[Haskell-cafe] announce: hgdbmi (GDB/MI interface)
Just in case someone else needed this, here you go: GDB/MI lets programs drive GDB. It can be used, for example, by GDB frontends. This module wraps attaching GDB to a process and parsing the (surprisingly complicated) GDB/MI output. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hgdbmi ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] runInteractiveCommand dying uncatchably?
If I run the following program, it never prints "done". If I uncomment the commented line, it does. import Prelude hiding (catch) import Control.Exception import System.Process import System.IO demo = do putStrLn "starting" (inp,out,err,pid) <- runInteractiveCommand "nonesuchcommand" putStrLn "writing to in on bad command" hPutStr inp "whatever" -- putStr "flushing" hFlush inp `catch` \e -> do print e; return () putStrLn "done" main = demo `catch` \e -> do print e; return () On my machine the output is: $ runhaskell test.hs starting writing to in on bad command $ It appears to exit at the hFlush call. (hClose has the same behavior.) I find this surprising -- I'd expect, even if I'm using an API incorrectly, to get an exception. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] parsing c
I'd like to parse some C headers for a toy project. It seems like c2hs probably has the functionality I want, but it's not packaged up as a library. So two questions: Is there an alternative C-parsing library? Has anyone looked into librarifying c2hs's parser? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] announce: (preliminary) dbus haskell bindings
"D-Bus is a message bus system, a simple way for applications to talk to one another." [1] It's particularly popular on free software desktops (Gnome, KDE). HDBus wraps the DBus APIs so your Haskell code can broadcast messages and make calls to services. For example, on my recent Ubuntu system, these bindings are sufficient to pop up balloon-tip-style notifications via a daemon I wasn't previously aware of. Very preliminary code, so please let me know if you find it useful. (Also, I don't know where it's appropriate to announce this, so please direct me to other mailing lists.) Home page: http://neugierig.org/software/hdbus/ Haddock: http://neugierig.org/software/hdbus/doc/ Repository browser: http://neugierig.org/software/darcs/browse/?r=hdbus;a=summary [1] http://www.freedesktop.org/wiki/Software/dbus ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] packaging modules with internal-only functions
I'm writing an FFI bindings module, and one of the pieces from the library I want to wrap is their "Error" type. module Error where To the user of the module, I'd like to only expose the nicely wrapped interface: data Error = Error String String instance Typeable Error where ... -- for throwDyn But within the module's implementation, I need to share some other, internal-only functions: type ErrorTag = () type ErrorP = Ptr ErrorTag withErrorP :: (ErrorP -> IO a) -> IO a Where withErrorP potentially throwDyns an Error, so it needs the first module. What is the proper way to divide these up in terms of package exports? The best options I can figure out are either to split these into multiple modules, or to have my "Error" module export them and mark them not to be documented by haddock... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Windows PowerShell "Monad"
On 7/16/06, Chad Scherrer <[EMAIL PROTECTED]> wrote: On 7/15/06, Krasimir Angelov <[EMAIL PROTECTED]> wrote: > Mostly coincidence. It isn't a good choice for name, I think but the > same is true for .NET. Each time when I am googling for .NET I receive > lots of irrelevant results. The same will happen with Monad now. It's not even a production release yet, and already the mainstream-to-be is taking over the google results. Googling for microsoft monad gives all powershell and no MS Research! Try: [monad site:research.microsoft.com]. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Filtering on data constructors with TH
On 6/1/06, Christophe Poucet <[EMAIL PROTECTED]> wrote: That's why today I have created an automated derivation for data constructor filtering. As I started coding someone mentioned that something similar can be done with list comprehensions, so I'm not certain about the scope of usefulness, however personally I have found the need for this at times. data T = A Int | B String deriving Show test1 = [A 3, B "hello", A 5] test2 = [x | x@(A _) <- test1] The key here is that pattern match failure in a monad calls fail: http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v%3Afail and fail in the List monad is []. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] parsing machine-generated natural text
On 5/21/06, Evan Martin <[EMAIL PROTECTED]> wrote: Thanks! I had looked at using the lexeme parser before but it didn't seem like you can make newlines significant. Upon further consideration I realized that you can mix lexeme-based parsers with "plain" parsers. I think I've mostly figured this out. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] parsing machine-generated natural text
On 5/21/06, Udo Stenzel <[EMAIL PROTECTED]> wrote: do power colon integer reserved "Supply centers," integer reserved "Units:" ((reserved "Builds" >> return id) <|> (reserved "Disbands" >> return negate)) `ap` integer reserved "units." <|> reserved "unit." Come on, it isn't nearly as bad as you make it sound. Use the combinators, they are far more powerful than ugly never-quite-correct regexes. Thanks! I had looked at using the lexeme parser before but it didn't seem like you can make newlines significant. Here's the beginning of the file, where it's not obvious to me how to distinguish elements in the "::" section from the rest of the file. :: Judge: USDP Game: dip Variant: standard :: Deadline: F1901M Mon 20 Feb 2006 20:00 PST :: URL: http://www.diplom.org/dpjudge?game=dip Movement results for Fall of 1901. (dip.F1901M) I guess I could make "Movement" a reserved word? Oh, and drop me a line when your Diplomacy bot is finished. :) It's actually just for rendering nicer maps of the game state. http://neugierig.org/software/hsdip/mapview.html (It's draggable, too.) I was trying to do it with Firefox's SVG+XUL but it's terribly slow, XUL isn't quite there yet, and doing a large app with JavaScript is painful. http://neugierig.org/software/darcs/xuldip/dip.xul (no install necessary; only works in Firefox) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] parsing machine-generated natural text
For a toy project I want to parse the output of a program. The program runs on someone else's machine and mails me the results, so I only have access to the output it generates, Unfortunately, the output is intended to be human-readable, and this makes parsing it a bit of a pain. Here are some sample lines from its output: France: Army Marseilles SUPPORT Army Paris -> Burgundy. Russia: Fleet St Petersburg (south coast) -> Gulf of Bothnia. England: 4 Supply centers, 3 Units: Builds 1 unit. The next phase of 'dip' will be Movement for Fall of 1901. I've been using Parsec and it's felt rather complicated. For example, a "location" is a series of words and possibly parenthesis, except if the word is SUPPORT. And that "Supply centers" line ends up being code filled with stuff lie "char ':'; skipMany space". I actually have a separate parser that's Javascript with a bunch of regular expressions and it's far shorter than my Haskell one, which makes sense as munging this sort of text feels to me more like a regexp job than a careful parsing job. I'm considering writing a preprocessing stage in Ruby or Perl that munges those output lines into something a bit more "machine-readable", but before I did that I thought I'd ask here if anyone had any pointers, hints, or better ideas. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [newbie] processing large logs
On 5/14/06, Eugene Crosser <[EMAIL PROTECTED]> wrote: main = printMax . (foldr processLine empty) . lines =<< getContents [snip] The thing kinda works on small data sets, but if you feed it with 250,000 lines (1000 distinct), the process size grows to 200 Mb, and on 500,000 lines I get "*** Exception: stack overflow" (using runhaskell from ghc 6.2.4). To elaborate on Udo's point: If you look at the definition of foldr you'll see where the stack overflow is coming from: foldr recurses all the way down to the end of the list, so your stack gets 250k (or attempts 500k) entries deep so it can process the last line in the file first, then unwinds. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] RE: transactional cache
On 5/13/06, Alberto G. Corona <[EMAIL PROTECTED]> wrote: > notglobal = newIORef True > main = do a <- notglobal > b <- notglobal Thanks. I got the poit more or less; Each invocation creates a new IORef instance. Another way of looking at this, that might be more instructive, is that notglobal is defined to be the action of creating a new IO ref. You can see that in its type: > :t newIORef True newIORef True :: IO (IORef Bool) I read that type as "an IO operation that produces an IORef Bool when executed". Then the code in main "executes" notglobal twice. Another way of looking at this is that you can always substitute the right side of an equals sign in for the left side. If you do that on this code this makes it plain that a and b will be different. (unsafePerformIO breaks this substitution rule.) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Code review: efficiency question
I remember reading a tutorial that pointed out that you can often avoid explicit recusion in Haskell and instead use higher-level operators. For your code, I think drawModals = foldr (flip (>>)) (return ()) . map drawModal works(?). On 5/2/06, Brian Hulley <[EMAIL PROTECTED]> wrote: Hi - I started off writing the following piece of monadic code: let drawModal :: Control -> ManagerM () drawModal c = do -- details omitted -- Prolog style coding... drawModals :: [Control] -> ManagerM () drawModals [] = return () drawModals (c:cs) = do drawModals cs drawModal c drawModals cs then it struck me that I should have not bothered with drawModals and instead should just have used: mapM_ drawModal (reverse cs) However, while this looks more elegant, it is less efficient? In other words, how much optimization can one assume when writing Haskell code? I'm trying to get a rough idea so I can decide whether to write helper functions such as drawModals in future or whether I should always just use the most elegant code instead. Any ideas? Thanks, Brian. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Newbie "Instance Of Floating Int" Error
On 4/28/06, Aditya Siram <[EMAIL PROTECTED]> wrote: > type Point = (Int,Int) > distBetween :: Point -> Point -> Float > >>ERROR - Type error in explicitly typed binding > *** Term : distBetween > *** Type : Point -> Point -> Int > *** Does not match : Point -> Point -> Float > > distBetween :: Point -> Point -> Int > >>Instance of Floating Int required for definition of distBetween It's saying that you explicitly gave the function the type "Point -> Point -> Int" but that it actually has "Point -> Point -> Int". If you look at the type of sqrt: Prelude> :t sqrt sqrt :: (Floating a) => a -> a You'll see that it returns a floating-point number. (Also, a minor style point: you should probably get in the habit of putting a space between the "sqrt" and its arguments. It'll make more sense as you gain more experience.) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
