- Haskell-Cafe - Haskell.org

Re: [Haskell-cafe] Toy application advice wanted
by Jon Cast 06 May '04

06 May '04

Duncan Coutts <duncan.coutts(a)worcester.oxford.ac.uk> wrote: > On Wed, 2004-05-05 at 16:24, Andrei de A. Formiga wrote: > > I'm finding wxHaskell very nice, and a wxWidgets > > binding is something many other "advanced" languages > > don't have (even OCaml). The only downside is having a > > 'Hello World' GUI application with 7 Mb... but it runs > > quite well and smooth once it's loaded. > > We have the same problem with gtk2hs. A stripped simple(ish) prog weighs > in at about 2.5Mb. > > I'm not quite sure what's in there that makes it so big. > > Duncan ghc doesn't support dynamic linking for Haskell libraries (a combination of the amount of work involved and the platform-specific nature of the work and the size of modern hard disks and the frequency with which ghc's ABI changes and the number of implementation details which ghc sticks into the exported ABI of a library anyway (via cross-module inlining)). So any Haskell libraries you use will get statically linked. Jon Cast

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Re: [Haskell-cafe] Toy application advice wanted
by mikeb＠manor.org 06 May '04

06 May '04

On Tue, 4 May 2004, Bill Walsh wrote: > I am amazed that you can even think of doing anything in a week. > I have been at it for at least 15 years: one project; one dead set > proof-of-concept . Well I'm sure you're doing something much more useful/worthwhile than I! =) I understand that the example program I initially thought of is rather, well...typically imperative. That's sort of the reason I chose it. Not only does it have real-world ramifications to my customer (the problem domain is similar) but it will hopefully show me the worst of the best. I.e., Haskell is a beautiful language [disclaimer: this comes from me not really being a Haskell programmer, but admiring it from afar if you will] and can express some unbelievably advanced concepts elegantly, but is it really nasty doing "normal" software crap like loading a bunch of data, popping up GUI windows, etc. etc.? I was hoping that I can piece together something fairly quickly within two weeks in those three languages. They don't have to be robust, or even beautiful. In fact, I can guarantee they won't be. But the real point of the exercise is for me to figure out which environment is the easiest for me to get along with. > I will follow your progress with intense interest. > Your are obviously an experienced programmer, but it is your analytical > skills which interest me most. Well, I am an experienced programmer, but certainly not in the same class as most lambda-junkies as yourselves. I have a long sordid history of programming in imperative languages and I've been bitching about switching for long enough that it's time to put my money where my mouth is, so to speak. I've dabbled in Scheme and Erlang and ML. To be frank, I've all but discarded Erlang as a viable language. Don't get me wrong...it's got some great features; I just think that I could easily implement Erlang in Scheme or Haskell and be quite happy. (At some point in the future when I'm smarter =) So to me, the real question is: Haskell, the pure, or Scheme, the dirty? Haskell is lazy all the time. That's awfully nice...I'm not sure if there's a performance penalty somewhere, but assuming there isn't, kudos to it. Scheme lets you be selectively lazy with macros. At least it's highly customizable (for instance, pattern matching can be implemented in Scheme with macros, whereas other languages that have fixed special forms are quite limited). But Scheme lets you change things if you want to! (The Haskell afficianados gasp). Let's face it...in most long-running applications, data changes a lot during the lifetime of a program. So somehow, you have to manage the repercussions of state changes. Haskell does this with monads. (I'm still wrapping my brain around them, but...) Apparently monads plus some syntactic sugar are like functions that return a value and the next function, which in turn returns a value and the next function, etc. so that referential transparency is maintained. This is a heckuva lot of work to do (set! foo 'bar). I hope I'm not far off base with this. I guess it boils down to this: Haskell ensures that your bindings are never ever ever corrupted, and thus the sematic value of your program is never compromised from the outside. The cost of this is a sharp learning curve, and quite possibly a performance hit. Scheme lets you tromp all over stuff (well, you get the picture), in effect letting you still have control over when you really need to do something imperative for performance or simplicity reasons. I'm not sure which I *like* better. So far neither is visually appealing, mostly because I'm not familiar with them. Scheme seems to have a slightly bigger population than Haskell, which of course means squat because if I really cared about how many programmers of language X there are out there I'd just code in Java (which, sadly, I'm doing now). Anyway, I'm starting to ramble, but I talked to a friend who has similar feelings but is actually pretty good at Common Lisp. He suggested I refocus my energies, and I agree: instead of biting off more than I can chew, and having to learn a whole wad of APIs that aren't really about the language (read: wxHaskell or gtk2hs/the like, or audio packages etc.), just code some really simple problems. Like the Sieve of Eratosthenes, in all three languages. Or a simple publish/subscribe framework with a "master" state holder and many slaves. Or quicksort. Etc. etc. So I'm going to head down that path right now, and try to get a feel for the languages in a slightly more pure fashion. I'll still try to get performance metrics out of them, but I'm not going to bang my head against the wall learning new languages, GUI toolkits, and FFIs all in two weeks. =) Thanks for the replies so far, I really appreciate them. -- Mike J. Bell This is all just my opinion. "Outside of a dog, a book is man's best friend. Inside it's too dark to read." mikeb(a)manor.org

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[Haskell-cafe] REMINDER - Contributions to HC&A Report (May 2004 edition)
by Arthur van Leeuwen 03 May '04

03 May '04

Dear Haskellers, we would like to remind you of the opportunity to contribute to the May 2004 edition of the Haskell Communities & Activities Report. Why not take the few minutes necessary to type up a new or updated entry and send it in? We would love to see people write on the following subject(s): - The Haskell Mailing List - The Haskell Cafe - The Haskell 98 reports - Concurrent Haskell - hierarchical libraries - HaskellDB - HXml - QuickCheck - Yale Haskell group - Parallel and Distributed Functional Languages Research Group at Heriot-Watt University Ofcourse, if you have done other interesting things with Haskell we would very much like to know about those as well! If at all possible, could you please send in your contribution by friday *this* week, i.e. May 7th 2004? We will update the topics list on http://www.haskell.org/communities/topics.html with a nice tickmark as soon as we have received your contribution, to show that you too support the Haskell Communities and Activities Report! Thanks, Arthur (interim editor, May 2004 edition) -- Haskell Communities and Activities Report (May 2004 edition) All contributions are due in by the end of next week! http://www.haskell.org/communities/

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Call for recommendation
by 无云 02 May '04

02 May '04

Hi, all I'm a newbie to Haskell and FP now, I need your help. Could anybody give me any advice on how to learn and master the Haskell language and thinking/programming in FP? I especially expect a list of some excellent books on Haskell. M.H.Fan 05/01/04 ======================================================== 是邮件你收有病毒我上！VIP邮箱全面保护！ http://vip.163.com 中国最大的免费邮箱在等你 25兆空间4兆附件！　　　　　 http://mail.163.com 点击网易泡泡惊喜无限全免费手机短信任你发!　　　　　　http://popo.163.com

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Is it possible to read existential types?
by S. Alexander Jacobson 30 Apr '04

30 Apr '04

Is is possible to read/show an existentially typed list? Would it be possible if, instead of using read/show, I defined some variant that relies on the typeof/typeable infrastructure? Is there a way to read in a typename for use in coercing a read? -Alex- _________________________________________________________________ S. Alexander Jacobson mailto:me@alexjacobson.com tel:917-770-6565 http://alexjacobson.com

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Re: sizeFM type
by Tomasz Zielonka 28 Apr '04

28 Apr '04

On Mon, Apr 26, 2004 at 08:43:44PM -0400, ajb(a)spamcop.net wrote: > > And re sizeFM, I would note that Google has more > > than 2^31 pages indexed in memory. > > I would note, in addition, that they don't have that many pages indexed > on a single machine. Almost nobody has a database with that many records > on a single machine, even those who have clusters of 64 bit machines. It seems I qualify as almost nobody, cause I've had a database with more than 2^34 records on a single IA32 machine. However, I wouldn't ever think of loading the entire database to RAM. Best regards, Tom -- .signature: Too many levels of symbolic links

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Re: [Haskell-cafe] Re: sizeFM type
by S. Alexander Jacobson 28 Apr '04

28 Apr '04

On Tue, 27 Apr 2004, Tomasz Zielonka wrote: > The data you provided is interesting. However, if I had such a machine, > my work could be much less challenging :) I would note that people today are making strenuous efforts to retain compatibility with a Haskell98 standard that it only 6 years old! If we are making choices intended to have a lifetime of e.g. 10 years (see <http://www.joelonsoftware.com/articles/fog0000000017.html>), then I would observe that the 24gb machine I specced out will, assuming Moore's law lasts, cost only $2k in 5-6 years. The Sun Fire 15k with 288GB of memory and 72 Sparcs (think GPH!), that today costs $2.6m will cost only $155k. Note, since you don't need 72 CPUs, you'll probably be able to get this machine for <$50k. So, perhaps the question here is: What is the planned lifetime of sizeFM? Do we prefer the safety of knowing our code will work at arbitrary scale or the ecstacy of having it run fast today? Put differently, would you rather cope with hardware limitations today or software limitations tomorrow? -Alex- _________________________________________________________________ S. Alexander Jacobson mailto:me@alexjacobson.com tel:917-770-6565 http://alexjacobson.com

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Re: [Haskell] Re: sizeFM type
by Ketil Malde 27 Apr '04

27 Apr '04

[Moved to -cafe at SPJ's request] "Serge D. Mechveliani" <mechvel(a)botik.ru> writes: > On Mon, Apr 26, 2004 at 10:09:18PM +0200, Ketil Malde wrote: >> "Serge D. Mechveliani" <mechvel(a)botik.ru> writes: >>> length :: [a] -> Integer >>> smallLength :: [a] -> Int >> Hmm...isn't it possible to use a class here? Perhaps even Num? > I think, for many functions, like length, it is most natural to > return Integer only. Well, perhaps Integral is a better choice. I was perhaps thinking of functions like: average xs = sum xs / length xs I'd rather have a polymorphic "length", than different versions for each possible return type. One problem could be that with average xs = sum xs / fromIntegral (length xs) the return type of length becomes ambigous? -kzm -- If I haven't seen further, it is by standing in the footprints of giants

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Data constructors
by Mark Carroll 27 Apr '04

27 Apr '04

I keep running into annoyance in having to name data constructors differently if they're for different types if they're in the same module or something. I wish that something like some Type.Constructor syntax worked in order to disambiguate. Or, better still, I have that problem with function names too (e.g. Data.List.union, Data.Set.union, IIRC) and it occurs to me that a lot of this can be resolved automatically because the types only make sense with one of the choices. I'm not really proposing any changes; more, I'm wondering what others' thinking is about this sort of thing - what annoys them, how they get around it, etc. -- Mark

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Hierarchical Library
by haskell＠alias.spaceandtime.org 24 Apr '04

24 Apr '04

Hello, Why does this fail? ========================== import System.Posix test = Temp.mkstemp ========================== Are the libraries hierarchical in name only? Thanks, James

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