ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANN: Haskell bindings for the igraph C library
Hi Haskellers, dear igraph community, I am pleased to announce the release of our (inofficial) Haskell bindings to the igraph C library. igraph is a powerfull library for creating and manipulating directed, undirected and weighted graphs. Our package offers a complete coverage of all functions on structural properties of graphs. Compared to the official packages for R and Python it is the first library that offers type level distinction between directed/undirected and weighted graphs. Haskells type system allows to keep track of the types of your nodes and whether or not your graph and its edges are directed or undirected, weighted or unweighted. Haskell graphs may contain any Haskell value as node values, kind of similar to Pythons attributes. igraph on hackage, the official package database for Haskell: http://hackage.haskell.org/package/igraph (requires the current igraph-0.6 C library) The official igraph website: http://igraph.sourceforge.net/index.html Until hackage generates the haddock documentation, the documentation is also available at: http://hs.nils.cc/igraph-0.1/html/index.html Any feedback is appreciated, - Nils Schweinsberg - George Giorgidze ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] haskell cryptogaphic libraries
Am 24.08.2012 14:47, schrieb marcmo: * AES Encryption/Decryption (CBC-Mode) For AES there is the SimpleAES package[1] which is super easy to use: import qualified Data.ByteString as BS import Data.ByteString.Lazy as BL import Codec.Crypto.SimpleAES key :: IO Key key = BS.readFile key encrypt :: ByteString - IO ByteString encrypt bs = do k - key encryptMsg CBC k bs decrypt :: ByteString - IO ByteString decrypt bs = do k - key return $ decryptMsg CBC k bs (note that the key is a strict ByteString while the encrypted/decrypted data is lazy) [1]: http://hackage.haskell.org/package/SimpleAES ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] GSoC proposal: Units for GHC
Hi Haskell-Cafe GHC-users! I'm looking to apply for the GSoC and since I've worked on GHC before I'd like to continue to do so. My proposal would be something that tempted me (as a physics student) for a while: Units for Haskell/GHC. This project has been suggested for a long time on the GHC wiki, and there is already a lot of work done for other languages like ML, F# etc[1]. I have tried to implement e.g. the unification algorithm from the Types for Units-of-Measure in F# talk[2] for an abstract syntax tree[3] and it was pretty much straight forward. As I see it, the project would consist of: 1.) Find appropriate rules/algorithms for unit analysis. Most (if not all?) of this should be covered in those papers/talks on [1]. 2.) Applying the rules to the Haskell syntax tree used in GHC. I have approximately 3 years of experience with Haskell, I worked for the database research group[4] at the University of Tübingen (Germany) on the Database Supported Haskell[5] library. I've done most of the coding for the monad comprehension[6] extension, which has been added to the latest GHC release version. I'm already quite familiar with the GHC internals of the compiler/typechecker, and even though I'd have to look up how exactly type interference etc. works in GHC (as I've only *used* it, but never tried to understand/modify it) I'm confident that the work on GHC itself should be doable in the given timeframe. So my questions would be: Do you think this is a appropriate GSoC project? What should I include in the application/project proposal? Anything else? Opinions, suggestions? I realize that I'm kind of late and probably should have written this email a long time ago. But there are still 2 days left for the student application and hopefully I'll get some good feedback by then. - Nils [1]: http://research.microsoft.com/en-us/um/people/akenn/units/index.html [2]: http://research.microsoft.com/en-us/um/people/akenn/units/MLWorkshop2008.pdf [3]: https://github.com/mcmaniac/units/blob/master/src/Unification.hs [4]: http://db.inf.uni-tuebingen.de/team [5]: http://hackage.haskell.org/package/DSH [6]: http://db.inf.uni-tuebingen.de/files/giorgidze/haskell2011.pdf ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] GSoC proposal: Units for GHC
Am 04.04.2012 13:48, schrieb Jurriën Stutterheim: This sounds pretty cool and useful. How much of this can be implemented in a library and how much of this would need to be supported on a compiler level? Ideally, most of this would be solved on the library level. The compiler would have to know how to typecheck units, e.g. the addition (+) would combine two values of the same unit, the (/) operation would divide them: (+) :: a - a - a (/) :: a - b - a/b The idea is to have the compiler complain whenever you try to add b to a or if you expect something other than a/b as result from a division. This would require modifications to GHC at compiler level. A library could offer some basic units (SI units for example) and maybe even unit aliases (N = kg*m/s^2), but I don't see how the core of this unit verification system could be placed into a library. - Nils ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] build-type: configure on windows
Hi, I'm having a few problems with cabals build-type configure on windows, especially with the packages curl and pcre-light. Both fail either with: * Missing C library: pcre ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] build-type: configure on windows
Hi, I'm having a few problems with cabals build-type configure on windows, especially with the packages curl and pcre-light. Both fail either with: configure: error: curl libraries not found, so curl package cannot be built Configuring pcre-light-0.4... cabal: Missing dependency on a foreign library: * Missing C library: pcre Both libraries (pcre3.dll and libcurl.dll) are in my PATH variable, and I can build other non-haskell-applications which are using these via mingws gcc compiler. But still, somehow cabal seems unable to find them. Using the recommanded --extra-include-dirs and --extra-lib-dirs won't help either. Or is cabal looking for different files than those two .dlls? Can anyone help me on this? Did anyone manage to build curl/pcre-light on windows? My current configuration is MinGW/msys with gcc 4.5, ghc 6.12.3, cabal-install 0.8.2, cabal 1.8.0.6. libcurl.dll and pcre.dll are the latest builds from the official webpages. Thanks for any Help, Nils PS: Sorry for the previous (incomplete) mail. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] build-type: configure on windows
Am 11.11.2010 13:41, schrieb Stephen Tetley: Do you have the headers installed as well as the dlls? For headers, MSys will have a search path of at least these two directories msys\1.0\local\include MinGW\include Is there an environment variable for this? As I said, I tried using --extra-include-dirs with MinGW\include. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] build-type: configure on windows
Am 11.11.2010 14:25, schrieb Stephen Tetley: I'm not sure about an environment variable. Adding the MinGW\ prefix looks wrong, you may have to experiment with paths and forward or back slash separators a bit. I can't remember which convention (Windows) cabal uses. I tried every possible combination. Apparently, the configure script is completly ignoring those --extra-..-dirs flags. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] windows network programming
Am 02.11.2010 01:20, schrieb Paulo Tanimoto: http://hackage.haskell.org/package/network You just have to remember that you need to call withSocketsDo on windows before doing anything with the network library. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] windows network programming
Am 02.11.2010 19:57, schrieb Michael Litchard: got any urls with examples? Sure, see this short server-client-ping-pong application. By the way, I noticed that you don't need withSocketsDo on windows 7, but I guess it's there for a reason for older windows versions. :) import Control.Concurrent import Network import System.IO main :: IO () main = withSocketsDo $ do forkIO waitAndPong ping -- The basic server waitAndPong :: IO () waitAndPong = do socket - listenOn (PortNumber 1234) (handle,_,_) - accept socket hSetBuffering handle LineBuffering incoming - hGetLine handle putStrLn ( ++ incoming) hPutStrLn handle pong -- The basic client ping :: IO () ping = do handle - connectTo localhost (PortNumber 1234) hSetBuffering handle LineBuffering hPutStrLn handle ping incoming - hGetLine handle putStrLn ( ++ incoming) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Parsing workflow
Hi! I'm having a really hard time to write a correct parser for a small language I've developed. I have been trying to write a parser using parsec, but always get a lot of error messages like unexpected \n, expected ..., new-line or... when trying to run the parser. Then I read about the happy parser and really liked the separation of lexing the text into tokens and parsing the actual logic behind those tokens. Since I couldn't get familiar with the lexer alex I gave up on the alex-happy-approach again and went back to parsec. But with that lexer-parser idea on my mind, my parser currently looks a lot like a lexer. So I came up with the idea of using a combination of parsec and happy, where I generate a list of tokens for my text via parsec and analyse it with happy. My questions would be: - Is this a valid approach? - What is your workflow on parsing complex data structures? - What about performance? Since my project is going to be an interpreted language parsing performance might be interesting aswell. I've read that happy is in general faster than parsec, but what if I combine both of them as I said above? I guess that parsing a simple list of tokens without any nested parser structures would be pretty fast? - Do you have any other ideas on how to improve my parser? - What are your general thoughts on happy vs. parsec? Thanks for any replies, Nils ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Parsing workflow
Am 31.10.2010 16:50, schrieb Ozgur Akgun: I don't know if you've already used it, but Parsec includes some kind of a lexer through the Language http://hackage.haskell.org/packages/archive/parsec/3.1.0/doc/html/Text-Parsec-Language.html and Token http://hackage.haskell.org/packages/archive/parsec/3.1.0/doc/html/Text-Parsec-Token.html modules. You can start by having a look at the makeTokenParser http://hackage.haskell.org/packages/archive/parsec/3.1.0/doc/html/Text-Parsec-Token.html#v:makeTokenParser function. Yeah, I've read about the TokenParser, but since my language is not a typical programming language it's use is very limited for me. My language is basicly a combination of a scripting language and a markup language like, for example, markdown. And parsing that scripting language isn't the difficult part so far... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Parsing workflow
Am 31.10.2010 16:53, schrieb Vo Minh Thu: I can't really tell from your description, but maybe this is because of the way Parsec works when it deals with alternatives. When you combine several parsers with e.g. '|' or 'choice', an alternative that can consume some input but fails will make the whole combined parser fail too. So you have to either factorize you parsers or use the 'try'. See the documentation for 'try' at http://hackage.haskell.org/packages/archive/parsec/3.1.0/doc/html/Text-Parsec-Prim.html . This is exactly what gives me headaches. It's hard to tell where you need try/lookAhead and where you don't need them. And I don't really feel comfortable wrapping everything into try blocks... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Ultra-newbie Question
Am 18.09.2010 09:51, schrieb Christopher Tauss: I am trying to write a function that takes a list and returns the last n elements. last_n n = fst . foldr step ([], n) where step _ (xs, 0) = (xs, 0) step x (xs, n) = (x:xs, n-1) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: happstack-auth-0.2
Am 17.09.2010 22:06, schrieb Nils Schweinsberg: [1] http://hackage.haskell.org/package/happstack-auth Hackage fails to build this package: http://hackage.haskell.org/packages/archive/happstack-auth/0.2/logs/failure/ghc-6.12 However, Crypto == 4.* should be on hackage: http://hackage.haskell.org/package/Crypto-4.2.1 Is there anything I can do with my package to get this to build? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANN: happstack-auth-0.2
Hey! I'd like to announce the release of happstack-auth-0.2 [1]. It offers an easy (and secure) way to implement user authentication for Happstack web applications with a lot of high level functions and a solid Happstack-State back-end. The original project got started by MightyByte, until I took it over and improved the whole package. As a result, the API has changed a lot and if you were using the old happstack-auth you might consider rewriting your application to use the new api.* However, your applications state will be completely compatible with the new version and be migrated automatically. The package got uploaded to hackage and can now be installed via cabal: cabal install happstack-auth It should build with both, the current stable release of happstack (0.5.0.2) and the latest darcs version (0.5.1). If there are any errors/bugs during building/running, please contact me! A demonstration website is up and running with about 30 lines of code (+ html templates and the actual happstack server code) at [2]. If you don't want to wait until hackage rendered the haddock pages, you can take a look at the (latest git version of the) API at [3]. Hope you enjoy it! :) - Nils Schweinsberg / McManiaC * You can still use the old state-query/update constructors by importing Happstack.Auth.Internal, although you'll miss a lot of features like session management etc. In addition, MightyBytes old repo should be still available at [4]. [1] http://hackage.haskell.org/package/happstack-auth [2] http://n-sch.de/happstack-auth [3] http://n-sch.de/hdocs/happstack-auth [4] http://github.com/mightybyte/happstack-auth ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Combining applicative with arrows?
Hey,
I just wondered if you can define Applicative instances for arrows?
Basicly what I thought of is:
I have a type for my arrow which is CollectA (using HXT here):
type CollectA a = SomeArrow XmlTree a
And my datatype which I want to construct:
data Test = Test
{ testString:: String
, testInt :: Int
}
With the functions:
collectString :: CollectA String
collectInt:: CollectA Int
Now, what I currently do is something like:
collectTest :: CollectA Test
collectTest = getChildren
someOtherArrow -- etc...
proc foo - do
s - collectString - foo
i - collectInt- foo
returnA - Test s i
With Applicatives that proc-do-part would become:
collectTest' :: CollectA Test
collectTest' = ... -- arrow stuff
Test $ collectString
* collectInt
Is something like this possible? I don't understand that proc part
good enough to see what it's actually doing there, maybe someone with a
better understanding for this could help out? :)
Thx,
- Nils
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Re: [Haskell-cafe] Style and a problem
Am 09.09.2010 22:55, schrieb Wanas: Hey all, So I have a two part question (I'm new to haskell, so you can throw all your mugs at me). a) I want to write a function that generates lists of lists of size $n$. All having the property that sum lst = sum [1..n]. a-1) After that, I want to remove all permutations. My idea of doing this is to get all lists from the first function and create a new list with the property that if sorted list A is not in the list, add it. b-2) I think that's too much questions, but I want to get the hang of this quickly (it was kickass for the few things I've tried out). Something like this? import Data.List newList :: Int - [[Int]] newList n = myNub [ l | l - undefined -- not really sure how you want -- to generate these lists :) , sum l == sum [1..n] ] myNub :: (Ord a) = [[a]] - [[a]] myNub = nubBy (\a b - sort a == sort b) - Nils ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is 'flip' really necessary?
On 26.07.2010 23:55, Ozgur Akgun wrote:
I think it is pretty cool as well. But I think there is a problem with
viewing it as a wildcard.
let's say we define the following:
(??) = flip
foo :: a - b - c
foo ?? x :: a - c
Perfect!
But saying ?? can be used as a wildcard might in the following wrong
perception:
foo x ?? :: b - c -- WRONG
This looks interesting. I played around with this for a bit:
{-# LANGUAGE MultiParamTypeClasses
, FunctionalDependencies
, FlexibleInstances
#-}
class Wildcard f v r | f - v r where
(??) :: f - v - r
instance Wildcard (a - b - c) b (a - c) where
(??) = flip
instance Wildcard (b - c) b c where
(??) = id
f :: String - Int - String
f s i = s ++ show i
a :: String - String
a = (f ?? 5)
b :: Int - String
b = (f Int: ??)
Sadly, this won't typecheck:
pattern.hs:19:0:
Couldn't match expected type `Int' against inferred type `[Char]'
Expected type: Int
Inferred type: String
When using functional dependencies to combine
Wildcard (b - c) b c,
arising from the dependency `f - a r'
in the instance declaration at pattern.hs:12:9
Wildcard (String - Int - String) Int (String - String),
arising from a use of `??' at pattern.hs:19:5-10
When generalising the type(s) for `a'
Ideas anyone? :)
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Re: [Haskell-cafe] Re: Is my code too complicated?
On Sun, 4 Jul 2010 15:47:21 +0200, Ertugrul Soeylemez e...@ertes.de wrote: This requires a bunch of type system extensions, though, most notably the UndecidableInstances extension. But it's safe to use here. Probably a bit off topic, but whats wrong with UndecidableInstances? Where is it safe to use, when would you avoid it and what can go wrong here? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] MState: A consistent State monad for concurrent applications
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 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] MState: A consistent State monad for concurrent applications
On 02.07.2010 20:05, Jason Dagit wrote: In other words, don't be shy! Ok, thanks for the reply! :) However, a question about haddock: evalMState :: Forkable m = MState t m a -- ^ Action to evaluate - t -- ^ Initial state value - m a This (and run-/execMState) gets rendered incorrectly. Action to evaluate is completly lost and Initial state value has moved one upwards to the MState t m a. Is that a haddock bug or my fault? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] MState: A consistent State monad for concurrent applications
And here wo go. MState on hackage: http://hackage.haskell.org/package/mstate My first hackage library. :) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Looking for GUI (WX) example code
On 02.07.2010 23:02, Günther Schmidt wrote: Hi all, I'd be interested in studying GUI (wxhaskell) code. Does anyone have links to good gui code? Not wxHaskell, but I just wrote a very small gtk2hs application.[1] Should give you a quick overview of how things work with gtk. :) [1] http://github.com/mcmaniac/whoLogin/blob/master/src/whologin.hs ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] MState: A consistent State monad for concurrent applications
On 03.07.2010 03:27, Matthew Gruen wrote: Awesome. I needed something like that once, too, down to the same type signature for the fork function. Here's an instance from my code: instance MonadFork (ReaderT s IO) where fork newT = ask= liftIO . forkIO . runReaderT newT I've added this instance to the Forkable class and a few other instances to the MState (Fix, Reader, Writer, Cont and Error). I hope they're all correct. Thanks! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: bitspeak 0.0.1
On 21.06.2010 23:50, Maurício CA wrote: Hi, all, bitspeak is a small proof of concept application that allows writing text using only two commands (yes/no, 1/2, top/down etc.). Looks cool! Did you forget any dependencies tho? I get the following error: 0:16 nils` cabal update Downloading the latest package list from hackage.haskell.org 0:17 nils` cabal install bitspeak Resolving dependencies... Configuring bitspeak-0.0.1... Preprocessing executables for bitspeak-0.0.1... Building bitspeak-0.0.1... src/Main.hs:7:7: Could not find module `Corpora': Use -v to see a list of the files searched for. cabal: Error: some packages failed to install: bitspeak-0.0.1 failed during the building phase. The exception was: ExitFailure 1 Thx, Nils ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
