- Haskell-Cafe - Haskell.org

A "less" complex median
by Michel Haber 28 May '19

28 May '19

Hello Cafe, I wanted to try and write a median filter with good complexity and performance. This is just an exercise, so there is no use looking for better performance algorithms (median of medians). Below is the code I came up with: import Control.Monad.State import System.Random type MyState s = State (Int, Int, [(Int, s)]) -- Inserts a value in its sorted place, -- Removes all expired values encountered, -- Returns the median value of the list. insertSorted :: (Ord a) => a -> MyState a a insertSorted v = do (size, index, list) <- get let flt = valid size index -- Filter: If too old remove value cmp (_,x) = v < x -- Compare: If v spot reached, add v ret = min index size `div` 2 -- The return value's index let (newList, med) = goThrough flt cmp ret (index, v) list put (size, index + 1, newList) return . snd $ med -- Internal implementation goThrough :: (a -> Bool) -> (a -> Bool) -> Int -> a -> [a] -> ([a], a) goThrough _ _ _ v [] = ([v], v) goThrough flt cmp idx v ls@(x:xs) | flt x && cmp x = if idx == 0 then (v:ls, v) else (v:ls, getTo idx (v:ls)) | flt x = let (ys, y) = goThrough flt cmp (max 0 (idx-1)) v xs in if idx == 0 then (x:ys, x) else (x:ys, y) | otherwise = goThrough flt cmp idx v xs -- Continues going through the list until we get to the element we want, or we -- run out of elements, in which case we take the last one getTo :: Int -> [a] -> a getTo _ [] = error "No value to return!" getTo _ [x] = x getTo 0 (x:_) = x getTo i (_:xs) = getTo (i-1) xs -- A value is valid if it still has a place in the list (hasn't expired) valid :: Int -> Int -> (Int, a) -> Bool valid size index (i,_) = index - i < size -- Clean up all the old values in the list. This is costly, and should be -- performed sparingly clean :: MyState Double () clean = do (size, index, list) <- get put (size, index, filter (valid size index) list) -- Insert n values with insertSorted insertList :: [Double] -> MyState Double [Double] insertList ls = sequence $ insertSorted <$> ls -- Example main :: IO () main = do values <- sequence $ replicate 10000 $ randomRIO (1,100::Double) print $ runState (insertList values <* clean) (10, 0, []) return () The code works, at least in the simple cases I've tried. It seems, however, way too complex and not very composable. So I was wondering if anyone could tell me where I went wrong, and how I can make the code simpler and smaller. Of course, it is completely possible to divide my insertion function, but the goal is to do all of the steps in one iteration over the list. This allows me to later compare what I have with divided functions to discover if the compiler would optimize them into one traversal. But even with its current logic, I believe the code can be better written. I just don't know how :p So I really appreciate any advice on how to make it better (or fix a bug I missed, or maybe even the logic of the whole algorithm). Cheers, Michel :)

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ANN: Elminator (Haskell to Elm code generator for Elm 0.19/0.18)
by sras 28 May '19

28 May '19

Happy to announce 'Elminator', a package for generating Elm source for type definitions and Json encoders/decoders from Haskell data type definitions. https://hackage.haskell.org/package/elminator, This package tries to address some issues with popular/existing packages in the same space. Some distinguishing features are.. 1. Supports generation of polymorphic types (as well as concrete ones) in Elm from possibly polymorphic Haskell types, including types with phantom type variables. 2. Supports generation of code for recursive types (direct/indirect) as long as the type is not polymorphic. 3. Generates code that does not depend on external Elm libraries. 4. Does not have limits on the number of fields that the constructors of your types can have. 5. Supports JSON encoding options exported by the Aeson library comprehensively. 6. Supports generation of code that depend on user defined types and encoders/decoders in Elm. Right now this package is tested by using a Haskell/Elm test app that round trips a bunch of data structures between an Elm front end and a Haskell back end, so as of now, there there aren't any automated tests included with this repo. Any feedback is welcome! Thanks.

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Emacs org-mode code block problems
by Lawrence Bottorff 27 May '19

27 May '19

I've got this in an Emacs org-mode code block: #+begin_src haskell :results output doubleSmallNumber4 x = if x > 0 then x else x * 2 #+end_src but when I try to run it (with C-c C-c) I get ... Prelude> doubleSmallNumber4 x = if x > 0 then x else x * 2 "org-babel-haskell-eoe" <interactive>:19:23: error: parse error (possibly incorrect indentation or mismatched brackets) Prelude> <interactive>:20:11: error: parse error (possibly incorrect indentation or mismatched brackets) Prelude> <interactive>:21:5-8: error: parse error on input ‘then’ Prelude> <interactive>:22:5-8: error: parse error on input ‘else’ Prelude> "org-babel-haskell-eoe" ... I can run #+begin_src haskell tripleMe x = x + x + x #+end_src just fine though -- which means I've done something right with my Emacs init. The REPL started is 8.6.3 stack-ghci. I've formatted with the org-mode C-c '

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How to make boolean logic with IO Monad more expressive?
by Magicloud Magiclouds 27 May '19

27 May '19

Hi, I think `a || b && c` is more clear than ``` if a then True else if b then if c then True else False else False ``` And some languages, `pureComputing || (ioOperation && pure2)` involves IO only when pureComputing is False. So in Haskell, is it possible to get both benefits? ``` status <- ioOperation -- IO-ed anyway return $ pureComputing || (status && pure2) ``` ``` if pureComputing then return True else do status <- ioOperation if status then return pure2 else return False -- Looks ugly ```

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Call for papers for IFL 2019 (Implementation and Application of Functional Languages)
by Jurriaan Hage 27 May '19

27 May '19

Hello, Please, find below the call for papers for IFL 2019. Please forward these to anyone you think may be interested. Apologies for any duplicates you may receive. best regards, Jurriaan Hage Publicity Chair of IFL --- ================================================================================ IFL 2019 31st Symposium on Implementation and Application of Functional Languages National University of Singapore September 25th-27th, 2019 http://2019.iflconference.org ================================================================================ ### Scope The goal of the IFL symposia is to bring together researchers actively engaged in the implementation and application of functional and function-based programming languages. IFL 2019 will be a venue for researchers to present and discuss new ideas and concepts, work in progress, and publication-ripe results related to the implementation and application of functional languages and function-based programming. Topics of interest to IFL include, but are not limited to: - language concepts - type systems, type checking, type inferencing - compilation techniques - staged compilation - run-time function specialization - run-time code generation - partial evaluation - (abstract) interpretation - metaprogramming - generic programming - automatic program generation - array processing - concurrent/parallel programming - concurrent/parallel program execution - embedded systems - web applications - (embedded) domain specific languages - security - novel memory management techniques - run-time profiling performance measurements - debugging and tracing - virtual/abstract machine architectures - validation, verification of functional programs - tools and programming techniques - (industrial) applications ### Keynote Speaker * Olivier Danvy, Yale-NUS College ### Submissions and peer-review Differently from previous editions of IFL, IFL 2019 solicits two kinds of submissions: * Regular papers (12 pages including references) * Draft papers for presentations ('weak' limit between 8 and 15 pages) Regular papers will undergo a rigorous review by the program committee, and will be evaluated according to their correctness, novelty, originality, relevance, significance, and clarity. A set of regular papers will be conditionally accepted for publication. Authors of conditionally accepted papers will be provided with committee reviews along with a set of mandatory revisions. Regular papers not accepted for publication will be considered as draft papers, at the request of the author. Draft papers will be screened to make sure that they are within the scope of IFL, and will be accepted for presentation or rejected accordingly. Prior to the symposium: Authors of conditionally accepted papers and accepted presentations will submit a pre-proceedings version of their work that will appear in the draft proceedings distributed at the symposium. The draft proceedings does not constitute a formal publication. We require that at least one of the authors present the work at IFL 2019. After the symposium: Authors of conditionally accepted papers will submit a revised versions of their paper for the formal post-proceedings. The program committee will assess whether the mandatory revisions have been adequately addressed by the authors and thereby determines the final accept/reject status of the paper. Our interest is to ultimately accept all conditionally accepted papers. If you are an author of a conditionally accepted paper, please make sure that you address all the concerns of the reviewers. Authors of accepted presentations will be given the opportunity to incorporate the feedback from discussions at the symposium and will be invited to submit a revised full article for the formal post-proceedings. The program committee will evaluate these submissions according to their correctness, novelty, originality, relevance, significance, and clarity, and will thereby determine whether the paper is accepted or rejected. ### Publication The formal proceedings will appear in the International Conference Proceedings Series of the ACM Digital Library. At no time may work submitted to IFL be simultaneously submitted to other venues; submissions must adhere to ACM SIGPLAN's republication policy: http://www.sigplan.org/Resources/Policies/Republication ### Important dates Submission of regular papers: May 31, 2019 Submission of draft papers: July 15, 2019 Regular and draft papers notification: August 1, 2019 Deadline for early registration: August 15, 2019 Submission of pre-proceedings version: September 15, 2019 IFL Symposium: September 25-27, 2019 Submission of papers for post-proceedings: November 30, 2019 Notification of acceptance: January 31, 2020 Camera-ready version: February 29, 2020 ### Submission details All contributions must be written in English. Papers must use the ACM two columns conference format, which can be found at: http://www.acm.org/publications/proceedings-template Authors submit through EasyChair: https://easychair.org/conferences/?conf=ifl2019 ### Peter Landin Prize The Peter Landin Prize is awarded to the best paper presented at the symposium every year. The honored article is selected by the program committee based on the submissions received for the formal review process. The prize carries a cash award equivalent to 150 Euros. ### Organization and Program committee Chairs: Jurrien Stutterheim (Standard Chartered Bank Singapore), Wei Ngan Chin (National University of Singapore) Program Committee: - Olaf Chitil, University of Kent - Clemens Grelck, University of Amsterdam - Daisuke Kimura, Toho University - Pieter Koopman, Radboud University - Tamas Kozsik, Eotvos Lorand University - Roman Leschinskiy, Facebook - Ben Lippmeier, The University of New South Wales - Marco T. Morazan, Seton Hall University - Sven-Bodo Scholz, Heriot-Watt University - Tom Schrijvers, Katholieke Universiteit Leuven - Alejandro Serrano, Utrecht University - Tony Sloane, Macquarie University - Simon Thompson, University of Kent - Marcos Viera, Universidad de la Republica - Wei Ngan Chin, NUS - Jurrien Stutterheim, Standard Chartered Bank ### Venue The 31st IFL is organized by the National University of Singapore. Singapore is located in the heart of South-East Asia, and the city itself is extremely well connected by trains and taxis. See the website for more information on the venue. ### Acknowledgments This call-for-papers is an adaptation and evolution of content from previous instances of IFL. We are grateful to prior organizers for their work, which is reused here. A part of IFL 2019 format and CFP language that describes conditionally accepted papers has been adapted from call-for-papers of OOPSLA conferences.

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Is there already a lib to work with filepath glob?
by Magicloud Magiclouds 26 May '19

26 May '19

Hi, Say for logic of Bash code `for f in /somePath/*/*; do ... done`, with filepath, directory packages, I have to do something like `listDirectoryContent "somePath" >>= mapM_ (\fp -> listDirectoryContent fp >>= action)`. It is not as expressive as the script. Especially when I'd like to use conduit to stream the folder. So is there already something I can use to make the logic expressive? PS: I know there are some libs to match a filepath against a glob string. But that is not what I want.

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haskell-src-exts - no more releases
by Matthew Pickering 26 May '19

26 May '19

Hi all, I have decided that I am not going to do any more releases of `haskell-src-exts`. (https://github.com/haskell-suite/haskell-src-exts) If anyone wants to become the maintainer then I will gladly transfer rights to the repo. I advise anyone who wants to parse Haskell programs to use the GHC API, specifically you can use `ghc-lib-parser`. https://hackage.haskell.org/package/ghc-lib-parser Cheers, Matt

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ANN: stack-2.1 release candidate
by Emanuel Borsboom 26 May '19

26 May '19

Announcing the first release candidate of Stack 2.1! You can download bindists for Linux, macOS, and Windows from https://github.com/commercialhaskell/stack/releases/tag/v2.1.0.1. ### Changes since v1.9.3 Major changes: * Switch over to pantry for managing packages. This is a major change to Stack's internals, and affects user-visible behavior in a few places. Some highlights: * Drop support for multiple package indices and legacy `00-index.tar` style indices. See [#4137](https://github.com/commercialhaskell/stack/issues/4137). * Support for archives and repos in the `packages` section has been removed. Instead, you must use `extra-deps` for such dependencies. `packages` now only supports local filepaths. * Add support for Git repositories containing (recursive) submodules. * Addition of new configuration options for specifying a "pantry tree" key, which provides more reproducibility around builds, and (in the future) will be used for more efficient package content downloads. You can also specify package name and version for more efficient config parsing. * __NOTE__ The new `stack freeze` command provides support for automatically generating this additional information. * Package contents and metadata are stored in an SQLite database in place of files on the filesystem. The `pantry` library can be used for interacting with these contents. * Internally, Stack has changed many datatypes, including moving to Cabal's definition of many data types. As a result of such changes, existing cache files will in general be invalidated, resulting in Stack needing to rebuild many previously cached builds in the new version. Sorry :(. * A new command, `stack freeze` has been added which outputs project and snapshot definitions with dependencies pinned to their exact versions. * The `ignore-revision-mismatch` setting is no longer needed, and has been removed. * Overriding GHC boot packages results in any other GHC boot packages depending on it being no longer available as a dependency, such packages need to be added explicitly when needed. See [#4510] (https://github.com/commercialhaskell/stack/issues/4510) * Cabal solver integration was not updated to support newer `cabal-install` versions so `stack solver` command was removed as well as a related option `--solver` from `stack new` and `stack init`. * Upgrade to Cabal 2.4 * Note that, in this process, the behavior of file globbing has been modified to match that of Cabal. In particular, this means that for Cabal spec versions less than 2.4, `*.txt` will match `foo.txt`, but not `foo.2.txt`. * Remove the `stack image` command. With the advent of Docker multistage builds, this functionality is no longer useful. For an example, please see [Building Haskell Apps with Docker]( https://www.fpcomplete.com/blog/2017/12/building-haskell-apps-with-docker) * Support building GHC from source (experimental) * Stack now supports building and installing GHC from source. The built GHC is uniquely identified by a commit id and an Hadrian "flavour" (Hadrian is the newer GHC build system), hence `compiler` can be set to use a GHC built from source with `ghc-git-COMMIT-FLAVOUR` * `stack.yaml` now supports a `configure-options`, which are passed directly to the `configure` step in the Cabal build process. See [#1438](https://github.com/commercialhaskell/stack/issues/1438) * Remove support for building GHCJS itself. Future releases of Stack may remove GHCJS support entirely. * Support for lock files for pinning exact project dependency versions Behavior changes: * `stack.yaml` now supports `snapshot`: a synonym for `resolver`. See [#4256](https://github.com/commercialhaskell/stack/issues/4256) * `stack script` now passes `-i -idir` in to the `ghc` invocation. This makes it so that the script can import local modules, and fixes an issue where `.hs` files in the current directory could affect interpretation of the script. See [#4538](https://github.com/commercialhaskell/stack/pull/4538) * When using `stack script`, custom snapshot files will be resolved relative to the directory containing the script. * Remove the deprecated `--upgrade-cabal` flag to `stack setup`. * Support the `drop-packages` field in `stack.yaml` * Remove the GPG signing code during uploads. The GPG signatures have never been used yet, and there are no plans to implement signature verification. * Remove the `--plain` option for the `exec` family of commands * Always use the `--exact-configuration` Cabal configuration option when building (should mostly be a non-user-visible enhancement). * No longer supports Cabal versions older than `1.19.2`. This means projects using snapshots earlier than `lts-3.0` or `nightly-2015-05-05` will no longer build. * Remove the `stack docker cleanup` command. Docker itself now has [`docker image prune`]( https://docs.docker.com/engine/reference/commandline/image_prune/) and [`docker container prune`]( https://docs.docker.com/engine/reference/commandline/container_prune/) which you can use instead. * Interleaved output is now turned on by default, see [#4702](https://github.com/commercialhaskell/stack/issues/4702). In addition, the `packagename> ` prefix is no longer included in interelaved mode when only building a single target. * The `-fhide-source-paths` GHC option is now enabled by default and can be disabled via the `hide-source-paths` configuration option in `stack.yaml`. See [#3784]( https://github.com/commercialhaskell/stack/issues/3784) * Stack will reconfigure a package if you modify your `PATH` environment variable. See [#3138](https://github.com/commercialhaskell/stack/issues/3138). * For GHC 8.4 and later, disable the "shadowed dependencies" workaround. This means that Stack will no longer have to force reconfigures as often. See [#3554](https://github.com/commercialhaskell/stack/issues/3554). * When building a package, Stack takes a lock on the dist directory in use to avoid multiple runs of Stack from trampling each others' files. See [#2730](https://github.com/commercialhaskell/stack/issues/2730). * Stack will check occassionally if there is a new version available and prompt the user to upgrade. This will not incur any additional network traffic, as it will piggy-back on the existing Hackage index updates. You can set `recommend-stack-upgrade: false` to bypass this. See [#1681](https://github.com/commercialhaskell/stack/issues/1681). * `stack list-dependencies` has been removed in favour of `stack ls dependencies`. * The new default for `--docker-auto-pull` is enabled. See [#3332](https://github.com/commercialhaskell/stack/issues/3332). Other enhancements: * Support MX Linux in get-stack.sh. Fixes [#4769](https://github.com/commercialhaskell/stack/issues/4769). * Defer loading up of files for local packages. This allows us to get plan construction errors much faster, and avoid some unnecessary work when only building a subset of packages. This is especially useful for the curator use case. * Existing global option `--color=WHEN` is now also available as a non-project-specific yaml configuration parameter `color:`. * Adopt the standard proposed at http://no-color.org/, that color should not be added by default if the `NO_COLOR` environment variable is present. * New command `stack ls stack-colors` lists the styles and the associated 'ANSI' control character sequences that stack uses to color some of its output. See `stack ls stack-colors --help` for more information. * New global option `--stack-colors=STYLES`, also available as a non-project-specific yaml configuration parameter, allows a stack user to redefine the default styles that stack uses to color some of its output. See `stack --help` for more information. * British English spelling of 'color' (colour) accepted as an alias for `--color`, `--stack-colors`, `stack ls stack-colors` at the command line and for `color:` and `stack-colors:` in yaml configuration files. * New build option `--ddump-dir`. (See [#4225]( https://github.com/commercialhaskell/stack/issues/4225)) * Stack parses and respects the `preferred-versions` information from Hackage for choosing latest version of a package in some cases, e.g. `stack unpack packagename`. * The components output in the `The main module to load is ambiguous` message now include package names so they can be more easily copy-pasted. * Git repos are shared across multiple projects. See [#3551](https://github.com/commercialhaskell/stack/issues/3551) * Use en_US.UTF-8 locale by default in pure Nix mode so programs won't crash because of Unicode in their output [#4095](https://github.com/commercialhaskell/stack/issues/4095) * Add `--tree` to `ls dependencies` to list dependencies as tree. [#4101](https://github.com/commercialhaskell/stack/issues/4101) * Add `--pedantic` to `ghci` to run with `-Wall` and `-Werror` [#4463](https://github.com/commercialhaskell/stack/issues/4463) * Add `--cabal-files` flag to `stack ide targets` command. * Add `--stdout` flag to all `stack ide` subcommands. * Use batches when unregistering packages with `ghc-pkg`. (See [#2662](https://github.com/commercialhaskell/stack/issues/2662)) * `get-stack` script now works on Windows CI machines of Appveyor, Travis and Azure Pipelines. See [#4535](https://github.com/commercialhaskell/stack/issues/4535)/ * Show snapshot being used when `stack ghci` is invoked outside of a project directory. See [#3651](https://github.com/commercialhaskell/stack/issues/3651) * The script interpreter now accepts a `--extra-dep` flag for adding packages not present in the snapshot. Currently, this only works with packages from Hackage, not Git repos or archives. * When using the script interpreter with `--optimize` or `--compile`, Stack will perform an optimization of checking whether a newer executable exists, making reruns significantly faster. There's a downside to this, however: if you have a multifile script, and change one of the dependency modules, Stack will not automatically detect and recompile. * `stack clean` will delete the entire `.stack-work/dist` directory, not just the relevant subdirectory for the current GHC version. See [#4480](https://github.com/commercialhaskell/stack/issues/4480). * Add `stack purge` as a shortcut for `stack clean --full`. See [#3863](https://github.com/commercialhaskell/stack/issues/3863). * Both `stack dot` and `stack ls dependencies` accept a `--global-hints` flag to bypass the need for an installed GHC. See [#4390](https://github.com/commercialhaskell/stack/issues/4390). * Add the `stack config env` command for getting shell script environment variables. See [#620]( https://github.com/commercialhaskell/stack/issues/620) * Less verbose output from `stack setup` on Windows. See [#1212](https://github.com/commercialhaskell/stack/issues/1212). * Add an optional `ignore-expiry` flag to the `hackage-security` section of the `~/.stack/config.yaml`. It allows to disable timestamp expiration verification just like `cabal --ignore-expiry` does. The flag is not enabled by default so that the default functionality is not changed. * Include default values for most command line flags in the `--help` output. See [#893](https://github.com/commercialhaskell/stack/issues/893). * Set the `GHC_ENVIRONMENT` environment variable to specify dependency packages explicitly when running test. This is done to prevent ambiguous module name errors in `doctest` tests. * Document the way stack interacts with the Cabal library. * `get-stack` script now works on Windows CI machines of Appveyor, Travis and Azure Pipelines. See [#4535](https://github.com/commercialhaskell/stack/issues/4535) * Warn when a Docker image does not include a `PATH` environment variable. See [#2472](https://github.com/commercialhaskell/stack/issues/2742) * When using `system-ghc: true`, Stack will now find the appropriate GHC installation based on the version suffix, allowing you to more easily switch between various system-installed GHCs. See [#2433](https://github.com/commercialhaskell/stack/issues/2433). * `stack init` will now support create a `stack.yaml` file without any local packages. See [#2465]( https://github.com/commercialhaskell/stack/issues/2465) * Store caches in SQLite database instead of files. * No longer use "global" Docker image database (`docker.db`). * User config files are respected for the script command. See [#3705](https://github.com/commercialhaskell/stack/issues/3705), [#3887](https://github.com/commercialhaskell/stack/issues/3887). * Set the `GHC_ENVIRONMENT` environment variable to `-` to tell GHC to ignore any such files when GHC is new enough (>= 8.4.4), otherwise simply unset the variable. This allows Stack to have control of package databases when running commands like `stack exec ghci`, even in the presence of implicit environment files created by `cabal new-build`. See [#4706](https://github.com/commercialhaskell/stack/issues/4706). * Use a database cache table to speed up discovery of installed GHCs * You can specify multiple `--test-arguments` options. See [#2226](https://github.com/commercialhaskell/stack/issues/2226) * Windows terminal width detection is now done. See [#3588](https://github.com/commercialhaskell/stack/issues/3588) * On Windows, informs users if the 'programs' path contains a space character and further warns users if that path does not have an alternative short ('8 dot 3') name, referencing the `local-programs-path` configuration option. See [#4726](https://github.com/commercialhaskell/stack/issues/4726) Bug fixes: * Ignore duplicate files for a single module when a Haskell module was generated from a preprocessor file. See [#4076](https://github.com/commercialhaskell/stack/issues/4076). * Only track down components in current directory if there are no hs-source-dirs found. This eliminates a number of false-positive warnings, similar to [#4076](https://github.com/commercialhaskell/stack/issues/4076). * Handle a change in GHC's hi-dump format around `addDependentFile`, which now includes a hash. See [yesodweb/yesod#1551](https://github.com/yesodweb/yesod/issues/1551) * Fix `subdirs` for git repos in `extra-deps` to match whole directory names. Also fixes for `subdirs: .`. See [#4292](https://github.com/commercialhaskell/stack/issues/4292) * Fix for git packages to update submodules to the correct state. See [#4314](https://github.com/commercialhaskell/stack/pull/4314) * Add `--cabal-files` flag to `stack ide targets` command. * Don't download ghc when using `stack clean`. * Support loading in GHCi definitions from symlinked C files. Without this patch, Stack will try to find object files in the directory pointed to by symlinks, while GCC will produce the object files in the original directory. See [#4402](https://github.com/commercialhaskell/stack/pull/4402) * Fix handling of GitHub and URL templates on Windows. See [commercialhaskell/stack#4394]( https://github.com/commercialhaskell/stack/issues/4394) * Fix `--file-watch` not responding to file modifications when running inside docker on Mac. See [#4506](https://github.com/commercialhaskell/stack/issues/4506) * Using `--ghc-options` with `stack script --compile` now works. * Ensure the detailed-0.9 type tests work. See [#4453](https://github.com/commercialhaskell/stack/issues/4453). * Extra include and lib dirs are now order-dependent. See [#4527](https://github.com/commercialhaskell/stack/issues/4527). * Apply GHC options when building a `Setup.hs` file. See [#4526](https://github.com/commercialhaskell/stack/issues/4526). * Stack handles ABI changes in FreeBSD 12 by differentiating that version from previous. * Help text for the `templates` subcommand now reflects behaviour in stack 1.9 — that it downloads and shows a help file, rather than listing available templates. * Fix detection of aarch64 platform (this broke when we upgraded to a newer Cabal version). * Docker: fix detecting and pulling missing images with `--docker-auto-pull`, see [#4598](https://github.com/commercialhaskell/stack/issues/4598) * Hackage credentials are not world-readable. See [#2159](https://github.com/commercialhaskell/stack/issues/2159). * Warnings are dumped from logs even when color is enabled. See [#2997](https://github.com/commercialhaskell/stack/issues/2997) * `stack init` will now work for cabal files with sublibraries. See [#4408](https://github.com/commercialhaskell/stack/issues/4408) * When the Cabal spec version is newer than the global Cabal version, build against the snapshot's Cabal library. See [#4488](https://github.com/commercialhaskell/stack/issues/4488) * Docker: fix detection of expected subprocess failures. This fixes downloading a compatible `stack` executable when the host `stack` is not compatible with the Docker image (on Linux), and doesn't show an unnecessary extra error when the in-container re-exec'ed `stack` exits with failure. * The `stack ghci` command's `--ghc-options` flag now parses multiple options. See [#3315](https://github.com/commercialhaskell/stack/issues/3315).

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Call For Papers: Workshop in OCL and Textual Modeling (OCL 2019)
by Achim D. Brucker 25 May '19

25 May '19

CALL FOR PAPERS 19th International Workshop on OCL and Textual Modeling Co-located with MODELS 2019 ACM/IEEE 22nd International Conference on Model Driven Engineering Languages and System, September 15-20, 2019, Munich, Germany http://oclworkshop.github.io The goal of this workshop is to create a forum where researchers and practitioners interested in building models using OCL or other kinds of textual languages (e.g., OCL, textual MOF, Epsilon, or Alloy) can directly interact, report advances, share results, identify tools for language development, and discuss appropriate standards. In particular, the workshop will encourage discussions for achieving synergy from different modeling language concepts and modeling language use. The close interaction will enable researchers and practitioners to identify common interests and options for potential cooperation. ## Topics of interest Topics of interest include (but are not limited to): - Mappings between textual modeling languages and other languages/formalisms - Mathematical models and/or formal semantics for textual modeling languages - Algorithms, evaluation strategies and optimizations in the context of textual modeling languages for: - validation, verification, and testing, - model transformation and code generation, - meta-modeling and DSLs, and - query and constraint specifications - Alternative graphical/textual notations for textual modeling languages - Evolution, transformation and simplification of textual modeling expressions - Libraries, templates and patterns for textual modeling languages - Tools that support textual modeling languages (e.g., verification of OCL formulae, runtime monitoring of invariants) - Model-driven security using textual modeling languages - Complexity results for textual modeling languages - Quality models and benchmarks for comparing and evaluating textual modeling tools and algorithms - Successful applications of textual modeling languages - Case studies on industrial applications of textual modeling languages - Experience reports: - usage of textual modeling languages and tools in complex domains, - usability of textual modeling languages and tools for end-users - Empirical studies about the benefits and drawbacks of textual modeling languages - Innovative textual modeling tools - Comparison, evaluation and integration of modeling languages - Correlation between modeling languages and modeling tasks We particularly encourage submissions describing applications and case studies of textual modeling as well as test suites and benchmark collections for evaluating textual modeling tools. ## Submissions Four types of submissions will be considered: * Presentation only submission (not included in the workshop proceedings), e.g., for already published work. Authors should submit a short (1 page) abstract of their presentation. * Short papers (between 5 and 7 pages) describing new ideas or position papers. * Tool papers (between 5 and 7 pages) describing tools supporting textual modeling tools * Full papers (between 10 and 14 pages). All submissions should follow the LNCS format guidelines and should be uploaded to [EasyChair](https://easychair.org/conferences/?conf=ocl2019). Accepted papers will be published online in [CEUR](http://www.ceur-ws.org). ## Important Dates - Submission of papers: 14 Jul 2019 - Notification: 25 Aug 2019 - Pre-Workshop CRC: 9 Sep 2019 - Post-Workshop CRC: 5 Oct 2019 -- Dr. Achim D. Brucker | Chair of Cybersecurity | University of Exeter https://www.brucker.ch | https://logicalhacking.com/blog @adbrucker | @logicalhacking

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Munich Haskell Meeting, 2019-05-27 @ 19:30
by Leah Neukirchen 24 May '19

24 May '19

Dear all, Next week, our monthly Munich Haskell Meeting will take place again on Monday, May 27 at Augustiner-Gaststätte Rumpler at 19h30. For details see here: http://muenchen.haskell.bayern/dates.html If you plan to join, please add yourself to this dudle so we can reserve enough seats! It is OK to add yourself to the dudle anonymously or pseudonymously. https://dudle.inf.tu-dresden.de/haskell-munich-may-2019/ Everybody is welcome! cu, -- Leah Neukirchen <leah(a)vuxu.org> http://leahneukirchen.org/

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