- Haskell-Cafe - Haskell.org

array documentation is missing
by Thomas Hartman 17 Dec '07

17 Dec '07

While trying to make Regex.TDFA 0.91 install on 6.8.2 I got [10 of 21] Compiling Text.Regex.TDFA.RunMutState ( Text/Regex/TDFA/RunMutState.\ hs, dist\build/Text/Regex/TDFA/RunMutState.o ) Text/Regex/TDFA/RunMutState.hs:601:9: Constructor `STUArray' should have 4 arguments, but has been given 3 In the pattern: STUArray _ _ msource In the definition of `copySTU': copySTU (STUArray _ _ msource) (STUArray _ _ mdest) = ST $ \ s1# -> case sizeofMutableByteArray# msource of n# ->\ ... ^[]0;~/hackageTarGzs/regexstuff/regex-tdfa-0.92^G ^[[32mhartthoma@dbnycws28816 ^[[33m~/hackageTarGzs/regexstuff/regex-tdfa-0.92^[\ [0m but I got stuck fixing it because the array documentation isn't there http://www.haskell.org/ghc/docs/latest/html/libraries/haskell98/Array.html assume I'm getting the above error because the array interface has changed thomas. --- This e-mail may contain confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and destroy this e-mail. Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden.

3 2

Patter matching beginner question
by Adam Smyczek 17 Dec '07

17 Dec '07

Hi all, I assume the following behavior has a trivial explanation. When I write: case name of "a" -> ... "b" -> ... everything works fine. But when I extract a and b to constants: c_a = "a" :: String c_b = "b" :: String case name of c_a -> ... c_b -> ... I get Patterns match(es) are overlapped. Adam

3 2

Implementing a MUD server in haskell
by Jack Kelly 16 Dec '07

16 Dec '07

Hi, I've been thinking about two things for some time now: 1. Sharpening my haskell 2. Implementing a MUD server I've been thinking about doing (1) and (2) at the same time but I've run into some problems with data structures. I need to be able to get a list of players from a room (for things like a 'look' command) and I need to be able to find which room contains a given player. I'm still looking at this problem through an imperative lens, so here's some sort-of-C: struct room{ ... struct player * players; ... }; struct player{ ... struct room * room; ... }; From what I can see, I'd use a record type for players and rooms, but I'm not sure how to replicate the pointer effects: keeping each player pointing to a single instance of a consistent world and maintaining the invariant that (given: p :: Player, r :: Room): p `elem` (Room.players r) => (Player.room p == r) This needs to stand up to concurrent modification of a shared world structure, but I think I'll set up the concurrency controls after I get my head around this. -- Jack

4 4

Re[2]: [Haskell-cafe] Execution of external command
by Bulat Ziganshin 16 Dec '07

16 Dec '07

Hello gwern0, Thursday, December 13, 2007, 4:43:02 PM, you wrote: > to get at stdout. I don't think this would go through cmd/sh, but > honestly, specifying a particular interpreter breaks your > portability anyway these scripts will be written by users so they don't need to be the same for win&unix. i guess that users will prefer to use perl or something like this for these scripts and afaiu in both windows and linux this need to go through sh/cmd it seems that script may be not terminated if its output isn't read, so better code should be (_, h, g, _) <- runInteractiveCommand "script params" result <- hGetLine h hGetContents h >>= evaluate.length hGetContents g >>= evaluate.length am i right? -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com

6 6

Cheap ByteString mmap
by Don Stewart 16 Dec '07

16 Dec '07

A little mmap binding for ByteStrings. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/bytestring-mmap-… Should be useful for managing file resources under pressure (cheaper than a readFile, and with different constraints). Posix only. the Win32 mmap for bytestrings is in the win32 package. -- Don

1 0

JOB OFFER / Haskell for commercial projects?
by Peter Verswyvelen 15 Dec '07

15 Dec '07

Hello Happy Haskellers, I had to abandon improving my newbie Haskell skills the past weeks; I was busy creating a new startup company and finalizing financial funding for a cool project related to realtime "2D/3D animation and games". As I'm the CTO of this new company, and since I kinda like Haskell, I might consider creating a first prototype of the project using Haskell. However, this will be a commercial project. The software will be freely downloadable but not open source. However, if succesful, a highly priced professional version of the software might be created. Although I'm pretty sure GHC can be used for creating a private inhouse prototype, the prototype might evolve into the final product, and so my question is, which Haskell compilers & tools can: (1) be used to build commercial projects (2) be shipped with commercial projects (our project might call into the interpreter/compiler at runtime.) (3) be indirectly used by commercial projects (in the sense that the user will have to manually download and install the compiler) Furthermore, is the Haskell community willing to provide the excellent help (as in this forum and on IIRC) for commercial Haskell projects? That said, anybody who might be interested in getting a (paid J) Haskell job (parttime or fulltime) in the field of computer animation and games (but also (visual) programming languages, interpreters & compilers), please mailto:peter@nazooka.com. Preferable you will work onsite (in Belgium / Antwerp - the city of diamonds J), although working remote is also an option. You will make software that will be initially used by computer artists (that among other things made parts of <http://www.cgchannel.com/gallery/viewimage.jsp?imgID=547> "The Girl", Xyanide <http://www.gamespot.com/xbox/action/xyanide/index.html> , and many commercials <http://www.nazooka.com/site/html/index.php?p=movieplayer&m=showreel> ), that will be demonstrated at SIGGRAPH <http://www.siggraph.org/> , and will be released to the public in a later stage. Cheers to all, Peter Verswyvelen

7 6

getMessage function in Win32 API
by Eric 15 Dec '07

15 Dec '07

Dear all, In the Graphics.Win32.Window package there is a function getMessage takes a value of type LPMSG. How can I construct a value of LPMSG so that I can call the function? E.

1 0

A Random Question
by Dominic Steinitz 15 Dec '07

15 Dec '07

I need to generate distinct arbitrary values for my quickcheck tests and they don't have to be arbitrary (although that doesn't matter). No problem I thought, I'll create my own random number generator (which will not be random at all) and use > choose :: forall a. (Random a) => (a, a) -> Gen a Here's my code: > import Test.QuickCheck > import System.Random > > data MyGen = MyGen Int > deriving (Eq, Show) > > myNext :: MyGen -> (Int, MyGen) > myNext (MyGen s1) = > (s1, MyGen (s1 + 1)) > > -- Assume we will never need this > mySplit :: MyGen -> (MyGen, MyGen) > mySplit = error "No split for predictable random generator" > > myGenRange :: MyGen -> (Int, Int) > myGenRange (MyGen s1) = (s1, s1) > > instance RandomGen MyGen where > next = myNext > split = mySplit > genRange = myGenRange > > data Foo = Foo Int > deriving (Eq, Show) > > myRandomR :: (Foo, Foo) -> MyGen -> (Foo, MyGen) > myRandomR (Foo lo, Foo hi) g = > let (n, g') = next g > in (Foo n, g') > > instance Random Foo where > randomR = myRandomR > random = undefined But I get > Supply.hs:33:13: > Couldn't match expected type `g' against inferred type `MyGen' > `g' is a rigid type variable bound by > the type signature for `randomR' at <no location info> > Expected type: (Foo, Foo) -> g -> (Foo, g) > Inferred type: (Foo, Foo) -> MyGen -> (Foo, MyGen) > In the expression: myRandomR > In the definition of `randomR': randomR = myRandomR > Failed, modules loaded: none. I have two questions: 1. Why can't I instantiate a type class with any function I like provided it fits the type signature? 2. Is this the right approach to generating predictable arbitrary values? Are there others? Thanks, Dominic.

5 7

Fw: hdbc odbc also crashes on 6.8.2 Re: [Haskell-cafe] HDBC-ODBC crashes on ghc 6.8
by Thomas Hartman 15 Dec '07

15 Dec '07

I just tried HDBC-ODBC on 6.8.2, but it still crashes. Works on 6.6.1. thomas. Thomas Hartman <thomas.hartman%2Bexternal(a)db.com> Sent by: haskell-cafe-bounces(a)haskell.org 11/19/2007 12:05 PM To haskell-cafe(a)haskell.org cc Subject [Haskell-cafe] HDBC-ODBC crashes on ghc 6.8 This minimal program below fails in 6.8.1, works for 6.6.1, for up to date HDBC-ODBC-1.1.3. (I tried installing both from package and from darcs head) Installed and running from cygwin. When I run it as runghc fail.hs I get a windows popup error "ghc.exe has encountered a problem and needs to close, sorry for the inconvenience". ghci, same behavior. When I run it as ghc -e 'main' fail.hs, I don't get a popup window, and no error message is output, but it fails all the same. (I know this because more complicated, non-minimal programs, fail.) So this would seem to be a problem with ghc 6.8.1. $ cat fail.hs import Database.HDBC import Database.HDBC.ODBC main = connectODBC "some valid connect string, works when run from 6.6.1, not from 6.8.1" --- This e-mail may contain confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and destroy this e-mail. Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe --- This e-mail may contain confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and destroy this e-mail. Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden.

2 1

New slogan for haskell.org
by gwern0＠gmail.com 15 Dec '07

15 Dec '07

FWIW to the discussion about changing the main page, I was reading the CUFP paper and I saw some germane comments (and the writer is apparently one Noel Welsh, whose name I don't see in the thread); the context is a discussion (pg 17) of various members or potential members of the Haskell community and how supported they are: "What are the needs of the potential programmer? People program to solve prob- lems; so there had better be a clear statement of what kinds of problem the language is good for. The Python community does a good job of this on python.org: "Python is a dynamic object-oriented programming language that can be used for many kinds of software development. It offers strong support for integration with other languages and tools, comes with extensive standard libraries, and can be learned in a few days." Compare this with the equivalent from haskell.org: "Haskell is a general purpose, purely functional programming language featuring static typing, higher-order functions, polymorphism, type classes, and monadic effects. Haskell compilers are freely available for almost any computer." If you understand all that, you don't need to be here: you're already a Haskell programmer." -- gwern

17 26