- Haskell-Cafe - Haskell.org

Re: [Haskell-cafe] Can we improve Show instance for non-ascii charcters?
by Miguel Mitrofanov 04 Feb '16

04 Feb '16

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Haskell game to translate
by Sergey Mironov 04 Feb '16

04 Feb '16

Hi, Cafe. My friend wants to improve her collaboration skills in the area of game development. She is a Translator and the plan is to learn Git by contributing some Russian/English/French (and maybe simple Korean) translations to a GitHub project. Could you recommend me (and my friend) some game project wich needs translation? Note, that It should support multylang features in some form, understandable for non-programmer. I'll help with required workplace setup. Haskell, Linux, etc. is OK. Regards, Sergey

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Hackage Docs
by Geraldus 04 Feb '16

04 Feb '16

Hi friends! Apologize, a lot of Hackage docs issues discussed here already, but I'll decided to bring this question one more time. I'm facing missing docs during last few weeks, both Hoogle and Hayoo links to Hackage and usual response I see is "Not found". Stackage helps a lot, but most of the time I have to manually search same term on Stackage again. Can we improve this sad situation finally?

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Month in Haskell Mode January 2016
by Gracjan Polak 04 Feb '16

04 Feb '16

Welcome Haskell Mode users, Haskell Mode progress report for January 2016. For previous issue see December 2015 <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-December…>. Reddit discussion <https://www.reddit.com/r/haskell/comments/441ukg/month_in_haskell_mode_janu…> . <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-January-…>What is Haskell Mode? Haskell Mode is an umbrella project for multiple Emacs tools for efficient Haskell development. Haskell Mode is an open source project developed by a group of volunteers constantly looking for contributions. For more information how to help see https://github.com/haskell/haskell-mode. <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-January-…>Important developments Haskell Mode 2015 retrospective <https://github.com/haskell/haskell-mode/wiki/Haskell-Mode-2015-retrospective> was published. Emacs 23 support was dropped. Last stable haskell-mode release that supports Emacs 23 is haskell-mode version 13.18 <https://github.com/haskell/haskell-mode/releases/tag/v13.18>. We have added code coverage reporting and it already helped to nail down some missing cases in our test suite for indentation and font locking. We are currently at 30% coverage. <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-January-…> Request Haskell Mode web presence is none at this point. I'd like to ask a volunteer to create a static web page deployed on github pages that will serve as Haskell Mode home page. Any takers? <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-January-…>Current project focus Current project focus is to lower entry barrier for newcomers by defining bite-sized tasks. Get 50 'well-defined-tasks' done as by the metric: https://github.com/haskell/haskell-mode/issues?q=is%3Aissue+label%3Awell-de… A 'well-defined-task' is a category of tasks that have the field cleared for them, questions already sorted out and detailed information how to get them done. So you can just sit, search for 'well-defined-task' label and enjoy the coding! The point is to lower the entry barrier for new users, new issue reporters and advanced programmers but Emacs lisp beginners to contribute to the project. Current status: 14 well-defined-tasks closed <https://github.com/haskell/haskell-mode/issues?q=is%3Aissue+label%3Awell-de…> plus 13 more open <https://github.com/haskell/haskell-mode/issues?q=is%3Aissue+label%3Awell-de…> . If only you can help with reaching our targets please do so! <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-January-…>Issues closed in January - [Discussion] Character class for apostrophe #549 <https://github.com/haskell/haskell-mode/issues/549> - Debugger triggered on "match c of", a typo for "case c of" #599 <https://github.com/haskell/haskell-mode/issues/599> - Interactive mode recognizes some lines as compiler errors incorrectly #635 <https://github.com/haskell/haskell-mode/issues/635> - make check should recompile files properly #709 <https://github.com/haskell/haskell-mode/issues/709> - haskell-process-suggest-pragma hangs emacs #754 <https://github.com/haskell/haskell-mode/issues/754> - ghc-mod / stack / dist dir #801 <https://github.com/haskell/haskell-mode/issues/801> - [Discussion] REPL vs IDE #809 <https://github.com/haskell/haskell-mode/issues/809> - haskell-mode becomes unresponsive when adding a language pragma #820 <https://github.com/haskell/haskell-mode/issues/820> - Drop Emacs 23 support #847 <https://github.com/haskell/haskell-mode/issues/847> - Can't press enter in haskell interactive mode #876 <https://github.com/haskell/haskell-mode/issues/876> - Mac OS X El Capitan: no such file or directory, ghci #908 <https://github.com/haskell/haskell-mode/issues/908> - Emacs hangs when typing behind whitespace #980 <https://github.com/haskell/haskell-mode/issues/980> - haskell-process-load-file error (wrong-type-argument number-or-marker-p nil) when code has an error #1004 <https://github.com/haskell/haskell-mode/issues/1004> - Regression quasi-quotes are not highlighted anymore #1041 <https://github.com/haskell/haskell-mode/issues/1041> - Custom Haskell variables don't retain their customization #1043 <https://github.com/haskell/haskell-mode/issues/1043> - Indentation point missing for record data declarations #1044 <https://github.com/haskell/haskell-mode/issues/1044> - Font lock Role annotations #1057 <https://github.com/haskell/haskell-mode/issues/1057> - Use undercover.el and https://coveralls.io/ #1062 <https://github.com/haskell/haskell-mode/issues/1062> - haskell-cabal-strip-list and haskell-cabal-listify #1076 <https://github.com/haskell/haskell-mode/issues/1076> - Indentation of guards does not work sensibly with haskell-indentation #1079 <https://github.com/haskell/haskell-mode/issues/1079> - Indentation of first data constructor does not work with haskell-indent #1080 <https://github.com/haskell/haskell-mode/issues/1080> - Annoying indentation behaviour when declaring data types #1081 <https://github.com/haskell/haskell-mode/issues/1081> - Can't indent, gets error. #1082 <https://github.com/haskell/haskell-mode/issues/1082> - [Discussion] Make haskell-indentation external, editor agnostic project #1086 <https://github.com/haskell/haskell-mode/issues/1086> - haskell-cabal-subsection-arrange-lines inserts superfluous commas #1094 <https://github.com/haskell/haskell-mode/issues/1094> - haskell-indentation misbehaves for comments #1101 <https://github.com/haskell/haskell-mode/issues/1101> - haskell-process-path-* now allowed to be lists #1112 <https://github.com/haskell/haskell-mode/issues/1112> - Wrong completion-at-point in Haskell interpreter with helm #1113 <https://github.com/haskell/haskell-mode/issues/1113> <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-January-…>Pull requests merged in January - Record indentation should follow tibell style #1047 <https://github.com/haskell/haskell-mode/pull/1047> - Defcustoms should not be autoloaded #1048 <https://github.com/haskell/haskell-mode/pull/1048> - Define url and some keywords/tags for haskell-mode #1049 <https://github.com/haskell/haskell-mode/pull/1049> - Make quasi quote more visible #1051 <https://github.com/haskell/haskell-mode/pull/1051> - Lexeme parsing improvements #1052 <https://github.com/haskell/haskell-mode/pull/1052> - Skip an indentation test for Emacs 25 #1053 <https://github.com/haskell/haskell-mode/pull/1053> - Require at least Emacs 24.1 #1055 <https://github.com/haskell/haskell-mode/pull/1055> - Add font lock type/data family declarations #1056 <https://github.com/haskell/haskell-mode/pull/1056> - User manual updates #1058 <https://github.com/haskell/haskell-mode/pull/1058> - Add literate font lock tests, remove unused parts #1059 <https://github.com/haskell/haskell-mode/pull/1059> - Fix typos in documentation strings #1060 <https://github.com/haskell/haskell-mode/pull/1060> - Use plain string face for quasi quotes #1061 <https://github.com/haskell/haskell-mode/pull/1061> - Add code coverage #1063 <https://github.com/haskell/haskell-mode/pull/1063> - Add keybinding for haskell-cabal-visit-file #1064 <https://github.com/haskell/haskell-mode/pull/1064> - Add type role to font lock #1066 <https://github.com/haskell/haskell-mode/pull/1066> - Add test for SQL font-lock #1067 <https://github.com/haskell/haskell-mode/pull/1067> - Add test for 'type role' font-lock #1068 <https://github.com/haskell/haskell-mode/pull/1068> - Remove turn-on/off-haskell-font-lock #1069 <https://github.com/haskell/haskell-mode/pull/1069> - More font lock tests #1070 <https://github.com/haskell/haskell-mode/pull/1070> - Add tests and fix for classify by first char #1071 <https://github.com/haskell/haskell-mode/pull/1071> - Disallow leading spaces in error regexp in interactive mode #1072 <https://github.com/haskell/haskell-mode/pull/1072> - Add some tests for indentation #1073 <https://github.com/haskell/haskell-mode/pull/1073> - Inline haskell-mode-jump-to-loc #1075 <https://github.com/haskell/haskell-mode/pull/1075> - Increase haskell-cabal.el coverage #1077 <https://github.com/haskell/haskell-mode/pull/1077> - Define haskell-package struct's slots #1083 <https://github.com/haskell/haskell-mode/pull/1083> - Utils coverage #1089 <https://github.com/haskell/haskell-mode/pull/1089> - Utils coverage #1090 <https://github.com/haskell/haskell-mode/pull/1090> - Improve haskell-utils-reduce-string. Add tests #1092 <https://github.com/haskell/haskell-mode/pull/1092> - Add post-command-hook related tests #1093 <https://github.com/haskell/haskell-mode/pull/1093> - Test utils #1095 <https://github.com/haskell/haskell-mode/pull/1095> - Add string tests #1096 <https://github.com/haskell/haskell-mode/pull/1096> - Follow comma style when arranging a Cabal section #1098 <https://github.com/haskell/haskell-mode/pull/1098> - Detect comma style #1099 <https://github.com/haskell/haskell-mode/pull/1099> - Implement haskell-goto-first-error #1100 <https://github.com/haskell/haskell-mode/pull/1100> - Bump version to 16.1-git #1102 <https://github.com/haskell/haskell-mode/pull/1102> - Honor equals on its own line in data decl #1105 <https://github.com/haskell/haskell-mode/pull/1105> - Honor equals on separate line after guards #1106 <https://github.com/haskell/haskell-mode/pull/1106> - Remove a stray parenthesis #1108 <https://github.com/haskell/haskell-mode/pull/1108> - Tidy up haskell-load.el: untabify, reindent. Fix some warnings. #1111 <https://github.com/haskell/haskell-mode/pull/1111> - Allow haskell-process-path-* to be lists. #1114 <https://github.com/haskell/haskell-mode/pull/1114> - Add haskell-indent tests #1115 <https://github.com/haskell/haskell-mode/pull/1115> - Prevent haskell-doc-mode to hang Emacs during user input waiting #1116 <https://github.com/haskell/haskell-mode/pull/1116> - Remove haskell-interactive-mode-completion-cache #1119 <https://github.com/haskell/haskell-mode/pull/1119> <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-January-…>Contributors active in January Arthur Fayzrakhmanov (Артур Файзрахманов), Bozhidar Batsov, Dan Aloni, Daniel Bergey, Fice-T, Gracjan Polak, Herbert Valerio Riedel, Kirill Ignatiev, Mike Sperber, Thomas Winant, U-Yuriy-PCYuriy, issue-dispenser, mrBliss <https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-January-…> Contributing Haskell Mode needs volunteers like any other open source project. For more information see: https://github.com/haskell/haskell-mode/wiki Also drop by our IRC channel: #haskell-emacs at irc.freenode.net. Thanks!

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Building / cross compile GHC for OpenBSD/macppc.
by Christoph R. Murauer 03 Feb '16

03 Feb '16

Hello ! I am new here - sorry, if I ask something what was asked before. OpenBSD provides for amd64 and other platforms GHC and, also the haskell-platform which works very good. I try to get one of the old PowerMac's with a G5 CPU and saw, that there is no GHC (yes, there is a very old version - something like 3.x) for OpenBSD/macppc. I got some informations about to cross compile and saw also the wiki at https://ghc.haskell.org/trac/ghc/wiki/Building/CrossCompiling now my main question is, are there more informations about it ? Available for cross compile is GHC and haskell-platform 7.10.3, gcc 4.2.1 20070719, llvm 3.5.20140228 all on amd64. The planned target platforms are Mac's / PowerMac's with G3, G4 and G5 CPU's. All versions of OpenBSD/macppc are 32 bit only (including the G5). A cross compile from Mac OS X is no option because the OpenBSD project should be able to cross build on their machines (security reasons). Thanks for informations and tips. Regards, Christoph

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Problems with cabal and stackage
by David Turner 03 Feb '16

03 Feb '16

Hi, Overnight there seems to have been a change to stackage where it's now issuing redirects from http to https URLs: ~$ cabal update Downloading the latest package list from stackage-lts-2.22 Warning: http error: Unable to handle redirect, unsupported scheme: https://www.stackage.org/snapshot/lts-2.22/00-index.tar.gz cabal: Failed to download http://www.stackage.org/snapshot/lts-2.22/00-index.tar.gz : ErrorMisc "Error HTTP code: 301" My cabal doesn't seem to like https and I think it's a recentish version: $ cabal --version cabal-install version 1.22.0.0 using version 1.22.0.0 of the Cabal library I'm probably using a bit of an old workflow (and I know that LTS-2 is pretty old too) but is there any simple way of getting this working again? Cheers,

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Accessing and Inspecting StgBindings in Ghci
by Michael Christensen 03 Feb '16

03 Feb '16

Hi all, I'm currently trying to understand how STG works, and my goal right now is to be able to inspect StgBinding values. I've written a short program, based on the wiki article GHC/As a library <https://wiki.haskell.org/GHC/As_a_library>, like below: -- Code.hs -- module Lib (printSTG, dumpSTG) where import Control.Monad.Ghc (lift, runGhcT) import CorePrep (corePrepPgm) import CoreToStg (coreToStg) import DynFlags (defaultFatalMessager, defaultFlushOut) import GHC hiding (runGhcT) import GHC.Paths (libdir) import HscMain (newHscEnv) import HscTypes (hsc_dflags, typeEnvTyCons) import Outputable (interppSP, showSDoc) import System.Environment (getArgs) import StgSyn (StgBinding) dumpSTG :: String -> IO [StgBinding] dumpSTG fileName = defaultErrorHandler defaultFatalMessager defaultFlushOut $ runGhcT (Just libdir) $ do sess <- getSession let dflags = hsc_dflags sess setSessionDynFlags dflags cm <- compileToCoreModule fileName let md = cm_module cm ml <- fmap ms_location $ getModSummary $ moduleName md lift $ do cp <- corePrepPgm sess ml <$> cm_binds <*> (typeEnvTyCons . cm_types) $ cm coreToStg dflags md cp printSTG = getArgs >>= \x -> case x of [] -> putStrLn "usage: Main <file.hs>" (fileName:_) -> do bindings <- dumpSTG fileName str <- runGhcT (Just libdir) $ do dflags <- getSessionDynFlags return $ showSDoc dflags $ interppSP bindings putStrLn str This works when I compile it to print out a Haskell file in STG format. However, *my question is*, is there a way so that I can call dumpSTG to get back that list of StgBindings, *from within Ghci*? Whenever I do so within Ghci, i.e. ghci> :l code.hs ghci> bindings <- dumpSTG "fileToTest.hs" <interactive>: panic! (the 'impossible' happened) (GHC version 7.10.3 for x86_64-unknown-linux): no package state yet: call GHC.setSessionDynFlags I know that it's saying I need to set the session dyn flags, but I'm not sure how that can get done from within Ghci, especially because that needs to get done within the GhcMonad. Part of my problem may stem from having a inadequate understanding of monads. Any help or pointers would be greatly appreciated! Thank you very much, Mike

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Is there a type class for boring types?
by David Feuer 03 Feb '16

03 Feb '16

Or, alternatively, some common class that lets me express that a type is boring (i.e., inhabited by precisely one fully-defined value)? lens has Settable, whose law ensures the type involved has a boring representation (in the sense of representable functor), but is there a more fundamental way? class Boring x where inhabitant :: x instance Boring () where inhabitant = () instance Boring (Proxy a) where inhabitant = Proxy instance Boring y => Boring (x -> y) where inhabitant = const inhabitant instance (Boring x, Boring y) => Boring (x, y) where inhabitant = (inhabitant, inhabitant) instance Boring x => Boring (Const x y) where inhabitant = Const inhabitant instance Boring x => Boring (Identity x) where inhabitant = Identity inhabitant ...

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[TFP 2016] 1st call for papers
by Peter Achten 02 Feb '16

02 Feb '16

----------------------------- C A L L F O R P A P E R S ----------------------------- ======== TFP 2016 =========== 17th Symposium on Trends in Functional Programming June 8-10, 2016 University of Maryland, College Park Near Washington, DC http://tfp2016.org/ The symposium on Trends in Functional Programming (TFP) is an international forum for researchers with interests in all aspects of functional programming, taking a broad view of current and future trends in the area. It aspires to be a lively environment for presenting the latest research results, and other contributions (see below). Authors of draft papers will be invited to submit revised papers based on the feedback receive at the symposium. A post-symposium refereeing process will then select a subset of these articles for formal publication. TFP 2016 will be the main event of a pair of functional programming events. TFP 2016 will be accompanied by the International Workshop on Trends in Functional Programming in Education (TFPIE), which will take place on June 7nd. The TFP symposium is the heir of the successful series of Scottish Functional Programming Workshops. Previous TFP symposia were held in * Edinburgh (Scotland) in 2003; * Munich (Germany) in 2004; * Tallinn (Estonia) in 2005; * Nottingham (UK) in 2006; * New York (USA) in 2007; * Nijmegen (The Netherlands) in 2008; * Komarno (Slovakia) in 2009; * Oklahoma (USA) in 2010; * Madrid (Spain) in 2011; * St. Andrews (UK) in 2012; * Provo (Utah, USA) in 2013; * Soesterberg (The Netherlands) in 2014; * and Inria Sophia-Antipolis (France) in 2015. For further general information about TFP please see the TFP homepage. (http://www.tifp.org/) == SCOPE == The symposium recognizes that new trends may arise through various routes. As part of the Symposium's focus on trends we therefore identify the following five article categories. High-quality articles are solicited in any of these categories: Research Articles: leading-edge, previously unpublished research work Position Articles: on what new trends should or should not be Project Articles: descriptions of recently started new projects Evaluation Articles: what lessons can be drawn from a finished project Overview Articles: summarizing work with respect to a trendy subject Articles must be original and not simultaneously submitted for publication to any other forum. They may consider any aspect of functional programming: theoretical, implementation-oriented, or experience-oriented. Applications of functional programming techniques to other languages are also within the scope of the symposium. Topics suitable for the symposium include, but are not limited to: Functional programming and multicore/manycore computing Functional programming in the cloud High performance functional computing Extra-functional (behavioural) properties of functional programs Dependently typed functional programming Validation and verification of functional programs Debugging and profiling for functional languages Functional programming in different application areas: security, mobility, telecommunications applications, embedded systems, global computing, grids, etc. Interoperability with imperative programming languages Novel memory management techniques Program analysis and transformation techniques Empirical performance studies Abstract/virtual machines and compilers for functional languages (Embedded) domain specific languages New implementation strategies Any new emerging trend in the functional programming area If you are in doubt on whether your article is within the scope of TFP, please contact the TFP 2016 program chair, David Van Horn. == BEST PAPER AWARDS == To reward excellent contributions, TFP awards a prize for the best paper accepted for the formal proceedings. TFP traditionally pays special attention to research students, acknowledging that students are almost by definition part of new subject trends. A student paper is one for which the authors state that the paper is mainly the work of students, the students are listed as first authors, and a student would present the paper. A prize for the best student paper is awarded each year. In both cases, it is the PC of TFP that awards the prize. In case the best paper happens to be a student paper, that paper will then receive both prizes. == SPONSORS == TFP is financially supported by CyberPoint, Galois, Trail of Bits, and the University of Maryland Computer Science Department. == PAPER SUBMISSIONS == Acceptance of articles for presentation at the symposium is based on a lightweight peer review process of extended abstracts (4 to 10 pages in length) or full papers (20 pages). The submission must clearly indicate which category it belongs to: research, position, project, evaluation, or overview paper. It should also indicate which authors are research students, and whether the main author(s) are students. A draft paper for which ALL authors are students will receive additional feedback by one of the PC members shortly after the symposium has taken place. We use EasyChair for the refereeing process. Papers must be submitted at: https://easychair.org/conferences/?conf=tfp2016 Papers must be written in English, and written using the LNCS style. For more information about formatting please consult the Springer LNCS web site: http://www.springer.com/computer/lncs?SGWID=0-164-6-793341-0 == IMPORTANT DATES == Submission of draft papers: April 8, 2016 Notification: April 15, 2016 Registration: May 13, 2016 TFP Symposium: June 8-10, 2016 Student papers feedback: June 14, 2016 Submission for formal review: July 14, 2016 Notification of acceptance: September 14, 2016 Camera ready paper: October 14, 2016 == PROGRAM COMMITTEE == Amal Ahmed Northeastern University (US) Nada Amin École Polytechnique Fédérale de Lausanne (CH) Kenichi Asai Ochanomizu University (JP) Małgorzata Biernacka University of Wroclaw (PL) Laura Castro University of A Coruña (ES) Ravi Chugh University of Chicago (US) Silvia Ghilezan University of Novi Sad (SR) Clemens Grelck University of Amsterdam (NL) John Hughes Chalmers University of Technology (SE) Suresh Jagannathan Purdue University (US) Pieter Koopman Radboud University Nijmegen (NL) Geoffrey Mainland Drexel University (US) Chris Martens University of California, Santa Cruz (US) Jay McCarthy University of Massachusetts, Lowell (US) Heather Miller École Polytechnique Fédérale de Lausanne (CH) Manuel Serrano INRIA, Sophia-Antipolis (FR) Scott Smith Johns Hopkins University (US) Éric Tanter University of Chile (CL) David Van Horn (Chair) University of Maryland (US) Niki Vazou University of California, San Diego (US)

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Instance match surprise
by Wojtek Narczyński 02 Feb '16

02 Feb '16

Dear List, Why does the first instance match? ANY is neither Eq nor Typeable. I thought I had some basic understanding of type classes, and now this... wojtek@biuro:~/src/he$ cat minimatch.hs {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE MultiParamTypeClasses #-} module MiniMatch where import Data.Typeable data A130 = A130 deriving (Eq) data ANY = ANY class AtmAcct a class Against q class (AtmAcct a, Against q) => Match a q where match :: a -> q -> Bool instance AtmAcct A130 instance Against ANY instance (Eq a, Eq q, Typeable a, Typeable q, AtmAcct a, Against q) => Match a q where match _ _ = False instance (AtmAcct a) => Match a ANY where match _ _ = True m1 = match A130 ANY -- offending line wojtek@biuro:~/src/he$ ghc minimatch.hs [1 of 1] Compiling MiniMatch ( minimatch.hs, minimatch.o ) minimatch.hs:21:6: error: • Overlapping instances for Match A130 ANY arising from a use of ‘match’ Matching instances: instance (Eq a, Eq q, Typeable a, Typeable q, AtmAcct a, Against q) => Match a q -- Defined at minimatch.hs:18:10 instance AtmAcct a => Match a ANY -- Defined at minimatch.hs:19:10 • In the expression: match A130 ANY In an equation for ‘m1’: m1 = match A130 ANY -- Thanks, Wojtek Narczyński

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