- Haskell-Cafe - Haskell.org

Nightly builds of GHC HEAD for OS X 10.8
by John Wiegley 22 Jun '13

22 Jun '13

Since mid-January, I’ve been running nightly builds of GHC on my Mac Pro for 10.8.x, 64-bit. I’ve decided to make these results publically downloadable here: http://ghc.newartisans.com. The installer tarballs are in dist, while the fulltest and nofib logs are in logs. According to Jenkins this build takes 8h15m minutes, so I figured this might save others some CPU heat. -- John Wiegley FP Complete Haskell tools, training and consulting http://fpcomplete.com johnw on #haskell/irc.freenode.net

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How to make this data type work?
by Magicloud Magiclouds 21 Jun '13

21 Jun '13

data ActionData = AD { oldData :: (FromJSON j, ToJSON j) => j , newData :: (FromJSON j, ToJSON j) => j} instance ToJSON ActionData where toJSON (AD o n) = object [ "oldData" .= o , "newData" .= n ] instance FromJSON ActionData where parseJSON (Object v) = AD <$> v .: "oldData" <*> v .: "newData" parseJSON _ = mzero I got when compile: No instance for (FromJSON (forall j. (FromJSON j, ToJSON j) => j)) arising from a use of `.:' Possible fix: add an instance declaration for (FromJSON (forall j. (FromJSON j, ToJSON j) => j)) In the second argument of `(<$>)', namely `v .: "oldData"' In the first argument of `(<*>)', namely `AD <$> v .: "oldData"' In the expression: AD <$> v .: "oldData" <*> v .: "newData" -- 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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TH clause Pat selection
by Brian Lewis 21 Jun '13

21 Jun '13

I want to use TH to generate functions like foo :: c -> h foo ... = ... foo ... = ... ... from lists of pairs :: [(c, h)] For example, $(genFoo ''Int ''Bool [(0,False), (1,True)]) would generate foo 0 = False foo 1 = True The problem is, I don't know how to generate the function's clauses. "foo 0 = ..." seems to be a LitP pattern. But "foo True = ..." seems to be a ConP pattern. The appropriate pattern depends on type c. Here's code with more explanation and examples: http://hpaste.org/90163

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Ann: Cascading 0.1.0, DSL for Cascading Style Sheets
by Ertugrul Söylemez 21 Jun '13

21 Jun '13

Hi there, I've just released the first version of [cascading], library for writing/generating Cascading Style Sheets (CSS) in Haskell. The API design is inspired by many other projects, including blaze-html, HSP and Yesod's Lucius. [cascading]: <http://hackage.haskell.org/package/cascading> Features: * Style sheets are monoids and can be MonadWritered. * All non-appendix properties of CSS level 2.1 are implemented and exposed through a type-safe API. It's easy enough to set properties for which no type-safe API exists. See the example below. * Easy to integrate into all monadic web frameworks, easy to interleave stylesheets with framework operations. * Builtin support for web-routes. * Color space awareness through the colour library. * Fully encoding-aware with one caveat: If you bypass PropValue and use ByteStrings as property values directly, then UTF-8 is assumed. Example: stylesheet :: (MonadWriter CSS m) => m () stylesheet = onAll $ do select ["p"] $ do margin . Edges $ [zeroLen] padding . Edges $ [_Em # 1, _Ex # 2] select ["em"] $ do fontWeight BolderWeight select ["ul", "ol"] . below ["li"] $ do borderColor (LeftEdge green) borderWidth (LeftEdge ThickWidth) vendors $ "borderRadius" $= ("3mm" :: PropValue) This results in the following stylesheet: p { margin: 0; padding: 1em 2ex } em { font-weight: bolder } ul li, ol li { border-left-color: #008000; border-left-width: thick; border-radius: 3mm; -moz-border-radius: 3mm; -ms-border-radius: 3mm; -o-border-radius: 3mm; -webkit-border-radius: 3mm } Please visit the [homepage]. Feedback is always welcome. If you find bugs, please don't hesitate to [report] them. [homepage]: <http://hub.darcs.net/ertes/cascading> [report]: <http://hub.darcs.net/ertes/cascading/issues> Greets, Ertugrul -- Not to be or to be and (not to be or to be and (not to be or to be and (not to be or to be and ... that is the list monad.

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Why isn't ArrowChoice a parent of of ArrowApply?
by Petr Pudlák 20 Jun '13

20 Jun '13

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Re: [Haskell-cafe] Remove Enum from Float and Double
by Doug McIlroy 20 Jun '13

20 Jun '13

> it's the entire Enum class which doesn't have a consistent or sensible semantics Yes, for a language with generally sound mathematical roots, Enum is an embarrassment. My pet peeve is that Rationals are enumerable, but not with Enum. And the differing lengths of [1,4..6] and [1.0,4.0..6.0] will shock even the non-mathematically inclined. Much of the craziness can be hidden if in place of [a..b] for nonintegral numeric types, one uses (map fromInteger [a..b]). Perhaps that should happen automatically. As for the horror mentioned at the end of the first paragraph, the language definition's oafish attempt to "get right" things like [0.0,0.1..1.0] needs major revision. Doug McIlroy

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GADTs and pattern matching
by Francesco Mazzoli 20 Jun '13

20 Jun '13

Hi list, I have stumbled upon a strange annoyance: {-# LANGUAGE GADTs #-} data Foo v where Foo :: Foo (Maybe v) -- This doesn't work foo1 :: a -> Foo a -> Int foo1 Nothing Foo = undefined foo1 (Just x) Foo = undefined -- This does foo2 :: a -> Foo a -> Int foo2 x Foo = foo2' x foo2' :: Maybe a -> Int foo2' Nothing = undefined foo2' (Just x) = undefined The first definition fails with the error Couldn't match expected type `a' with actual type `Maybe t0' `a' is a rigid type variable bound by the type signature for foo1 :: a -> Foo a -> Int at /tmp/foo_flymake.hs:8:9 In the pattern: Nothing In an equation for `foo1': foo1 Nothing Foo = undefined Now, GHC can clearly derive and use the type equalities correctly, given that the second definition works, but why can’t I pattern match directly? Thanks, Francesco

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ANNOUNCE: Ajhc 0.8.0.6 Release
by Kiwamu Okabe 20 Jun '13

20 Jun '13

We are happy to announce Ajhc 0.8.0.6. Major change on the release is supporting THREAD. Yeah! You can get Ajhc using "cabal install ajhc" command. Ajhc's project web site is found at http://ajhc.metasepi.org/. You find the source code at https://github.com/ajhc/ajhc/tags. Welcome sending any bugs or your ideas to https://github.com/ajhc/ajhc/issues. ## Good news * You can use forkOS interface on Ajhc. * Your program runs on pthread with compiling -fpthread option. See below. $ cat Main.hs import Control.Monad import Control.Concurrent main :: IO () main = do l <- putStrLn "Type some string and enter." >> getLine forkOS $ (forever $ putChar '*') forkOS $ (forever $ putStr l) forever $ putChar '.' $ ajhc -fpthread Main.hs $ ./hs.out ## Bad news * Ajhc guards critical section only for the runtime. * Example: StablePtr isn't guarded with lock. * Ajhc's thread can't share any objects without Ptr type. * And you may find funny pthread bugs. Please send us the report! ## Other changes * No more depend on DrIFT. * Add _JHC_JGC_LIMITED_NUM_GC_STACK flag to set number of limited gc_stack entries. * Add _JHC_JGC_FIXED_MEGABLOCK flag to set number of limited megablock entries. * Add compile flags -fcustomthread -fpthread -fnothread. * You can implement your own thread API for Ajhc, if you choose -fcustomthread. Enjoy! ;) - - - Metasepi team

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ANN: Nomyx 0.2 beta, the game where you can change the rules
by Corentin Dupont 19 Jun '13

19 Jun '13

Hello everybody! Here it comes, the second beta release [1] of Nomyx, the only game where You can change the rules!! This is an implementation of a Nomic [2] game in Haskell (I believe the first complete implementation of a Nomic game on a computer). In a Nomyxgame you can change the rules of the game itself while playing it. The players can submit new rules or modify existing ones, thus completely changing the behaviour of the game through time. The rules are managed and interpreted by the computer. They must be written in the Nomyx language, which is a subset of Haskell. At the beginning, the initial rules are describing: - how to add new rules and change existing ones. For example a unanimity vote is necessary to have a new rule accepted. - how to win the game. For example you win the game if you have 5 rules accepted. But of course even that can be changed! Here is a video introduction and first tutorial of the game: http://vimeo.com/58265498 The game is running here: www.nomyx.net:8000/Nomyx I have set up a forum where players can learn about Nomyx and discuss the rules they intend to propose: www.nomyx.net/forum The example file gives a lot of examples of rules that you can submit: www.nomyx.net:8000/src/Language/Nomyx/Examples.hs Changes from V0.1: - new login system: you can now login with your Google, Yahoo, Live Journal, Myspace, OpenId or Facebook accounts (thanks to happstack-authenticate)! - new DSL for voting (see below) - styling: rule code colorized, better settings and help - use cookies to store the user ID (as suggested on this mailing list) - new error system to handle exceptions in rules (with ErrorT) - use lenses I set up a little DSL to create elections (elect one of the players for a special role) or referendums (a yes/no question). You create in one line within Nomyx an vote with unanimity or majority, a quorum and different ballot systems. See here: http://www.nomyx.net/forum/viewtopic.php?f=3&t=1518 Let's test it! If you are interested, please go to this forum thread and we'll set up a small team to start a match! http://www.nomyx.net/forum/viewtopic.php?f=4&t=1517 The demo game is running here: www.nomyx.net:8000/Nomyx then select game "demo2". As the first player of the game, I changed the initial unanimity vote to a simple majority, with a minimum of 2 players voting. Having your new rules accepted will be easy! Let's see who will win :) Cheers, Corentin [1] http://hackage.haskell.org/package/Nomyx [2] www.nomic.net

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hand over maintenance of a package
by Corentin Dupont 19 Jun '13

19 Jun '13

Hi Cafe, How to hand over the maintenance of a hackage package? Thanks Corentin

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