- Glasgow-haskell-users

XML-RPC For Haskell
by Ronald Legere 08 Jan '02

08 Jan '02

Is anyone out there working on an XML-rpc binding for haskell? This probably is not so hard, using HaXml and Sockets (as soon as sockets is working again...) But if someone has/is already done/doing it/it then i would rather just use that :) Cheers! __________________________________________________ Do You Yahoo!? Send FREE video emails in Yahoo! Mail! http://promo.yahoo.com/videomail/

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Re: State Transformer
by Ketil Z Malde 08 Jan '02

08 Jan '02

Jorge Adriano <jadrian(a)mat.uc.pt> writes: > Anyway, I was coding some simple GA, and as you probably know I need to use > random values. The most elegant way I could think of was to generate some [...] > Monads! (right?) Well, I suppose so. Generally speaking. But, you might want to consider using the standard random generation routines from the (IO) top level of your program, and just split the random generator for each function that uses it. IOW, passing each function its own random generator, instead of worrying about returning the "rest" of a global random sequence. (I don't have any good example code, I'm afraid, but at leat have a look at the chapter on Random in the library report on http://haskell.org) -kzm -- If I haven't seen further, it is by standing in the footprints of giants

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State Transformer
by Jorge Adriano 07 Jan '02

07 Jan '02

Hi, I'm studying, among other things, Genetic Algorithms and Neural Networks and I decided I'd use haskell to code some simple GAs and NNs along with my study. Well, maybe it was not such a good idea after all, because I've been spending way more time learning more Haskell then GAs and NNs :( Anyway, I was coding some simple GA, and as you probably know I need to use random values. The most elegant way I could think of was to generate some infinite list of random values and pass them around as arguments to the functions that need those values. I called data which wraped this list Environment, and at first it seemed a nice way to solve the problem. Well, now I think it gets kind of weird because some functions will end up to have type something -> (otherthing, Environment), to update those lists... it's just ugly. Beside those lists I'd also like to control some statistics like the number of mutations, n. of crossovers, best fitness value in each generation, etc... I figured out that there should be a better way to do this then just chaging all the signatures and passing all this values around. Monads! (right?) Till then I had just read what I needed to be able to use the IO Monad. Seems to me like having a State Transformer monad its the best way to do it. Now I've read a great deal of Richard Birds Book chap 10 (Monads), as well as the "Monads for the Haskell Working Programmer"[1] by Theodore Norvell. I was going to try to make my own simple examples using a ST. A State Monad seemed something like would most probably be in some Standard Library, or at least in some GHC library. And it was (section 4.31.ST in the hslibs documentation) I wanted to use this ST, but then I noticed it was different from the one described in tutorial[1]. I was expecting the ST Monad ghc module to provide an apply function, analogue to the > applyST :: StateTrans s a -> s -> (s, a) > applyST (ST p) s = p s in the tutorial. I also expected to have general functions to access and change State. I can't implement them myself since the ST constructor is (obviously) not exported. But this ST module seems to work in a completely diferent way. >From what I can tell it is not suposed to be applyed to an initial state, instead it starts with an 'empty' state... State is controled with Referencies (mutable variables). Ok, now my problem, how do I use this? I can't really see how to change this referencies from within some function. (Got an example in the end to explain better waht I mean with that [Example1]) I'd also appreciate some coments on: Using a ST monad (good idea, bad?) Using the Ghc ST monad? Chromosomes defined as arrays? - either IArray or Diff array got to give it some more thought... (don't want Ints + bitwise operations right now...) Well, any other comments or hints that you think that might be usefully are welcome. I've already checked out the paper from the TAIGA project[2], it's not exactly done the way I'm thinking about doing it, but I got some usefull tips from there, like the use of a Monad to control statistics. One of my main problems so far as been *knowing what do I need to know*! I don't know anyone that codes in haskell, not having anyone to talk to and share ideas doesn't helps much either. Things get complicated where you (you - the guy that comes from the imperative paradigm) less expects it too... the space leaks, using monads to control state... if you still have not read about this stuff, IMO, it is easy to feel like you already know enough to do some solve some kind of problems when you actually don't. Any newbie to C or Pascal can make a few randoms here and there, and keep track of statistics... when you already spent some time with haskell you don't even question whether you already know enough to do something like *that*. Only when you start to work, and thing start to get messy, you begin to think that *maybe you need something you still don't know about*, and then you got to find out what it is... Documentation, I also feel like it could be more and better... the ST module in ghc for instance... would it be that hard to put at least some simple example there? No, just the type signatures... Well, this is just my opinion anyway. Thanks for your atention, and happy 2002 ;-) J.A. [Example1] How can I do this for instance, with the Ghc ST Monad: ------------------------------------------------------------------------ -- the State Trans defined as in the tutorial newtype StateTrans s a = ST( s -> (s, a) ) instance Monad (StateTrans s) where -- (>>=) :: StateTrans s a -> (a -> StateTrans s b) -> StateTrans s b (ST p) >>= k = ST( \s0 -> let (s1, a) = p s0 (ST q) = k a in q s1 ) -- return :: a -> StateTrans s a return a = ST( \s -> (s, a) ) applyST :: StateTrans s a -> s -> (s, a) applyST (ST p) s = p s -- just change the state putST :: (Char,Int) -> StateTrans (Char,Int) () putST (c',n') = ST(\(c,n)->((c',n'),())) -- get the state getST :: StateTrans (Char,Int) (Char,Int) getST = ST(\(x,y)-> ((x,y), (x,y))) testfunc :: StateTrans (Char,Int) Int testfunc = do foo bar (c,n)<-getST return n foo = do (c,n)<-getST putST ('a',n+1) bar = do (c,n)<-getST putST (c,n+2) tryTestFunc = applyST testfunc ('x',0) ------------------------------------------------------------------------ I is something like this? ---------------------------------------- stupidFunc runST ( do { initstate <- newSTRef ('x',0) -- and now what? }) ----------------------------------------- [1] http://www.engr.mun.ca/~theo/Misc/haskell_and_monads.htm [2] http://www.scms.rgu.ac.uk/staff/db/Taiga/ http://www.scms.rgu.ac.uk/staff/db/Taiga/APGA2000.ps.gz

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RE: weird compiler bug/failed to load interface
by Simon Peyton-Jones 07 Jan '02

07 Jan '02

Hal, Do please say what version of GHC you are using when reporting bugs! I can reproduce this with -O2, but not with -O. That's good, because it's a bug we fixed last week. It'll be fixed in the upcoming 5.02.2 release. thanks for reporting it. The workaround is not to use -O2 for Pattern.hs Simon | -----Original Message----- | From: Hal Daume III [mailto:hdaume@ISI.EDU] | Sent: 04 January 2002 17:36 | To: GHC Users Mailing List | Subject: weird compiler bug/failed to load interface | | | There's one module I wrote that I use in a lot of my programs | and for some reason, whenever I compile a program using this | module with -O or -O2, make changes to the Main, and then | recompile, I get the following error from ghc: | | Skipping Pattern ( Pattern.hs, Pattern.o ) | | failed to load interface for `Pattern': | Could not find interface file for `Pattern' | | Failed to find interface decl for `Pattern.a' | from module `Pattern' | | if I "ls Pattern.*" I get Pattern.hi, Pattern.hs and Pattern.o. | | In order to get it to compile correctly, I have to rm | Pattern.o and then rerun ghc on the Main module. | | I've attached the Pattern.hs fyi. If anyone has any | suggestions, please let me know. (btw, I'm using --make) | | Thanks! | | - Hal | | -- | Hal Daume III | | "Computer science is no more about computers | hdaume(a)isi.edu | than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume |

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Haggis
by Tom Bevan 05 Jan '02

05 Jan '02

Has anyone had any success compiling Haggis for linux. I've tried but get the response, Configuring for a i386-debian-linux host. checking how to run the C preprocessor... gcc -E checking for flex... flex checking for -lfl... yes checking whether ln -s works... yes checking whether make sets ${MAKE}... yes ./configure: .: filename argument required .: usage: . filename Any ideas what this might mean? Tom

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weird compiler bug/failed to load interface
by Hal Daume III 04 Jan '02

04 Jan '02

There's one module I wrote that I use in a lot of my programs and for some reason, whenever I compile a program using this module with -O or -O2, make changes to the Main, and then recompile, I get the following error from ghc: Skipping Pattern ( Pattern.hs, Pattern.o ) failed to load interface for `Pattern': Could not find interface file for `Pattern' Failed to find interface decl for `Pattern.a' from module `Pattern' if I "ls Pattern.*" I get Pattern.hi, Pattern.hs and Pattern.o. In order to get it to compile correctly, I have to rm Pattern.o and then rerun ghc on the Main module. I've attached the Pattern.hs fyi. If anyone has any suggestions, please let me know. (btw, I'm using --make) Thanks! - Hal -- Hal Daume III "Computer science is no more about computers | hdaume(a)isi.edu than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume

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RE: Setting up ghc for GPH and GranSim
by Simon Peyton-Jones 04 Jan '02

04 Jan '02

You can't use any old GHC for GpH, I'm afraid. (GpH modifies GHC internally.) Best thing to do is to go to the GpH website and get your GHC from there. http://www.cee.hw.ac.uk/~dsg/gph/ There's a GpH mailing list, which I'm ccing. Perhaps they are planning a new release? Simon | -----Original Message----- | From: matthew_bentham(a)yahoo.com [mailto:matthew_bentham@yahoo.com] | Sent: 21 December 2001 17:52 | To: glasgow-haskell-users(a)haskell.org | Subject: Setting up ghc for GPH and GranSim | | | Hi all, | | I'm new to both this list and Haskell, so apologies if these | questions have been answered before or seem obvious. I've | trawled the website and my suspicion is that I'm using a 'too | new' version of the compiler that doesn't support GranSim. Anyway: | | I'm trying to set up a ghc. I want to compile GPH programs | and run them on GranSim. | | With my current setup (details at the bottom of the mail) I | get the following error when I try to compile a GPH program: | [mjb67@mjb67 mjb67]$ ghc -gransim -fvia-c -fglasgow-exts | --make parfib.hs | ghc-5.02.1: can't find module `Prelude' | | Does anyone have any idea what I might be doing wrong? The | error is reported even when the program is normal Haskell, | whenever I use the -gransim or -parallel options to the | compiler. I presume this is some sort of library issue? | | My compiler was set up in the following way: | | I installed the binary RPMs: | http://www.haskell.org/ghc/dist/5.02.1/ghc-5.02.1-rh71-1.i386. rpm http://www.haskell.org/happy/dist/1.11/happy-1.11-1.i386.rpm I downloaded the source RPM from: http://www.haskell.org/ghc/dist/5.02.1/ghc-5.02.1-rh71-1.src.rpm I unpacked the source. I then typed (in the source root directory) ./configure --enable-gransim make make install Thanks in advance, Matthew _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users(a)haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

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Socket library ghc 5.02.1
by Sven Eric Panitz 30 Dec '01

30 Dec '01

It seems that the Socket library does still not work with ghc 5.02.1. I tried the simple test: > main = > do > d <- connectTo "localhost" (PortNumber 80) > hPutStr d "GET / HTTP/1.0\n\n" > hFlush d > c <- hGetContents d > putStr c On Windows2000 I get the known error: *** Exception: does not exist Action: getProtocolByName Reason: no such protocol entry whereas on Linux I get the following error: *** Exception: failed Action: connect Reason: Unknown error 142731264 The error number changes for every invocation and every 20th time or so it works on the linux machine. Can anyone recommend me, how to get a working Socket library with ghc 5.02. (I really need it now...) Sven Eric

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Next ghc
by senganb＠ia.nsc.com 27 Dec '01

27 Dec '01

Will the next version of ghc use libgmp 4.0? I would like to use its new gmp_sscanf. Thanks, Sengan

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simple program crash (GHC 5.02, Hugs)
by Oleg Galbert 22 Dec '01

22 Dec '01

I'm a newbie in Haskell. I tryed to compare performance of GHC compiled code and Ocaml compiled code on a small example: test n cosx | n==0 = cosx | otherwise = test (n-1) (cosx+cos(cosx)) main = print ( test 10000000 0.0 ) I compiled it on Win NT : ghc -o test_haskell.exe test_haskell.hs When I run the program I got the following message: Stack space overflow: current size 1048576 bytes. Use `+RTS -Ksize' to increase it. Hugs 98 (December 2001) version just fails with "Application Error" message. Does a stack usage depends on number of recursive calls? Is there a tail recursion optimization? In Ocaml version of this program everything goes well. The program produced the result without any complains. Oleg Galbert

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