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[ANN] brick-users discussion list

General haskell list - Mon, 03/07/2016 - 7:56pm
Hi, If you use the 'brick' library then you might like to know that there is now a library discussion list for it:
Categories: Incoming News

Magnus Therning: Final version of JSON to sum type

Planet Haskell - Mon, 03/07/2016 - 6:00pm

After some feedback on my previous post I ended up with the following implementation.

instance FromJSON V.VersionRange where parseJSON = withObject "VersionRange" go where go o = V.thisVersion <$> o .: "ThisVersion" <|> V.laterVersion <$> o .: "LaterVersion" <|> V.earlierVersion <$> o .: "EarlierVersion" <|> V.WildcardVersion <$> o .: "WildcardVersion" <|> nullaryOp V.anyVersion <$> o .: "AnyVersion" <|> binaryOp V.unionVersionRanges <$> o .: "UnionVersionRanges" <|> binaryOp V.intersectVersionRanges <$> o .: "IntersectVersionRanges" <|> V.VersionRangeParens <$> o .: "VersionRangeParens" nullaryOp :: a -> Value -> a nullaryOp = const binaryOp f [a, b] = f a b

Thanks David for your suggestions.

Categories: Offsite Blogs

Tagged instances for Aeson overlapped

haskell-cafe - Mon, 03/07/2016 - 4:37pm
Hello, I tried to compile my project with GHC 8 (from HEAD). And I got One of instances should be removed probably. I suppose that instance for removing should be instance in Data.Tagged. But version in Aeson should be PolyKinded. What do you think? Best regards, Dmitry _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe< at >
Categories: Offsite Discussion

Trouble on Travis CI with recent cabal versions

haskell-cafe - Mon, 03/07/2016 - 10:19am
For my OpenGLRaw project, I'm using a .travis.yml generated by Herbert's and the corresponding PPA. Recently things broke on Travis CI, and there are a few strange things: * The cabal-install-head package seems to be based on cabal 1.23, which is older than cabal-install-1.24. Is this intended? * The OpenGLRaw package has no test suite, and this seems to be OK for cabal-install-head (, while cabal-install-1.24 fails in the "cabal test" step ( This is a regression: I think that "cabal test" for a package without a test suite should be a no-op, at least that used to be the case. * Why does "cabal test" say "Re-configuring with test suites enabled. If this fails, please run configure manually." when "cabal configure" has already been run (including --enable-tests)? This looks li
Categories: Offsite Discussion

1-to-many preprocessor in stack/Cabal builds

haskell-cafe - Mon, 03/07/2016 - 8:53am
Hi, I'm writing a package which uses custom preprocessor for creating some of the source files. It takes one IDL file as input and writes several .hs modules, depending on IDL contents. I need to compile this modules with a few normal ones and link them as a library, preferably with generated modules exposed. It doesn't look like a complex task and never was in with make/etc, but I run into some problems now. Obviously, cabal supports 1-to-1 preprocessors to create one Haskell module from one source file (alex, happy, etc), but I can't find anything for 1-to-many preprocessors. So, I decided to use hookedPrograms and hooks and do it myself. The call to preprocessor in the postConf hook worked just fine and created source files and module list. Cabal pre-* hooks seems to be right place to read this module list and use it, but are presenting two problems: can only modify other-modules, not exposed-modules, which is tolerable, and there is no access to build configuration. The latter is fatal, I need to know
Categories: Offsite Discussion

PolyKind for Fixed and HasResolution from Data.Fixed

haskell-cafe - Sun, 03/06/2016 - 7:29pm
Hi all! If we define HasResolution and Fixed like that: class HasResolution (a :: k) where resolution :: p a -> Integer newtype Fixed (a :: k) = Fixed Integer We can do something like that: instance KnownNat a => HasResolution a where resolution = natVal 2.3 :: Fixed 1
Categories: Offsite Discussion

GADTs and Exponentiated Functors

haskell-cafe - Sun, 03/06/2016 - 2:11pm
Hi, I have been recently playing around with GADTs, using them to keep track of how many times a functor has been applied. This provides a solution to what seems to be a long standing problem, summarized here: If the nesting depth is part of the type, it is possible to apply fmap automatically as needed. This allows you to write fairly elegant expressions like: data Person = Person { name :: String, age :: Integer, gender :: String, status :: String } deriving Show let persons = fromList' [Person {name="Alice", age=20, gender="F", status="Good"}, Person {name="Bob", age=18, gender="M", status="Good"}, Person {name="Chuck", age=16, gender="M", status="Bad"}] :: NList N1 Person persons `select` age
Categories: Offsite Discussion

Test email

libraries list - Thu, 03/03/2016 - 7:54pm
Please disregard -- sorry for the noise. Gershom
Categories: Offsite Discussion

New gtk2hs 0.12.4 release

gtk2hs - Wed, 11/21/2012 - 12:56pm

Thanks to John Lato and Duncan Coutts for the latest bugfix release! The latest packages should be buildable on GHC 7.6, and the cairo package should behave a bit nicer in ghci on Windows. Thanks to all!


Categories: Incoming News