Re: [Haskell-cafe] Wanted: Haskell binding for libbdd (buddy)
Peter Gammie peteg42 at gmail.com writes: My hBDD bindings are on Hackage. Great! Perhaps add category: logic in the cabal file? J.W. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Lazy decoding of a list with Data.Binary
I just encountered the following problem: http://stackoverflow.com/questions/11695373/lazy-decoding-of-a-list-with-data-binary If I get that correctly, there once was a discussion about adding a Data.Binary.Lazy to binary: http://www.haskell.org/pipermail/haskell-cafe/2007-November/034758.html What happened to this? And if binary is strict by default now, shouldn't the binary-strict package be deprecated? Is there an alternative these days how to lazily write/read binary? Thanks Niklas ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Pure and monadic functions using the Repa arrays
Hi Haskellers, I have been playing with the Repa functions and trying the Repa-examples. In order to gain experience with the Repa functions I have written some small linear algebra utilities and import this module to a bigger project. In the beginning of my project I used the mmultP function from the repa-examples to calculate a big matrix, therefore I have and array of type: arr :: Monad m = m (Array U DIM2 Double) Then I carried this array in a lot of functions which become Monadic function and then it is necessary to introduce the monadic machinery for manipulating this functions . The Question is then if there is the possibility to work with a pure function in place of the monadic version? There is something like a runRepa function? runRepa :: Monad m = m (Array U DIM2 Double) - Array U DIM2 Double or could I used the unsafePerformIO function ? or the evaluation of the parallel arrays must be postponed until the Repa.Array is called in the main function? Thanks in Advance, Felipe. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [Haskell] Compositional Compiler Construction, Oberon0 examples available
On Aug 21, 2012, at 13:46 , Heinrich Apfelmus apfel...@quantentunnel.de wrote: Doaitse Swierstra wrote: Heinrich Apfelmus wrote: I have a small question: Last I remember, you've mainly been using your UUAGC preprocessor to write attribute grammars in Haskell, especially for UHC. Now that you have first-class attribute grammars in Haskell (achievement unlocked), what do you intend to do with the preprocessor? How do these two approaches compare at the moment and where would you like to take them? On the page http://www.cs.uu.nl/wiki/bin/view/Center/CoCoCo there is a link (http://www.fing.edu.uy/~mviera/papers/VSM12.pdf) to a paper we presented at LDTA (one of the ETAPS events) this spring. It explains how UUAGC can be used to generate first class compiler modules. We have also a facility for grouping attributes, so one can trade flexibility for speed. The first class approach stores list of attributes as nested cartesian products, access to which a clever compiler might be able to optimize. This however would correspond a form of specialisation, so you can hardly say that we have really independent modules; as always global optimisation is never compositional). From the point of view of the first class approach such grouped non-termionals are seen as a single composite non-terminal. Ah, I see. So the custom syntax offered by UUAGC is still appreciated, but you now intend to compile it to first-class attribute grammars instead of bare metal Haskell. Makes sense. Thanks! It is not much that it is our intention, but it is an easy way to make an existing compiler extensible. The main (fixed) part of the compiler is constructed in the old way from an UUAGC description, and those attributes are grouped (and quite a bit more efficient). On top of this you can define extra attributes and computations, which plug in to the old system. Notice that there is a main difference between the two approaches is that the uuagc route gives you fast compilers, because we can analyse the grammar, and generate efficient tree walking evaluators, whereas the first-class approach gives you great flexibility and the possibility to abstract from common patterns for which others prefer to get lost in stacks of monads, or find out that monads do not work at all since they cannot feed back information into a computation easily. Doaitse Best regards, Heinrich Apfelmus -- http://apfelmus.nfshost.com ___ Haskell mailing list hask...@haskell.org http://www.haskell.org/mailman/listinfo/haskell ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] phantom types
On Aug 19, 2012, at 5:29 , wren ng thornton w...@freegeek.org wrote:
On 8/17/12 5:35 AM, TP wrote:
Hi,
I am currently reading documentation on Generalized Algebraic Data Types:
http://en.wikibooks.org/wiki/Haskell/GADT
I have a question concerning this page. Let us consider the following code
proposed in the page:
--
-- Phantom type variable a (does not appear in any Expr: it is just a
-- dummy variable).
data Expr a = I Int
| B Bool
| Add (Expr a) (Expr a)
| Mul (Expr a) (Expr a)
| Eq (Expr a) (Expr a)
deriving (Show)
[...]
I don't understand. When we write eval (I n) = n, as I is a constructor
which takes an Int as argument, we are able to deduce that the type of n is
Int; so the type of eval should be in this case Expr Int - Int.
What do I miss?
Perhaps it'd help to rewrite the above ADT using GADT syntax (but note that
its the exact same data type):
data Expr :: * - * where
I :: Int - Expr a
B :: Bool - Expr a
Add :: Expr a - Expr a - Expr a
Mul :: Expr a - Expr a - Expr a
Eq :: Expr a - Expr a - Expr a
But if you use the real power of GADT's you would write:
{-# LANGUAGE KindSignatures, GADTs #-}
data Expr :: * - * where
I :: Int - Expr Int
B :: Bool - Expr Bool
Val :: a- Expr a
Add :: Expr Int - Expr Int - Expr Int
Mul :: Expr Int - Expr Int - Expr Int
Eq :: Eq a = Expr a - Expr a - Expr Bool
eval :: Expr a - a
eval (I i) = i
eval (B b) = b
eval (Val v) = v
eval (Add e1 e2) = eval e1 + eval e2
eval (Mul e1 e2) = eval e1 * eval e2
eval (Eq e1 e2) = eval e1 == eval e2
Note that the I and B cases are actually superfluous, and are covered by the
val case. This has all nothing to do with phnatom types, but with a proper
understanding of the GADT concept.
Doaitse
So, when looking at the pattern (I n), since I :: Int - Expr a we know that
n :: Int and that (I n) :: Expr a.
--
Live well,
~wren
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Re: [Haskell-cafe] Pure and monadic functions using the Repa arrays
On 08/21/12 09:19, felipe zapata wrote: Hi Haskellers, I have been playing with the Repa functions and trying the Repa-examples. In order to gain experience with the Repa functions I have written some small linear algebra utilities and import this module to a bigger project. In the beginning of my project I used the mmultP function from the repa-examples to calculate a big matrix, therefore I have and array of type: arr :: Monad m = m (Array U DIM2 Double) Then I carried this array in a lot of functions which become Monadic function and then it is necessary to introduce the monadic machinery for manipulating this functions . The Question is then if there is the possibility to work with a pure function in place of the monadic version? There is something like a runRepa function? runRepa :: Monad m = m (Array U DIM2 Double) - Array U DIM2 Double or could I used the unsafePerformIO function ? or the evaluation of the parallel arrays must be postponed until the Repa.Array is called in the main function? When this change was introduced (there wasn't always the arbitrary monad m around everything), I remember I just wrapped my one big repa function in the identity monad and it worked fine. For example, -- Grid.hs import Control.Monad.Identity (Identity) ... zoom :: Values3D - ScaleFactor - Identity Values3D -- Main.hs import Control.Monad.Identity (runIdentity) ... let output = runIdentity $ zoom dbl_data zoom_factor This gives you the warm/fuzzy of knowing that the function is pure, but I think I eventually just let it run in IO to avoid introducing mtl as a dependency. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] salvia
Hi. Does anybody know anything about Sebastiaan Visser, the maintainer of Salvia-* packages (web server) ? Looks like his email is dead. Sergey ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] fclabels 0.5
just what I was looking for, thanks! 2012/8/20 Erik Hesselink hessel...@gmail.com: Untested, but this should be about right: osi (Bij f b) = iso (Bij b f) Erik On Mon, Aug 20, 2012 at 2:35 PM, Sergey Mironov ier...@gmail.com wrote: Hi. I'm porting old code, which uses fclabels 0.5. Old fclabels define Iso typeclass as follows: class Iso f where iso :: a :-: b - f a - f b iso (Lens a b) = osi (b - a) osi :: a :-: b - f b - f a osi (Lens a b) = iso (b - a) Newer one defines iso: class Iso (~) f where iso :: Bijection (~) a b - f a ~ f b instance Arrow (~) = Iso (~) (Lens (~) f) where iso bi = arr ((\a - lens (fw bi . _get a) (_set a . first (bw bi))) . unLens) instance Arrow (~) = Iso (~) (Bijection (~) a) where iso = arr . (.) but no osi. I'm not a guru in categories, can you help me define osi? Thanks Sergey. ___ 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] Combining databases from packages installed with cabal install
Hi. I'm configuring haddock via cabal install (see [0]) to build the hoogle database. The database is being installed in ~/.cabal/share/doc/$package-$version/html/$package.txt, but is not being combined with the default database. That is, if right after the installation I try to search with the hoogle command for some a function, it will not work. I wrote the following script, which I called cabal-install: #!/bin/sh set -e set -x cabal \ install \ --enable-documentation \ --enable-library-profiling \ --haddock-hyperlink-source \ --haddock-hoogle \ --haddock-html \ $@ cd ~/.cabal/share/hoogle-4.2.13/databases/ for file in ~/.cabal/share/doc/*/html/*.txt do hoo=`echo $file | sed 's/.txt$/.hoo/;s#.*/##'` if [ ! -f $hoo ] then hoogle convert $file $hoo || true hoogle combine default.hoo $hoo -o /tmp/cabal-install-$$.hoo mv /tmp/cabal-install-$$.hoo default.hoo fi done Basically, it searches for .txt hoogle databases installed that were not combined yet with the default database, and combines them. I think it would be good if this was the default behaviour of cabal install when called with --haddock-hoogle. Is this a bug? Greetings. 0: http://hackage.haskell.org/trac/hackage/ticket/517 -- marcot http://marcot.eti.br/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Galois internships available
* ANNOUNCING: * INTERNSHIP AT GALOIS, Inc. Galois, Inc. www.galois.com has an internship available in Portland, Oregon, USA. PROJECT OVERVIEW: The project is a 4+ year research project on build high-assurance autonomous vehicles. Galois will be working on three aspects of this problem: * Synthesizing software components from Haskell-based embedded DSLs. * Building/porting a hardware platform for testing our prototypes. * Performing static/dynamic analysis on C/C++ code to detect vulnerabilities. We intend to release open-source most (if not all) source code developed on the project and we will be publishing on our research results. Being an intern for repeated terms is a possibility. LOGISTICS: The length and start date of the internship are all negotiable: anytime from this fall through next fall is acceptable. Ideally, you can be at Galois for at least 3 continuous months. The internship is paid competitively, and the intern will be responsible for her own living arrangements (although we can certainly help you find arrangements). Galois is located in the heart of downtown, with multiple public transportation options available and world-class bicycle infrastructure, so living here without an automobile is a viable option. QUALIFICATIONS: * MUST-HAVES: * The ability to be geographically located in Portland during the internship. * Good knowledge of C/C++. * Some experience with low-level/embedded design. * Excellent software engineering ability and aptitude. * NICE-TO-HAVES (not necessary, but let me know if you have these qualifications!): * Experience with Haskell and particularly embedded DSLs. * Experience with microcontrollers (particularly ARM Cortex M). * Experience with control systems. * Interest in/experience with real-time systems and RTOSes. * Interest in/experience with software security. * Interest in/experience with static analysis. * Experience with ArduPilot http://code.google.com/p/ardupilot-mega/ or other autopilot systems. * Good writing skills/experience in writing technical papers. * DO NOT NEED: * A specific degree (we're interested in hearing from anyone from post-docs to undergrads). ABOUT GALOIS: Galois, Inc. is located in Portland, Oregon with a mission to create trustworthiness in critical systems. We're in the business of taking blue-sky ideas and turning them into real-world technology solutions. We've been developing real-world systems for over 10 years using Haskell. To get a sense of life at Galois, one of our previous interns documented his internship here: http://blog.ezyang.com/2010/08/day-in-the-life-of-a-galois-intern/. TO APPLY: In one email, * Please attach a C.V. (PDF, plain text, or markdown only). * In the body of the email, include a brief non-HTML note stating your interest and experience and any other relevant details. Send this to Lee Pike (leepike at galois.com) with the subject line Internship 2012. If you follow these directions, you'll get a confirmation from me. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] regex-pcre is not working with UTF-8
On 08/18/2012 06:16 PM, José Romildo Malaquias wrote: Hello. It seems that the regex-pcre has a bug dealing with utf-8: I hope this bug can be fixed soon. Is there a bug tracker to report the bug? If so, what is it? You need something like that let pat = makeRegexOpts (compUTF8 .|. defaultCompOpt) defaultExecOpt (@'(.+?)'@ :: B.ByteString) and than pat will match correctly. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] salvia
On Tue, Aug 21, 2012 at 5:02 PM, Sergey Mironov wrote: Hi. Does anybody know anything about Sebastiaan Visser, the maintainer of Salvia-* packages (web server) ? Looks like his email is dead. I responded to Sergey off-list, so others don't have to. Regards, Sean ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] regex-pcre is not working with UTF-8
On Tue, Aug 21, 2012 at 10:25:53PM +0300, Konstantin Litvinenko wrote: On 08/18/2012 06:16 PM, José Romildo Malaquias wrote: Hello. It seems that the regex-pcre has a bug dealing with utf-8: I hope this bug can be fixed soon. Is there a bug tracker to report the bug? If so, what is it? You need something like that let pat = makeRegexOpts (compUTF8 .|. defaultCompOpt) defaultExecOpt (@'(.+?)'@ :: B.ByteString) and than pat will match correctly. The bug is related to String (not ByteString) in a UTF-8 locale. Until it is fixed, I am using the workaround of converting the regular expression and the text to ByteString, doing the matching, and then converting the results back to String. Romildo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] explicit annotations on kind polymorphism for data types
Hello All: I'm working through Giving Haskell a Promotion. Section 2.4 presents an explicitly annotated data type declaration similar to the following: data EqRefl (a::X)(b::X) where Refl :: forall X. forall (a::X). EqRefl a a Has this been implemented in GHC 7.4.2? 7.8.3 in the GHC User Guide leads me to believe it has not. -- dude ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Cloud Haskell real usage example
Hello everyone. I'm taking my first steps in Cloud Haskell and got some unexpected behaviors. I used the code from Raspberry Pi in a Haskell Cloud [1] as a first example. Did try to switch the code to use Template Haskell with no luck, stick with the verbose style. I changed some of the code, from ProcessId-based messaging to typed channel to receive the Pong; using startSlave to start the worker nodes; and changed the master node to loop forever sending pings to the worker nodes. The unexpected behaviors: - Dropping a worker node while the master is running makes the master node to crash. - Master node do not see worker nodes started after the master process. In order to fix this, I tried to findSlaves at the start of the master process and send ping to only these ones, ignoring the list of NodeId enforced by the type signature of startMaster. Now the master finds new slaves. The bad thing is that when I close one of the workers, the master process freezes. It simply stop doing anything. No more messages and no more Pings to other slaves. :( My view of Cloud Haskell usage would be something similar to this: a master node sending work to slaves; slave instances getting up or down based on demand. So, the master node should be slave-failure-proof and also find new slaves somehow. Am I misunderstanding the big picture of Cloud Haskell or doing anything wrong in the following code? Code (skipped imports and wiring stuff): -- newtype Ping = Ping (SendPort Pong) deriving (Typeable, Binary, Show) newtype Pong = Pong ProcessId deriving (Typeable, Binary, Show) worker :: Ping - Process () worker (Ping sPong) = do wId - getSelfPid say Got a Ping! sendChan sPong (Pong wId) master :: Backend - [NodeId] - Process () master backend _ = forever $ do workers - findSlaves backend say $ Slaves: ++ show workers (sPong, rPong) - newChan forM_ workers $ \w - do say $ Sending a Ping to ++ (show w) ++ ... spawn w (workerClosure (Ping sPong)) say $ Waiting for reply from ++ (show (length workers)) ++ worker(s) replicateM_ (length workers) $ do (Pong wId) - receiveChan rPong say $ Got back a Pong from ++ (show $ processNodeId wId) ++ ! (liftIO . threadDelay) 200 -- Wait a bit before return main = do prog - getProgName args - getArgs case args of [master, host, port] - do backend - initializeBackend host port remoteTable startMaster backend (master backend) [worker, host, port] - do backend - initializeBackend host port remoteTable startSlave backend _ - putStrLn $ usage: ++ prog ++ (master | worker) host port -- [1] http://alenribic.com/writings/post/raspberry-pi-in-a-haskell-cloud ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Cloud Haskell real usage example
On Tue, Aug 21, 2012 at 9:01 PM, Thiago Negri evoh...@gmail.com wrote: My view of Cloud Haskell usage would be something similar to this: a master node sending work to slaves; slave instances getting up or down based on demand. So, the master node should be slave-failure-proof and also find new slaves somehow. Am I misunderstanding the big picture of Cloud Haskell or doing anything wrong in the following code? (Disclaimer: I can't speak for Cloud Haskell's developers.) AFAIK this is CH's goal. However, they're not quite there yet. Their network implementation is still a lot naive as you're seeing =). Cheers, -- Felipe. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Cloud Haskell real usage example
On Wed, Aug 22, 2012 at 8:30 AM, Felipe Almeida Lessa felipe.le...@gmail.com wrote: On Tue, Aug 21, 2012 at 9:01 PM, Thiago Negri evoh...@gmail.com wrote: My view of Cloud Haskell usage would be something similar to this: a master node sending work to slaves; slave instances getting up or down based on demand. So, the master node should be slave-failure-proof and also find new slaves somehow. Am I misunderstanding the big picture of Cloud Haskell or doing anything wrong in the following code? (Disclaimer: I can't speak for Cloud Haskell's developers.) AFAIK this is CH's goal. However, they're not quite there yet. Their network implementation is still a lot naive as you're seeing =). I believe this behavior is due to the usage of channel, you just need to implement some kind of timeout function. Cheers, -- Felipe. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- http://yi-programmer.com/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
