Re: [Haskell-cafe] H98, OOHaskell - getting started with objects in Haskell
Thanks to all of You, I think I learnt really a lot just on this thread about Haskell and also OO in general. I fear I'm too busy in the near future to come up with a good example and some more questions. Might happen later, because this topic is really interesting. Till then -- Thanks Philipp -- View this message in context: http://haskell.1045720.n5.nabble.com/H98-OOHaskell-getting-started-with-objects-in-Haskell-tp3338991p3346982.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] H98, OOHaskell - getting started with objects in Haskell
Am Sonntag, den 16.01.2011, 14:48 -0800 schrieb gutti: Looking at life u probably could save time, if u only would evaluate code on cells, where the neighbors have changed status. So rather than triggering them all centrally and each checks its neighbours, we could use the concept: - let the active ones trigger the neighbours so pass on activity But then you would have to take care to avoid cycles. You could also use on-demand updates with a centralized approach, and a centralized approach would probably make cycle detection easier. Best wishes, Wolfgang ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] H98, OOHaskell - getting started with objects in Haskell
On Mon, Jan 17, 2011 at 1:44 AM, Wolfgang Jeltsch g9ks1...@acme.softbase.org wrote: Am Sonntag, den 16.01.2011, 14:48 -0800 schrieb gutti: Looking at life u probably could save time, if u only would evaluate code on cells, where the neighbors have changed status. So rather than triggering them all centrally and each checks its neighbours, we could use the concept: - let the active ones trigger the neighbours so pass on activity But then you would have to take care to avoid cycles. You could also use on-demand updates with a centralized approach, and a centralized approach would probably make cycle detection easier. Don't forget about the double buffering you will need to do if you have a simultaneous rule. It doesn't take long before the dragons in imperative programming start messing with your easy specification. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] H98, OOHaskell - getting started with objects in Haskell
On Fri, 14 Jan 2011 12:36:22 -0800 (PST) Wolfgang Jeltsch-2 [via Haskell] ml-node+3341886-976283800-146...@n5.nabble.com wrote: Is this really ideal for OO? I thought that in a cellular automaton, all cells have to change synchronously. In addition, cells have to access the old states of their neighbours to compute their new states. So you would have to heavily synchronize the objects. In this light, I’d say that the distributed OO approach isn’t very practical. A global control of the whole system might be better. Note that I’m by no way an expert in cellular automata. I’m just thinking of the game of life. :-) Best wishes, Wolfgang Hi Wolfgang, I don't yet have experience with cellular automata either. What u say seems plausible, but then the life game might have been coded that way, because most OO language don't offer concurrent objects and the distributed OO approach (seems to be a very recent concept). Looking at life u probably could save time, if u only would evaluate code on cells, where the neighbors have changed status. So rather than triggering them all centrally and each checks its neighbours, we could use the concept: - let the active ones trigger the neighbours so pass on activity ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe __ View message @ http://haskell.1045720.n5.nabble.com/H98-OOHaskell-getting-started-with-objects-in-Haskell-tp3338991p3341886.html To unsubscribe from H98, OOHaskell - getting started with objects in Haskell, visit http://haskell.1045720.n5.nabble.com/template/NamlServlet.jtp?macro=unsubscribe_by_codenode=3338991code=cGhpbGlwcC5ndXR0ZW5iZXJnQGdteC5uZXR8MzMzODk5MXwxNDUxNzE5MDIw -- View this message in context: http://haskell.1045720.n5.nabble.com/H98-OOHaskell-getting-started-with-objects-in-Haskell-tp3338991p3343767.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] H98, OOHaskell - getting started with objects in Haskell
Hi Nick, thanks a lot -- timber-lang seems very interesting, but seems still too young for productive useage. That language probably needs 2 more years to stabilise, but its defintely good that its so haskell related. The other links are very interesting (especially the coding examples), but I'll need some time to digest. -- Might come back with some questions. Cheers Phil -- View this message in context: http://haskell.1045720.n5.nabble.com/H98-OOHaskell-getting-started-with-objects-in-Haskell-tp3338991p3343777.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] H98, OOHaskell - getting started with objects in Haskell
If you want to use an OO approach: try thinking of a sparse array of objects (previous and current generations) where each object knows its coordinates by being linked into a sparse array data structure. Quoting gutti philipp.guttenb...@gmx.net: On Fri, 14 Jan 2011 12:36:22 -0800 (PST) Wolfgang Jeltsch-2 [via Haskell] ml-node+3341886-976283800-146...@n5.nabble.com wrote: Is this really ideal for OO? I thought that in a cellular automaton, all cells have to change synchronously. In addition, cells have to access the old states of their neighbours to compute their new states. So you would have to heavily synchronize the objects. In this light, I?d say that the distributed OO approach isn?t very practical. A global control of the whole system might be better. Note that I?m by no way an expert in cellular automata. I?m just thinking of the game of life. :-) Best wishes, Wolfgang Hi Wolfgang, I don't yet have experience with cellular automata either. What u say seems plausible, but then the life game might have been coded that way, because most OO language don't offer concurrent objects and the distributed OO approach (seems to be a very recent concept). Looking at life u probably could save time, if u only would evaluate code on cells, where the neighbors have changed status. So rather than triggering them all centrally and each checks its neighbours, we could use the concept: - let the active ones trigger the neighbours so pass on activity ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] H98, OOHaskell - getting started with objects in Haskell
Am Donnerstag, den 13.01.2011, 15:23 -0800 schrieb gutti: I'm especially interestes in engineering calculation tasks where cellular automata could be used. In that case all u have to do is to give the class the right properties and that let it grow. Such a localised intelligence approach seems an ideal OO - task. I don't know whether something functional could achieve the same. Is this really ideal for OO? I thought that in a cellular automaton, all cells have to change synchronously. In addition, cells have to access the old states of their neighbours to compute their new states. So you would have to heavily synchronize the objects. In this light, I’d say that the distributed OO approach isn’t very practical. A global control of the whole system might be better. Note that I’m by no way an expert in cellular automata. I’m just thinking of the game of life. :-) Best wishes, Wolfgang ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] H98, OOHaskell - getting started with objects in Haskell
On 11-01-13 06:23 PM, gutti wrote: I'm especially interestes in engineering calculation tasks where cellular automata could be used. In that case all u have to do is to give the class the right properties and that let it grow. Such a localised intelligence approach seems to be exactly existential type and/or message passing. It looks OO because people's first exposure to existential type and message passing is through OO. But OO also bundles a lot of things not needed for this, for example I doubt that inheritance is needed. You could use OO but you don't need OO. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] H98, OOHaskell - getting started with objects in Haskell
Hi Philipp, depending on what engineering calculations you are interested in, you might like http://timber-lang.org/ , a direct descendant of O'Haskell, targeted at embedded real-time systems. If you are just stepping out of the OO programming world, it might be helpful to imagine OO as a rather narrow specialization of a concept called type, so that from the FP perspective it is just one of so many alternatives so that it gets lost a little -- which may be a useful translation to use. So the short answer to where's OO? in Haskell might just be data, while the expressive freedom of type classes / families might surprise you. There have been some people playing with cellular automata, Google helps, e.g.: http://mjsottile.wordpress.com/ http://trac.haskell.org/gloss/ Both cases might give you an impression how it's done with Haskell types. If you really are interested in using the OO class concept together with the Haskell type system by a more than practical motivation, an expert in the field who is interested in the subject for a long time is Peter Padawitz (http://fldit-www.cs.uni-dortmund.de/~peter/ http://fldit-www.cs.uni-dortmund.de/%7Epeter/); he has presented a beautiful synthesis based on category theory, swinging types (http://fldit-www.cs.uni-dortmund.de/~peter/Swinging.html http://fldit-www.cs.uni-dortmund.de/%7Epeter/Swinging.html). Of course, he did also use O'Haskell for his programming works in the past. Cheers, Nick On 01/14/2011 12:23 AM, gutti wrote: Hi, thanks for all Your answers (and again I'm amazed how active and good this forum is). I expected OOHaskell to be on the somewhat extended side, but I didn't expect it to be so uncommon. This very strong and clear feedback is indeed very valuable. I think I see the complexities of OO-programming in larger programs (unforeseen interactions), but I'm still doubtfull, that functional programming can equally adress all tasks equally efficient. I'm especially interestes in engineering calculation tasks where cellular automata could be used. In that case all u have to do is to give the class the right properties and that let it grow. Such a localised intelligence approach seems an ideal OO - task. I don't know whether something functional could achieve the same. Sounds like a nice challenge. -- I'll chew on a small example. Cheers Phil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] H98, OOHaskell - getting started with objects in Haskell
Hi! 2011/1/14 gutti philipp.guttenb...@gmx.net I'm especially interestes in engineering calculation tasks where cellular automata could be used. In that case all u have to do is to give the class the right properties and that let it grow. Such a localised intelligence approach seems an ideal OO - task. I don't know whether something functional could achieve the same. Thanks to your question, I took another look and the old and wonderful OOHaskell paper. It is very well written and describes almost exhaustively the haskell alternatives and their shortcomings: http://homepages.cwi.nl/~ralf/OOHaskell/paper.pdf Honestly, with the information I can have, my view is that the ·let it grow issue in the full is only achievable by following the OOHaskell path, but you can use the other ways paying a little price. This past discussion also applies: http://www.haskell.org/pipermail/haskell-cafe/2006-January/013925.html Sounds like a nice challenge. -- I'll chew on a small example. Cheers Phil -- View this message in context: http://haskell.1045720.n5.nabble.com/H98-OOHaskell-getting-started-with-objects-in-Haskell-tp3338991p3340604.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] H98, OOHaskell - getting started with objects in Haskell
gutti philipp.guttenberg at gmx.net writes: Hi, I wanted to check whether Haskell offers reasonably easy object oriented programming -- I already had a look into Haskell's overlooked object system und A Gentle Introduction to Haskell 98 [H98] I think you're better off starting by describing your problem, reason why do you actually need to use OO for. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] H98, OOHaskell - getting started with objects in Haskell
Hi, thanks for all Your answers (and again I'm amazed how active and good this forum is). I expected OOHaskell to be on the somewhat extended side, but I didn't expect it to be so uncommon. This very strong and clear feedback is indeed very valuable. I think I see the complexities of OO-programming in larger programs (unforeseen interactions), but I'm still doubtfull, that functional programming can equally adress all tasks equally efficient. I'm especially interestes in engineering calculation tasks where cellular automata could be used. In that case all u have to do is to give the class the right properties and that let it grow. Such a localised intelligence approach seems an ideal OO - task. I don't know whether something functional could achieve the same. Sounds like a nice challenge. -- I'll chew on a small example. Cheers Phil -- View this message in context: http://haskell.1045720.n5.nabble.com/H98-OOHaskell-getting-started-with-objects-in-Haskell-tp3338991p3340604.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] H98, OOHaskell - getting started with objects in Haskell
gutti wrote: I wanted to check whether Haskell offers reasonably easy object oriented programming -- I already had a look into Haskell's overlooked object system und A Gentle Introduction to Haskell 98 [H98] Its probably a bad idea to try and write Java style OO code in Haskell. Trying to do this with be playing against Haskell's strengths (type safe functional programming) and you will likely find a whole bunch of weakness that regular Haskell programmers never bump into. 2. is OOHaskell the right way to go - is it standardised (H98) or is it extension and is it widely used and recommended ? It is not widely used, the topic of OOHaskell rarely comes up in this mailing list or on the #haskell IRC channel. Since its not widely used, I would also think its not really recommended. 3. Haskell 98 offers datatypes and some sort of monadic classes -- is it possible to build simple objects without OOHaskell ? Haskell is not an OO langauge. Trying to write Java style OO code in Haskell will be painful. 4. When I want object properties to change, when should I use IORef when STRef ? Thats a really, really bad idea. Haskell is designed to be a pure functional language where mutable data is only used in limited circumstances when there is no other way. HTH, Erik -- -- Erik de Castro Lopo http://www.mega-nerd.com/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] H98, OOHaskell - getting started with objects in Haskell
Phil: I wanted to check whether Haskell offers reasonably easy object oriented programming It depends on what you're looking for, but in general, you won't find the same thing you may be used to in native OO languages. 1. OOHaskell doesn't seem to be available in the HackageDB (cabal) -- so how do I install it especially on Debian ? The paper and source are available via links on the website: http://homepages.cwi.nl/~ralf/OOHaskell/ . It appears that you could use darcs with the new repository: http://code.haskell.org/OOHaskell/ . 2. is OOHaskell the right way to go - is it standardised (H98) or is it extension and is it widely used and recommended ? It uses several language extensions beyond H98. AFAIK, it is not widely used. It was an interesting demonstration of the potential of the Haskell type system. I worked with it once, and it's nice research, but it hasn't yet been shown to be useful in practice. 3. Haskell 98 offers datatypes and some sort of monadic classes -- is it possible to build simple objects without OOHaskell ? 4. When I want object properties to change, when should I use IORef when STRef ? Once you become comfortable with Haskell, you will most likely find other ways to do things than the OO way. If you ask questions on this list about something you want to do, I'm sure you will get answers on how to do it the functional way. Sean ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] H98, OOHaskell - getting started with objects in Haskell
gutti wrote: I wanted to check whether Haskell offers reasonably easy object oriented programming If you really insist on doing OO programming in a functional language you may want to look at Scala and Ocaml, both of which have proper OO additions. I haven't used Scala myself but have done quite a bit of coding in Ocaml. My adivce for anyone coming from an imperative OO language to Ocaml is to avoid the OO stuff to start with and learn to write good, clean, pure functional code before starting to use references and OO. The only time I ever used objects in Ocaml was when I was writing code that used Ocaml's GTK+ GUI widget set bindings. These bindings expose classes/objects to the programmer so the programmer has to use OO. Erik -- -- Erik de Castro Lopo http://www.mega-nerd.com/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
