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sending values between actions
by Nuno Silva 17 Dec '01

17 Dec '01

can anyone tell me how to send values from one action to another??? I have main0 = do s <- getLine writeFile "text.txt" s main1 = do .... I'd like to use main0 info on main1 action to build a nXm multisquares box... anyone understood this???? please help... __________________________________________________ Do You Yahoo!? Check out Yahoo! Shopping and Yahoo! Auctions for all of your unique holiday gifts! Buy at http://shopping.yahoo.com or bid at http://auctions.yahoo.com

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Re: Pointers in Haskell??
by Jeff Dalton 16 Dec '01

16 Dec '01

The answers are making this question seem trickier than I'd thought it was, because so far they (both) make it sound like structure-sharing is tied very closely to names / variables. For instance: > In Haskell, you can arrange for a large data structure to be shared by > giving it a name, and then using the name wherever you'd use a pointer in > some other language. The idea here seems to be that you have a name that refers specifically to the struccture you wish to share (as opposed to needing only an expression whose value is that structure), and then there are two possible interpretations: One possible interpretation is: this is *a* way to get sharing, to show that it's possible to have shared structures. The other possible interpretation is: this is *the* (only) way to do it. What I'd expected was that it would suffice to have an expression (and indeed that implementationally it would be much like Lisp or Java so that values were always (except in exceptional cases) secretly "pointers to".) -- Jeff

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Error message
by victoria borisovna rozhkova 16 Dec '01

16 Dec '01

Hello, what does it mean: Variable definition clashes the import. thank you Vika

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modules, classes, instances
by David Feuer 16 Dec '01

16 Dec '01

Well, I've been doing some more stupid thinking, and I've decided that I am not satisfied with the module system in haskell, or the way it deals with namespaces. It seems to me that there are four kinds of things that need to be dealt with: classes, instances, types, values, and possibly some kind of ML-style structures/functors. I see no good reason not to treat a class declaration similarly to the way Haskell treats modules. For example, if I have a class class A x where f1::... f2::... I would like to access the functions by writing A.f1, A.f2, etc. There should, however, be some way to unqualify the names, the way ML allows structures to be opened. Of course, this can be done in Haskell by putting the class declaration inside a module, but doing so can be annoying, and I think this style clearly attaches the method to the class it belongs to. It thereby lets you have a List l=>List.empty::l and also a Bag b=>Bag.empty::b automatically. Then there are types and instance declarations. I have the strange feeling that they go together. So I'm thinking it might be good to have some kind of type/instance module that can export types and instances. I can't understand why it is that instance declarations can't contain nested declarations other than the required ones. I think it would be nice if they could contain other declarations, as modules can. Also, instances could be imported (not just as part of a module, but separately) ML-style structures/functors. For everything else. Finally: I want nested modules!!! They probably couldn't be compiled separately, but they'd provide some namespace control. -- /Times-Bold 40 selectfont/n{moveto}def/m{gsave true charpath clip 72 400 n 300 -4 1{dup 160 300 3 -1 roll 0 360 arc 300 div 1 1 sethsbcolor fill}for grestore 0 -60 rmoveto}def 72 500 n(This message has been)m (brought to you by the)m(letter alpha and the number pi.)m(David Feuer) m(David_Feuer(a)brown.edu)m showpage

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drawing grids
by Nuno Silva 14 Dec '01

14 Dec '01

hello can anyone tell me how to draw grids?? it's like this: Imagine that I say that I want the grid to be 5X6, it will compute the distbetween the limits and then draw them. if I want a 6X10, it will do the same. thanks __________________________________________________ Do You Yahoo!? Check out Yahoo! Shopping and Yahoo! Auctions for all of your unique holiday gifts! Buy at http://shopping.yahoo.com or bid at http://auctions.yahoo.com

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overloading efficiency
by David Feuer 14 Dec '01

14 Dec '01

I have read that using overloaded functions is expensive because overloading is implemented by passing dictionaries around. These various sources seem to agree that this in necessary to allow separate compilation. I don't understand why this is... Couldn't the functions be specialized at link time? -- /Times-Bold 40 selectfont/n{moveto}def/m{gsave true charpath clip 72 400 n 300 -4 1{dup 160 300 3 -1 roll 0 360 arc 300 div 1 1 sethsbcolor fill}for grestore 0 -60 rmoveto}def 72 500 n(This message has been)m (brought to you by the)m(letter alpha and the number pi.)m(David Feuer) m(David_Feuer(a)brown.edu)m showpage

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Re: drawing costumized squared boxes
by Yoann Padioleau 12 Dec '01

12 Dec '01

Nuno Silva <nunopedrosilva(a)yahoo.com> writes: > hello I'm new to Haskell and I'm having trouble > drawing squares in the screen... it's like the game > minesweeper, we will have to define how many squares > we want the game to have and automatically draw them. > if anyone could help me I'd be gratefull borrow the book The Haskell School of Expression: Learning Functional Programming through Multimedia : Paul Hudak Cambridge university press to your library, and read it. > > __________________________________________________ > Do You Yahoo!? > Check out Yahoo! Shopping and Yahoo! Auctions for all of > your unique holiday gifts! Buy at http://shopping.yahoo.com > or bid at http://auctions.yahoo.com > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > -- Yoann Padioleau, INSA de Rennes, France, Opinions expressed here are only mine. Je n'écris qu'à titre personnel. **____ Get Free. Be Smart. Simply use Linux and Free Software. ____**

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drawing costumized squared boxes
by Nuno Silva 12 Dec '01

12 Dec '01

hello I'm new to Haskell and I'm having trouble drawing squares in the screen... it's like the game minesweeper, we will have to define how many squares we want the game to have and automatically draw them. if anyone could help me I'd be gratefull __________________________________________________ Do You Yahoo!? Check out Yahoo! Shopping and Yahoo! Auctions for all of your unique holiday gifts! Buy at http://shopping.yahoo.com or bid at http://auctions.yahoo.com

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Re: haxml
by Christopher Milton 11 Dec '01

11 Dec '01

--- David Smallwood <drs(a)dmu.ac.uk> wrote: > Does anyone know of a mirror site where I can download the latest > version of HaXml. (Connection to York is - and has been for a > while - apparently down: > ftp://ftp.cs.york.ac.uk/pub/haskell/HaXml/HaXml-1.02.tar.gz, that is) It's up now, unlike Hypatia, which needs a new maintainer. [ http://hypatia.dcs.qmul.ac.uk/ ] And, no, I don't have the server space to do it. Chris Milton just noticing Google has Usenet going back to 1981... http://groups.google.com/groups?q=clock+functional+programming&hl=en&rnum=2… __________________________________________________ Do You Yahoo!? Check out Yahoo! Shopping and Yahoo! Auctions for all of your unique holiday gifts! Buy at http://shopping.yahoo.com or bid at http://auctions.yahoo.com

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Re: (no subject)
by Ashley Yakeley 11 Dec '01

11 Dec '01

At 2001-12-10 16:07, uma kompella wrote: >i am new to haskell and am having a problem to write >function which takes a boolean expression and returns >a truthvalue stating whether or not it is a tautology. If you really want to impress your tutor, see if you can find a function that does this in polynomial time. -- Ashley Yakeley, Seattle WA

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