- Haskell-Cafe - Haskell.org

[ANN] karya, music editor
by Evan Laforge 02 Jun '18

02 Jun '18

This is an announcement for Karya, which is a music editor written in Haskell. There are more details at: http://ofb.net/~elaforge/karya/doc/overview.md.html or if you just want to listen to music: http://ofb.net/~elaforge/karya/doc/examples.md.html Source is at: https://github.com/elaforge/karya Even if you're not interested in the music part, it's an example of a haskell program with a GUI, REPL based interface, tests, profiling, and a shake-based build system, although probably idiosyncratic implementations of all of the above. It should run on OS X (well tested) and X11 (poorly tested). If you are interested in the music part, this is basically in the "score writing" genre of software, in that it's suitable for writing a score in a textual non-realtime way. But though non-realtime, it's still interactive, so you can hear what you just wrote. And though textual and language-oriented, it's also semi-graphical, so it's closer to the sequencer / music editor type application than a music-oriented DSL like Haskore. It's hard to describe because as far as I know there's nothing else similar. If you have used a DAW but wanted to define higher level abstractions, or if you used Haskore (or similar) but found it difficult to write music purely textually, you might be interested in this. Or if you want to use your own tunings or scales, or do expressive control of pitch and dynamics. You'll need an external MIDI synthesizer though. There is a direct synthesis backend, but it's not practically usable yet. It's somewhat mature, in that I've been using for all my own music for the last 5 years or so, but of course also has many areas of active development, from graphics, to language design and interpretation, to music notation design, to audio synthesis and numerics. There is some documentation, but it's undoubtedly sparse since I'm the only user. Ask if you have questions! Details will be materialized on demand. Some things not mentioned on the "official" page since they're in progress: - A DSL to notate solkattu, which is Carnatic percussion syllables, and is a sort of instrument-independent notation for rhythmic structures, along with rules for realizing on various instruments. This is closer to a traditional music DSL like Haskore, but winds up different since it's rhythmically oriented. There's a small library of compositions. - An offline synthesis framework, including a sampler and FAUST-based synthesizer, built on a streaming audio library. I'm currently working on implementing off-line incremental audio rendering, which as far as I know is unique.

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PLMW@ICFP: CALL FOR SCHOLARSHIP APPLICATIONS and PARTICIPATION (deadline June 30!)
by Niki Vazou 01 Jun '18

01 Jun '18

PLMW@ICFP: CALL FOR SCHOLARSHIP APPLICATIONS and PARTICIPATION (deadline June 30!) ACM SIGPLAN Programming Languages Mentoring Workshop Co-located with ICFP'18 PLMW web page: https://icfp18.sigplan.org/track/PLMW-ICFP-2018 The purpose of the programming languages mentoring workshop (PLMW) is to encourage senior undergraduate and early career (first or second year) to pursue careers in programming language research. We are specifically interested in attracting groups who have traditionally not had the opportunity to participate in research in functional programming. This workshop will be a combination of learning about the work being done in several areas of programming language research and mentoring with respect to helping students prepare for graduate school and the rest of their career. We will bring together leaders in programming language research from academia and industry to give talks on the kind of research typically performed after obtaining a Ph.D. The workshop will engage students, specifically interested in programming language research, in a process of imagining how they might contribute to the world. We especially encourage women and underrepresented minority students to attend PLMW. This workshop is part of the activities surrounding ICFP, the International Conference on Functional Programming, and takes place the day before the main conference. One goal of the workshop is to make ICFP conference more accessible to newcomers. We hope that participants will stay through the entire conference. ## Travel Scholarship Applications (Due 30 June) Please fill out this form https://goo.gl/forms/7o4nENLxzAo2zwYy1. by 30 June to apply for travel funding. See the PLMW web page for additional details. The workshop registration is open to all. Students with alternative sources of funding are welcome. Best, Niki Vazou

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ANN: fast-arithmetic 0.6.0.7
by Vanessa McHale 31 May '18

31 May '18

Hi all, I have just published a new version of fast-arithmetic <https://hackage.haskell.org/package/fast-arithmetic>. It provides fast primitives for number theory and combinatorics on Linux and Mac. The latest release has few dependencies and thus builds should be quite robust.

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Re: [Haskell-cafe] ANN: primitive 0.6.4.0
by Dr.Koster 31 May '18

31 May '18

I have make some comments on reddit, but still I want to record them here: After reading the new code, I got a feeling that there're some API lacking considerations. Here is some of my personal concerns: The generalized MVar is basically useless because ST is meant to seal its state token, you won't want to add a forkST. You can argue that the atomic operations on MutVar is already added, but still I want to justify its usefulness. There're too much combinators added to PrimArray, is there a plan to port these to other arrays? If we ever provide toList operations, then I would really want it to be a good producer in base's fold-build fusion' view, it's robust and easy to implement, and folding is basically the same speed with List.fold and toList. Anyway it seems I missed the bike shedding, but still I want to thank for all the efforts, I'll try to follow new GitHub workflow more closely. Cheers Winter 发自我的iPhone ------------------ Original ------------------ From: Carter Schonwald <carter.schonwald(a)gmail.com> Date: Thu,May 31,2018 2:55 AM To: haskell-cafe <haskell-cafe(a)haskell.org>, Haskell Libraries <libraries(a)haskell.org> Subject: Re: [Haskell-cafe] ANN: primitive 0.6.4.0 This is a pretty exciting (albeit minor version) I'd like to especially thank David Feuer (treeowl ) and Andrew Martin (andrewthad) for their contributions the change log has a huge number of bug fixes relative to 0.6.2-3 also we added some new modules of features PrimArray --- unboxed nonsliceable vectors MVar -- Mvars that run in any PrimMonad augmented the Data.Primitive exports for increased consistency (the new .Ptr and .Mvar modules aren't exported in this minor version so users can easily migrate) Changes in version 0.6.4.0 Introduce Data.Primitive.PrimArray, which offers types and function for dealing with a ByteArray tagged with a phantom type variable for tracking the element type. Implement isByteArrayPinned and isMutableByteArrayPinned. Add Eq1, Ord1, Show1, and Read1 instances for Array and SmallArray. Improve the test suite. This includes having property tests for typeclasses from base such as Eq, Ord, Functor, Applicative, Monad, IsList, Monoid, Foldable, and Traversable. Fix the broken IsList instance for ByteArray. The old definition would allocate a byte array of the correct size and then leave the memory unitialized instead of writing the list elements to it. Fix the broken Functor instance for Array. The old definition would allocate an array of the correct size with thunks for erroring installed at every index. It failed to replace these thunks with the result of the function applied to the elements of the argument array. Fix the broken Applicative instances of Array and SmallArray. The old implementation of <*> for Arrayfailed to initialize some elements but correctly initialized others in the resulting Array. It is unclear what the old behavior of <*> was for SmallArray, but it was incorrect. Fix the broken Monad instances for Array and SmallArray. Fix the implementation of foldl1 in the Foldable instances for Array and SmallArray. In both cases, the old implementation simply returned the first element of the array and made no use of the other elements in the array. Fix the implementation of mconcat in the Monoid instance for SmallArray. Implement Data.Primitive.Ptr, implementations of Ptr functions that require a Prim constraint instead of a Storable constraint. Add PrimUnlifted instances for TVar and MVar. Use compareByteArrays# for the Eq and Ord instances of ByteArray when building with GHC 8.4 and newer. Add Prim instances for lots of types in Foreign.C.Types and System.Posix.Types. Reexport Data.Primitive.SmallArray and Data.Primitive.UnliftedArray from Data.Primitive. Add fold functions and map function to Data.Primitive.UnliftedArray. Add typeclass instances for IsList, Ord, and Show. Add defaultSetByteArray# and defaultSetOffAddr# to Data.Primitive.Types.

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Config Files and monoids
by Olaf Klinke 31 May '18

31 May '18

Dear cafe, a recent post here [1] mentioned that configurations, such as the ones read from a config file, can be given Monoid instances, where mempty is the empty or default configuration and mappend merges two partial configurations, producing a more complete one. The vgrep package explicitly does this, for instance. Although the ConfigParser type from the ConfigFile package has a binary 'merge' operation, it does define neither a Monoid not a Semigroup instance. I'm struggling to make the concept of monoidal configuration work when there is no sensible default configuration. Suppose my configuration type is data Config = Config {foo :: Bool, bar :: Int} with no reasonable default, e.g. emptyConfig = Config { foo = error "you did not specify option foo", bar = error "you did not specify option bar" } Some configuration monoids seem to have the second operand override the first, or the other way around. However, I wish that when cfg1 = emptyConfig {foo = True} cfg2 = emptyConfig {bar = 4} then cfg1 <> cfg2 == Config {foo = True, bar = 4}. So it seems that for mappend to work as intended one needs a terminating function that tells me if a record field is already defined, e.g. when all fields are Maybes. Vgrep.Environment.Config.Monoid does it this way. My solution so far was to resort to the monoid of endofunctions (as the getflag package does), that is, define cfg1, cfg2 :: Config -> Config cfg1 = \cfg -> cfg {foo = True} cfg2 = \cfg -> cfg {bar = 4} And then build (cfg1.cfg2) emptyConfig. (Alternatively, one might structure these as lenses instead of endofunctions, see e.g. Data.Monoid.Endo.Fold in the endo package.) Thus I arrived at class Config cfg where emptyConfig :: cfg -- may contain some defaults configOptions :: [Parser (cfg -> cfg)] Do you think every other concept of configuration parsing can be cast into this typeclass? -- Olaf [1] https://mail.haskell.org/pipermail/haskell-cafe/2018-May/129063.html

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Re: [Haskell-cafe] (names for) invariants for Eq and Ord?
by Olaf Klinke 31 May '18

31 May '18

Prelude> import qualified Data.Map as M Prelude M> let k = 0/0 in let v = 0 in M.lookup k (M.insert k v M.empty) == Just v False This one is not surprising because the presence of 0/0 destroys the total order of Double, so strictly speaking this should not have an Ord instance. Olaf

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ANN: primitive 0.6.4.0
by Carter Schonwald 31 May '18

31 May '18

This is a pretty exciting (albeit minor version) I'd like to especially thank David Feuer (treeowl ) and Andrew Martin (andrewthad) for their contributions the change log has a huge number of bug fixes relative to 0.6.2-3 also we added some new modules of features PrimArray --- unboxed nonsliceable vectors MVar -- Mvars that run in any PrimMonad augmented the Data.Primitive exports for increased consistency (the new .Ptr and .Mvar modules aren't exported in this minor version so users can easily migrate) Changes in version 0.6.4.0 - Introduce Data.Primitive.PrimArray, which offers types and function for dealing with a ByteArray tagged with a phantom type variable for tracking the element type. - Implement isByteArrayPinned and isMutableByteArrayPinned. - Add Eq1, Ord1, Show1, and Read1 instances for Array and SmallArray. - Improve the test suite. This includes having property tests for typeclasses from base such as Eq, Ord, Functor, Applicative, Monad, IsList, Monoid, Foldable, and Traversable. - Fix the broken IsList instance for ByteArray. The old definition would allocate a byte array of the correct size and then leave the memory unitialized instead of writing the list elements to it. - Fix the broken Functor instance for Array. The old definition would allocate an array of the correct size with thunks for erroring installed at every index. It failed to replace these thunks with the result of the function applied to the elements of the argument array. - Fix the broken Applicative instances of Array and SmallArray. The old implementation of <*> for Arrayfailed to initialize some elements but correctly initialized others in the resulting Array. It is unclear what the old behavior of <*> was for SmallArray, but it was incorrect. - Fix the broken Monad instances for Array and SmallArray. - Fix the implementation of foldl1 in the Foldable instances for Array and SmallArray. In both cases, the old implementation simply returned the first element of the array and made no use of the other elements in the array. - Fix the implementation of mconcat in the Monoid instance for SmallArray. - Implement Data.Primitive.Ptr, implementations of Ptr functions that require a Prim constraint instead of a Storable constraint. - Add PrimUnlifted instances for TVar and MVar. - Use compareByteArrays# for the Eq and Ord instances of ByteArray when building with GHC 8.4 and newer. - Add Prim instances for lots of types in Foreign.C.Types and System.Posix.Types. - Reexport Data.Primitive.SmallArray and Data.Primitive.UnliftedArray from Data.Primitive. - Add fold functions and map function to Data.Primitive.UnliftedArray. Add typeclass instances for IsList, Ord, and Show. - Add defaultSetByteArray# and defaultSetOffAddr# to Data.Primitive.Types.

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Selecting a transformer in a monad transformer stack
by Paul Brauner 30 May '18

30 May '18

Hello, I have a newtype for a monad transformer stack: newtype MyMonad a = MyMonad { runMyMonad :: ((ReaderT Env (ExceptT String (StateT Store (ListT Identity)))) a) } and I'd like to it derive MonadPlus. The default instance for MonadPlus I get via GeneralizedNewtypeDeriving is the ExceptT one because it is the outermost transformer implementing MonadPlus. I would like to use the ListT instance instead. The best solution I have come up with is to define: instance MonadPlus MyMonad where mzero = MyMonad $ ReaderT $ \e -> ExceptT $ StateT $ \s -> ListT $ Identity [] mplus a b = MyMonad $ ReaderT $ \e -> ExceptT $ StateT $ \s -> ListT $ Identity $ let run x = runIdentity (runListT (runStateT (runExceptT (runReaderT (runAbstract x) e)) s)) as = run a bs = run b in as ++ bs My questions are: - Is there a shorter way to define mplus? - Is there maybe some variation of monad transformer stacks where the layers are named and can be accessed by name? (I know of effects handlers but I'd like to stick to monad transformers for now.) Paul

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8.4.2 FreeBSD bindist not working with gold & lld
by Sumit Raja 30 May '18

30 May '18

Hi, Just got 8.4.2 running in my FreeBSD 11 environment and am getting the following: cabal: Failed to build entropy-0.4.1.1 (which is required by exe:test-ghoa from oauth2-simple-0.1.0.0). The failure occurred during the configure step. The exception was: dieVerbatim: user error (cabal: '/usr/local/bin/ghc' exited with an error: /usr/local/bin/ld.gold: error: /usr/local/lib/ghc-8.4.2/rts/libHSrts_thr.a(RTS.thr_o): unexpected reloc 8 in object file LLD fails with configure step. The exception was: dieVerbatim: user error (cabal: '/usr/local/bin/ghc' exited with an error: /usr/bin/ld.lld: error: do not know how to handle relocation 'R_X86_64_RELATIVE' (8) Saw another thread that discussed this but there was no resolution. Any ideas on how to fix this? Thanks Sumit

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Fwd: Safe TCP accept loop
by Sumit Raja 30 May '18

30 May '18

Hi, I sent this to beginners but got no responses so I'm hoping someone here can help. I’ve looked at https://wiki.haskell.org/Concurrency_demos/Graceful_exit and used(2) Using throwTo without the use of block and unblock. It runs on 8.2.1 with my limited testing. I can’t find out much about what the > 7.x GHC replacement for block/unblock is other than mask. What does the unblock do in acceptConnections'? Does this method of handling an accept loop still need masking of async exceptions ? If so where does this need to be done? I've got a version with async running for my specific application (https://bitbucket.org/sumitraja/hvrr/src/6927216597a35a9a0d7f2e55cca83fa5b7…) but I don't know if I need to unmask at any point so was hoping for some guidance. Thanks Sumit

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