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Re: [Haskell-cafe] what is a stack overflow?
by S. Alexander Jacobson 26 Jan '05

26 Jan '05

Thank you iavor. But the -K option doesn't appear to work with ghci. And I guess the bigger question is what sort of code causes a stack overflow. If 5M is enough stack for most programs then I obviously have some basic coding error which is causing a stack overflow... What sort of code causes that? -Alex- ______________________________________________________________ S. Alexander Jacobson tel:917-770-6565 http://alexjacobson.com On Mon, 24 Jan 2005, Iavor Diatchki wrote: > hi, > programs compile with GHC have a bunch of command line switches. > you can see them by typing: > myProg +RTS -help > one of them enables you to specify stack space, e.g. > myPorg +RTS -K5M > > (very briefly) the stack is a part of memory used by the compiler to > pass around arguments > to functions, and for temporary computations. > -iavor > > > > > On Mon, 24 Jan 2005 17:16:08 -0500 (Eastern Standard Time), S. > Alexander Jacobson <alex(a)alexjacobson.com> wrote: >> GHC assumes the user knows the difference between >> the heap and the stack. I don't. No matter how >> much heap I specify on the GHCi command line, I >> get a stack overflow exception. I have no idea >> what that means or how to remedy it. Hints? >> >> Note: My program is basically creating a few 100k >> item FiniteMaps. I don't think that should exceed >> the memory on my laptop.... >> >> -Alex- >> >> ______________________________________________________________ >> S. Alexander Jacobson tel:917-770-6565 http://alexjacobson.com >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe >> >

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Hugs for Zaurus
by John Goerzen 25 Jan '05

25 Jan '05

Hello, I have built a fixed Hugs for the Zaurus PDA running the OpenZaurus distribution. Download here: http://quux.org/devel/zaurus/hugs_hugs98-Nov2003-r1_arm.ipk Every module except Posix signals appears to be working. -- John

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Recantation and updated views
by Daniel Fischer 25 Jan '05

25 Jan '05

Okay, I was stupid, having ignored my own advice to always look at the sources. I stupidly assumed IO a was not a function-type. On retrospect, I can't imagine, how that came to me. I've looked it up now, and for ghc, I found newtype IO a = IO (State# RealWorld -> (# State# RealWorld, a #)) which is more or less what I've arrived at, eventually. For hugs, it's newtype IO a = IO ((IOError -> IOResult) -> (a -> IOResult) -> IOResult), which I find somewhat more contrived. So I apologize for all the nonsense that came from that and happily agree that getChar &c are well defined values of IO a. Whether we have putStrLn "hello" >> mzero === mzero depends on what raiseIO# exactly does, I've no idea. Again, sorry for all the fuss. Thanks to (in alphabetical order) Jorge, Jules and Ketil for helping me out of my error. Daniel

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RE: [Haskell-cafe] can't 'make install-docs'
by Simon Marlow 25 Jan '05

25 Jan '05

On 21 January 2005 23:24, Daniel Fischer wrote: > I've just installed ghc-6.2.2, but couldn't get the docs made. > I got the following: > Text/Regex.raw-hs Text/Regex/Posix.raw-hs Text/Show.raw-hs > Text/Show/Functions.raw-hs \ > --package=base \ > --dump-interface=base.haddock \ > --use-index=../doc-index.html --use-contents=../index.html \ > > /bin/sh: line 1: t: command not found > gmake[2]: [html/haddock.css] Error 127 (ignored) > /usr/bin/install -c -m 644 html/* > /usr/local/share/ghc-6.2.2/html/libraries/base > /usr/bin/install: cannot stat `html/*': No such file or directory > gmake[2]: *** [install-docs] Error 1 > gmake[1]: *** [install-docs] Error 1 > gmake[1]: Leaving directory `/usr/lib/ghc-6.2.2/libraries' > gmake: *** [install-docs] Error 1 > > What can I do about it? Looks like you need to install Haddock. Cheers, Simon

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what is a stack overflow?
by S. Alexander Jacobson 25 Jan '05

25 Jan '05

GHC assumes the user knows the difference between the heap and the stack. I don't. No matter how much heap I specify on the GHCi command line, I get a stack overflow exception. I have no idea what that means or how to remedy it. Hints? Note: My program is basically creating a few 100k item FiniteMaps. I don't think that should exceed the memory on my laptop.... -Alex- ______________________________________________________________ S. Alexander Jacobson tel:917-770-6565 http://alexjacobson.com

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File path programme
by Mark Carroll 25 Jan '05

25 Jan '05

I tried writing a little command-line utility to find the relative path of one thing from another thing (with Unix-like systems in mind). For example, $ ./pathfromof /etc/init.d/ /etc/X11/XF86Config-4 ../X11/XF86Config-4 $ ./pathfromof /tmp/baz/ /tmp/foo/ . $ ls -l /tmp/baz lrwxr-xr-x 1 markc markc 8 2005-01-20 12:01 /tmp/baz -> /tmp/foo It turned out surprisingly complex, though, and doesn't feel very neat or tidy at all, nor is it very portable given that I couldn't find generic library functions for manipulating bits of filepaths. Anyhow, it's at http://www.chiark.greenend.org.uk/~markc/PathFromOf.hs and may yet have egregious bugs. It seems to me like it could certainly be improved in various ways. If anyone has any thoughts, as to how I could improve my style, make more use of standard libraries, etc., I'd certainly appreciate them. Thanks, Mark

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HaXmL and the IO Monad
by John Goerzen 25 Jan '05

25 Jan '05

I've been playing with HaXmL lately. I've had a need to convert one XML document to another, and HaXmL was very nice for that. Along the way, I've discovered that I need to do some I/O as part of the conversion (specifically due to timezone-related calculations). Much of HaXML is based around the CFilter type: type CFilter = Content -> [Content] That is, most of the stuff one does in HaXML is a function with that type. Try as I might, I could not figure out a nice way to integrate I/O into this system. A simple IO CFilter wouldn't work, since there has to be input available when it runs. Content -> IO [Content] didn't work either, since the IO ripples up all the way to the top, messing up the nice code everywhere. I finally resorted to unsafePerformIO to get it done. But I'd like to know the proper solution. I do hope that this is not it :-) Thanks, John

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Re: [Haskell-cafe] weird behavior using HUnit
by Keith Wansbrough 24 Jan '05

24 Jan '05

> > GHC's memory profiling? > > I just gave it a try: when compiled with -prof -auto-all, my program > is memory hungry in both cases, so I cannot really compare... [cc'd back to list in case anyone else finds this useful; hope that's OK] Ah. The cost-centre annotations get in the way of the optimiser, preventing certain optimisations from being performed. It's possible that the new entry point you introduce with testParseLog is similarly preventing something from being inlined. The way to tell (sadly!) is to look at the intermediate code being generated by GHC. In fact there are several intermediate codes to look at. Most of the optimisation work is done while the program is in a form called "Core"; if you look at the result of the optimiser (sometimes called the "simplifier", confusingly) just before this Core is translated to STG you will get the most readable and useful information. http://www.haskell.org/ghc/docs/latest/html/users_guide/options-debugging.h… tells you how, and also explains how to read the output. -ddump-simpl is probably what you want, but it's a while since I've had a look - I could be wrong. Compare what you get with and without that HUnit line that's causing trouble, and see how the critical function is affected. HTH. --KW 8-)

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weird behavior using HUnit
by Frédéric Gobry 24 Jan '05

24 Jan '05

Hello, I just experienced a weird problem while using HUnit. My code (a simple apache log analyser) used to run in constant space (thanks to the good suggestions and examples I received from the list :-)), and I wanted to add some unit tests. To my great surprise, the code started to eat up lots of memory again. I've isolated the problem down. It seems that if I declare my test suite with the line: testParseLog = HUnit.runTestTT (HUnit.TestList [_testUpdate]) then my code does not run in constant space anymore. Note that the testParseLog is not actually used, but only exported from the module, so that I can run it with ghc -e testParseLog. The code is attached. The line in question is at the end of ParseLog.hs, and I compiled the whole with ghc-6.2.2 (debian testing) Any hint ? thanks in advance, Frédéric -- Frédéric Gobry Infoscience DIT-KIS / EPFL Tel: +41216932288 http://people.epfl.ch/frederic.gobry

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Randomly balanced binary trees
by Dominic Fox 23 Jan '05

23 Jan '05

Some more code that might be of interest to someone. Based on a suggestion by Alistair Turnbull, I've written a Haskell implementation of a randomly balanced binary tree. This merges tree updates with a stream of random numbers, which are used to shuffle the order of nodes in the tree so that it remains balanced. The code is posted together with a short explanation here: http://codepoetics.com/poetix/index.php?p=72 I would be especially interested in any suggestions relating to optimisation. Dominic

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