- Haskell-Cafe - Haskell.org

ANN: utility for deriving rules from a nominal table
by Hans van Thiel 09 Apr '07

09 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 08 Apr '07

08 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 06 Apr '07

06 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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Automatic derivation (TemplateHaskell?)
by Joel Reymont 06 Apr '07

06 Apr '07

Folks, I have very uniform Parsec code like this and I'm wondering if I can derive it using TemplateHaskell or DrIFT or some other tool. Any ideas? Note that 1) The reserved word matches the constructor 2) No arguments equals no parens 3) More than one argument is separated with a comma 4) For every invocation of numExpr, strExpr or boolExpr, the type of the constructor argument is NumExpr, StrExpr and BoolExpr respectively. This is just a handful of functions and I have to tackle about 100 more, thus my asking :-). Thanks, Joel --- strCall = choice [ do { reserved "NewLine" ; return NewLine } , do { reserved "GetSymbolName" ; return GetSymbolName } , do { reserved "ELDateToString" ; arg1 <- parens numExpr ; return $ ELDateToString arg1 } , do { reserved "TextGetString" ; arg1 <- parens numExpr ; return $ TextGetString arg1 } , do { reserved "Description" ; return Description } , do { reserved "GetExchangeName" ; return GetExchangeName } , do { reserved "LeftStr" ; parens $ do { arg1 <- strExpr ; comma ; arg2 <- numExpr ; return $ LeftStr arg1 arg2 } } , do { reserved "RightStr" ; parens $ do { arg1 <- strExpr ; comma ; arg2 <- numExpr ; return $ RightStr arg1 arg2 } } , do { reserved "LowerStr" ; arg1 <- parens strExpr ; return $ LowerStr arg1 } , do { reserved "UpperStr" ; arg1 <- parens strExpr ; return $ UpperStr arg1 } , do { reserved "Spaces" ; arg1 <- parens numExpr ; return $ Spaces arg1 } , do { reserved "SymbolRoot" ; return SymbolRoot } , do { reserved "MidStr" ; parens $ do { arg1 <- strExpr ; comma ; arg2 <- numExpr ; comma ; arg3 <- numExpr ; return $ MidStr arg1 arg2 arg3 } } , do { reserved "NumToStr" ; parens $ do { arg1 <- numExpr ; comma ; arg2 <- numExpr ; return $ NumToStr arg1 arg2 } } ] -- http://wagerlabs.com/

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Short-circuiting a fold
by Kurt Hutchinson 06 Apr '07

06 Apr '07

Here's a bit of Thursday afternoon fun. Mission: Define "ssfold," a short-circuiting fold. It evaluates to the "folded value" that first satisfies the given predicate. > ssfold :: ( a -> Bool ) -> ( a -> b -> a ) -> a -> [b] -> a Here are two of mine. Straightforward: > ssfold p f z = head . dropWhile ( not . p ) . scanl f z Monadic: > data Done a b = Done { undone :: a } | NotDone b > instance Monad ( Done a ) where > ( NotDone i ) >>= f = f i > ( Done r ) >>= _ = Done r > return = NotDone > > ssfold p f z = undone . foldM (\ v e -> if p v then Done v else NotDone ( f v e ) ) z I want to see some real creativity here, so pull out all the stops. Kurt

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Parsing unordered parameter list with Parsec
by Will Newton 05 Apr '07

05 Apr '07

Hi all, I'm new to Haskell and trying to do some parsing with Parsec. It's been extremely good so far. I have run into a problem I can't seem to see the solution to though. I hope someone on the list can help me out! I have a command with a parameter list like this: CMD PARAM1 foo PARAM2 100 PARAM3 200 Which is easy enough to parse, but it turns out the grammar is not particularly well defined, and it's considered acceptable to swap parameter order round pretty much arbitrarily. Is there a simple way to handle this? I would like to only allow one of each parameter, some parameters may also be optional. It feels like I might have to write my own combinator to do this but I'm not sure I'm quite ready of that yet! Thanks,

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Tracking characters and a timestamp ?
by Marc Weber 05 Apr '07

05 Apr '07

============= ======================================================= {- This program should read characters from stdin, stop on 's' and print the character along with a timestamp You need ghc-6.6 because of Date.Time. When not using mapM addTimeCode I'll get the lines printed on stdout instantly -} import Data.Time.Clock import Data.Time import Control.Monad handleChar :: Show a => (Char, a) -> IO () handleChar ('s', _) = exitWith (ExitFailure 1) handleChar tuple = print tuple addTimeCode a = liftM ( (,) a) getCurrentTime main = do hSetBuffering stdin NoBuffering hGetContents stdin >>= mapM addTimeCode >>= mapM_ handleChar ============= ====================================================== When running and typing a b c it should print ('a', <timestamp>) ('b', <timestamp>) ('c', <timestamp>) It seems to wait till the end of the infinite list. Why? When using a take 10 I'll get those 10 events after having typed the 10th character. Do I need continuation passing style? Would unsafeInterleaveIO help? The final goal is writing a timetracker which sums up the time you've spent on different wmii tags (= you can think of them beeing different screens ) Marc Weber

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`Expect'-like lazy reading/Parsec matching on TCP sockets
by Scott Bell 05 Apr '07

05 Apr '07

Hello all, I'm writing an application to interact with other applications remotely though TCP sockets (primarily), and in the future with local apps also. So far I have a Parsec parser to match the input that I want to see, which works if the remote connection is particularly speedy - but the final goal is to obtain the following behavior: Match the Parsec parser against the input as soon as a match is available, but fail if the match is unavailable after a timeout value if no further data is available on the socket. The parser will be matching some input pattern such as (string "login:"), for example. What's the best approach to take while leveraging laziness if possible? Thanks, - Scott Bell

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Haskell implementation for .NET with performance results
by Monique Monteiro 05 Apr '07

05 Apr '07

Hi all, does anyone know about any Haskell implementation for .NET platform with published performance results? Thanks in advance, -- __________________________________________________________ Monique Monteiro, MSc MCP .NET Framework 2.0 / SCJP / IBM OOAD http://www.cin.ufpe.br/~mlbm http://thespoke.net/blogs/moniquelouise/default.aspx monique(a)qualiti.com.br +55 81 34198137 Project Manager Recife Microsoft Innovation Center

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Type classes to 'reflect' constructor structure
by Jules Bean 05 Apr '07

05 Apr '07

In the thread 'automatic derivation', Joel Reymont is looking for metaprogramming functionality with which he wants to automatically derive a parser and a pretty printer for his ADT (which is an AST for a minilanguage). I replied showing that a significant amount of the boilerplate could be removed anyway just using haskell's built in ability to process parsers as 'data'. I could completely automate the nullary constructions, but I needed type information for n-ary ones. A bit of poking around with typeclasses showed a proof-of-concept for getting the type-checker to extract that information for us: {-# OPTIONS -fglasgow-exts #-} import Data.Typeable -- Stage 1 is just counting the arguments class CountArgs s where numArgs :: s -> Integer data TestType = Nullary | Unary Int | Binary Int String | OtherBinary String Int instance CountArgs TestType where numArgs x = 0 instance CountArgs (a->TestType) where numArgs x = 1 instance CountArgs (a->b->TestType) where numArgs x = 2 -- *Main> numArgs Nullary -- 0 -- *Main> numArgs Unary -- 1 -- *Main> numArgs Binary -- 2 -- Stage 2 actually lists the types of the arguments -- I'll use a seperate ADT to make the types concrete data ArgTypes = JInt | JStr deriving (Show) class ConcreteType t where makeAT :: t -> ArgTypes instance ConcreteType Int where makeAT _ = JInt instance ConcreteType String where makeAT _ = JStr class DescribeArgs s where descArgs :: s -> [ArgTypes] instance DescribeArgs TestType where descArgs _ = [] instance ConcreteType a => DescribeArgs (a->TestType) where descArgs _ = [makeAT (undefined::a)] instance (ConcreteType a, ConcreteType b) => DescribeArgs (a->b->TestType) where descArgs _ = [makeAT (undefined::a), makeAT (undefined::b)] -- *Main> descArgs Nullary -- [] -- *Main> descArgs Unary -- [JInt] -- *Main> descArgs Binary -- [JInt,JStr] -- *Main> descArgs OtherBinary -- [JStr,JInt] -- Stage 3 is just the Data.Typeable version of the stage 2 class DescribeArgs2 s where descArgs2 :: s -> [TypeRep] instance DescribeArgs2 TestType where descArgs2 _ = [] instance Typeable a => DescribeArgs2 (a->TestType) where descArgs2 _ = [typeOf (undefined::a)] instance (Typeable a, Typeable b) => DescribeArgs2 (a->b->TestType) where descArgs2 _ = [typeOf (undefined::a), typeOf (undefined::b)] -- *Main> descArgs2 Nullary -- [] -- *Main> descArgs2 Unary -- [Int] -- *Main> descArgs2 Binary -- [Int,[Char]] -- *Main> descArgs2 OtherBinary -- [[Char],Int] There are still some things this approach fails on: it can't give you a complete list of all constructors of TestType, for example. (Such a list would necessarily an existential type, like [exists x . DescribeArgs x -> x]). I'm sure my thoughts aren't original. Have other people taken this further into interesting directions? Where is the line beyond which you need 'true' metaprogramming? Jules

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25k lines of ASP to 4.2k lines of Haskell, with considerably more functionality
by Adam Peacock 05 Apr '07

05 Apr '07

Haskell in the real world: http://braintreehemp.com.au/ Source available from: darcs get http://braintreehemp.com.au/www.braintreehemp.com.au-WASH/ The site features: - Written in Haskell, using WASH http://www.informatik.uni-freiburg.de/~thiemann/WASH/ - Shopping basket and checkout - Google Maps - Google Analytics - Google Webmaster tools - Template Haskell for HaskellDB description (describe a table or a field in one line) - GPL, execpt where stated otherwise. - Heavyweight Content Management System (CMS) -- Froogle RSS generator -- Configurable help for each page -- Concept of inventory levels -- Concept of users and permissions -- Naive-user management of products, users, and page content -- XML import tool and wizard for inventory level reconciliation between warehouse and site database CMS screen shots at: http://braintreehemp.com.au/screenshots/index.html Why did I write the site in Haskell? First, I was ask to fix the site that was selling products they didn't have in stock. Once I looked at the source code, 25000 lines of ASP, I reckoned it would be easier to rewrite it in a real language. Second, I couldn't find any commercial sites written in Haskell, and I thought this would be a good chance. The new site has considerably more functionality and is a little over 4200 lines of Haskell. The original site could only display and sell products, without any consideration of whether any were currently in stock. Furthermore, the site content could only be maintained by an expert user. See the old site at http://web.archive.org/web/20060503232646/www.braintreehemp.com.au/retail/ . If anyone wants to have a play with the CMS, email me privately, and I'll give you a nobody login. Adam

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Re: [Haskell-cafe] My Unification Sorrows
by Stefan O'Rear 05 Apr '07

05 Apr '07

I seem to have did an accidental reply-to-sender at first: On Wed, Apr 04, 2007 at 01:37:44PM -0700, Paul Berg wrote: > Ok, so I decided to implement an algorithm to build Strongly Typed Genetic > Programming trees in Haskell, in an effort to learn Haskell, > and I'm way over my head on this unification problem. > > The unification seems to work well, as long as I include the occurs check. > growFullTree returns a lazy list of all possible syntax trees in random > order that are well typed. So, with the occurs check: > > head $ growFullTree 4 TInt 0 [] (mkStdGen 5) > > Gives me a nice, random, well typed tree. So far so good, although > I am wary of the efficiency... perhaps I need some applySubst calls > in there somewhere to keep the constraint list down? > > Anyway now, we comment out the occurs check in the unify function and > do the same thing again. Now we get what appears to be an infinite > constraint! The unify is supposed to be terminating without the occurs > check, so something is very wrong here! > > Worse, now we run: > > head $ growFullTree 5 TInt 0 [] (mkStdGen 7) > > This one never even begins printing! Although it appears the bug is > tail recursive in this case. Other random number seeds will cause it > to blow stack. > > I have gone over and over this code and cannot find the issue due to my > lack of experience with both Haskell and Unification algorithms in general. > > I was hoping someone here could give pointers on where the bug might lie, > eg. > what is my algorithm doing wrong that makes it a mostly, but not completely > correct unification algorithm, as well as give me pointers on how this > code could be > made cleaner and/or more concise, as I'm trying very hard to get my brain > around > this language, and this problem. > > Here's the basic code, which should be fully runnable: The problem is with this type: data Type = TInt | TReal | TVar TVName | Type :-> Type Because it is impossible to observe sharing in Haskell values, we are forced to explore the entire type; but without the occurs check the type can be infinite! In my infinite-types unifier, I used this: data Bin = Sum | Fun | Prod deriving (Eq, Show, Ord) data Zen = ZTup deriving (Eq,Show,Ord) data DictElt = EZen Zen | EBin Bin Type Type deriving (Eq, Show, Ord) type Dict = M.Map Int DictElt Changing to use Paul's set of types: data DictElt = TInt | TReal | TVar | Int :-> Int type Dict = M.Map Int DictElt IE, we use Ints explicitly as pointers. However this representation costs a lot in terms of clarity, since everything must be explicitly indirected through the 'heap'. Also fixtypes was a very old project of mine; were I to do it again I would probably use explicit mutable references: data Tinfo s = TInt | TReal | TVar | Type s :-> Type s type Type s = STRef s (Tinfo s) This may conflict with your method of backtracking tree generation; I haven't read that far in the code yet. Stefan ----- End forwarded message -----

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Re: [Haskell] Fixpoint combinator without recursion
by Stefan Holdermans 05 Apr '07

05 Apr '07

Edsko, (Moved to Haskell Cafe.) > It is well-known that negative datatypes can be used to encode > recursion, without actually explicitly using recursion. As a little > exercise, I set out to define the fixpoint combinator using negative > datatypes. I think the result is kinda cool :) Comments are welcome :) Yeah, it's rather cool. IIRC, this style of encoding of recursion operators is attributed to Morris. Before the advent of equality coercions, GHC typically had problems generating code for these kinds of definitions. Did you test this with a release version? If so, how did you get around the code- generation problem? Is it the NOINLINE pragma that does the trick? Cheers, Stefan

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QuickCheck: Arbitrary for a complex type
by Joel Reymont 05 Apr '07

05 Apr '07

Suppose I have a type describing a statement and that I'm trying to make it an instance of arbitrary. The type looks like this: data Statement = InputDecs [InputDecl] | VarDecs [VarDecl] | ArrayDecs [ArrayDecl] | Compound [Statement] | Assign (VarIdent, Expr) | ArrayAssign (VarIdent, [Expr], Expr) Assuming that other types involved were instances of arbitrary, how do I write arbitrary for Statement? Poking around various bits of source code I think that for a type like the following data Style = StyleValue Expr | Solid | Dashed | Dotted | Dashed2 | Dashed3 deriving Show I can write instance Arbitrary Style where arbitrary = oneOf [ StyleValue . arbitrary, elements [ Solid , Dashed , Dotted , Dashed2 , Dashed3 ] ] I'm not sure if this is correct, though, so any help is appreciated! Thanks in advance, Joel -- http://wagerlabs.com/

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My Unification Sorrows
by Paul Berg 05 Apr '07

05 Apr '07

Ok, so I decided to implement an algorithm to build Strongly Typed Genetic Programming trees in Haskell, in an effort to learn Haskell, and I'm way over my head on this unification problem. The unification seems to work well, as long as I include the occurs check. growFullTree returns a lazy list of all possible syntax trees in random order that are well typed. So, with the occurs check: head $ growFullTree 4 TInt 0 [] (mkStdGen 5) Gives me a nice, random, well typed tree. So far so good, although I am wary of the efficiency... perhaps I need some applySubst calls in there somewhere to keep the constraint list down? Anyway now, we comment out the occurs check in the unify function and do the same thing again. Now we get what appears to be an infinite constraint! The unify is supposed to be terminating without the occurs check, so something is very wrong here! Worse, now we run: head $ growFullTree 5 TInt 0 [] (mkStdGen 7) This one never even begins printing! Although it appears the bug is tail recursive in this case. Other random number seeds will cause it to blow stack. I have gone over and over this code and cannot find the issue due to my lack of experience with both Haskell and Unification algorithms in general. I was hoping someone here could give pointers on where the bug might lie, eg. what is my algorithm doing wrong that makes it a mostly, but not completely correct unification algorithm, as well as give me pointers on how this code could be made cleaner and/or more concise, as I'm trying very hard to get my brain around this language, and this problem. Here's the basic code, which should be fully runnable: module Evaluator where import Maybe import Random import Monad -- | Expressions. data Exp = Prim String -- A Primitive Function | App Exp Exp -- An un-evaluated application | Func (Exp -> Exp) -- A partially applied function | LitInt Integer | LitReal Double deriving Show -- | We name type variables by uniquely picking values of this type. type TVName = Int -- | Describes possible types in our language data Type = TInt | TReal | TVar TVName | Type :-> Type deriving (Eq, Show) -- | Type arrows are right associative to match Haskell's native type arrows. infixr 9 :-> -- | Constraints are simply a pair of Types which are equal. type Constraint = (Type, Type) -- | Returns a new type variable name, given an old one. getNextName :: TVName -> TVName getNextName n = n + 1 -- | Evaluate an expression. eval :: Exp -> Exp eval (Prim s) = fst . fromJust $ lookup s primitives eval (App f x) = apply f x eval x = x -- | Apply a function. apply :: Exp -> Exp -> Exp apply a@(App _ _) x = eval $ App (eval a) x apply p@(Prim _) x = eval $ App (eval p) x apply (Func f) x = eval $ f x apply f x = error $ (show f) ++ " was applied to " ++ (show x) ++ " and is not a valid function." -- | Given a set of constraints (possibly empty), the next available variable name and an expression, -- return a triple which consists of the inferred type of the expression, the next available variable name, -- and a list of constraints for the new type. infer :: [Constraint] -> TVName -> Exp -> (Type, TVName, [Constraint]) infer _ nvar (LitInt _) = (TInt, nvar, []) infer _ nvar (LitReal _) = (TReal, nvar, []) infer _ nvar (Prim s) = (t, nvar', []) where (nvar', t, _) = substvars nvar (snd . fromJust $ lookup s primitives) [] infer ctx nvar (App t1 t2) = (TVar nvar'', getNextName nvar'', newconstr : (ctx' ++ ctx'')) where (tyT1, nvar', ctx') = infer ctx nvar t1 (tyT2, nvar'', ctx'') = infer ctx nvar' t2 newconstr = (tyT1, tyT2 :-> TVar nvar'') infer _ _ (Func _) = error "Type Inferrence of partially applied functions not supported" -- | Given a unified constraint list and a type, return a simplified type applySubst :: Type -> [Constraint] -> Type applySubst tyT ctx = foldl (\tyS (tyX,tyC) -> substinty tyX tyC tyS) tyT (reverse ctx) -- | We need to substitute all the type variables in a primitive with new -- ones that do not clash with the variables already defined in our -- constraint set. This function does that, by taking the next available -- variable name and creating a set of substitutions over a type that -- replace the old variable names with newly generated ones substvars :: TVName -> Type -> [(TVName, TVName)] -> (TVName, Type, [(TVName, TVName)]) substvars nvar (TVar n) ctx = case lookup n ctx of (Just n') -> (nvar, TVar n', ctx) Nothing -> (getNextName nvar, TVar nvar, (n, nvar) : ctx) substvars nvar (t1 :-> t2) ctx = (nvar'', t1' :-> t2', ctx'') where (nvar', t1', ctx') = substvars nvar t1 ctx (nvar'', t2', ctx'') = substvars nvar' t2 ctx' substvars nvar t ctx = (nvar, t, ctx) -- | returns the type of an expression if it has one typeof :: Exp -> Maybe Type typeof e = fmap (applySubst t) (unify ctx) where (t, _, ctx) = infer [] 0 e -- | Substitutes a type for a type variable substinty :: Type -> Type -> Type -> Type substinty tyX tyT (s1 :-> s2) = (substinty tyX tyT s1) :-> (substinty tyX tyT s2) substinty tyX tyT tyS@(TVar _) | tyS == tyX = tyT | otherwise = tyS substinty _ _ tyS = tyS -- | Substitutes a type for another type in a constraint set. substinconstr :: Type -> Type -> [Constraint] -> [Constraint] substinconstr tyX tyT = map (\(x,y) -> (substinty tyX tyT x, substinty tyX tyT y)) -- | Checks to see if a type occurs in another type. This is used to identify -- infinite types. occursIn :: Type -> Type -> Bool occursIn tx (ty1 :-> ty2) = (occursIn tx ty1) || (occursIn tx ty2) occursIn tx ty = tx == ty -- | Given a list of constraints, unify those constraints, -- finding values for the type variables unify :: (Monad m, Functor m) => [Constraint] -> m [Constraint] unify [] = return [] unify ((t1 , t2) :rest) | t1 == t2 = unify rest unify ((tyS, tyX@(TVar _)) :rest) -- Problems start by commenting out this line | tyX `occursIn` tyS = fail "Infinite Type" | otherwise = fmap (++ [(tyX,tyS)]) (unify $ substinconstr tyX tyS (reverse rest)) unify ((tyX@(TVar _), tyT) :rest) = unify $ (tyT,tyX) : rest unify ((tyS1 :-> tyS2,tyT1 :-> tyT2):rest) = unify $ (tyS1,tyT1) : (tyS2,tyT2) : rest unify _ = fail "Unsolvable" -- | The basic primitives used to construct expressions. primitives :: [(String, (Exp, Type))] primitives = [("B", (b_, ((TVar 0) :-> (TVar 1)) :-> ((TVar 2) :-> (TVar 0)) :-> (TVar 2) :-> (TVar 1))), ("I", (i_, (TVar 0) :-> (TVar 0))), ("K", (k_, (TVar 0) :-> (TVar 1) :-> (TVar 0))), ("S", (s_, ((TVar 0) :-> (TVar 1) :-> (TVar 2)) :-> ((TVar 0) :-> (TVar 1)) :-> (TVar 0) :-> (TVar 2))), ("Add", (add, TInt :-> TInt :-> TInt)), -- ("Y", (y_, (TVar 0 :-> TVar 0) :-> TVar 0)), ("Uno", (LitInt 1, TInt))] -- Some primitives to play with s_ = Func (\x -> Func (\y -> Func (\z -> App (App x z) (App y z)))) k_ = Func (\x -> Func (\_ -> x)) i_ = Func (\x -> x) y_ = Func (\f -> let x = (App f x) in x) b_ = Func (\f -> Func (\g -> Func (\x -> App f (App g x)))) add = Func (\x -> Func (\y -> case (eval x,eval y) of ((LitInt x', LitInt y')) -> LitInt $ x' + y' _ -> error "Addition applied to non integers not implemented")) -- | given a Type and a list of constraints for that type, and another primitive type and the next available type variable, -- return a new next available type variable, the type of the primitive and a new list of constraints, if the type -- is unifiable. primitiveUnifies :: (Monad m, Functor m) => Type -> [Constraint] -> Type -> TVName -> m (TVName, Type, [Constraint]) primitiveUnifies t1 cs t2 nvar = fmap construct (unify $ (t2',t1):cs) where (nvar',t2',_) = substvars nvar t2 [] construct x = (nvar', t2', x) -- | Given a type, the next available type variable, and a list of constraints, -- return a list of primitives which unify to that type, the type of the primitive, a new next available -- type variable, and a new list of constraints findTypeMatch :: Type -> TVName -> [Constraint] -> [(String, Type, TVName, [Constraint])] findTypeMatch t nvar c = foldr foldFunc [] primitives where construct name (nvar', ty, constr) = (name, ty, nvar', constr) foldFunc (name,(_,ty)) xs = let result = primitiveUnifies t c ty nvar in maybe xs (:xs) $ fmap (construct name) result -- | Give the depth of the tree, they type to return, the next available type variable, a list of constraints on type variables, -- and a random generator, and this will return a list of full-depth trees meeting those constraints from the primitives. growFullTree :: Int -> Type -> TVName -> [Constraint] -> StdGen -> [(Exp, TVName, [Constraint], StdGen)] growFullTree 0 ty nvar c g | optionlist == [] = mzero | otherwise = do (func, _, nvar', c') <- optionlist return (Prim func, nvar', c', g') where (optionlist, g') = shuffle (findTypeMatch ty nvar c) g growFullTree depth ty nvar c g = do (func, nvar', c', g') <- growFullTree (depth - 1) (TVar nvar :-> ty) (getNextName nvar) c g (param, nvar'', c'', g'') <- growFullTree (depth - 1) (TVar nvar) nvar' c' g' return ((App func param), nvar'', c'', g'') -- | Insert a value into a list at the given index insert_ix :: Int -> a -> [a] -> [a] insert_ix 0 a lst = a : lst insert_ix (k + 1) a (l:ls) = l : insert_ix k a ls -- | insert a value into a list at a random index insert_rand :: (RandomGen g) => a -> [a] -> g -> ([a], g) insert_rand a lst g1 = let (ix,g2) = randomR (0,length lst) g1 in (insert_ix ix a lst, g2) -- | Shuffle a list shuffle :: (RandomGen g) => [a] -> g -> ([a], g) shuffle [] g1 = ([], g1) shuffle (x:xs) g1 = let (xs', g2) = shuffle xs g1 in insert_rand x xs' g2

2 1

Re: [Haskell] Fixpoint combinator without recursion
by Stefan Holdermans 05 Apr '07

05 Apr '07

Mike, > For those of us who aren't type theorists: What's a "negative > datatype"? A type that has a recursive call in negative position. Negative positions are the argument positions in function types. (But if a function type appears in a negative position, then its own argument position is denoted positive and its result position negative.) Cheers, Stefan

1 0

ReadP - take first succesful parser ?
by Marc Weber 04 Apr '07

04 Apr '07

Brief: I want to make the parser choice [string "dummy", anystring ] where anystring = many get return the first match. (Thus if "dummy" matches disregarg all following parsers) ..) details: I want to parse some wmii events. They all look this way ClientFocus 2 ClientFocus 2 LeftBarClick 1 web At this moment I only need two of them (FocusTag and UnfocusTag) So I've created the data type type O = String data WMIIEvent = FocusTag Int | UnfocusTag Int | Unkown String -- to be implemented Now I want to create a simple ReadP parser which looks like this: ============= parser code ============================================ instance Read WmiiEvent where readsPrec _ = readP_to_S (foldr1 takeFirst [ rp "FocusTag" FocusTag , rp "UnfocusTag" UnfocusTag , rpUnkown ]) where rp str f = fmap f $ string str >> skipSpaces >> liftM read (many get) rp :: (Read a) => String -> (a -> WmiiEvent) -> ReadP WmiiEvent rpUnkown = (many get) >>= return . Unkown rpUnkown :: ReadP WmiiEvent But I'm getting an ambiguous parse. (because "UnfocusTag 3" makes two parsers of the choice list succeed. How is this done?

1 1

QuickCheck's co-arbitrary
by Joel Reymont 04 Apr '07

04 Apr '07

Folks, I understand that arbitrary defines the possible values. How do I generally come up with co-arbitrary, though? Would someone kindly explain the choice of co-arbitrary in the following cases, specially the very last bit with "variant 1 . coarbitrary a"? instance Arbitrary Char where arbitrary = elements ([' ', '\n', '\0'] ++ ['a'..'h']) coarbitrary c = variant (fromEnum c `rem` 4) instance Arbitrary Ordering where arbitrary = elements [LT, EQ, GT] coarbitrary LT = variant 0 coarbitrary EQ = variant 1 coarbitrary GT = variant 2 instance Arbitrary a => Arbitrary (Maybe a) where arbitrary = frequency [ (1, return Nothing) , (3, liftM Just arbitrary) ] coarbitrary Nothing = variant 0 coarbitrary (Just a) = variant 1 . coarbitrary a Thanks, Joel -- http://wagerlabs.com/

2 1

Which pretty printer?
by Joel Reymont 04 Apr '07

04 Apr '07

Should I prefer Daan Leijen's pretty printer [1] to the Hughes-SPJ one that comes with GHC? Has anyone looked at both and is able to tell the difference? I need to pretty-print a Pascal-like language as well as C#. Thanks, Joel [1] http://www.cs.uu.nl/~daan/download/pprint/pprint.html -- http://wagerlabs.com/

1 1

Josephus problem and style
by Anthony Chaumas-Pellet 04 Apr '07

04 Apr '07

Hello, I've written a function to compute the general Josephus problem, giving both the number of the survivor and the order in which the others are killed. However, I am not overly fond of my actual Haskell implementation, so I would like some comments on elegance. My current function is as follow:: josephus k n = josephus' k 1 [1..n] [] where josephus' k i (x:xs) sorted | xs == [] = (x, reverse sorted) | i `mod` k == 0 = josephus' k (i+1) xs ([x] ++ sorted) | otherwise = josephus' k (i+1) (xs ++ [x]) sorted The biggest difficulty I had is representing the circle (a continuous unit, unlike the list). The only solution I've found is to explicitly concatenate lists during each iteration, using an index to check whether the current element should be kept. It seems to me that manupilating lists so often makes the resulting function unclear, and hides the basic principle behind the Josephus sequence. So, I'm looking for a better way to write this function, but enlightenment eludes me. I've taken up Haskell in earnest a couple weeks ago, after a fairly long stay in Lisp land (perhaps it shows). My previous "Eureka!" moment in Haskell was matrix multiplication, along the lines of: matProd a b = [[sum (zipWith (*) x y) | y <- transpose b]| x <- a] Thanks! Anthony Chaumas-Pellet

7 8

Memory leak in streaming parser
by Oren Ben-Kiki 04 Apr '07

04 Apr '07

I refactored the code and uploaded a new version to Hackage (YamlReference-0.2). It is cleaner now and much more efficient. It is still "leaking" memory though. The profiler hints at "bindReply" as the culprit retaining State and Reply objects, but it isn't clear to me why the code would do that. Trying to `seq` things again either kills streaming or has no effect. Perhaps my basic approach is wrong... Any advice would be appreciated, Oren Ben-Kiki

1 0

SmallCheck and parser testing
by Joel Reymont 04 Apr '07

04 Apr '07

Folks, I'm trying to figure out how to test a Parsec-based parser with Smallcheck [1]. My test AST is below and the goal is to return StyleValue <Int here> if the parser is fed an integer, or return Solid when parsing "Solid", etc. data Style = StyleValue Expr | Solid | Dashed | Dotted | Dashed2 | Dashed3 deriving Show I figure that the following is needed somehow: instance Serial Style where series = cons1 StyleValue . depth 0 \/ cons0 Solid \/ cons0 Dashed \/ cons0 Dashed2 \/ cons0 Dashed3 \/ cons0 Dotted My parser is 'style', so I would be passing it as p below run p input = case (parse p "" input) of Left err -> do { putStr "parse error at " ; print err } Right x -> x How do I go from here to making sure my parser is valid? I thought of the following property (thanks sjanssen) prop_parse p s = show (run p s) == s but I don't know how to proceed from here. Thanks, Joel [1] http://www.cs.york.ac.uk/fp/darcs/smallcheck/ -- http://wagerlabs.com/

3 2

A question about functional dependencies and existential quantification
by oleg＠pobox.com 04 Apr '07

04 Apr '07

Jean-Marie Gaillourdet wrote > I am trying to do something like the following: > > {-# OPTIONS -fglasgow-exts -fallow-undecidable-instances #-} > > module TestCase where > > > > data Any root = forall pos sel . T root pos sel => ANY pos > > > > class T root pos sel | pos -> root, root -> sel where > > f :: pos -> sel -> Bool > > > > instance T root (Any root) sel where > > f (ANY p) s = f p s The code as posted seems to have a problem. The problem is noted by GHC 6.4 and hugs but is accepted by GHC 6.6. Such a change in GHC seems strange. The problem is not related to existentials, so we just drop them > {-# OPTIONS -fglasgow-exts -fallow-undecidable-instances #-} > module TestCase where > > data Any root = ANY > > class T root pos sel | pos -> root, root -> sel where > f :: pos -> sel -> Bool > instance T root (Any root) sel > > test x = f ANY x Hugs and GHC 6.4 both complain about the instance of T: Hush (September 2006 version) says ERROR "/tmp/j.hs":9 - Instance is more general than a dependency allows and GHC 6.4.2 says Illegal instance declaration for `T root (Any root) sel' (the instance types do not agree with the functional dependencies of the class) In the instance declaration for `T root (Any root) sel' I concur. The class declares T as being a ternary relation such that the following holds forall r p p' s s'. T(r,p,s) && T(r,p',s') -> s = s' Now, the instance `T root (Any root) sel' is satisfied when root=Int, sel = Bool and when root=Int, sel = Int. Does it not? That falsifies the above proposition. In other words, the instance T is not functional with respect to the first and the third arguments. That is not surprising. What is surprising is why GHC 6.6 accepts such an instance?

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Re: [Haskell-cafe] Why the Prelude must die
by Vivian McPhail 03 Apr '07

03 Apr '07

I agree with Sven, but... What I want to push is a 'mathematically sound' numeric prelude. A proper numerical prelude should have bona fide mathematical obects like groups, rings, and fields underlying common numerical classes. It would be edifying to the student who discovered that the particular data type he is using is an inhabitant of a known class and can thus take advantage of known properties, presupplied as class methods. Reasoning and communication about programs, data types, and functions would be enhanced. [Conjecture 1 (2007). Haskell Mathematical Prelude and Mathematicians] If Haskell had a mathematically sound prelude then more mathematicians would use Haskell. Cheers, Vivian > > Message: 1 > Date: Sat, 24 Mar 2007 17:56:11 +0100 > From: Sven Panne <sven.panne(a)aedion.de> > Subject: Re: [Haskell-cafe] Why the Prelude must die > To: haskell-cafe(a)haskell.org > Cc: libraries(a)haskell.org > Message-ID: <200703241756.11121.sven.panne(a)aedion.de> > Content-Type: text/plain; charset="iso-8859-1" > > On Saturday 24 March 2007 03:48, Stefan O'Rear wrote: > > 1. Namespace pollution > > > > The Prelude uses many simple and obvious names. Most > programs don't > > use the whole Prelude, so names that aren't needed take up > namespace > > with no benefit. [...] > > Even though I think that the current Prelude is far from > perfect, one should not forget that is a very solid > foundation of a "common language": If one sees e.g. '(.)' or > 'map', it is immediately clear to everybody what this means, > without having to scan through (perhaps long) import lists. > Of course one could hide some parts of the Prelude etc., but > I think in the long run this only leads to confusion. > Redefining common things, heavy use of tons of self-defined > operators etc. all make maintenance much harder. > > Try reading Lisp code with heavy use of macros or C++ code > with tons of overloadings. This is more like Sudoku solving > than anything else, because there is no "common language" > between the author and the reader anymore. > > And taking away the prelude is a little bit like taking away > 'int', 'double', 'for', 'while' etc. from the C programmer... > > > 11. Committeeism > > > > Because the Prelude has such a wide audience, a strong committee > > effect exists on any change to it. This is the worst kind of > > committeeism, and impedes real progress while polluting the Prelude > > with little-used features such as fail in Monad (as opposed to > > MonadZero) and until. > > Depending on your viewpoint, you can see this as a plus. > Everybody agrees that finalizers are evil, but propose the > removal of that method from java.lang.Object to the Java people. :-) > > My proposal would be to incrementally improve the Prelude, > modularize it a bit more, fix the Num hierarchy, but > basically leave it as it is. > > Cheers, > S. > >

13 14

ANN: HSH 1.2.0
by John Goerzen 03 Apr '07

03 Apr '07

Hi, I'm pleased to announce HSH 1.2.0. Since version 1.0.0 was announced a few days ago, there have been some improvements: * run is now a function with a polymorphic return type. Depending on the value expected, it can return to you a String representing all output, an exit code, a list of lines of output, etc. runS is now removed. * A number of new helper functions in ShellEquivs. Fixes to readlink and readlinkabs there. * New helper functions runIO (to force an IO () context) and runSL (returns a single line of output, \n stripped) * There are now 82 unit tests. Get it at: http://software.complete.org/hsh -- John Goerzen Author, Foundations of Python Network Programming http://www.amazon.com/exec/obidos/tg/detail/-/1590593715

10 29

was Re: ANN: HSH 1.2.0
by Thomas Hartman 03 Apr '07

03 Apr '07

I'm still trying to figure out how to do this on ubuntu. If this winds up being a garden path I'll try on debian next, but at least I'm learning a lot about getting haskell stuff built. Anyway, since I'm on a virtualized linux box, I decided to get a fresh start, unmounted my original OS profile and installed a fresh dapper 6. I then changed /etc/apt/sources.list to be okay for grabbing .debs from feisty. (No longer doing the build from source thing.) apt-get install ghc6, ok from feisty. (Is there another repo that gets all the extra libs at one go?) sudo apt-cache search -o APT::Cache-Limit=25165824 ghc6 | grep -i missing libghc6-hdbc-missingh-dev - Integration of HDBC with MissingH, GHC version libghc6-missingh-dev - Library of utility functions for Haskell, GHC6 package thartman@linodehaskell:~/haskellinstalls/hsh>sudo apt-cache search -o hoorah, my apt cache search command seems ok. sudo apt-cache search -o APT::Cache-Limit=25165824 ghc6 | grep -i hsh thartman@linodehaskell:~/haskellinstalls/hsh> too bad, still no hsh in ubuntu repo. darcs get http://darcs.complete.org/hsh/ (Or should I have used something else?) runghc Setup.hs configure same problems as before. But starting afresh seems to have detangled the issues I was having with packaging confusion. At least now I can apt-get install missingh And some other dependency following is made easier. Finally configure for hsh works. But then thartman@linodehaskell:~/haskellinstalls/hsh>sudo runghc Setup.lhs install Setup.lhs: Warning: The field "hs-source-dir" is deprecated, please use hs-source-dirs. Installing: /usr/local/lib/HSH-1.2.1/ghc-6.6 & /usr/local/bin HSH-1.2.1... Setup.lhs: Error: Could not find module: HSH with any suffix: ["hi"] So, I seem to be stuck at this point. 2007/4/2, Thomas Hartman <tphyahoo(a)gmail.com>: > Well, I guess I spoke to soon. After building ghc6 from feisty as > described above, I tried building missingh and have basically what I > started with. > > Is there something I can tweak to get the above straightened out using > those nice deb packages, or do I have to do all the dependency chasing > involved with building from source? Or is there another way? > > If this is too debian oriented please yell at me and I will ask about > this on a deb/ubuntu forum. > > thanks... > > Note, should have mentioned, after doing as my above post describes, I > installed all the newly generated deb packages with > > dpkg -i *.deb > > **************** > > thartman@linodewhyou:~/haskellInstalls/missingh>runghc Setup.hs configure > Configuring MissingH-0.18.3... > configure: /usr/lib/ghc-6.6/bin/ghc-pkg > configure: Dependency unix-any: using unix-1.0 > Setup.hs: cannot satisfy dependency network-any > > thartman@linodewhyou:~/haskellInstalls/missingh>which runghc > /usr/lib/ghc-6.6/bin/runghc > > # note, definitely the thing I installed today: > thartman@linodewhyou:~/haskellInstalls/missingh>ls -l `which runghc` > -rwxr-xr-x 1 root root 300716 Apr 2 09:17 /usr/lib/ghc-6.6/bin/runghc > thartman@linodewhyou:~/haskellInstalls/missingh> > > # and I installed it from deb ghc6, dpkg recognizes it > > thartman@linodewhyou:~/haskellInstalls/missingh>dpkg -S > /usr/lib/ghc-6.6/bin/runghc > ghc6: /usr/lib/ghc-6.6/bin/runghc > > # it does seem like ghc6 comes with a network package > thartman@linodewhyou:~/learning/haskell>apt-cache showpkg ghc6 | grep -i network > 6.4.1-2ubuntu2 - libghc6-readline-dev libghc6-stm-dev libghc6-hgl-dev > libghc6-x11-dev libghc6-fgl-dev libghc6-mtl-dev libghc6-hunit-dev > libghc6-quickcheck-dev libghc6-network-dev libghc6-haskell-src-dev > libghc6-parsec-dev libghc6-cabal-dev libghc6-unix-dev > libghc6-template-haskell-dev libghc6-haskell98-dev libghc6-base-dev > libghc6-rts-dev ghc haskell-compiler > > # I get lost here. Do I have libghc6-network-dev, or don't I? > > thartman@linodewhyou:~/haskellInstalls/missingh>sudo apt-get install > libghc6-network-dev > Reading package lists... Done > Building dependency tree... Done > Note, selecting ghc6 instead of libghc6-network-dev > ghc6 is already the newest version. > You might want to run `apt-get -f install' to correct these: > The following packages have unmet dependencies: > hat-ghc6: Depends: ghc6 (< 6.4.1+) but 6.6-3 is to be installed > libghc6-cabal-dev: Depends: ghc6 (< 6.4.2) but 6.6-3 is to be installed > E: Unmet dependencies. Try 'apt-get -f install' with no packages (or > specify a solution). > > > > > > > 2007/4/2, Thomas Hartman <tphyahoo(a)gmail.com>: > > > As you have built ghc6.6 from sources I think that you also need to build > > > all haskell libs from sources. So, do > > > > I did this, and got the feeling this would probably work, but is a > > real sad world of dependency chasing with no (clear) end in sight. > > > > So I investigated your second suggestion > > > > > Another way is to take ghc6 and all haskell libs from fiesty. > > > > which to me seems much preferrable. > > > > http://old.pupeno.com/blog/unstable-packages-on-ubuntu/ > > > > Was indispensible in helping me figure out how to do this. > > > > To give some details on this (which is really more apt packaging know > > how than haskell but whatever), I did something like > > > > 1) change /etc/apt/sources.list to add > > > > deb-src http://archive.ubuntu.com/ubuntu/ feisty main restricted > > universe multiverse > > > > note, only add deb-src line here, not deb line, see article above for why. > > > > sudo aptitude install fakeroot (needed utility) > > fakeroot apt-get source --build ghc6 > > -- complains, some dependencies are missing > > > > sudo aptitude install ..... > > install packages with above command, not from source. it's my first > > time using the aptitude command, I wonder if this does the same thing > > as apt-get install, which is what I usually do. Whatever the case... > > > > fakeroot apt-get source --build ghc6 > > > > works :) > > > > 2007/3/21, Max Vasin <max.vasin(a)gmail.com>: > > > >>>>> "Thomas" == Thomas Hartman <tphyahoo(a)gmail.com> writes: > > > > > > Thomas> Furthermore (as the above messages suggest and locate confirms), I > > > Thomas> seem to have mtl already > > > > > > Thomas> I took a wild guess and tried specifying this with ghc -i > > > > > > Thomas> like > > > > > > Thomas> sudo runghc -i/usr/lib/ghc6-mtl-dev Setup.lhs configure > > > Thomas> and sudo runghc -i/usr/lib/ Setup.lhs configure > > > > > > Thomas> but no dice. > > > > > > Thomas> *************** > > > > > > Thomas> thartman@linodewhyou:~/haskellInstalls/hsh$ locate libghc6-mtl-dev > > > Thomas> /home/thartman/libghc6-mtl-dev_1.0-3_i386.deb > > > Thomas> /usr/lib/libghc6-mtl-dev > > > Thomas> /usr/lib/libghc6-mtl-dev/register.sh > > > Thomas> /usr/lib/libghc6-mtl-dev/unregister.sh > > > Thomas> /usr/share/doc/libghc6-mtl-dev > > > Thomas> /usr/share/doc/libghc6-mtl-dev/changelog.Debian.gz > > > Thomas> /usr/share/doc/libghc6-mtl-dev/copyright > > > Thomas> /var/lib/dpkg/info/libghc6-mtl-dev.list > > > Thomas> /var/lib/dpkg/info/libghc6-mtl-dev.md5sums > > > Thomas> /var/lib/dpkg/info/libghc6-mtl-dev.postinst > > > Thomas> /var/lib/dpkg/info/libghc6-mtl-dev.prerm > > > > > > As you have built ghc6.6 from sources I think that you also need to build > > > all haskell libs from sources. So, do > > > > > > $ apt-get source libghc6-mtl-dev > > > $ cd <haskell-mtl-or-whatever-dir-is-named> > > > $ runhaskell Setup.lhs configure > > > $ runhaskell Setup.lhs build > > > $ sudo runhaskell Setup.lhs install > > > > > > Another way is to take ghc6 and all haskell libs from fiesty. > > > > > > -- > > > WBR, > > > Max Vasin. > > > > > > _______________________________________________ > > > Haskell-Cafe mailing list > > > Haskell-Cafe(a)haskell.org > > > http://www.haskell.org/mailman/listinfo/haskell-cafe > > > > > >

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Matlab/BLAS/LAPack and Re: [Haskell-cafe] Mathematics in Haskell Re: Why the Prelude must Die
by Alexander McPhail 03 Apr '07

03 Apr '07

Since I brought this up (search haskell' list) I should probably volunteer to help. If people agree I can coordinate an effort to build a mathematically sound hierarchy. Unfortunately my mathematical knowledge is less than ideal for this purpose (I am actively remedying this at university). However, if there is an administrative burden I volunteer to shoulder it. On a related note I have written a binding to Matlab data files and arrays if anyone is interested, and I am embarking on a project to bind to CBLAS and CLAPack. Vivian > > Jacques Carette wrote: > > > >> perhaps i was mistaken in thinking that there is a group of > >> math-interested haskellers out there discussing, developing, and > >> documenting the area? or perhaps that group needs introductory > >> tutorials presenting its work? > > My guess is that there are a number of people "waiting in > the wings", > > waiting for a critical mass of features to show up before really > > diving in. See http://www.cas.mcmaster.ca/plmms07/ > > for my reasons for being both interested and wary). > > > > Probably the simplest test case is the difficulties that people are > > (still) encountering doing matrix/vector algebra in Haskell. One > > either quickly encounters efficiency issues (although PArr might > > help), or typing issues (though many tricks are known, but not > > necessarily simple). Blitz++ and the STL contributed > heavily to C++ > > being taken seriously by people in the scientific computation > > community. Haskell has even more _potential_, but it is > definitely unrealised potential. > > > > I am one of those mathematicians "waiting in the wings." > Haskell looked > very appealing at first, and the type system seems perfect, > especially for > things like multilinear algebra where currying and duality is > fundamental. > I too was put off by the Num issues though--strange mixture > of sophisticated > category theory and lack of a sensible hierarchy of algebraic objects. > > However, I've decided I'm more interested in helping to fix > it than wait; > so count me in on an effort to make Haskell more > mathematical. For me that > probably starts with the semigroup/group/ring setup, and good > arbitrary-precision as well as approximate linear algebra support. > > -- > > I've been watching this thread for quite a while now, and it seems to > me that there is quite a bit of interest in at least working on a new > Prelude. I've also noticed a 'The Other Prelude' page on the wiki > [http://haskell.org/haskellwiki/The_Other_Prelude] and they seem to > have a start on this. So it seems that we should actually start this, > because people will contribute. Can somebody with good Cabal skills > and maybe access to darcs.haskell.org start a new library for people > to start patching? > > Bryan Burgers > > > > On Apr 2, 2007, at 3:24 PM, Andrzej Jaworski wrote: > > >> I too was put off by the Num issues though--strange mixture of > >> sophisticated > >> category theory and lack of a sensible hierarchy of algebraic > >> objects. > > > > Perhaps we should replace CT with lattice theoretic thinking (e.g. > > functor = monotonic > > function) before cleaning up the type-related mess? > > See: http://citeseer.ist.psu.edu/269479.html > > > >> so count me in on an effort to make Haskell more mathematical. > >> For me that > >> probably starts with the semigroup/group/ring setup, and good > >> arbitrary-precision as well as approximate linear algebra support. > > > > I agree: semigoups like lattices are everywhere. > > Then there could be a uniform treatment of linear algebra, > > polynomial equations, operator > > algebra, etc. So, perhaps haste is not a good advice here? > > > > -Andrzej > >

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Fwd: darcs.haskell.org access for maths hierarchy
by Alexander McPhail 03 Apr '07

03 Apr '07

I have set up a page on the wiki for discussion: http://www.haskell.org/haskellwiki/Haskell_and_mathematics/Hierarchy And about a darcs repo for people to patch against: ---------- Forwarded message ---------- From: Simon Marlow <simonmarhaskell(a)gmail.com> Date: 03-Apr-2007 20:28 Subject: Re: darcs.haskell.org access for maths hierarchy To: Alexander McPhail <haskell.vivian.mcphail(a)gmail.com> Hi there, The plan is to set up a separate server for hosting community projects. Right now we have the server, but we still have to set it up. Hopefully it should be available soon, we'll announce something when it is. Cheers, Simon Alexander McPhail wrote: > Hi, > > There is some movement on the haskell-cafe mailing list to set up a repo > to develop a mathematically sound algebraic class hierarchy. I have > volunteered to coordinate this. > > What is the policy on giving access to darcs.haskell.org > <http://darcs.haskell.org>? > Cheers, > > Vivian > >

1 0

Keeping a symbol table with Parsec
by Joel Reymont 03 Apr '07

03 Apr '07

Folks, Are there any examples of keeping a symbol table with Parsec? I'm translating a parser from OCaml and I do this OUTPUT COLON ID LP NUMERIC_SIMPLE RP { add $3 TypNumOut; SimpleOutputDec ($3, Number) } Meaning that if a keyword Output is followed by ":" and an identifier and then "(NumericSimple)" then add identifier to the symbol table as a Number and box it in a constructor. Then in my lexer I do a lookup to check if I have seen this identifier and if I have seen one of type TypeNumOut I return the token NUM instead of ID. This ensures that I can have rules with the token NUM as opposed to ID everywhere. How would I accomplish the same with Parsec, that is 1) update a symbol table and 2) check identifiers and "return a different token"? Thanks, Joel -- http://wagerlabs.com/

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String to Word64 Conversion
by Dominic Steinitz 03 Apr '07

03 Apr '07

> [Haskell-cafe] String to Word64 Conversion > Ian Sefferman iseff at iseff.com > Sun Apr 1 15:42:07 EDT 2007 > Previous message: [Haskell-cafe] Josephus problem and style > Next message: [Haskell-cafe] Data.ByteStream.Char8.words performance > Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] > I've been spending a lot of time trying to find a clean way to convert > from a String to a Word64 for the Crypto library. > > Specifically, we're trying to encrypt the strings with Blowfish. The > type for the encrypt function is: > > encrypt :: (Integral a) => a -> Word64 -> Word64 > > I assume I would want something like: > toWord64s :: String -> [Word64] > toWord64s = .... > > myEncrypt string = map (Blowfish.encrypt myKey) (toWord64s string) > > I would have to imagine that encrypting strings is a fairly common > thing to do, so a conversion should be trivial, but I can't seem to > find anything on it. I feel like I must be missing something rather > obvious here. Am I? > > Thanks, > Ian Ian, Maybe something like this. I've pretty much taken it from http://darcs.haskell.org/crypto/Data/Digest/SHA1.hs. fromBytes :: (Bits a) => [a] -> a fromBytes input = let dofb accum [] = accum dofb accum (x:xs) = dofb ((shiftL accum 8) .|. x) xs in dofb 0 input blockWord8sIn64 :: [Word8] -> [[Word8]] blockWord8sIn64 = unfoldr g where g [] = Nothing g xs = Just (splitAt 8 xs) getWord64s :: [Word8] -> [Word64] getWord64s = map fromBytes . map (map fromIntegral) . blockWord8sIn64 Don't forget you will need to pad http://www.haskell.org/crypto/doc/html/Codec.Encryption.Padding.html. I don't know what your application is but I suggest NOT using ECB mode which your code suggests you are thinking of doing. The only mode currently supported in the crypto library is CBC but other modes should be trivial to add. Dominic.

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Binary I/O
by Daniel Brownridge 02 Apr '07

02 Apr '07

Hello. I am a Computer Science student attempting to write an emulator using Haskell. One of my main design choices is how to deal with machine code. Clearly it is possible to represent 0's and 1's as ASCII characters, however it strikes me that it would be much nicer to the I/O using raw binary. I don't seem to be able to find much documentation on this. Does anybody know how it's done, or can point me in the direction of some resources. Many thanks Daniel

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Re: [Haskell-cafe] Memory leak in streaming parser
by Oren Ben-Kiki 02 Apr '07

02 Apr '07

On Mon, 2007-04-02 at 13:54 +0100, Malcolm Wallace wrote: > An observation about your state setter functions, ... > You can shorten your code considerably by using the standard named-field > update syntax for exactly this task: > > setDecision :: String -> State -> State > setDecision decision state = state { sDecision = decision } If I do that, the run time insists on the state being "more" evaluated before it changes that specific field. This kills streaming, enforcing each production (including the top one) to be fully parsed before I can access its generated tokens. So the GC won't be hanging on to State objects, but memory still explodes - with unconsumed Token objects. And there's no output from the program until it dies :-( > Not only is it shorter, but it will often be much more efficient, since > the entire structured value is copied once once, then a single field > updated, rather than being re-built piece-by-piece in 15 steps. I know! Is there an efficient way to lazily modify just one field record? > You probably want to be strict in the state component, but not in the > output values of your monad. So as well as replacing > let ... in (finalState, rightResult) > with > let ... in finalState `seq` (finalState, rightResult) > in the (>>=) method in your Monad instance (and in the separate defn of For some strange reason, adding this didn't solve the problem - the GC still refuses to collect the state objects. BTW, forcing the evaluation of the intermediate states (originalState, leftState, rightState etc.) doesn't help either. I have tried to ensure that when '>>=' and '/' will allow the GC to discard old states "as soon as possible", but I'm obviously missing something. Is there a way to get more detailed retainer information than what's available with '-hr'? > you might also need to make all the named fields of your State datatype > strict. If I make any of them strict, streaming goes away :-( Writing a streaming parser in Haskell is turning out to be much harder than I originally expected. Every fix I tried so far either broke streaming (memory blows up due to tokens) or had no effect (memory blows up due to states). I am assuming that there's a magic point in the middle where tokens are consumed and states are GC-ed... but it has eluded me so far. Thanks, Oren Ben-Kiki P.S. I uploaded the package to Hackage. I added a debug-leak production to make it easier to profile this with even less productions involved. ``yes '#' | yaml2yeast -p debug-leak''.

1 0

Memory leak in streaming parser
by Oren Ben-Kiki 02 Apr '07

02 Apr '07

I just created an initial version of a "streaming" parser. This parser is intended to serve as a reference parser for the YAML spec. Efficiency isn't the main concern; the priority was to have it use the BNF productions from the spec without any changes (ok, with tiny, minor, insignificant changes :-) and to allow it to stream large files. I'm happy to say I achieved the first goal, and the parser .hs file simply #includes a file that is, for all intents and purposes, a BNF file. I didn't have as much luck with the second goal. After putting a lot of effort into it, I have got to the point it is "streaming". That is, I can "cat" a large YAML file to the wrapper program and it will "immediately" start spitting out parsed tokens. This took some doing to ensure the resulting token stream is accessible while it is being generated, in the presence of potential parsing failures and, of course, parsing decision points. I must have done "too good a job" converting things to lazy form because, while the parser is streaming, it also hangs on to old state objects for no "obvious" reason. At least it isn't obvious to me after profiling it in any way I could think of and trying to `seq` the "obvious" suspects. Adding a `seq` in the wrong place will of course stop it from being a streaming parser... I'd take it as a kindness if someone who had some deeper knowledge of the Haskell internals would peek at it. It is packaged as Cabal .tar.gz file in http://www.ben-kiki.org/oren/YamlReference - it includes the wrapper program and a regression-test program. To watch it consume all available memory using a very small set of BNF productions, yes '#' | yaml2yeast -p s-l-comments (This basically matches "l-comment*" - each '#\n' is a comment line). You'll get a stream of parsed tokens to stdout and an ever-climbing memory usage in top (or htop). Any advice would be appreciated, Oren Ben-Kiki

2 1

Mutable variables eliminated from .NET | Lambda the Ultimate
by dons＠cse.unsw.edu.au 02 Apr '07

02 Apr '07

As seen on reputable language news site, Lambda the Ultimate. http://lambda-the-ultimate.org/node/2164 Mutable variables eliminated from .NET Redmond, WA: At an unusual press conference held this Sunday morning, Bill Taylor, Microsoft's General Manager of Platform Strategy, announced that after much research into the causes of security holes and instabilities, Microsoft will eliminate mutable variables from the .NET platform and its languages, including C# and VB.NET. "One of our top researchers found that mutable variables were the major root cause preventing us from achieving the great user experience we always strive to deliver," said Taylor. "Once we realized that, eliminating them from .NET was a no-brainer." Given that this announcement was made on a Sunday, reactions have been limited so far, but one prominent VB.NET developer commented that "Compared to the switch from VB6 to VB.NET, this ought to be a breeze." A C# developer was heard to say, "After anonymous delegates, monads shouldn't be a problem." To ensure wide penetration of this significant update, Microsoft will be issuing updated Windows CDs to all licensed customers, free of charge. The new CDs can be identified by the distinctive holographic "Haskell Inside" logo, featuring a holographic version of this[1] portrait of Simon Peyton-Jones, grinning from ear to ear. [1] http://research.microsoft.com/~simonpj/GIFs/spj-snow.jpg

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Re: [Haskell-cafe] ghc-6.7.20070330 on Mac OS X
by Ruben Zilibowitz 02 Apr '07

02 Apr '07

Hi, I managed to build it eventually using the instructions on: http://hackage.haskell.org/trac/ghc/wiki/Building/MacOSX Sorry to Greg - I accidentally sent this to your personal email address first. Ruben On 02/04/2007, at 4:34 AM, Gregory Wright wrote: > > Hi Ruben, > > The GHC wiki also has information on this, and should be your first > stop if you are experiencing build problems: > > http://hackage.haskell.org/trac/ghc/wiki/Building/MacOSX > > At least under MacPorts, I have had no trouble building 6.7-20070330. > I will be releasing a new portfile for ghc-devel in a few days that > will > build the latest from the darcs repository. > > Best Wishes, > Greg > > On Apr 1, 2007, at 11:50 AM, Pepe Iborra wrote: > >> (redirecting to glasgow-haskell-users) >> >> It is well known that the readline lib that comes with OS X is no >> good, and you need to use a replacement. A nice post from the >> blogosphere explaining all this: >> >> http://mult.ifario.us/articles/2006/10/17/ghc-6-6-and-mac-os-x- >> readline-quick-fix >> >> If that doesn't help, please post the errors that you get when >> building the readline package. >> >> Cheers >> pepe >> >

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Re: [Haskell-cafe] Data.ByteStream.Char8.words performance
by Duncan Coutts 02 Apr '07

02 Apr '07

On Sun, 2007-04-01 at 17:25 +0200, Thomas Schilling wrote: > On 31 mar 2007, at 04.09, Duncan Coutts wrote: > > > > The ByteString libs was more-or-less the first high performance thing > > that we wrote and we've learnt plenty more since then. I think > > there's a > > good deal more performance too eek out of it yet, both at the low and > > high level. > > Is there some document available explaining those findings (other > than the ByteString paper)? Not yet. Duncan

1 0

String to Word64 Conversion
by Ian Sefferman 02 Apr '07

02 Apr '07

I've been spending a lot of time trying to find a clean way to convert from a String to a Word64 for the Crypto library. Specifically, we're trying to encrypt the strings with Blowfish. The type for the encrypt function is: encrypt :: (Integral a) => a -> Word64 -> Word64 I assume I would want something like: toWord64s :: String -> [Word64] toWord64s = .... myEncrypt string = map (Blowfish.encrypt myKey) (toWord64s string) I would have to imagine that encrypting strings is a fairly common thing to do, so a conversion should be trivial, but I can't seem to find anything on it. I feel like I must be missing something rather obvious here. Am I? Thanks, Ian

1 0

ghc-6.7.20070330 on Mac OS X
by Ruben Zilibowitz 01 Apr '07

01 Apr '07

I am trying to build this version of GHC on Mac OS X. I'm currently using GHC 6.6. The build is failing with the following error: ghci/InteractiveUI.hs:69:7: Could not find module `System.Console.Readline': Use -v to see a list of the files searched for. <<ghc: 310591992 bytes, 51 GCs, 4238510/9457140 avg/max bytes residency (4 samples), 26M in use, 0.02 INIT (0.00 elapsed), 2.11 MUT (15.73 elapsed), 0.31 GC (0.36 elapsed) :ghc>> make[2]: *** [depend] Error 1 make[1]: *** [stage2] Error 2 make: *** [bootstrap2] Error 2 So it seems I need to install the Readline library. But building the Readline library is also giving me errors on my system. Just wondering if someone else has managed to build ghc-6.7.x on Mac OS X? If so, what did you need to do? Cheers, Ruben

1 0

Why the Prelude must die
by Stefan O'Rear 01 Apr '07

01 Apr '07

This is a ranty request for comments, and the more replies the better. 1. Namespace pollution The Prelude uses many simple and obvious names. Most programs don't use the whole Prelude, so names that aren't needed take up namespace with no benefit. 2. Monomorphism The Prelude defines many data types (e.g Lists), and operations on these types. Because the Prelude is imported automatically, programmers are encouraged to write their programs in terms of non-overloaded operators. These programs then fail to generalize. This is a highly non-academic concern. Many widely used libraries, such as Parsec, operate only on lists and not the newer and more efficient sequence types, such as bytestrings. 3. Supports obsolete programming styles The Prelude uses, and by means of type classes encourages, obsolete and naive programming styles. By providing short functions such as nub automatically while forcing imports to use sets, the Prelude insidiously motivates programmers to treat lists as if they were sets, maps, etc. This makes Haskell programs even slower than the inherent highlevelness of laziness requires; real programs use nub and pay dearly. More damagingly, the Prelude encourages programmers to use backtracking parsers. Moore's law can save you from nub, but it will never clarify "Prelude.read: no parse". 4. Stagnation Because every program uses the Prelude, every program depends on the Prelude. Nobody will willingly propose to alter it. (This is of course Bad; I hope Haskell' will take the fleeting opportunity to break to loop) 5. Inflexibility Because of Haskell's early binding, the Prelude always uses the implementation of modules that exists where the Prelude was compiled. You cannot replace modules with better ones. 6. Dependency Because every module imports the Prelude every module that the Prelude depends on, mutually depends with the Prelude. This creates huge dependency groups and general nightmares for library maintainers. 7. Monolithicity Every module the Prelude uses MUST be in base. Even if packages could be mutually recursive, it would be very difficult to upgrade any of the Prelude's codependents. 8. Monolithic itself Because the Prelude handles virtually everything, it is very large and cannot be upgraded or replaced piecemeal. Old and new prelude parts cannot coexist. 9. One-size-fits-all-ism Because the Prelude must satisfy everyone, it cannot be powerful, because doing so would harm error messages. Many desirable features of Haskell, such as overloaded map, have been abandoned because the Prelude needed to provide crutches for newbies. 10. Portability Because the Prelude must be available everywhere, it is forced to use only least-common-denominator features in its interface. Monad and Functor use constructor classes, even though MPTC/FD is usefully far more flexible. The Class_system_extension_proposal, while IMO extremely well designed and capable of alleviating most of our class hierarchy woes, cannot be adopted. 11. Committeeism Because the Prelude has such a wide audience, a strong committee effect exists on any change to it. This is the worst kind of committeeism, and impedes real progress while polluting the Prelude with little-used features such as fail in Monad (as opposed to MonadZero) and until. 12. There is no escape Any technical defect in Map could be fixed by someone writing a better Map; this has happened, and the result has been accepted. Defects in the PackedString library have been fixed, with the creation and adoption of ByteString. Defects in System.Time have been fixed, by the creation and adoption of Data.Time. Ditto for Binary and Arrays and Network and Regex. But this will never happen for the Prelude. A replacement Prelude cannot be adopted because it is so easy to take the implicit import of the default one. Nobody will go out of their way to 'import Prelude() ; import FixedPrelude'. Psychology trumps engineering. 13. There can be no escape The Prelude was designed by extremely smart people and was considered close to perfect at the time. It is almost universally hated now. Even if all the issues I describe could be fixed (which I consider unlikely), the Prelude will almost certainly be hated just as universally five years hence. 14. My future Given all these issues, I consider the only reasonable option is to discard the Prelude entirely. There will be no magic modules. Everything will be an ordinary library. HOFs like (.) are available from Control.Function. List ops come from Data.List. Any general abstractions can be added in abstract Sequence, Monad, etc. modules. Haskell will regain the kind of organic evolution whose lack currently causes Haskell to lose its lead over Python et al by the day. Stefan

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HGL on Mac OS X
by Ruben Zilibowitz 01 Apr '07

01 Apr '07

Hi, Has anyone got the GHC module HGL to work on Mac OS X? If so I'd be very interested to know how. Cheers, Ruben

2 1

Parsing words with parsec
by paolino 31 Mar '07

31 Mar '07

Hi, I had a bad time trying to parse the words of a text. I suspect I miss some parsec knowledge. In the end it seems working, though I haven't tested much and this example contains the main features I was looking. *Main> parseTest (parseLine eof) "paolo@gmail sara,mimmo! 9ab a9b ab9 cd\n" ["paolo@gmail","sara","mimmo","cd"] --------------------- manyTillT body terminator joiner = liftM2 joiner (manyTill body (lookAhead terminator)) terminator wordChar = letter <|> oneOf "_@" <?> "a valid word character" nonSeparator = wordChar <|> digit wordEnd = do x <- wordChar notFollowedBy nonSeparator return x word = manyTillT wordChar (try wordEnd) (\b t -> b ++ [t]) <?> "a word" wordStart = do (try nonSeparator >> unexpected "non separator") <|> anyChar lookAhead wordChar nextWord = manyTill anyChar (try wordStart) >> (try word <|> nextWord) parseLine end = do f <- option [] $ return `fmap` try word r <- many $ try nextWord manyTill anyChar end return (f ++ r) ----------- Any comment to simplify this code is welcome. Paolino.

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Data.ByteStream.Char8.words performance
by Dino Morelli 31 Mar '07

31 Mar '07

I noticed something about ByteStream performance that I don't understand. I have a test text document: $ ls -sh test-text-file 956K test-text-file Running this program, using the Prelude's IO functions: > module Main where > > main = do > content <- readFile "test-text-file" > let l = length . words $ content > print l I get: $ time ./a.out 174372 real 0m0.805s user 0m0.720s sys 0m0.008s Running a version of the same thing using Data.ByteStream.Char8: > module Main where > > import qualified Data.ByteString.Char8 as B > > main = do > content <- B.readFile "test-text-file" > let l = length . B.words $ content > print l I see a time that is quite a bit slower: $ time ./a.out 174372 real 0m1.864s user 0m1.596s sys 0m0.012s Changing it to incorporate similar code to the implementation of B.words: > module Main where > > import qualified Data.ByteString.Char8 as B > import Data.Char (isSpace) > > main = do > content <- B.readFile "test-text-file" > let l = length $ filter (not . B.null) $ B.splitWith isSpace > content > print l I see a similar time as with B.words: $ time ./a.out 174372 real 0m1.835s user 0m1.628s sys 0m0.012s And then if I change this to use B.split ' ' instead of isSpace: > module Main where > > import qualified Data.ByteString.Char8 as B > > main = do > content <- B.readFile "test-text-file" > let l = length $ filter (not . B.null) $ B.split ' ' content > print l I get a time that's much more reasonable-looking, compared to the original Prelude.words version: $ time ./a.out 174313 real 0m0.389s user 0m0.312s sys 0m0.004s It seems like the B.splitWith isSpace code is really slow for some reason. Anybody have any idea what's going on? The actual implementation is using isSpaceWord8 which is a case statement looking for a pile of different whitespace characters. -- .~. Dino Morelli /V\ email: dino(a)ui3.info /( )\ irc: dino- ^^-^^ preferred distro: Debian GNU/Linux http://www.debian.org

3 3

Lambdabot not running on XP
by Iain Alexander 31 Mar '07

31 Mar '07

I eventually persuaded Plugin.Pl.Transform.hs to compile by disabling the optimisation, and with other bits of hackery got lambdabot to build. When I run it as lambdabot I get Initialising plugins..... (with lots of '.'s, presumably one '.' per plugin) and then the command prompt returns. There is no sign of a lambdabot running. Any idea where I can start to diagnose what's going wrong? (ghc-6.4.1, lambdabot-4.0, WinXP SP2) -- Iain Alexander ia(a)stryx.demon.co.uk

4 4