[Haskell-cafe] Bad interface problem.
Hi, This had never happened to me. And I have no idea what to do. $ cabal --upgrade-dependencies --enable-documentation --force-reinstalls --solver=topdown QuickCheck-2.5 Test/QuickCheck/All.hs:15:1: Bad interface file: /home/magicloud/.cabal/lib/template-haskell-2.6.0.0/ghc-7.4.2/Language/Haskell/TH.hi Something is amiss; requested module template-haskell-2.6.0.0:Language.Haskell.TH differs from name found in the interface file template-haskell:Language.Haskell.TH $ cabal --version cabal-install version 0.15.0 using version 1.15.0 of the Cabal library -- 竹密岂妨流水过 山高哪阻野云飞 And for G+, please use magiclouds#gmail.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Haskell Implementors' Workshop talk proposals due in one week!
Call for Talks ACM SIGPLAN Haskell Implementors' Workshop http://haskell.org/haskellwiki/HaskellImplementorsWorkshop/2012 Copenhagen, Denmark, September 14th, 2012 The workshop will be held in conjunction with ICFP 2012 http://www.icfpconference.org/icfp2012/ Important dates Proposal Deadline: 10th July 2012 Notification: 27th July 2012 Workshop: 14th September 2012 The Haskell Implementors' Workshop is to be held alongside ICFP 2012 this year in Copenhagen, Denmark. There will be no proceedings; it is an informal gathering of people involved in the design and development of Haskell implementations, tools, libraries, and supporting infrastructure. This relatively new workshop reflects the growth of the user community: there is a clear need for a well-supported tool chain for the development, distribution, deployment, and configuration of Haskell software. The aim is for this workshop to give the people involved with building the infrastructure behind this ecosystem an opportunity to bat around ideas, share experiences, and ask for feedback from fellow experts. We intend the workshop to have an informal and interactive feel, with a flexible timetable and plenty of room for ad-hoc discussion, demos, and impromptu short talks. Scope and target audience - It is important to distinguish the Haskell Implementors' Workshop from the Haskell Symposium which is also co-located with ICFP 2012. The Haskell Symposium is for the publication of Haskell-related research. In contrast, the Haskell Implementors' Workshop will have no proceedings -- although we will aim to make talk videos, slides and presented data available with the consent of the speakers. In the Haskell Implementors' Workshop, we hope to study the underlying technology. We want to bring together anyone interested in the nitty-gritty details behind turning plain-text source code into a deployed product. Having said that, members of the wider Haskell community are more than welcome to attend the workshop -- we need your feedback to keep the Haskell ecosystem thriving. The scope covers any of the following topics. There may be some topics that people feel we've missed, so by all means submit a proposal even if it doesn't fit exactly into one of these buckets: * Compilation techniques * Language features and extensions * Type system implementation * Concurrency and parallelism: language design and implementation * Performance, optimisation and benchmarking * Virtual machines and run-time systems * Libraries and tools for development or deployment Talks - At this stage we would like to invite proposals from potential speakers for a relatively short talk. We are aiming for 20 minute talks with 10 minutes for questions and changeovers. We want to hear from people writing compilers, tools, or libraries, people with cool ideas for directions in which we should take the platform, proposals for new features to be implemented, and half-baked crazy ideas. Please submit a talk title and abstract of no more than 200 words to: johan.tib...@gmail.com We will also have a lightning talks session which will be organised on the day. These talks will be 2-10 minutes, depending on available time. Suggested topics for lightning talks are to present a single idea, a work-in-progress project, a problem to intrigue and perplex Haskell implementors, or simply to ask for feedback and collaborators. Organisers -- * Lennart Augustsson (Standard Chartered Bank) * Manuel M T Chakravarty (University of New South Wales) * Gregory Collins - co-chair (Google) * Simon Marlow (Microsoft Research) * David Terei(Stanford University) * Johan Tibell - co-chair(Google) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Using syntactic to implement the lambda calculus
(This is intended as a simplification of the problem I actually need to solve.) I'm trying to implement the lambda calculus (with CBV evaluation) using the syntactic package, in such a way that a simple extension is also simple to implement. I am stuck on the fact that it seems that the Value type needs to be parametrized over the Expr type and I can't seem to figure out how to do it. I've read this posthttp://www.haskell.org/pipermail/haskell-cafe/2011-May/091770.htmlfrom the archives, but I still seem to be missing something. Does anyone have any suggestions? -- Lambda calculus type Ident = String data Value = VLam Ident Expr data Expr = Var Ident | Lam Ident Expr | App Expr Expr eval :: Expr - Value eval e = case e of Var _ - error not closed Lam i e' - VLam i e' App e1 e2 - case eval e1 of Lam i e' - subst e' (eval e2) i _ - error illegal application -- Lambda calculus with integers and addition data Value = VLam Ident Expr | VInt Integer data Expr = Var Ident | Lam Ident Expr | App Expr Expr | Plus Expr Expr eval e = case e of ... Plus e1 e2 - case (eval e1, eval e2) of (VInt x1, VInt x2) - VInt $ x1 + x2 _ - error illegal addition -- Alex R ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] existential types and cast
Actually, using cast seems to be a perfect solution here. I can't see anything wrong with it. Отправлено с iPad 03.07.2012, в 20:33, Corentin Dupont corentin.dup...@gmail.com написал(а): Hi all, I read somewhere (here: http://stackoverflow.com/questions/2300275/how-to-unpack-a-haskell-existential-type) that it's bad to try to unbox an existential type using a cast. OK, but without I really can't figure out how to do what I want: data NewPlayer = NewPlayer deriving (Typeable, Eq) data NewRule = NewRule deriving (Typeable, Eq) class (Eq e, Typeable e) = Event e where data EventData e instance Event NewPlayer where data EventData NewPlayer = P Int instance Event NewRule where data EventData NewRule = R Int instance Typeable1 EventData where typeOf1 _ = mkTyConApp (mkTyCon EventData) [] data EventHandler = forall e . (Event e) = EH e (EventData e - IO ()) addEvent :: (Event e) = e - (EventData e - IO ()) - [EventHandler] - [EventHandler] addEvent e h ehs = (EH e h):ehs triggerEvent :: (Event e) = e - (EventData e) - [EventHandler] - IO () triggerEvent e d ehs = do let r = find (\(EH myEvent _) - cast e == Just myEvent) ehs case r of Nothing - return () Just (EH _ h) - case cast h of Just castedH - castedH d Nothing - return () How to remove the casts from triggerEvent? All that I want is to apply the handler found on the data passed in parameter. I tried to add a function apply in the class, without success: apply :: (EventData e - IO ()) - (EventData e) - IO () apply = ($) Thanks! Corentin ___ 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] Martin Odersky on What's wrong with Monads
On Tue, Jun 26, 2012 at 6:19 PM, Tillmann Rendel ren...@informatik.uni-marburg.de wrote: How would you implement this requirement in Haskell without changing the line amount (Leaf x) = x? The hflags library [http://hackage.haskell.org/package/hflags] seems to do that, however... (I actually see three ways of doing this in Haskell, but all have serious drawbacks and do not fully solve the problem). ...it uses the unsafe IO trick [http://www.haskell.org/haskellwiki/Top_level_mutable_state], which may be one of those three ways you aren't fond of. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Martin Odersky on What's wrong with Monads
On Thu, Jun 28, 2012 at 2:53 PM, Dominique Devriese dominique.devri...@cs.kuleuven.be wrote: 2012/6/27 Tillmann Rendel ren...@informatik.uni-marburg.de: How would you implement this requirement in Haskell without changing the line amount (Leaf x) = x? I may be missing the point here, but having worked on large code bases with a wide variety contributors before, I find it very advantageous that programmers are prevented from writing an amount function whose behaviour depends on command line arguments without at least an indication in the type. The fact that the function can not perform stuff like that is precisely the guarantee that the Haskell type gives me... I don't think there's an answer that's uniformly right; it depends on whether you think of the input to the program, e.g. the environment, command-line arguments, etc. as 'constant' and in some sense, pure. The latter are constant in the sense that they never change, but they are not fixed at compile-time. Other languages effectively treat them as pure (by passing them directly to main), whereas Haskell chooses not to, which is probably the reason why getArgs has IO in its type (something that seems unintuitive at first.) That precedent supports the view that e.g. a command-line flag shouldn't affect behavior without the type reflecting it, e.g. by doing IO, but the de facto use of the unsafe IO trick means not everyone agrees. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
