December 2008 - Haskell-Cafe

Re: Compiling regex-posix-0.93.2 on windows
by Chris Kuklewicz 17 Jan '09

17 Jan '09

I am not sure what is going wrong. I have not been using Haskell on windows. I am also copying this reply to haskell-cafe and libaries mailing lists. Does anyone know? Parnell Flynn wrote: > I am having a terrible time compiling the 0.93.2 version of the > regex-posix library on windows XP. > > I have Cygwin and MinGW installed and I have a version of the regex.h > header in C:/cygwin/usr/include what shared libraries do I need? > > Here is a copy of the error it finds the include but is unable to link. > > This links to the standard c library version of regular expressions. > > The corresponding c header file is regex.h and there is a chance you > > will need to edit the end of the regex-posix.cabal file to find the > > include directory and/or library. > > Preprocessing library regex-posix-0.93.2... > > dist/build/Text/Regex/Posix/Wrap_hsc_make.o(.text+0x85):Wrap_hsc_make.c: > undefined reference to `_impure_ptr' > > dist/build/Text/Regex/Posix/Wrap_hsc_make.o(.text+0xc9):Wrap_hsc_make.c: > undefined reference to `_impure_ptr' > > dist/build/Text/Regex/Posix/Wrap_hsc_make.o(.text+0xf1):Wrap_hsc_make.c: > undefined reference to `_impure_ptr' > > dist/build/Text/Regex/Posix/Wrap_hsc_make.o(.text+0x125):Wrap_hsc_make.c: > undefined reference to `_impure_ptr' > > dist/build/Text/Regex/Posix/Wrap_hsc_make.o(.text+0x159):Wrap_hsc_make.c: > undefined reference to `_impure_ptr' > > dist/build/Text/Regex/Posix/Wrap_hsc_make.o(.text+0x18d):Wrap_hsc_make.c: > more undefined references to `_impure_ptr' follow > > collect2: ld returned 1 exit status > > linking dist\build\Text\Regex\Posix\Wrap_hsc_make.o failed > > command was: y:\ghc\ghc-6.8.2\bin\ghc.exe -optl-LC:/cygwin/lib > dist\build\Text\Regex\Posix\Wrap_hsc_make.o -o > dist\build\Text\Regex\Posix\Wrap_hsc_make.exe > > bash-3.2$ > > Thanks, > > Parnell > > Parnell Flynn • 230 South Lasalle Street • Suite 400 • Chicago, IL 60604 > • 312.244.5317 (o) • parnell___.flynn(a)ronin-capital.com_ > <mailto:parnell.flynn@ronin-capital.com> >

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ANNOUNCE: gitit 0.2 release - wiki using HAppS, git, pandoc
by John MacFarlane 16 Jan '09

16 Jan '09

I've uploaded an early version of gitit, a Haskell wiki program, to HackageDB. Gitit uses HAppS as a webserver, git for file storage, pandoc for rendering the (markdown) pages, and highlighting-kate for highlighted source code. Some nice features of gitit: - Pages and uploaded files are stored in a git repository and may be added, deleted, and modified directly using git. - Pages may be organized into subdirectories. - Pandoc's extended version of markdown is used, so you can do tables, footnotes, syntax-highlighted code blocks, and LaTeX math. (And you can you pandoc to convert pages into many other formats.) - Math is rendered using jsMath (which must be installed separately). - Source code files in the repository are automatically rendered with syntax highlighting (plain/text version is also available). You can check it out on my webserver: http://johnmacfarlane.net:5001/ Or try it locally: cabal update cabal install pandoc -fhighlighting cabal install gitit gitit # note: this will create two subdirectories in the working directory # then browse to http://localhost:5001. There's a git repository at http://github.com/jgm/gitit/tree/master. Comments and patches are welcome. John

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concurrent haskell: thread priorities
by Neal Alexander 12 Jan '09

12 Jan '09

From what i understand (correct me if I'm wrong): The threaded RT creates an OS thread for each CPU/core on the system and uses them to multiplex userland threads. These are context switched whenever they block/yield/gc and no priorities can be assigned. It seems like we could get some priority based scheduling (and still be slackers) if we allow marked green threads to be strictly associated with a specific OS thread (forkChildIO?). Its not a very good solution, but it seems easy to implement and would be nice for the few problems that really need priority based scheduling. How many of those problems involve having 1 thread running at high/realtime priority? Maybe most?

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GHC libraries documentation and links to source files
by Manlio Perillo 09 Jan '09

09 Jan '09

Hi. I have noted that recent versions of the GHC libraries documentation, no longer have links to the source code. What is the reason? I find it very useful. Thanks Manlio Perillo

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Updating doubly linked lists
by S. Günther 07 Jan '09

07 Jan '09

Hello, I was trying to wrap my head around the stuff at http://haskell.org/haskellwiki/Tying_the_Knot (again) and along the way came a question: Is it possible to change a particular node of the doubly linked list? That is to say, that would like to have a function: update :: DList a -> a -> DList a where update node newValue returns a list where only the value at the node which is passed in is set to the new Value and all other values are the same. All this of course in a pure way, that is without using (M/T/TM)Vars or IORefs. I do apologize if the answer is really obvious and am thankfull for any hints. Thanks in advance Stephan Günther

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Lack of inlining -> slow parsing with Data.Binary
by Eugene Kirpichov 06 Jan '09

06 Jan '09

Hi, I'm parsing Java classfiles with Data.Binary, the code is here: http://paste.org/index.php?id=4625 The problem is that the resulting code parses rt.jar from JDK6 (about 15K classes, 47Mb zipped) in 15 seconds (run the program with main -mclose rt.jar, for instance), which is 10 times slower than my Java version of the same code. I compile the program with -O2 ; I tried -ddump-inlinings and it turns out that my readByte/readWord16/readWord32 functions don't get inlined, despite being simply aliases for 'get::Get WordXX'; so, in places where my Java version does a pointer access (after being JIT-compiled), the Haskell version does two function calls. What can be the reason of this lack of inlining? Or how do I understand the output of -ddump-inlinings? -- Eugene Kirpichov

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Pattern combinators
by Andrew Wagner 06 Jan '09

06 Jan '09

All, Wadler posted a blog entry the other day about a paper on pattern-matching in Haskell (http://wadler.blogspot.com/) I've taken a first stab at turning it into actual code for hackage (http://hpaste.org/13215) There are two commented-out definitions that don't type-check, though, and the types are too wild for me to grok. Anybody have any suggestions for 1.) How to fix it and/or 2.) How to use data/type/newtype to simplify the types and make it more manageable? Thanks!

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Threads with high CPU usage
by Günther Schmidt 06 Jan '09

06 Jan '09

Hi, in an application of mine I start a long-running operation in a thread via forkIO so that the UI process doesn't get blocked. It just so happens, that the long-running process also takes the CPU to nearly 100% while it runs. During that time the run-time system does *not* switch back and forth between the UI-process and the long-running task, it seems that the UI process only gets woken up *after* the high CPU thread finishes completely. To the effect of course that it makes no difference at all to the UIs responsiveness whether I use forkIO or not. The long running process is pretty atomic, it's a single query to the database which takes up to a minute to complete so I don't see a chance to squeeze a "mainIteration" in there. What can I do? Günther

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building HSQL MySQL on windows (Was: FFI imported function names)
by Daniil Elovkov 06 Jan '09

06 Jan '09

Ok, enough talking to myself :) If anybody ever wants to build hsql-mysql on windows and has the same problems as I had, here's how it should be done. The problem I had seemed to be that libmysql.dll uses stdcall, but names its functions without @<n> decoration. Thus, when linking a Haskell program against it, names with @<n> cannot be resolved. The solution is pretty much a hack. Somebody from the Ruby community used to run into the same problem, from the same situation -- namely building ruby mysql bindings. Here is the procedure one person suggests http://rubydotnetproxy.rubyforge.org/mysql_win.html It worked perfectly for me. Of course, with some cabal specifics, which is obviously not described in the above page. The solution was to create a def file listing the names which could not be resolved and creating a .a file based on the dll and this def file. 2008/12/24 Daniil Elovkov <daniil.elovkov(a)googlemail.com>: > Mm, actually I didn't change the calling convention ffi imports when I > thought I did. I tried to do it through defines... > > Well, by explicitly saying ccall I get the names without @<n> > decoration. And it all links well. But I get segault when I run the > code, which should mean that calling conventions didn't match. > > Actually I found some ramblings on the internet that there's something > wrong with libmysql.dll and libmysql.lib in this respect, but they > were from 2004. > > Thus the question: how do I link against a lib file in ghc? When I say > -lmysql on command line it strictly searches for dll and complains if > it's not found. Adding lib exlpicitly on the cmd line doesn't seem to > have any effect. > > Thanks > > > 2008/12/24 Daniil Elovkov <daniil.elovkov(a)googlemail.com>: >> Hello >> >> How is decided whether the name of imported function gets the ending >> of the form @4 in ghc? >> >> I'm having this problem on Windows trying to use HSQL MySQL on windows. >> >> I compile HSQL Oracle backend and I get names without that. It's ok. >> With HSQL MySQL I get names with that stuff. It prevents me from >> further linking to dll. Supplying in the ghc command-line the "lib" >> file where names have those marks doesn't have any effect. >> >> The linker says that fname@NN cannot be resolved. >> >> Can I control that? >> >> The ffi calling convention doesn't (and shouldn't as I understand) >> affect this. The only difference is that in the case of mysql the >> header file itself where functions are described marks it STDCALL. Is >> that the reason? >> >> Also I changed ffi import line from "hsmysql.h func" to just "func", >> to no avail. >> >> ghc 6.8.2 >> >> I'm lost. Please help. >> >> -- >> Daniil Elovkov >> > > > > -- > Daniil Elovkov > -- Daniil Elovkov

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GHC 6.10.1 for Solaris i86
by Donald Halomoan 05 Jan '09

05 Jan '09

I am waiting for GHC 6.10. 1 binary for Solaris i86. Thanks.

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