January 2017 - Haskell-Cafe

Re: [Haskell-cafe] Strange encoding issue with Text and Servant
by David Turner 14 Jan '17

14 Jan '17

Ok, so there's definitely a difference of some kind client-side. It'd be useful to see the network traffic nonetheless, as the source of the '!D(MISSING)' is still a bit of a mystery and you may see something suggestive in the raw bytes. I can't find the string 'MISSING' anywhere in servant or its dependencies, even looking in libs and binaries. Any chance of tracking its source down using `find` and `grep` and `strings`? On 14 Jan 2017 19:48, "Jan von Löwenstein" <jan.loewenstein(a)gmail.com> wrote: Actually the code I pointed at _is_ the swagger-codegen generated client. I have got a very small wrapper around it: ``` listService :: (MonadIO m, MonadCatch m, MonadReader Config m, MonadLog Text m) => Text -> m ServiceList.ServiceList listService labelSelector = namespacedF $ \namespace -> Kube.listNamespacedService namespace Nothing (Just labelSelector) Nothing Nothing Nothing Nothing listSecret :: (MonadIO m, MonadThrow m, MonadReader Config m, MonadLog Text m) => Text -> m SecretList.SecretList listSecret labelSelector = namespacedF $ \namespace -> Kube.listNamespacedSecret namespace Nothing (Just labelSelector) Nothing Nothing Nothing Nothing namespacedF :: (MonadIO m, MonadThrow m, MonadReader Config m, MonadLog Text m) => NamespacedF model -> m model namespacedF f = do config <- ask result <- let baseUrl = apiEndpoint config tlsSettings = Base.tlsSettings baseUrl (credentials config) kubeNamespace = namespace config in do manager <- liftIO $ newManager $ (mkManagerSettings tlsSettings Nothing) { managerModifyRequest = \req -> return req { checkResponse = \req res -> do Text.IO.hPutStrLn stderr (Text.pack (show req)) responseMessage <- showResponse res Text.IO.hPutStrLn stderr responseMessage return () } } liftIO $ runExceptT $ f kubeNamespace manager baseUrl either throwM return result ``` I call them like: ``` do let Just agentId = ... selector = "agentId" <> "=" <> agentId logMessage $ "listSecret selector: '" <> selector <> "'" secretList <- listSecret selector ``` `logMessage` gives a literal equals sign in both cases. `Text.IO.hPutStrLn stderr (Text.pack (show req))` from namespacedF gives `%3D` and `%!D(MISSING)` depending on which function I call. >From what I understand this is definitely happening on the client side. Do you still think a tcpdump might be worth it? ``` listSecret selector: 'agentId=b49d4406-8020-44e6-7788-6f92d5c0e732' Request { host = "192.168.99.100" port = 8443 secure = True requestHeaders = [("Accept","application/json")] path = "/api/v1/namespaces/default/secrets" queryString = "?labelSelector=agentId%!D( MISSING)b49d4406-8020-44e6-7788-6f92d5c0e732" method = "GET" proxy = Nothing rawBody = False redirectCount = 10 responseTimeout = ResponseTimeoutDefault requestVersion = HTTP/1.1 } ``` ``` listService selector: 'agentId=24f99a4b-1682-44da-7ba4-dba935d107d2' Request { host = "192.168.99.100" port = 8443 secure = True requestHeaders = [("Accept","application/json")] path = "/api/v1/namespaces/default/services" queryString = "?labelSelector=agentId%3D24f99a4b-1682-44da-7ba4- dba935d107d2" method = "GET" proxy = Nothing rawBody = False redirectCount = 10 responseTimeout = ResponseTimeoutDefault requestVersion = HTTP/1.1 } ``` Thanks for the time you already invested. I am completely puzzled because I see no chance how the code could behave as it does. (From my experience that points out I am looking at the wrong place ;) ) Best Jan David Turner <dct25-561bs(a)mythic-beasts.com> schrieb am Sa., 14. Jan. 2017 um 20:08 Uhr: > Grasping at straws a little bit here, but can you (a) do a packet capture > (e.g. `tcpdump -X`) to see what's going back and forth on the wire, just to > make absolutely sure all of the oddness is on the client's end? > > A string like `!D(MISSING)` sorta looks like a decoding error so perhaps > it will be instructive to look at the bytes on the wire it's trying to > decode, although I can't think what could be confused with an equals sign. > It's not like that blooming Greek question mark ( > http://www.fileformat.info/info/unicode/char/037e/index.htm) > > Cheers, > > > > > On 14 January 2017 at 18:47, Nigel Rantor <wiggly(a)wiggly.org> wrote: > > On 14/01/17 17:37, Jan von Löwenstein wrote: > > Oh, it happens with servant on the client side. > > I use a swagger-codegen generated servant based client to access > kubernetes. > Calling https://github.com/soundcloud/haskell-kubernetes/blob/ > master/lib/Kubernetes/Api/ApivApi.hs#L475 works > Calling https://github.com/soundcloud/haskell-kubernetes/blob/ > master/lib/Kubernetes/Api/ApivApi.hs#L473 doesn't. > > From what I see the `QueryParam"labelSelector" Text`is the same in both. > > Logging the value gives the literal `=` as expected. Logging the > (http-client) requests shows the difference. > > > So I went ahead and wrote a simple client by hand and when I call the two > functions on a local endpoint that shows me the request URL I get the > following. > > Same arguments for 'pretty' and 'labelSelector' in both cases. > > Code: > > runListSecret :: Manager -> BaseUrl -> ClientM SecretList > > runListSecret manager baseUrl = listSecret (Just "prettyArg") (Just "=") > Nothing Nothing Nothing Nothing manager baseUrl > > > > runListService :: Manager -> BaseUrl -> ClientM ServiceList > > runListService manager baseUrl = listService (Just "prettyArg") (Just "=") > Nothing Nothing Nothing Nothing manager baseUrl > > Server log: > > 127.0.0.1 - - [14/Jan/2017:18:39:49 +0000] "GET /api/v1/secrets?pretty=prettyArg&labelSelector=%3D > HTTP/1.1" 404 - 0.0003 > 127.0.0.1 - - [14/Jan/2017:18:39:49 +0000] "GET /api/v1/services?pretty=prettyArg&labelSelector=%3D > HTTP/1.1" 404 - 0.0003 > > I haven't used swagger-codegen but the servant-client code works for me so > I would look more into that. > > Swagger codegen looks like it might take me a while to get my head into so > maybe you could look at the generated code, or sling it to me here or > directly. > > The two calls are so similar that I can't see why the generated client > would behave differently in those cases. > > Regards, > > n > > Best > Jan > > Nigel Rantor <wiggly(a)wiggly.org <mailto:wiggly@wiggly.org>> schrieb am > > Sa., 14. Jan. 2017 um 18:11 Uhr: > > On 13/01/17 19:28, Jan von Löwenstein wrote: > > Hi, > > > > I have got a two places with a `QueryParam "q" Text` and call it > with a > > Text that contains a `=` literal. In one place the `=` is correctly > > encoded as %3D, in the other I see a `!D(MISSING)`. > > > > This has to happen somewhere in Servant or the lower layers. Both > Texts > > print out nicely with an `=` sign if I just print them to stdout. > > > > Google does not find `!D(MISSING)` anywhere. > > > > Any idea what could possibly be the problem here? > > It would be really useful to see exactly how you are 'calling' this. > > Do you have a curl command line or are you using some other client? > > n > > _______________________________________________ > Haskell-Cafe mailing list > To (un)subscribe, modify options or view archives go to: > http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe > Only members subscribed via the mailman list are allowed to post. > > > _______________________________________________ > Haskell-Cafe mailing list > To (un)subscribe, modify options or view archives go to: > http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe > Only members subscribed via the mailman list are allowed to post. > > >

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Calling Haskell from C
by Dominic Steinitz 14 Jan '17

14 Jan '17

I've been trying to get the example in https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/ffi-chap.ht… working. I have a cabal file name: test-via-c version: 0.1.0.0 homepage: TBD license: MIT author: Dominic Steinitz maintainer: idontgetoutmuch(a)gmail.com category: System build-type: Simple cabal-version: >=1.10 executable Foo.dylib main-is: Foo.hs other-extensions: ForeignFunctionInterface build-depends: base >=4.7 && <4.10, primitive >=0.6 && <0.7 hs-source-dirs: src default-language: Haskell2010 include-dirs: src ghc-options: -O2 -shared -fPIC -dynamic extra-libraries: HSrts-ghc8.0.1 which installs /Users/dom/Library/Haskell/ghc-8.0.1/lib/test-via-c-0.1.0.0/bin/Foo.dylib I then compile the C with gcc-6 Bar.c /Users/dom/Library/Haskell/ghc-8.0.1/lib/test-via-c-0.1.0.0/bin/Foo.dylib -I/Library/Frameworks/GHC.framework/Versions/8.0.1-x86_64/usr/lib/ghc-8.0.1/include -L/Library/Frameworks/GHC.framework/Versions/8.0.1-x86_64/usr/lib/ghc-8.0.1/rts -lHSrts-ghc8.0.1 Sadly when I try to run the executable I get ~/Dropbox/Private/TestU01-1.2.3/examples/src $ ./a.out dyld: Library not loaded: @rpath/Foo.dylib Referenced from: /Users/dom/Dropbox/Private/TestU01-1.2.3/examples/src/./a.out Reason: image not found Trace/BPT trap: 5 I am guessing the executable is looking for the dynamic library. I copied Foo.dylib to the current directory but still get the same error. I know this is really an OS X question but I am hoping someone who has done before will be able to help. Dominic Steinitz dominic(a)steinitz.org http://idontgetoutmuch.wordpress.com

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module is a package module error
by Lana Black 14 Jan '17

14 Jan '17

Hi, I'm trying to use hint [1] to compile in runtime externally supplied haskell code. The compiled code must have certain modules imported. The problem is that I'm getting this error when loading modules >WontCompile [GhcError {errMsg = "<no location info>: error: module >\8216Internal\8217 is a package module"}] I'm not really sure what to do with this. One way to fix this is to move Internal to a separate package so that hint could load it through cabal, but that's something I'd like to avoid. Is there any way I could make hint use the same modules from the package it's being called from? The code is located at [2]. [1]: http://hackage.haskell.org/package/hint [2]: https://github.com/greydot/hint-test/

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Feedback needed: CLI app + guide
by Carlo Matteo Scalzo 13 Jan '17

13 Jan '17

Hi all, I've already posted this in beginners@, but I thought it might be of interest to a wider audience too (apologies for double-posting). I started learning Haskell about a year ago, and I couldn't find any example of a simple, real world application written in Haskell, so as usual I ended up writing my own :-) The code is available for free (it's a simple command-line app), and I've also written a short guide that uses the application as a case study to talk about Haskell's features. Could you guys please download the guide (for free, of course) and let me know if you find it useful? You can get the guide here: https://fifohaskell.com Please send me your feedback either here or to my personal email address (it's on the website), and thank you very much for your help! Carlo

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brainstorm help
by Michael Litchard 13 Jan '17

13 Jan '17

Hi There. I'm looking for ideas to flesh out a writing project I'm beginning. What I am looking for is a set of five games in increasing complexity that would allow for a wide discussion of Haskell. I originally began this project by centering the writing around one large game, but this idea has proven to be brittle. The set of five should include a discussion of: (1) Types (2) folds, maps, filters (3) monoids, functors, applicatives, and monads Thanks for what ever storms your brains bring forth. :)

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Can I allow multiple rigid type variables?
by Cody Goodman 13 Jan '17

13 Jan '17

I know my question doesn't quite make sense and you can't have "multiple rigid type variables" but I couldn't think of a better way to characterize it or explain it. So I'll also try to give more detail below along with the code example and error at the end. I have an inner join function using vinyl which does cool stuff like giving a type error if you try to join on a column that doesn't exist. I previously had an implementation that blindly built an index based on the left argument. I then tried to dispatch based on the lengths of the left and right producer arguments. The problem is my return type is: Rec f (as ++ bs) That means I have two different producers, one of as and one of bs. I then do a case statement on the lengths and I want to store the producer to use for a given piece in that variable. The problem is ghc "pins" the type variable as either (Rec f as) or (Rec f bs) when I need to make that choice at runtime. My code and error is both at github here: https://github.com/codygman/frames-diff/blob/inner-join-fix/Frames/Diff.hs#… and below: -- | Performs an inner join and keeps any duplicate column -- Recommend keeping columns in producers disjoint because accessing -- anything but the leftmost duplicate column could prove difficult. -- see: https://github.com/VinylRecords/Vinyl/issues/55#issuecomment-269891633 innerJoin :: (MonadIO m, Ord k) => Producer (Rec f leftRows) IO () -- leftProducer -> Getting k (Rec f leftRows) k -- leftProducer lens -> Producer (Rec f rightRows) IO () -- rightProducer -> Getting k (Rec f rightRows) k -- rightProducer lens -> m (P.Proxy P.X () () (Rec f (leftRows ++ rightRows)) IO ()) innerJoin leftProducer leftLens rightProducer rightLens = do leftProducerLen <- P.liftIO $ P.length leftProducer rightProducerLen <- P.liftIO $ P.length rightProducer let curProducer = case rightProducerLen < leftProducerLen of True -> rightProducer -- False -> leftProducer let curKeymapProducer = case rightProducerLen < leftProducerLen of True -> leftProducer -- False -> rightProducer let curLensLookup = case rightProducerLen < leftProducerLen of True -> rightLens -- False -> leftLens let curLensInsert = case rightProducerLen < leftProducerLen of True -> leftLens -- False -> rightLens let appender km row = case rightProducerLen < leftProducerLen of True -> case M.lookup (view curLensLookup row) km of Just otherRow -> pure $ rappend otherRow row Nothing -> P.mzero -- False -> case M.lookup (view curLensLookup row) km of -- Just otherRow -> pure $ rappend row otherRow -- Nothing -> P.mzero keyMap <- P.liftIO $ P.fold (\m r -> M.insert (view curLensInsert r) r m) M.empty id curKeymapProducer pure $ curProducer >-> P.mapM (\r -> appender keyMap r) -- error if I uncomment my false cases (specifically the False case for curProducer) -- [5 of 5] Compiling Frames.Diff ( Frames/Diff.hs, interpreted ) -- Frames/Diff.hs:125:32: error: -- • Couldn't match type ‘leftRows’ with ‘rightRows’ -- ‘leftRows’ is a rigid type variable bound by -- the type signature for: -- innerJoin :: forall (m :: * -> *) k (f :: * -- -> *) (leftRows :: [*]) (rightRows :: [*]). -- (MonadIO m, Ord k) => -- Producer (Rec f leftRows) IO () -- -> Getting k (Rec f leftRows) k -- -> Producer (Rec f rightRows) IO () -- -> Getting k (Rec f rightRows) k -- -> m (P.Proxy P.X () () (Rec f (leftRows ++ rightRows)) IO ()) -- at Frames/Diff.hs:113:14 -- ‘rightRows’ is a rigid type variable bound by -- the type signature for: -- innerJoin :: forall (m :: * -> *) k (f :: * -- -> *) (leftRows :: [*]) (rightRows :: [*]). -- (MonadIO m, Ord k) => -- Producer (Rec f leftRows) IO () -- -> Getting k (Rec f leftRows) k -- -> Producer (Rec f rightRows) IO () -- -> Getting k (Rec f rightRows) k -- -> m (P.Proxy P.X () () (Rec f (leftRows ++ rightRows)) IO ()) -- at Frames/Diff.hs:113:14 -- Expected type: Producer (Rec f rightRows) IO () -- Actual type: Producer (Rec f leftRows) IO () -- • In the expression: leftProducer -- In a case alternative: False -> leftProducer -- In the expression: -- case rightProducerLen < leftProducerLen of { -- True -> rightProducer -- False -> leftProducer } -- • Relevant bindings include -- curProducer :: Producer (Rec f rightRows) IO () -- (bound at Frames/Diff.hs:123:7) -- rightLens :: Getting k (Rec f rightRows) k -- (bound at Frames/Diff.hs:119:47) -- rightProducer :: Producer (Rec f rightRows) IO () -- (bound at Frames/Diff.hs:119:33) -- leftLens :: Getting k (Rec f leftRows) k -- (bound at Frames/Diff.hs:119:24) -- leftProducer :: Producer (Rec f leftRows) IO () -- (bound at Frames/Diff.hs:119:11) -- innerJoin :: Producer (Rec f leftRows) IO () -- -> Getting k (Rec f leftRows) k -- -> Producer (Rec f rightRows) IO () -- -> Getting k (Rec f rightRows) k -- -> m (P.Proxy P.X () () (Rec f (leftRows ++ rightRows)) IO ()) -- (bound at Frames/Diff.hs:119:1)

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ANN: `dump-core` a prettier GHC core viewer
by Iavor Diatchki 13 Jan '17

13 Jan '17

Hello, Over the holidays I wrote a small GHC plugin to help me do some low-level optimizations of Haskell code. I thought it might be of use to other people too, so please try it out! When enabled, the plugin will save the Core generated by GHC in JSON format, and also render it in HTML for human inspection. The plugin is available on Hackage: http://hackage.haskell.org/package/dump-core The instructions on how to use it are in the README file. You may also read about it at the github page: http://hackage.haskell.org/package/dump-core There are many things that could probably be improved, just let me know. Also, if you are good at design, I could use some help making things look prettier :) Happy hacking, -Iavor

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[ANN] wiringPi-0.1.0.0
by Patrick Pelletier 10 Jan '17

10 Jan '17

https://hackage.haskell.org/package/wiringPi-0.1.0.0 https://github.com/ppelleti/hs-wiringPi This is a Haskell binding to the wiringPi library, which allows you to interface with the GPIO pins on the Raspberry Pi. Unlike some other solutions for using the Raspberry Pi's GPIO pins, wiringPi provides access to more advanced features, such as enabling the internal pull-up or pull-down resistors. To use this library, you must either run as root, or set the WIRINGPI_GPIOMEM environment variable. (Set it to anything; the value does not matter.) However, PWM will not work if WIRINGPI_GPIOMEM is set. This library will only build on the Raspberry Pi. Before building this library, you must install the "wiringPi" C library on your Raspberry Pi, like this: sudo apt-get install wiringpi Tested on a Raspberry Pi Model B, with Raspbian Jessie Lite, using the system-provided Haskell compiler. (GHC 7.6.3.) This Haskell binding is licensed under the 3-clause BSD license, and the examples in the examples directory are in the public domain. However, be aware that the wiringPi C library itself is licensed under the LGPLv3+. --Patrick

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[ANN] powermate-1.0
by Patrick Pelletier 10 Jan '17

10 Jan '17

As the new maintainer of the "powermate" package, I'm pleased to announce the first new release in nearly 9 years! This library is for interfacing the Griffin PowerMate USB (a big silver knob you can turn and click) with Haskell on Linux. You can read events from the PowerMate, and control the brightness, pulse speed, and pulse waveform of the built-in blue LED. https://hackage.haskell.org/package/powermate-1.0 https://github.com/ppelleti/powermate Version 1.0 is a major release with some breaking changes. The complete list of changes since version 0.1 is: * Now works with GHC 7.2.2 - 8.0.1. * Added Eq, Ord, Show, and Read instances for Event and Status. * Added example programs powermate-print and powermate-pulse. * Added documentation. * An open PowerMate is now represented by the opaque type 'PowerMate' instead of 'Handle'. A new function 'closeDevice' exists to close the opaque 'PowerMate' type. * Fixed a bug where the PowerMate would get confused and start dropping button presses if you set the LED. * Removed extraneous printing to stdout. * Removed getUSBName and readEventWithSkip; I didn't see the utility in these functions. * readEvent no longer returns a Maybe. There was no meaning to 'Nothing' and it just had to be ignored. * Removed the MPD module. It wasn't directly related to the PowerMate functionality, and the "libmpd" package seems to be an alternative which is more complete and better maintained. --Patrick

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Call for interest: Haskell in middle school math education
by Chris Smith 08 Jan '17

08 Jan '17

Hello fellow Haskellers! Are you interested in getting Haskell into middle school (ages 11-14) math or other classes? I'd love to hear from you! Many of you are probably already aware that I've spent the last several years teaching Haskell to children and teens via my CodeWorld project ( http://code.world and http://github.com/google/codeworld) Well, 2017 is my year to make a bigger success of the whole effort. So, let's get Haskell into K-12 schools as a part of mathematics education. By incorporating a programming language like Haskell that's faithful to modeling using true functions, variables, and equations, we can make mathematical modeling and algebraic reasoning tangible and creative in a way it's never been before. There's a lot that's already been done, but the task is still daunting. With some help from some coworkers of mine at Google, and in conjunction with the New York Haskell User Group, I've put together a small budget of around $60K in USD, to start this ball rolling a bit faster with some paid help. Some possible goals include: - Produce quality instructional materials to help teachers around the world incorporate Haskell into their classes and after-school activities. - Produce videos and online resources to support students learning on their own. - Build software features make the CodeWorld tools more helpful, easier to use, easier for students share their work more broadly, and more supportive when students need help. - Make what we already have available to more students, and educate more teachers. - Spread the word and look for more support so we can keep up the effort after the initial investment is finished. Everything produced as part of the project will be distributed under either the Apache 2.0 open source license, or the latest Creative Commons attribution-only license, so that it's freely available for any educational institution (or anyone else) to use, modify, redistribute, etc. So here's where you can step in: - Join the codeworld-discuss@ mailing list (https://groups.google.com/ forum/#!forum/codeworld-discuss) - Introduce yourself, and tell us a bit about what vision you have, and what role you might want to play. This could be a spectator, teacher at a school near you, volunteer contributions on the side, or even a leadership role with a salary attached! Cognizant that solo decisions can be poor ones, I hope to follow some initial sharing of ideas with gathering a small handful of like-minded individuals - I know you're out there - to make decisions about the best way to manage the effort, and go from there. Some background reading: - Blog post on the defining decisions of my effort so far <https://cdsmith.wordpress.com/2016/05/22/codeworlds-big-decisions/> - The web site and its source code <https://github.com/google/codeworld> - A huge bag of partially incomplete stuff already produced <https://drive.google.com/drive/u/1/folders/0B-qIu_nqxaMoYTQ4ODZjMjMtNWRiOC0…> - A similarly motivated project using Racket <http://www.bootstrapworld.org/> that gets a lot right I look forward to hearing from you.

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