Re: [Haskell-cafe] enumerators: exception that can't be catched
This is partially guesswork, but the code to catchWSError looks dubious: catchWsError :: WebSockets p a - (SomeException - WebSockets p a) - WebSockets p a catchWsError act c = WebSockets $ do env - ask let it = peelWebSockets env $ act cit = peelWebSockets env . c lift $ it `E.catchError` citwhere peelWebSockets env = flip runReaderT env . unWebSockets Look at `cit`. It runs the recovery function, then hands the underlying Iteratee the existing environment. That's fine if `act` is at fault, but there are Iteratee- and IO-ish things in WebSocketsEnv---if one of `envSink` or `envSendBuilder` is causing the exception, it'll just get re-thrown after `E.catchError`. (I think. That's the guesswork part.) So check how `envSendBuilder` is built up, and see if there's a way it could throw an exception on client disconnect. On Tue, Aug 27, 2013 at 10:28 AM, Yuras Shumovich shumovi...@gmail.comwrote: Hello, I'm debugging an issue in websockets package, https://github.com/jaspervdj/websockets/issues/42 I'm not familiar with enumerator package (websockets are based on it), so I'm looking for help. The exception is throws inside enumSocket enumerator using throwError ( http://hackage.haskell.org/packages/archive/network-enumerator/0.1.5/doc/html/src/Network-Socket-Enumerator.html#enumSocket), but I can't catch it with catchError. It is propagated to run function: interactive: recv: resource vanished (Connection reset by peer) The question is: how is it possible? could it be a bug in enumerator package? Thanks, Yuras ___ 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 flags: optghc
That's not a GHC flag; it's a haddock flag. Haddock (which, in case you're not familiar with it, is a program to generate documentation from Haskell source code) uses GHC, and the `optghc` flag lets you pass options to GHC when you invoke Haddock. See [the Haddock docs of the 6.12 era][1], on page 3. It's also entirely possible that some program besides Haddock uses a flag of the same name (for the same purpose, one would hope). [1]: http://www.haskell.org/ghc/docs/6.12.3/haddock.pdf 2013/8/23 jabolo...@google.com Hi, I am using GHC version 6.12.1. What is optghc ? I can't find that information anywhere... Thanks, Jose -- Jose Antonio Lopes Ganeti Engineering Google Germany GmbH Dienerstr. 12, 80331, München Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg Geschäftsführer: Graham Law, Christine Elizabeth Flores Steuernummer: 48/725/00206 Umsatzsteueridentifikationsnummer: DE813741370 ___ 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] Teaching FP with Haskell
Helium seems interesting, but the code is a little stale, no? The last updates seem to be from 2008-2009. I couldn't get it to build with ghc 7.6.3, not that I tried too terribly hard. On Tue, May 21, 2013 at 6:07 AM, Andrew Butterfield andrew.butterfi...@scss.tcd.ie wrote: Rustom, you should look at Helium - http://www.cs.uu.nl/wiki/bin/view/Helium/WebHome Andrew. On 21 May 2013, at 10:55, Rustom Mody wrote: We are offering a MOOC on haskell : https://moocfellowship.org/submissions/the-dance-of-functional-programming-languaging-with-haskell-and-python Full Announcement on beginners list : http://www.haskell.org/pipermail/beginners/2013-May/012013.html One question that I have been grappling with in this regard: How to run ghc in lightweight/beginner mode? 2 examples of what I mean: 1. gofer used to come with an alternative standard prelude -- 'simple.pre' Using this, gofer would show many of the type-class based errors as simple (non-type-class based) errors. This was very useful for us teachers to help noobs start off without intimidating them. 2. Racket comes with a couple of levels. The easier numbers were not completely consistent with scheme semantics, but was gentle to beginners Any thoughts/inputs on this will be welcomed Rusi ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe Andrew Butterfield Tel: +353-1-896-2517 Fax: +353-1-677-2204 Lero@TCD, Head of Foundations Methods Research Group Director of Teaching and Learning - Undergraduate, School of Computer Science and Statistics, Room G.39, O'Reilly Institute, Trinity College, University of Dublin http://www.scss.tcd.ie/Andrew.Butterfield/ ___ 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] Backward compatibility
You might want to check out FPCompletehttps://www.fpcomplete.com/page/about-us, if you haven't already. They're far more focused on making it easy for organizations to adopt Haskell than the community can be. As they say: Where the open-source process is not sufficient to meet commercial adoption needs, we provide the missing pieces. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Backward compatibility
What pray tell are those missing pieces? Aren't they mostly building a browser based ide plus doing training courses ? Sure, and I believe they plan to have that browser-based IDE talk to a virtual server, with a compiler and set of libraries they maintain. That'd solve Adrian's problems, no? So long as he can bring himself to use Yesod over WASH? Perhaps more importantly, they're well-spoken and business-savvy, and they can persuasively promise that they'll make a risk-averse corporation's (overblown) worries go away. If he's in a management battle, he ought to know where to hire some mercenaries. On Sat, May 4, 2013 at 2:03 PM, Carter Schonwald carter.schonw...@gmail.com wrote: What pray tell are those missing pieces? Aren't they mostly building a browser based ide plus doing training courses ? On May 4, 2013 1:42 PM, Ben Doyle benjamin.peter.do...@gmail.com wrote: You might want to check out FPCompletehttps://www.fpcomplete.com/page/about-us, if you haven't already. They're far more focused on making it easy for organizations to adopt Haskell than the community can be. As they say: Where the open-source process is not sufficient to meet commercial adoption needs, we provide the missing pieces. ___ 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] haskell build phase is very slow
yi is pretty heavy, as these things go. So it's not too surprising that it's taking a while. GHC does try to recompile as little as possible...but as little as possible can be quite a lot. Inlining, and other optimizations GHC performs, makes the recompilation checker's job tricky; see [1]. Generally if you change a file you'll need to recompile its dependencies, and *their* dependencies, and so on. If you're coding along and just need a typecheck, ghci is your friend. Specifically, the :reload command tends to be fast. (You'll need to :load yourFile.hs the first time, of course.) You might also see if yi's -fhacking flag is helpful. It looks like it might be relevant, though I don't know either yi or your use case well enough to say for sure. General advice on speeding compilation is here: [2]. Most of it isn't all that relevant to you at the moment, since you're hacking on someone else's package. But always good to know. Best of luck, Ben [1]: http://www.haskell.org/ghc/docs/latest/html/users_guide/separate-compilation.html#recomp [2]: http://www.haskell.org/ghc/docs/latest/html/users_guide/sooner-faster-quicker.html#sooner ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Undo records
I think acid-state (http://hackage.haskell.org/package/acid-state) might do what you want, at least in broad strokes. It uses a durable transaction log to store query and update events. As far as I know, the interface to the library doesn't expose an undo/rollback function, so you'd have a bit of work to do to extend it to your use case. But the core functionality to make it possible should be there. Can you use ghc extensions aside from Template Haskell? Template Haskell you can do without with acid-state, but without GADTs and so on you'll have problems. On Sun, Jan 6, 2013 at 12:01 PM, Casey Basichis caseybasic...@gmail.comwrote: Hi, I am still getting a hang of Haskell. Sorry if the answer is obvious. What sorts of packages and approaches should I be looking at if I was looking to store something like an Undo stack into a database. Each table would refer to a function. Each records input and outputs would specify both a table ID and record ID. The records would also have a data and a Process ID to associate all functions to a specific process and give them an order. No records are ever deleted. Rolling something back is instead a process of recreating a new, modified graph by taking the old graph from the database. I should note that while I can generate some of the boiler parts from template haskell in advance I'm ultimately using a stage 1 compiler with no GHCI o template haskell. Thanks, Casey -- Casey James Basichis Composer - Cartoon Network http://www.caseyjamesbasichis.com caseybasic...@gmail.com 310.387.7540 ___ 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] Monads with The contexts?
On Thu, Jul 12, 2012 at 11:01 AM, Takayuki Muranushi muranu...@gmail.comwrote: sunPerMars :: [Double] sunPerMars = (/) $ sunMass * marsMass Sadly, this gives too many answers, and some of them are wrong because they assume different Earth mass in calculating Sun and Mars masses, which led to inconsistent calculation. I think what you want to do is factor out the Earth's mass, and do your division first: sunPerMars'' = (/) $ sunMassCoef * marsMassCoef The mass of the earth cancels. That gives a list of length 9, where your approach gave 16 distinct results. But I think that's just floating point rounding noise. Try the same monadic calculation with integers and ratios. The moral? Using numbers in a physics calculation should be your last resort ;) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Installing pandoc / json with ghc 6.12.1
Am I doing something wrong here? Well, you're using ghc-6.12 ... :-) The most recent version of pandoc that Hackage claims to have built with ghc 6.12 looks to be 1.6. Rolling back that far eliminates the json dependency entirely, so I think it would solve your issue. Or you could use the Pandoc in Debian stable, which appears to be 1.5.1. A more recent ghc would probably also work, of course, but I imagine you're trying the Debian stable version for a reason. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] mapping a concept to a type
I wonder if you want a typeclass here, rather than a type? A Normal Rule is pretty much a State Transformer, while a Meta Rule seems like a higher-order function on Normal Rules[*]. These are different kinds of things --- and I say kind advisedly --- so perhaps better to define the specific commonalities you need than to try to shoehorn them both into one type. [*]: Possibly related question: Can a Meta Rule depend upon an implementation detail of a Normal rule? In other words, does rule1 g == rule2 g imply myMetaRule rule1 == myMetaRule rule2 ? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
