February 2019 - Haskell-Cafe

Let's plan BayHac 2019!
by Dan Burton 04 Feb '19

04 Feb '19

It's time to start thinking about the next BayHac! I am assembling a group of organizers for next year's event. Anyone who has been involved in organizing past BayHac events will be automatically accepted. (I have BCCed a number of past organizers; please reach out to any you know in case I missed anyone.) Anyone else who is interested in helping to plan BayHac, please contact me. Depending on how many past organizers rejoin, we will discuss the applicants and accept 1 to 3 new organizers. BayHac is a weekend of learning, sharing, and hacking on a variety of projects for the Haskell community. BayHac usually occurs in San Francisco, California, Mountain View, California, or thereabouts. I'd like to aim for April/May 2019, though that is, of course, subject to change. A rough outline, in rough chronological order, of what the BayHac organizers will be doing: 0. Assemble the organizers. 1. Select date and venue for BayHac 2019. 2. Secure corporate sponsors to cover costs (mainly, food). 3. Invite talk proposals and select speakers. 4. Open online registration and publicize the event. 5. Plan details like catering, registration desk, recording, and make it happen! If any of that sounds like fun to you, then I'd love to hear from you! -- Dan Burton

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ANN: libtelnet-0.1.0.0
by Jack Kelly 03 Feb '19

03 Feb '19

I've just made an initial release of libtelnet[1], a close binding of the C libtelnet[2]. It allows you to write telnet clients/servers in Haskell, if for some bizarre reason that's something you still want to do in 2019. [1]: https://hackage.haskell.org/package/libtelnet-0.1.0.0 [2]: https://github.com/seanmiddleditch/libtelnet Best, -- Jack

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Implementing `MonadBaseControl IO` for application type
by Magnus Therning 02 Feb '19

02 Feb '19

Hi, I'm getting stuck on implementing `MonadBaseControl IO` for my application context type. What I have so far (in a minimized example) is ``` data Env = Env {envBalance :: !(TVar Int)} newtype AppM a = AppM { unAppM :: ReaderT Env IO a } deriving (Functor, Applicative, Monad, MonadIO, MonadReader Env) instance MonadBase IO AppM where liftBase = liftIO instance MonadBaseControl IO AppM where type StM AppM a = a liftBaseWith f = undefined restoreM = return ``` I'm so utterly stuck on the definition of `liftBaseWith`... but I'm not 100% sure on the other bits either, though it "feels right". Any tips on how I should go about it? /M

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ANN: hledger-1.13
by Simon Michael 02 Feb '19

02 Feb '19

I'm pleased to announce the release of hledger 1.13, the first hledger release of 2019! Thank you release contributors Jakob Schöttl and Dmitry Astapov. hledger is a robust, cross-platform plain text accounting tool, for tracking money, time, stocks, cryptocurrencies or any other commodity, using double-entry accounting, private or shared plain text files, revision control, and command-line, curses or web UIs. Find out more at http://hledger.org and http://plaintextaccounting.org. Release notes (condensed, see http://hledger.org/release-notes) ------------- project-wide changes for 1.13 - packaging: A docker image providing the main hledger tools is now linked on the download page. This is another way to get up-to-date hledger tools without building them yourself (and, a way to run hledger-ui on windows ?) (Dmitry Astapov, Simon Michael) - doc: fixed pandoc typography conversion in web manuals. Eg -- was being rendered as en-dash. (#954). hledger 1.13 - cli: reorganised commands list. Addons now have a + prefix. - cli: the command line help and manual section for all hledger’s commands are now consistent, and generated from the same source. - cli: comprehensive bash completion support is now provided (in shell-completion/). See how-to in the Cookbook. (Jakob Schöttl) - balance –budget: budget amounts now aggregate hierarchically, like account balances. Unbudgeted accounts can be shown with -E/–empty (along with zero-balance accounts), and the –show-budgeted flag has been dropped. (Dmitry Astapov) - balance: new –transpose flag switches the rows and columns of tabular balance reports (in txt and csv output formats). (Dmitry Astapov) - close: generated balance assertions now have exact amounts with all decimal digits, ignoring display precision. Also, balance assertion amounts will no longer contain prices. (#941, #824, #958) - files: now shows up in the commands list - import: be silent when there’s nothing to import - roi: percentages smaller than 0.01% are displayed as zero (Dmitry Astapov) - stats, ui: correct file order is preserved when using –auto (#949) - journal: account directive: the account name can now be followed by a comment on the same line - journal: account directive: account types for the bs/bse/cf/is commands can now be set with a type: tag, whose value is Asset, Liability, Equity, Revenue, Expense, A, L, E, R or X (case-insensitive). The previous syntax (account assets A) is now deprecated. - journal: account directive: account sort codes like account 1000 (introduced in 1.9, deprecated in 1.11) are no longer supported. - journal: transaction modifiers (auto postings) can affect periodic transactions (–auto can add postings to transactions generated with –forecast). (Dmitry Astapov) - journal: balance assertion errors now show exact amounts with all decimal digits. Previously it was possible, in case of a commodity directive limiting the display precision, to have a balance assertion error with asserted and actual amounts looking the same. (#941) - journal: fixed a periodic transaction parsing failure (#942) (Dmitry Astapov) hledger-ui 1.13 - on posix systems, control-z suspends the program - control-l now works everywhere and redraws more reliably - the top status info is clearer Getting started: ---------------- All install methods are described at http://hledger.org/download : windows binaries, system packages, docker, nix, cabal, stack, hledger installer, etc. Some of these might take a few days to become up to date. On systems with bash installed, the hledger installer is a reliable way to get the latest release of hledger: $ curl -s https://raw.githubusercontent.com/simonmichael/hledger/master/hledger-insta… > hledger-install.sh $ less hledger-install.sh # satisfy yourself that the script is safe $ bash hledger-install.sh Then try: $ hledger # list available commands $ hledger help # list built-in manuals Tutorials and all other docs: http://hledger.org Chat: #hledger on Freenode or Matrix - http://irc.hledger.org or http://riot.hledger.org . New and old users, contributors, all feedback, always welcome! Best, -Simon

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Patents on Maybe and Tuple
by Henk-Jan van Tuyl 01 Feb '19

01 Feb '19

L.S., I just read the article "Apple Patents Swift".[0] It says that Apple has two patents regarding Swift: [1][2]; these patents state, amongst others, that there are new types of variables: "Additionally, an embodiment of the new language introduces advanced types not found in Objective-C. These types include Tuples and Optionals. Tuples enable a developer to create and pass groupings of values. Tuples group multiple values into a single compound value." and "In one embodiment, an optional type is provided that handles the absence of a value. Optionals are a way to say either “there is a value, and it equals x” or “there isn't a value at all.”" I hope we don't get arrested for using the Maybe monad or tuples in Haskell. Regards, Henk-Jan van Tuyl [0] https://www.i-programmer.info/news/98-languages/12495-apple-patents-swift.h… [1] https://patents.google.com/patent/US9952841B2 [2] https://patents.google.com/patent/US9329844B2 -- Message from Stanford University: Folding@home What if you could share your unused computer power to help find a cure? In just 5 minutes you can join the world's biggest networked computer and get us closer sooner. Watch the video. http://foldingathome.stanford.edu/ -- http://members.chello.nl/hjgtuyl/tourdemonad.html Haskell programming --

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