- Haskell-Cafe - Haskell.org

Re: [Haskell-cafe] Unable to profile program using Data.ByteString.Lazy
by dons＠cse.unsw.edu.au 27 Sep '06

27 Sep '06

lists: > Donald Bruce Stewart wrote: > >Probably you didn't build fps with profiling as well? You can rebuild > >fps with: > > runhaskell Setup.hs configure -p > >as the first step. > > > That worked on my Windows box at home, but on my Linux box at work, I > got "unrecognized flag -p". You're cabal version is too old then. Try updating either Cabal or GHC. -- Don

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Re: Creating DLLs with GHC
by Cyril Schmidt 27 Sep '06

27 Sep '06

Matthew, As regards the symbols that end with _closure, I believe you can resolve them by adding -package parsec to the ghc command line (as far as I can see, all the symbols you list come from the parsec package). I don't know, though, what to do with the undefined symbols from matrixstack. You can try to check two things: 1) That the options you specify with -optl really reach the linker (e.g. try to give a non-existent library in -optl option and see if it complains). 2) That matrixstack.lib is understood by the linker (that is, it must be created with dlltool) 3) That the symbols it is looking for do exist in matrixstack.lib (you can check it with objdump, for instance). Cheers, Cyril ___ Matthew Bromberg wrote: >ghc --mk-dll -o netsim.dll ExternLib.o ExternLib_stub.o dllNet.o src1.o >src1_stub.o src2.o -optl-lmatrixstack -optl-L"." >My external C library is in matrixstack.dll and it has a corresponding >static link stub library matrixstack.lib in the same directory as all >the sources. It has references in one of the sources (say src1.hs). >Unfortunately I get a host of undefined references to basically all the >functions in matrixstack.dll and also some undefined references of the form >Parsefile.o:ghc2996_0.hc:(.text+0x130): undefined reference to >`TextziParserCombinatorsziParsecziError_show_closure'

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Re: [Haskell] MR details (was: Implicit type of numeric constants)
by Bernie Pope 27 Sep '06

27 Sep '06

On 23/09/2006, at 4:33 AM, Christian Sievers wrote: > Hello, > > I don't take my advice to go to haskell-cafe :-) I will take your advice :) > > The discussion continued outside the mailing list, and now I have > two questions myself: > > 1. Why do the rules of the monomorphism restriction explicitly mention > *simple* pattern bindings? > Where is the difference, especially as there is a translation to > simple pattern bindings? > Why should > > p | "a"=="b" = 2 > | otherwise = 3 > > be treated different than > > p = if "a"=="b" then 2 else 3 They are the same (both are simple pattern bindings). The report says in section 4.4.3.2 that the first can be translated into the second. A simple pattern binding is one where the lhs is a variable only. If a pattern binding is not simple, it must have a data constructor on the lhs, therefore it cannot be overloaded. So the (dreaded) MR only applies to simple pattern bindings. Cheers, Bernie.

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Re: Haskell DLL crashes Excel
by Cyril Schmidt 26 Sep '06

26 Sep '06

A few people recently asked how to pass a string between a Haskell DLL and Excel. I attach the proof-of-concept code that I wrote a while ago; it demonstrates passing a string from Excel to Haskell and the other way. Most of the C++ code is taken from code examples at http://msdn.microsoft.com Beware, though, that the code has never been thoroughly tested. I ran it, and it did not crash -- that's almost all I can say. I even do not know if it leaks any memory. Use it at your own peril. The tar file contains a sample Excel sheet, and the sources of two DLLs: a COM DLL which interfaces with Excel, and a Haskell DLL which is invoked by the COM DLL. You will need Visual Studio 7.1 to build the COM DLL. The Haskell DLL exports one function, hString2String, which takes a C-style string, and returns the reverse of it. To build the Haskell DLL, run build.bat. To build (and register) the COM DLL, open Excel2Haskell.sln in Visual Studio, and hit Build. Once the two libraries are built, open Worksheet.xls and see how the function is invoked. Note that the COM DLL can be used not only by Excel, but by any other program or script that understands COM. For example, VBA scripts in Word, or VB and Javascript run by Wscript or Cscript. Hope this helps. Regards, Cyril ___

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Haskell.org down
by dons＠cse.unsw.edu.au 26 Sep '06

26 Sep '06

Just in case it has gone unnoticed, haskell.org seems to have been down for a few hours now. Do we have an admin looking into this? -- Don

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Haskell.org down (again)
by dons＠cse.unsw.edu.au 26 Sep '06

26 Sep '06

Something's going on. Haskell.org seems to be down again. That's the 3rd time in 4 days. -- Don

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haskell.org down again
by Pasqualino 'Titto' Assini 26 Sep '06

26 Sep '06

_____ From: HostTracker Notifier [mailto:noreply@host-tracker.com] Sent: 26 September 2006 01:19 To: tittoassini(a)gmail.com Subject: Error Alert Hello, The following url is down: http://haskell.org the error detected is: Http error:Http_client.No_reply Error was detected at 2006-09-26 01:14:41 Your login:titto -- Best regards, http://host-tracker.com/ support team uid:957058 tid:188350 eid:188350-209-0-0-4eee7afa9e44102989dd000c7651f68b

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Curious Functor Class
by Ashley Yakeley 26 Sep '06

26 Sep '06

Is there anything useful about the class of functors which foralls can move across? In other words, functors f, for which for any function g there is this isomorphism f (forall a. g a) <=> forall a. f (g a) In this Haskell snippet I've called the class Hoistable and the isomorphism is (hoist,unhoist): newtype All g = MkAll (forall a. g a); class (Functor f) => Hoistable f where { hoist :: forall g. (f (All g) -> (forall a. f (g a))); hoist = fmap (\(MkAll ga) -> ga); unhoist :: forall g. ((forall a. f (g a)) -> f (All g)); }; Functors that can be made instances of Hoistable: data Singleton a = MkSingleton newtype Identity a = MkIdentity a (->) p -- forall p. data Pair a = MkPair a a data Extra p a = MkExtra p a -- forall p. data Compose p q a = MkCompose (p (q a)) -- forall p q. (Hoistable p,Hoistable q) => On the other hand, Maybe and Either cannot. The key seems to be in only having one "form", i.e. no "|"s in the definition. Does this class actually have a use, or is it merely a curiosity? -- Ashley Yakeley Seattle WA

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Re: Haskell DLL crashes Excel
by Cyril Schmidt 25 Sep '06

25 Sep '06

Nikunj, The symptoms that you describe hint at some incorrect pointer handling. I believe the culprit is that pesky BSTR. I will try to dig up the code that I wrote a while ago to pass a BSTR to Haskell. Meanwhile, another hint. The GHC FAQ 1.4.1 says: "For utterly horrible reasons, programs that use more than 128Mb of heap won't work when compiled dynamically on Windows (they should be fine statically compiled)." (See http://haskell.org/haskellwiki/GHC:FAQ#My_program_that_uses_a_really_large_….) I have no clue what those horrible reasons might be, but you can limit the heap used by the Haskell DLL by setting the environment variable GHCRTS=-M128m Regards, Cyril ___ > | From: Gupta, Nikunj (London) [mailto:Nikunj_Gupta@ml.com] > | Sent: 25 September 2006 10:31 > | To: Simon Peyton-Jones > | Subject: RE: [Haskell-cafe] Haskell DLL crashes Excel > | > | Hello Simon, > | > | Nice to hear from you. I haven't really been working with Haskell but > I > | posted the message to that list since that was the only list I was > able > | to locate even remotely referring to the problem I was facing. > | I have a c++ code which I try to compile as a dll. When debugging the > | code works fine but as soon as I compile it for release and launch an > | independent process not attached to VC++ it crashes. Do you have any > | suggestions with regards to the project settings that might be causing > | the same. > | > | Any sort of help would be much appreciated > | Regards > | Nikunj >

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Writing forum software in Haskell
by David House 25 Sep '06

25 Sep '06

Hi all. The recent thread on email vs. forums inspired a bit of interest to get some forum software on haskell.org. Were we to go ahead with this, I think it'd be great to have this software written in Haskell itself. I'd also love to be involved in a collaboration should one be drummed up to write this kind of thing. Therefore, my questions: * What kind of forum are we aiming at? In my eyes, it'd be less like the bloated phpBBs out there full of oversized signatures and avatars, and more like the minimalistic bbPress on show at, for example, the WordPress support forums [1]. * What would be a compulsory feature list? * What would be a list of things to avoid like the plague? * Which web platform (HAppS, Hope, ...) would make the most appropriate target? Appreciate thoughts and opinions. -- -David House, dmhouse(a)gmail.com

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