- Haskell-Cafe - Haskell.org

[off-topic / administrative] List Reply-to
by Matthias Fischmann 14 Oct '06

14 Oct '06

In my last post, I hit the wrong button again, with the effect of some noise in innocent mailboxes (sorry!). Some lists have the Reply-To: set to the list address. I think you can even configure the From: to be haskell-cafe instead of the poster, making the poster merely identifiable by the Sender: field. Do you have strong opinions on this subject? I would opt for setting Reply-To:; I think most of the follow-ups here are of some public interest, or easily filterable if not. cheers, matthias

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function result caching
by Silviu Gheorghe 14 Oct '06

14 Oct '06

hello,I'm new to Haskell and I'm using it to do some simulations for a game, and I have a some functions that have as argument just one int (the current situation), but they do a lot of computations after that (future evolutions etc) I'd like to know if the results are "cached" by the compiler (there are only a few thousand values i call the functions on, but they are distributed on a fairly large interval (0-1000000), because of the codification. if they are not I'd like to know what is the best way to cache them manually, and where can I read more about this, and the optimizations the compiler does, because I've searched the web before and i found very little on this topic. thank you very much Silviu P.S. sorry for my English :)

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What's going on in our courses?
by Walt Potter 14 Oct '06

14 Oct '06

All, Last Spring my Functional Programming class implemented a Genetic Algorithm with Neural Networks that learned to play Nim. The students had a really good time--they also learned lots about Functional Programming with Haskell. Part of the final exam was a tournament. This Fall in AI we'll be doing GA's again and Genetic Programming. Is there a list or forum that talks about teaching our students about Haskell? Thanks, Walt

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Howto Haskell in PocketPC?
by Iván Pérez Domínguez 14 Oct '06

14 Oct '06

Hi. Here a simple question: Is there any haskell compiler/interpreter or similar for PocketPC?

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Fwd: [GHC] #939: Possible bug building wxhaskell
by Jason Dagit 14 Oct '06

14 Oct '06

I reported the following bug and received the response below. Any wxhaskell hackers up to the challenge? I'd really love to see the makefiles go away and see wxhaskell just use cabal but I don't know if that's possible given the wxhaskell build requirements. Any help is much appreciated. Thanks Jason ---------- Forwarded message ---------- From: GHC <trac(a)galois.com> Date: Oct 13, 2006 5:21 PM Subject: Re: [GHC] #939: Possible bug building wxhaskell To: dagit(a)codersbase.com #939: Possible bug building wxhaskell -------------------------------------+-------------------------------------- Reporter: dagit(a)codersbase.com | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 6.6 Severity: normal | Resolution: invalid Keywords: | Difficulty: Unknown Architecture: x86 | Os: Unknown -------------------------------------+-------------------------------------- Changes (by duncan): * resolution: => invalid * status: new => closed Comment: It's not a GHC bug. It's a problem with the way wxHaskell is built. Admitidedly this is due to a slight change in the way GHC manages packages but it's not a bug as such, wxHaskell just needs fixing. What needs to happen is that the packages must be registered locally before they get used in other packages. Also, instead of importing the modules from the other package directly from the directory with -i foo/, it must be via -package foo. So you'll need to get in contact with someone who knows enough about wxHaskell's build system to fix it. Try asking on the ghc-users or haskell-cafe mailing lists. ------------------------ The bug report: I appologize if this isn't a GHC bug but since it started happening after a GHC upgrade I suspect it's a GHC bug. After upgrading to ghc6.6 on windows (using the release binary) I tried to install the current wxhaskell release found here: http://wxhaskell.sourceforge.net/download.html (version wxhaskell-src-0.9.4-1.zip) I have used wxhaskell on this machine before with older version of ghc (including ghc6.5, specifically visual haskell) so my environment for building the wxhaskell source was already setup. When I first got the error below I thought maybe my version of wxhaskell was messed up so I redownloaded the above zip file and unzipped a fresh copy. I unziped the source then I typed: configure && make Things went along fairly smoothly for a while then suddenly I got this error message: ghc -c wx/src/Graphics/UI/WX/Types.hs -o out/wx/imports/Graphics/UI/WX/Types.o -iout/wx/imports -odir out/wx/imports -hidir out/wx/imports -fvia-C -package-name wx -iout/wx/imports wx/src/Graphics/UI/WX/Types.hs:94:0: Bad interface file: out/wx/imports/Graphics/UI/WXCore/Types.hi Something is amiss; requested module wx:Graphics.UI.WXCore.Types differs from name found in the interface file wxcore:Graphics.UI.WXCore.Types make: *** [out/wx/imports/Graphics/UI/WX/Types.o] Error 1

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Re: [Haskell-cafe] Gtk2Hs and Glade Tutorial
by Duncan Coutts 13 Oct '06

13 Oct '06

On Fri, 2006-10-13 at 15:18 +0200, Hans van Thiel wrote: > Hello Duncan, > > Thanks for your reply, and here's the pdf. Thanks. > One of the things to be improved, which I note myself, is something on > how to do it on the Windows platform. It's much the same of course, but yes that would be nice. > (This is assuming there is a Glade for Windows.) There is. It comes with the dev flavour of the Gtk+ installer. > Another thing is the terminology, for example about handles, actions and > functions. Glade uses 'signals' and 'callback functions' and you can > specify them visually. I believe (I'll have to check this) you can look > up the names in a file 'callbacks.c'. Of course you have to substitute > those for the Gtk2Hs equivalents, but it might make it easier to find > the appropriate ones in the Gtk2Hs API. We do have slightly different terminology in a few places and usually for good reason. For example the idea of a callback function makes a lot of sense in C where you really do have to have a named function that gets called in response to a signal. I Haskell we don't need a named function of course we can just say: onClicked button $ do ... ... > I'll check out the link you provided in the next few days, and I'm > looking forward to your comments. I'll also have to wait and see what > Eddy Ahmed, the author of the Glade tutorial, thinks about this idea. > It would be nice to reuse that, and to put the Haskell version on his > more general web site as well. Why re-invent the wheel.. I'll send you some more comments when I've had a full read through. Perhaps we should use the haskell.org wiki for this. Duncan

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Porting content from the old wiki
by dons＠cse.unsw.edu.au 13 Oct '06

13 Oct '06

The main thing holding up porting of content from the old wiki is licensing. In order to help this, could people who've written for the old wiki, and are happy to have that work moved to the new wiki and relicensed, add their names to the list here: http://haskell.org/haskellwiki/HaWiki_migration Or email me and I'll add the name. Then anyone can move your work over, which should really speed things up. Thanks, Don

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quick trivial question on records
by Imam Tashdid ul Alam 13 Oct '06

13 Oct '06

I was reading Daan's paper on scoped labels and it struck me... has anyone tried a variation of the language where records are by dafault strict? and unboxed when appropriate? extended question: doesn't it makes more sense? laziness and partial applications go very well together, and the ADT constructors are often partially applied... __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

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A type in search of a name...
by Brian Hulley 13 Oct '06

13 Oct '06

Hi, You'll never believe it but I've been struggling last night and all of today to try and think up a name for the following type and I'm still nowhere near a solution: data ??? = VarId | VarSym | ConId | ConSym this is part of a type to describe Haskell lexemes: data Token = TName !??? !ByteString.T | ... Here are some of my attempts to fill in ??? and my reasons for rejecting them: 1) VarConIdSym - the problem is that it's too long and the first letter is 'v' which could be confused with the letter 'V' in "VarId" or "VarSym" 2) Name - the problem is that this suggests the string itself rather than the VarId/VarSym/ConId/ConSym'ness of the token 3) NameType - I'm trying to avoid using the words "Type" "Kind" etc because I'll probably want to use these later for other things and in any case NameType suggests the type of a lexical name ie Token itself 4) Space - this can be confused with something to represent whitespace or the namespaces introduced by modules 5) Just using data Token = TVarId !BS.T | TVarSym !BS.T | ... -- explodes into too many different cases when you add tokens for qualified names and all their variations (since I'm also representing incomplete tokens like "Foo." and "Foo.where" (as a prefix of "Foo.whereas" etc since it can't stand by itself because "where" is a reserved word)) 6) Using Bool as in data Token = TName !Bool !Bool !BS.T -- problem is that then I won't get any help from the typechecker if I accidentally confuse the order of Bools when matching etc. I could use the record syntax but then code can become very clunky to look at and it would still allow the Bools to get confused when they are passed about Any ideas? I must say that trying to think up names for things is absolutely the most difficult task in programming imho. The problem is that once fixed down, a name gets used all over the place and becomes totally entrenched in the code and affects how one thinks about the code thereby influencing its whole future development in a very deep and pervasive way (think suffixes/ prefixes/ relationships with other concepts etc). I would also be satisfied with just good names for the following types: data ???1 = Var | Con data ???2 = Id | Sym data ???3 = Op | Plain (I just combined ???1 and ???2 in ??? to try and save some space in the representation but ideally they would be separate types if only there were a way to tell the compiler to represent each by 1 bit in a word at the machine level like C's struct {VarCon vc : 1; IdSym is : 1;}) Any suggestions welcome, Thanks, Brian. -- Logic empowers us and Love gives us purpose. Yet still phantoms restless for eras long past, congealed in the present in unthought forms, strive mightily unseen to destroy us. http://www.metamilk.com

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nightnightita
by George Brewster 13 Oct '06

13 Oct '06

hope you're feeing better too.

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