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ANN: utility for deriving rules from a nominal table
by Hans van Thiel 08 Apr '07

08 Apr '07

Hello All, I'd like to announce the availability of Emping, a utility that reads a table in a csv format that can be generated from Open Office Calc, derives all shortest rules for a selected attribute, and writes them to a .csv file that can be read by OO Calc. See http://j-van-thiel.speedlinq.nl/emp/empug.html for more and, if you're interested, a download. The package is built by Cabal. However, I couldn't install it myself from there with Cabal. Configuration seemed to go OK, but build generated a message that ghc found no source files. I couldn't get it right, but I'm leaving it at that, because (1) I'm assuming the package itself is OK and (2) it's a standalone utility so maybe Cabal is overkill anyway (though it's nice how Cabal forces a structure). Just compiling the source modules is, probably, the preferred option here. Thanks, Hans van Thiel

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ANN: XMPP 0.0.1
by Magnus Henoch 08 Apr '07

08 Apr '07

I'm hacking a library for writing XMPP clients, and just decided that my work is good enough to call it version 0.0.1. Find source and documentation here: http://www.dtek.chalmers.se/~henoch/text/hsxmpp.html It contains a werewolf bot as an example. I wanted the bot to speak several languages, but I couldn't find any library that would make that easier, so I wrote one myself, in Translate.hs. Is there any other way to do that? What do other projects use? The library contains an event loop: it waits for data from the network, treats it as events and handles them. (the loop is in runXMPP in XMPPMonad.hs, and the actual waiting is in getString in TCPConnection.hs) I can imagine that it might be useful to integrate this in another event loop, e.g. to create a chat client with a GUI. Do you have any thoughts on whether and how to do that? Magnus

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Yi Source
by Dave Feustel 08 Apr '07

08 Apr '07

Is the full source of Yi suitable for building on non-linux platforms (ie OpenBSD) (going to be) available? Thanks, Dave Feustel http://RepublicBroadcasting.org - Because You CAN Handle The Truth!

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Re: `Expect'-like lazy reading/Parsec matching on TCP sockets
by Scott Bell 07 Apr '07

07 Apr '07

> you should write compiler version and OS for such problems. Of course, this was 6.7-20070404 on Linux x86. I haven't had a change to test it on my 6.6 build. > I/O in Windows threaded RTS was fixed after initial 6.6 release and > afaik hWaitForInput should work better now. alternatively, you can try > with hand-made timeout solution I'm not sure what the status is on hWaitForInput with the snapshot that I am using -- any other ideas what I could try to further isolate the problem? - Scott Bell

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MPTC and type classes issue (polymorphic '+')
by Joel Reymont 07 Apr '07

07 Apr '07

Folks, I'm trying to save time when typing in my ASTs so I thought I would create a Plus class like this (I do hide the one from Prelude) class PlusClass a b c | a b -> c where (+) :: a -> b -> c {- instance (Integral a, Integral b) => PlusClass a b Expr where a + b = NumExpr (NumOp Plus (Int (fromIntegral a)) (Int (fromIntegral b))) instance Integral a => PlusClass a Double Expr where a + b = NumExpr (NumOp Plus (Int (fromIntegral a)) (Double b)) -} instance PlusClass Integer Integer Expr where a + b = NumExpr (NumOp Plus (Int a) (Int b)) instance PlusClass Double Integer Expr where a + b = NumExpr (NumOp Plus (Double a) (Int b)) instance PlusClass NumExpr NumExpr Expr where a + b = NumExpr (NumOp Plus a b) instance PlusClass Integer NumExpr Expr where a + b = NumExpr (NumOp Plus (Int a) b) instance PlusClass NumExpr Integer Expr where a + b = NumExpr (NumOp Plus a (Int b)) instance PlusClass String String Expr where a + b = StrExpr (StrOp StrPlus (Str a) (Str b)) NumExpr and StrExpr return Expr whereas Int, Double return NumExpr and Str returns StrExpr. This is all so that I could type in input2 = [ InputDecs [ inp "emaLength" TyNumber (20 + 40) ] ] Still, I get the following error Easy/Test/ParserAST.hs:76:44: No instance for (PlusClass t t1 Expr) arising from use of `+' at Easy/Test/ParserAST.hs:76:44-50 Possible fix: add an instance declaration for (PlusClass t t1 Expr) In the third argument of `inp', namely `(20 + 40)' In the expression: inp "emaLength" TyNumber (20 + 40) In the first argument of `InputDecs', namely `[inp "emaLength" TyNumber (20 + 40)]' and get an overlapped instances error if I uncomment the top portion. Any suggestions on how to resolve this? Thanks, Joel -- http://wagerlabs.com/

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Re: Trouble trying to find packages for ubuntu linux
by Chad Scherrer 07 Apr '07

07 Apr '07

Brian, I had this exact problem, and I found this approach to work wonderfully: http://pupeno.com/2006/12/17/unstable-packages-on-ubuntu/ Chad

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Building c2hs on a mac
by manu 06 Apr '07

06 Apr '07

Hello, I'd be interested to know if anybody had managed to build c2hs on a mac recently because I've tried the current darcs version, c2hs-0.14.5, c2hs-0.14.3, c2hs-0.13.6, etc... to no avail I get this with c2hs-0.14.5 : ./Setup.hs configure ./Setup.hs:11:57: Couldn't match expected type `Distribution.PackageDescription.PackageDescription' against inferred type `LocalBuildInfo' Probable cause: `addWrapperAndLib' is applied to too many arguments In the `postInst' field of a record In the first argument of `defaultMainWithHooks', namely `defaultUserHooks {postInst = addWrapperAndLib}' Any help appreciated, thanks E.D

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How can I refactor this code?
by Joel Reymont 06 Apr '07

06 Apr '07

http://hpaste.org/127 It looks quite ugly to me so any help is appreciated! Thanks in advance, Joel -- http://wagerlabs.com/

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Shiqi has Tagged you! :)
by Shiqi Cao 06 Apr '07

06 Apr '07

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ANN: Atom - Yet another Haskell HDL
by Tom Hawkins 05 Apr '07

05 Apr '07

Hi, Haskell has a rich history of embedded hardware description languages. Here's one more for the list. Inspired by the work of Arvind, Hoe, and all the sharp folks at Bluespec, Atom is a small HDL that compiles conditional term rewriting systems down to Verilog RTL. In Atom, a circuit description is composed of a set of state elements (registers) and a set of rules. Each rule has two components: an enabling condition and a collection of actions, or state updates. When a rule is enabled, it's actions may be selected to execute atomically. In contrast to Verilog "always" blocks, multiple rules can write to the same state element. Here's an enabled counter in Atom: counter :: Int -> Signal -> System Signal counter width enable = do count <- reg "count" width 0 rule "updateCount" $ do when enable count <== value count +. one width return $ value count Enjoy! http://funhdl.org/ -Tom A few details: The Atom compiler attempts to maximize the number of rules that can execute in a given clock cycle without breaking the semantics of "one-rule-at-a-time". For simplicity, rules are assigned a global, linear priority. Data dependencies between rules form a graph. A acyclic graph is ideal, because all rules become "sequentially composable". The compiler attempts to order the rules to minimize the number of edges feeding back from lower to higher priority rules. This is equivalent to the feedback arc set problem. (Atom's FAS optimization is pretty poor at the moment.) In a rule-data dependency graph, many of the edges are irrelevent because pairs of rules are often mutually exclusive, ie. can not be enabled at the same time. MiniSat is used to hunt and prune edges from mutually exclusive rules. By only looking back to primary inputs and registers, the SAT procedure is not guaranteed to find all mutually exclusive rules, but it does a pretty good job.

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