November 2012 - Haskell-Cafe

Haskell Weekly News: Issue 251
by Daniel Santa Cruz 21 Nov '12

21 Nov '12

Welcome to issue 251 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers the week of November 4 to 17, 2012. Quotes of the Week * Ralith: [why some people don't use conduits/pipes] also, I think at least some people are waiting for edwardk to write his version. * edwardk: f -| g means that f a -> b is isomorphic to a -> g b (for arrows in the appropriate categories) * edwardk: @type (^.) lambdabot: s -> Getting a s t a b -> a byorgey: I would not like to be getting a stab, thank you * edwardk: I mean we're so oop even our member accessors have diagrams explaining their member accessors. * shapr: hylo! That's the category theorist greeting. * shachaf: type AbstractAlgebra a = Abstract a -> a * nicoo: Yet many Writers concern themselves with issues of State, imaginary or real * rwbarton: when you learn C, watch out for the keyword "return", it doesn't do what you'd expect * Oleg: We show how to program with the law of excluded middle. We specifically avoid call/cc, which is overrated. Top Reddit Stories * Haskell Platform 2012.4.0.0 is out Domain: self.haskell, Score: 89, Comments: 21 On Reddit: [1] http://goo.gl/BPno4 Original: [2] http://goo.gl/BPno4 * A Khan Academy style tutorial on generalized algebraic data types Domain: apfelmus.nfshost.com, Score: 56, Comments: 7 On Reddit: [3] http://goo.gl/kXQ0a Original: [4] http://goo.gl/NWn3B * Cartesian Closed Comic #17: Typing Domain: ro-che.info, Score: 53, Comments: 24 On Reddit: [5] http://goo.gl/6c4Uy Original: [6] http://goo.gl/dZeDx * Cartesian Closed Comic #18: Equality Domain: ro-che.info, Score: 53, Comments: 8 On Reddit: [7] http://goo.gl/8Qf9d Original: [8] http://goo.gl/XCyuB * Natural Language Processing for the Working Programmer (in Haskell!) Domain: nlpwp.org, Score: 50, Comments: 17 On Reddit: [9] http://goo.gl/3yLTZ Original: [10] http://goo.gl/BleWX * Waiting for garbage collection can kill parallelism? Domain: ics.p.lodz.pl, Score: 50, Comments: 7 On Reddit: [11] http://goo.gl/iUPlD Original: [12] http://goo.gl/N0kiV * foldr is made of monoids Domain: byorgey.wordpress.com, Score: 47, Comments: 12 On Reddit: [13] http://goo.gl/Y0mz5 Original: [14] http://goo.gl/IxKov * Solving Cabal Hell: vetted packages, multiple hackages Domain: yesodweb.com, Score: 46, Comments: 67 On Reddit: [15] http://goo.gl/dkzMz Original: [16] http://goo.gl/lDjuj * Parallel falling sand game with Repa Domain: github.com, Score: 45, Comments: 16 On Reddit: [17] http://goo.gl/G6MGG Original: [18] http://goo.gl/cP1zH * Agda, Epigram or Idris. Which one to learn Domain: self.haskell, Score: 38, Comments: 61 On Reddit: [19] http://goo.gl/3PGVo Original: [20] http://goo.gl/3PGVo * Fun with Fay - A ring oscillator Domain: skybluetrades.net, Score: 38, Comments: 6 On Reddit: [21] http://goo.gl/mGvcZ Original: [22] http://goo.gl/bJxCI * Introduction to Category Theory 1: Course Overview Domain: youtube.com, Score: 37, Comments: 6 On Reddit: [23] http://goo.gl/fbfYR Original: [24] http://goo.gl/Nx5SH * HALO: Haskell to Logic through Denotational Semantics [PDF] Domain: research.microsoft.com, Score: 35, Comments: 6 On Reddit: [25] http://goo.gl/V0RWs Original: [26] http://goo.gl/oCzUw * How to write Python in Haskell: State and Either Domain: stackoverflow.com, Score: 34, Comments: 25 On Reddit: [27] http://goo.gl/Z80yb Original: [28] http://goo.gl/W933i * What is foldr made of? Domain: web.jaguarpaw.co.uk, Score: 30, Comments: 22 On Reddit: [29] http://goo.gl/LdS9X Original: [30] http://goo.gl/I2uzX * How to shoot yourself in the foot with Haskell Domain: ics.p.lodz.pl, Score: 29, Comments: 34 On Reddit: [31] http://goo.gl/CcvZB Original: [32] http://goo.gl/SJYvd * Happstack, Fay, & Acid-State: Shared Datatypes are Awesome Domain: happstack.com, Score: 29, Comments: 8 On Reddit: [33] http://goo.gl/AUtj6 Original: [34] http://goo.gl/cYQr1 * ANN: OpenGL packages update Domain: haskell.org, Score: 28, Comments: 7 On Reddit: [35] http://goo.gl/0SN7O Original: [36] http://goo.gl/PbtlT * How can I cleanly/consistently work with 3 different Exception-raising schemes? Domain: self.haskell, Score: 28, Comments: 22 On Reddit: [37] http://goo.gl/Xf4sq Original: [38] http://goo.gl/Xf4sq Top StackOverflow Questions * What are paramorphisms? votes: 39, answers: 1 Read on SO: [39] http://goo.gl/V6rXq * In pure functional languages, is there an algorithm to get the inverse function? votes: 35, answers: 9 Read on SO: [40] http://goo.gl/wBtqv * What are free monads? votes: 26, answers: 5 Read on SO: [41] http://goo.gl/NAx8n * What's the status of current Functional Reactive Programming implementations? votes: 23, answers: 3 Read on SO: [42] http://goo.gl/FmRYF * What does the “world” mean in functional programming world? votes: 22, answers: 7 Read on SO: [43] http://goo.gl/dyM8c * Type-safe difference lists votes: 20, answers: 1 Read on SO: [44] http://goo.gl/TlvF4 * Is it possible to annotate a function's special properties (e.g. surjectivity)? votes: 12, answers: 3 Read on SO: [45] http://goo.gl/uzanF * Under what circumstances are monadic computations tail-recursive? votes: 12, answers: 2 Read on SO: [46] http://goo.gl/lPJef * Should I use new Haskell language extensions in favour of the old ones? votes: 12, answers: 2 Read on SO: [47] http://goo.gl/xkc78 Until next time, Daniel Santa Cruz References 1. http://www.reddit.com/r/haskell/comments/12pxiq/haskell_platform_2012400_is… 2. http://www.reddit.com/r/haskell/comments/12pxiq/haskell_platform_2012400_is… 3. http://apfelmus.nfshost.com/blog/2010/06/01-gadts-video.html 4. http://www.reddit.com/r/haskell/comments/12ou1p/a_khan_academy_style_tutori… 5. http://ro-che.info/ccc/17.html 6. http://www.reddit.com/r/haskell/comments/12nm3w/cartesian_closed_comic_17_t… 7. http://ro-che.info/ccc/18.html 8. http://www.reddit.com/r/haskell/comments/138crz/cartesian_closed_comic_18_e… 9. http://nlpwp.org/book/ 10. http://www.reddit.com/r/haskell/comments/13a0ut/natural_language_processing… 11. http://ics.p.lodz.pl/~stolarek/blog/2012/11/waiting-for-garbage-collection-… 12. http://www.reddit.com/r/haskell/comments/13cpm3/waiting_for_garbage_collect… 13. http://byorgey.wordpress.com/2012/11/05/foldr-is-made-of-monoids/ 14. http://www.reddit.com/r/haskell/comments/12prpr/foldr_is_made_of_monoids/ 15. http://www.yesodweb.com/blog/2012/11/solving-cabal-hell 16. http://www.reddit.com/r/haskell/comments/1306wn/solving_cabal_hell_vetted_p… 17. https://github.com/tranma/falling-turnip 18. http://www.reddit.com/r/haskell/comments/133nja/parallel_falling_sand_game_… 19. http://www.reddit.com/r/haskell/comments/132kg0/agda_epigram_or_idris_which… 20. http://www.reddit.com/r/haskell/comments/132kg0/agda_epigram_or_idris_which… 21. http://www.skybluetrades.net/blog/posts/2012/11/13/fay-ring-oscillator/inde… 22. http://www.reddit.com/r/haskell/comments/134tr6/fun_with_fay_a_ring_oscilla… 23. http://www.youtube.com/watch?v=eu0rj5C2Otg 24. http://www.reddit.com/r/haskell/comments/12vvn2/introduction_to_category_th… 25. http://research.microsoft.com/en-us/people/dimitris/hcc-popl.pdf 26. http://www.reddit.com/r/haskell/comments/12wovt/halo_haskell_to_logic_throu… 27. http://stackoverflow.com/a/13432926/208257 28. http://www.reddit.com/r/haskell/comments/13cz6b/how_to_write_python_in_hask… 29. http://web.jaguarpaw.co.uk/~tom/blog/posts/2012-11-04-what-is-foldr-made-of… 30. http://www.reddit.com/r/haskell/comments/12mnhu/what_is_foldr_made_of/ 31. http://ics.p.lodz.pl/~stolarek/blog/2012/11/how-to-shoot-yourself-in-the-fo… 32. http://www.reddit.com/r/haskell/comments/12rlgt/how_to_shoot_yourself_in_th… 33. http://www.happstack.com/c/view-page-slug/15/happstack-fay-acid-state-share… 34. http://www.reddit.com/r/haskell/comments/1375q0/happstack_fay_acidstate_sha… 35. http://www.haskell.org/pipermail/haskell-cafe/2012-November/104329.html 36. http://www.reddit.com/r/haskell/comments/12mk7h/ann_opengl_packages_update/ 37. http://www.reddit.com/r/haskell/comments/12relk/how_can_i_cleanlyconsistent… 38. http://www.reddit.com/r/haskell/comments/12relk/how_can_i_cleanlyconsistent… 39. http://stackoverflow.com/questions/13317242/what-are-paramorphisms 40. http://stackoverflow.com/questions/13404208/in-pure-functional-languages-is… 41. http://stackoverflow.com/questions/13352205/what-are-free-monads 42. http://stackoverflow.com/questions/13341937/whats-the-status-of-current-fun… 43. http://stackoverflow.com/questions/13340458/what-does-the-world-mean-in-fun… 44. http://stackoverflow.com/questions/13346200/type-safe-difference-lists 45. http://stackoverflow.com/questions/13281316/is-it-possible-to-annotate-a-fu… 46. http://stackoverflow.com/questions/13379060/under-what-circumstances-are-mo… 47. http://stackoverflow.com/questions/13422610/should-i-use-new-haskell-langua…

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Common function names for '(.) . (.)', '(.) . (.) . (.)' ...?
by Thomas Bereknyei 21 Nov '12

21 Nov '12

I use .@. (sometimes ...) .#. .$. for the two three and four dot variations.

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Re: [Haskell-cafe] [Haskell] [ANN] gtk2hs-0.12.4
by Roman Cheplyaka 21 Nov '12

21 Nov '12

* wagnerdm(a)seas.upenn.edu <wagnerdm(a)seas.upenn.edu> [2012-11-21 13:48:35-0500] > Today, we welcome into the world version 0.12.4 of Gtk2Hs[1], a set > of Haskell bindings to many of the libraries included in the > Gtk+/Gnome platform. Gtk+ is an extensive and mature multi-platform > toolkit for creating graphical user interfaces. Great — thanks to you and John for keeping it alive. Roman

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AST Rewriting
by Steve Severance 21 Nov '12

21 Nov '12

Hi Everyone, I am trying to build a function to rewrite and AST. I have and AST which is designed to represent a computation graph. I will present a simplified version here designed to illustrate the problem. I have tried numerous ways of rewriting it including uniplate, recursion and Edward Kmett's implementation of plate in his lens package. My AST is defined using GADTs as follows: class (ReflectDescriptor a, Typeable a, Wire a) => ProtoBuf a data Expression a b where OpenTable :: (ProtoBuf b) => Int -> Table -> Expression () b OpenFile :: (ProtoBuf b) => Int -> String -> Expression () b WriteFile :: (Typeable a, ProtoBuf b) => Int -> String -> Expression a b -> Expression b () WriteTable :: (Typeable a, ProtoBuf b) => Int -> Table -> Expression a b -> Expression b () Map :: (ProtoBuf a, ProtoBuf b, ProtoBuf c) => Int -> (a -> b) -> Expression c a -> Expression a b LocalMerge :: (ProtoBuf a) => Int -> [Expression c a] -> Expression c a The user can create code inside a Monad Transformer like so: q <- query $ do table <- openTable myTable transform <- map someFunc table writeTable otherTable transform As part of this language the compiler I am building would need to for instance transform OpenTable into a series OpenFile nodes with a LocalMerge to merge the results together. So uniplate cannot work over GADTs if I recall correctly. I exchanged emails with Edward and he explained that for the lens case I would need something like an indexed lens family from his indexed package which is not implemented yet but which may be in the future. The issue with recursion is that as you recurse through the AST the a b on the Expression change and GHC cannot compile it because it wants the a b to be the same on each recursive call. My question to the Haskell community is how might one develop AST rewriting functionality. One possible solution is stripping the types away from GHC and doing all the type checking myself. That doesn't seem very good. Another possibility that I have looked at was using hoopl. It seems very compatible given that it is built for describing and optimizing data flow which I am doing however the learning curve looks quite steep. I have been reluctant so far to invest the time in it. Has anyone developed something similar? What recommendations do you have? Thanks. Steve

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Common function names for '(.) . (.)', '(.) . (.) . (.)' ...?
by Daniel Trstenjak 21 Nov '12

21 Nov '12

Greetings, Daniel

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Re: [Haskell-cafe] cabal install... Trying to recover
by Gregory Guthrie 21 Nov '12

21 Nov '12

Thanks for the suggestion, I’ll do that. Here goes: I deleted the ../user/appdata/roaming/ghc and ../cabal files, an uninstalled Haskell-platform. (No trace of anything "ghc" on the disk.) Then reinstalled Haskell, and ran “cabal update”, it said there was a new cabal-install, but trying to install it fails (below), so I went ahead with the current version. The error seems odd to me (cabal-install-1.16.0.2 depends on Cabal-1.16.0.3 which failed to install.), that an older version depends on a newer one? So now I have; (from Windows - Haskell-platform 2012.4.0.0) GHCi = The Glorious Glasgow Haskell Compilation System, version 7.4.2 Cabal = cabal-install version 0.14.0, using version 1.14.0 of the Cabal library I then tried to reload all my previous packages, (all at once?!), but it fails, "out of memory" (w/8GB of memory!) So I split it into sections, and tried the first one; it lists a lot of new installs, and then fails (full list at http://pastebin.com/5ywdUjgX) The first chunk of installs gives this: ... cabal: The following packages are likely to be broken by the reinstalls: QuickCheck-2.4.2 haskell-platform-2012.4.0.0 Use --force-reinstalls if you want to install anyway. I don't understand how it can want to break the Haskell-platform, sounds dangerous! And the second this: G:\Cabal>cabal install Boolean Craft3e Craft3e GLFW GLURaw GLUT HTTP IORefCAS Me moTrie MonadCatchIO-mtl NumInstances ObjectName OpenGL OpenGLRaw QuickCheck SDL SHA StateVar Tensor abstract-deque abstract-par active aeson alex ansi-terminal array asn1-data attoparsec attoparsec-conduit base-unicode-symbols base64-bytest ring bits-atomic blaze-builder blaze-builder-conduit blaze-html blaze-markup bla ze-svg bmp buildwrapper byteorder cabal-dev case-insensitive cereal certificate clientsession cmdargs colour comonad conduit contravariant cookie cpphs cprng-ae s cpu criterion crypto-api crypto-conduit crypto-pubkey-types cryptocipher crypt ohash css-text data-default date-cache diagrams-core diagrams-lib diagrams-svg d list email-validate entropy erf failure fast-logger file-embed filepath filesyst em-conduit ghc-paths gloss gtk2hs-buildtools Resolving dependencies... In order, the following would be installed: Boolean-0.1.1 (new package) ... cabal: The following packages are likely to be broken by the reinstalls: regex-posix-0.95.1 regex-compat-0.95.1 regex-posix-0.94.4 regex-compat-0.93.1 parsec-3.1.1 fgl-5.4.2.4 fgl-5.4.2.3 QuickCheck-2.4.0.1 network-2.3.1.0 haskell-platform-2012.4.0.0 cgi-3001.1.7.4 HTTP-4000.2.5 regex-posix-0.95.2 regex-compat-0.95.1 regex-posix-0.95.1 regex-compat-0.95.1 Use --force-reinstalls if you want to install anyway. So I have a typical situation where it won't install, and gives an option to –force, but that seems to lead to more problems? Do I just have some packages which are intrinsically incompatible, and I have to choose between them? Not sure how to proceed. Any help or hints appreciated! :-) –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––- > Cabal install cabal-install Configuring Cabal-1.16.0.3... Warning: This package indirectly depends on multiple versions of the same package. This is highly likely to cause a compile failure. package process-1.1.0.1 requires base-4.5.0.0 package pretty-1.1.1.0 requires base-4.5.0.0 package old-time-1.1.0.0 requires base-4.5.0.0 package old-locale-1.0.0.4 requires base-4.5.0.0 package filepath-1.3.0.0 requires base-4.5.0.0 package directory-1.1.0.2 requires base-4.5.0.0 package deepseq-1.3.0.0 requires base-4.5.0.0 package containers-0.4.2.1 requires base-4.5.0.0 package bytestring-0.9.2.1 requires base-4.5.0.0 package array-0.4.0.0 requires base-4.5.0.0 package Win32-2.2.2.0 requires base-4.5.0.0 package filepath-1.3.0.0 requires base-4.5.1.0 package Cabal-1.16.0.3 requires base-4.5.1.0 package Cabal-1.16.0.3 requires filepath-1.3.0.0 package process-1.1.0.1 requires filepath-1.3.0.0 package directory-1.1.0.2 requires filepath-1.3.0.0 package integer-gmp-0.4.0.0 requires ghc-prim-0.2.0.0 package bytestring-0.9.2.1 requires ghc-prim-0.2.0.0 package base-4.5.0.0 requires ghc-prim-0.2.0.0 package integer-gmp-0.4.0.0 requires ghc-prim-0.2.0.0 package base-4.5.1.0 requires ghc-prim-0.2.0.0 package base-4.5.1.0 requires integer-gmp-0.4.0.0 package base-4.5.0.0 requires integer-gmp-0.4.0.0 Building Cabal-1.16.0.3... Preprocessing library Cabal-1.16.0.3... <command line>: cannot satisfy -package-id array-0.4.0.0-3cf1bc3f5cd0078adea24752c18081b9 (use -v for more information) cabal: Error: some packages failed to install: Cabal-1.16.0.3 failed during the building phase. The exception was: ExitFailure 1 cabal-install-1.16.0.2 depends on Cabal-1.16.0.3 which failed to install. (more -v details at: http://pastebin.com/Y2BuMjBP ) ------------------------------------------- From this email and some of the previous emails it seems that your package DB is in a pretty bad state, most likely from using --force-reinstalls. When Cabal warns you that this will break stuff it actually means it. :) My suggestion is that you rm -rf ~/.ghc/x86_64-linux-7.6.1 # or equivalent on your system. Then reinstall all the packages you want by listing them all at once cabal install pkg1 pkg2 pk3 By listing them all together cabal-install tries to come up with an install plan that is globally consistent for all of them. -- Johan

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Re: [Haskell-cafe] cabal install... Trying to recover
by Niklas Larsson 21 Nov '12

21 Nov '12

You should have a ghc directory under appdata, with i386-mingw32-7.4.2\package.conf.d under it. There GHC tracks what packages it knows about. Niklas From: Gregory Guthrie Sent: 2012-11-21 15:11 To: Johan Tibell Cc: haskell-cafe(a)haskell.org Subject: Re: [Haskell-cafe] cabal install... Trying to recover Thanks for the suggestion, I’ll do that. Here goes: I deleted the ../user/appdata/roaming/ghc and ../cabal files, an uninstalled Haskell-platform. (No trace of anything "ghc" on the disk.) Then reinstalled Haskell, and ran “cabal update”, it said there was a new cabal-install, but trying to install it fails (below), so I went ahead with the current version. The error seems odd to me (cabal-install-1.16.0.2 depends on Cabal-1.16.0.3 which failed to install.), that an older version depends on a newer one? So now I have; (from Windows - Haskell-platform 2012.4.0.0) GHCi = The Glorious Glasgow Haskell Compilation System, version 7.4.2 Cabal = cabal-install version 0.14.0, using version 1.14.0 of the Cabal library I then tried to reload all my previous packages, (all at once?!), but it fails, "out of memory" (w/8GB of memory!) So I split it into sections, and tried the first one; it lists a lot of new installs, and then fails (full list at http://pastebin.com/5ywdUjgX) The first chunk of installs gives this: ... cabal: The following packages are likely to be broken by the reinstalls: QuickCheck-2.4.2 haskell-platform-2012.4.0.0 Use --force-reinstalls if you want to install anyway. I don't understand how it can want to break the Haskell-platform, sounds dangerous! And the second this: G:\Cabal>cabal install Boolean Craft3e Craft3e GLFW GLURaw GLUT HTTP IORefCAS Me moTrie MonadCatchIO-mtl NumInstances ObjectName OpenGL OpenGLRaw QuickCheck SDL SHA StateVar Tensor abstract-deque abstract-par active aeson alex ansi-terminal array asn1-data attoparsec attoparsec-conduit base-unicode-symbols base64-bytest ring bits-atomic blaze-builder blaze-builder-conduit blaze-html blaze-markup bla ze-svg bmp buildwrapper byteorder cabal-dev case-insensitive cereal certificate clientsession cmdargs colour comonad conduit contravariant cookie cpphs cprng-ae s cpu criterion crypto-api crypto-conduit crypto-pubkey-types cryptocipher crypt ohash css-text data-default date-cache diagrams-core diagrams-lib diagrams-svg d list email-validate entropy erf failure fast-logger file-embed filepath filesyst em-conduit ghc-paths gloss gtk2hs-buildtools Resolving dependencies... In order, the following would be installed: Boolean-0.1.1 (new package) ... cabal: The following packages are likely to be broken by the reinstalls: regex-posix-0.95.1 regex-compat-0.95.1 regex-posix-0.94.4 regex-compat-0.93.1 parsec-3.1.1 fgl-5.4.2.4 fgl-5.4.2.3 QuickCheck-2.4.0.1 network-2.3.1.0 haskell-platform-2012.4.0.0 cgi-3001.1.7.4 HTTP-4000.2.5 regex-posix-0.95.2 regex-compat-0.95.1 regex-posix-0.95.1 regex-compat-0.95.1 Use --force-reinstalls if you want to install anyway. So I have a typical situation where it won't install, and gives an option to –force, but that seems to lead to more problems? Do I just have some packages which are intrinsically incompatible, and I have to choose between them? Not sure how to proceed. Any help or hints appreciated! :-) –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––- > Cabal install cabal-install Configuring Cabal-1.16.0.3... Warning: This package indirectly depends on multiple versions of the same package. This is highly likely to cause a compile failure. package process-1.1.0.1 requires base-4.5.0.0 package pretty-1.1.1.0 requires base-4.5.0.0 package old-time-1.1.0.0 requires base-4.5.0.0 package old-locale-1.0.0.4 requires base-4.5.0.0 package filepath-1.3.0.0 requires base-4.5.0.0 package directory-1.1.0.2 requires base-4.5.0.0 package deepseq-1.3.0.0 requires base-4.5.0.0 package containers-0.4.2.1 requires base-4.5.0.0 package bytestring-0.9.2.1 requires base-4.5.0.0 package array-0.4.0.0 requires base-4.5.0.0 package Win32-2.2.2.0 requires base-4.5.0.0 package filepath-1.3.0.0 requires base-4.5.1.0 package Cabal-1.16.0.3 requires base-4.5.1.0 package Cabal-1.16.0.3 requires filepath-1.3.0.0 package process-1.1.0.1 requires filepath-1.3.0.0 package directory-1.1.0.2 requires filepath-1.3.0.0 package integer-gmp-0.4.0.0 requires ghc-prim-0.2.0.0 package bytestring-0.9.2.1 requires ghc-prim-0.2.0.0 package base-4.5.0.0 requires ghc-prim-0.2.0.0 package integer-gmp-0.4.0.0 requires ghc-prim-0.2.0.0 package base-4.5.1.0 requires ghc-prim-0.2.0.0 package base-4.5.1.0 requires integer-gmp-0.4.0.0 package base-4.5.0.0 requires integer-gmp-0.4.0.0 Building Cabal-1.16.0.3... Preprocessing library Cabal-1.16.0.3... <command line>: cannot satisfy -package-id array-0.4.0.0-3cf1bc3f5cd0078adea24752c18081b9 (use -v for more information) cabal: Error: some packages failed to install: Cabal-1.16.0.3 failed during the building phase. The exception was: ExitFailure 1 cabal-install-1.16.0.2 depends on Cabal-1.16.0.3 which failed to install. (more -v details at: http://pastebin.com/Y2BuMjBP ) ------------------------------------------- >From this email and some of the previous emails it seems that your package DB is in a pretty bad state, most likely from using --force-reinstalls. When Cabal warns you that this will break stuff it actually means it. :) My suggestion is that you rm -rf ~/.ghc/x86_64-linux-7.6.1 # or equivalent on your system. Then reinstall all the packages you want by listing them all at once cabal install pkg1 pkg2 pk3 By listing them all together cabal-install tries to come up with an install plan that is globally consistent for all of them. -- Johan _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

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cabal install...
by Gregory Guthrie 21 Nov '12

21 Nov '12

Hmm, Now when I tried to run Leksah, I get not only some broken packages (which I can avoid for my current project), but: <command line>: cannot satisfy -package-id base-4.5.1.0-7c83b96f47f23db63c42a56351dcb917: base-4.5.1.0-7c83b96f47f23db63c42a56351dcb917 is unusable due to missing or recursive dependencies: integer-gmp-0.4.0.0-c15e185526893c3119f809251aac8c5b (use -v for more information) So I tried to install base, then re-install it, but both fail; Any hints? ------------------------------- C:\Users\guthrie>cabal install base Resolving dependencies... All the requested packages are already installed: base-4.5.1.0 Use --reinstall if you want to reinstall anyway. C:\Users\guthrie>cabal install --reinstall base Resolving dependencies... cabal: Could not resolve dependencies: next goal: base (user goal) rejecting: base-3.0.3.2 (conflict: base => base>=4.0 && <4.3) rejecting: base-3.0.3.1 (conflict: base => base>=4.0 && <4.2) rejecting: base-4.6.0.0, 4.5.1.0, 4.5.0.0, 4.4.1.0, 4.4.0.0, 4.3.1.0, 4.3.0.0, 4.2.0.2, 4.2.0.1, 4.2.0.0, 4.1.0.0, 4.0.0.0 (only already installed instances can be used) C:\Users\guthrie>ghc-pkg list base WARNING: there are broken packages. Run 'ghc-pkg check' for more details. e:/Plang/Haskell Platform\lib\package.conf.d: base-4.3.1.0 base-4.5.0.0 base-4.5.1.0 The following packages are broken, either because they have a problem listed above, or because they depend on a broken package. HTTP-4000.2.3 haskell-platform-2012.2.0.0 Can I just unregister the old Haskell platform, I now use a newer one? Ghc-pkg list : ... {haskell-platform-2012.2.0.0} haskell-platform-2012.4.0.0 haskell-src-1.0.1.4 haskell-src-1.0.1.4 haskell-src-1.0.1.5 haskell-src-1.0.1.5 (haskell2010-1.0.0.0) (haskell2010-1.1.0.1) (haskell2010-1.1.0.1) haskell98-1.1.0.1 (haskell98-2.0.0.1) (haskell98-2.0.0.1) -------------------------------------------

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Hackage dependencies problem.
by Magicloud Magiclouds 20 Nov '12

20 Nov '12

Hi, I am having ghc 7.6.1 working here. But anytime I installed something with cabal-install, I got prompts like: Warning: The following packages are likely to be broken by the reinstalls: haskell98-2.0.0.2 ghc-7.6.1 Cabal-1.16.0 bin-package-db-0.0.0.0 directory-1.2.0.0 hpc-0.6.0.0 Continuing even though the plan contains dangerous reinstalls. And even worse, then I got: <command line>: cannot satisfy -package Cabal-1.16.0: Cabal-1.16.0-dd0ce1db6fea670a788547ee85411486 is unusable due to missing or recursive dependencies: directory-1.2.0.0-8edf300597b0da609c8eccc9aa6d0cc3 process-1.1.0.2-03ae5757aa509ffbe497f42660cba52c unix-2.6.0.0-4bc27fc415f60036a88211de7cde3e9a (use -v for more information) What should I do? Why user space directory and process would interrupt Cabal in global space? -- 竹密岂妨流水过山高哪阻野云飞 And for G+, please use magiclouds#gmail.com.

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Instead of Haskell running on the JVM is there a way for Haskell to call a JVM language ...
by KC 20 Nov '12

20 Nov '12

Instead of Haskell running on the JVM is there a way for Haskell to call a JVM language (or generate bytecode) to access the Java class libraries when needed? Or Is there a way for a JVM language or bytecode to call Haskell when needed? -- -- Regards, KC

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