[Haskell-cafe] Re: Ideas of a polymorphic Tree in Haskell
On Thu, 2010-05-13 at 10:06 -0300, Edgar Z. Alvarenga wrote: Hi, I created a small Genetic Algorithm program, replicating this work (Statistical mechanics of program systems - JP Neirotti, N. Caticha, Journal of Physics A Math and Gen) made in Lisp. When a restricted the problem just for one type, the Haskell program worked perfectly with much less lines and a lot faster than the Lisp program. The problem was when I tried to generalize to polymorphic types. I'm using this datatype to represent a program: data Tree a = Bin (String, (a - a - a)) (Tree a) (Tree a) | Un (String, (a - a)) (Tree a) | V And can convert a Tree to a function with: treeToFunc :: Tree a - a - a treeToFunc (Bin f l r) = (snd f) $ treeToFunc l * treeToFunc r treeToFunc (Un f u) = (snd f).(treeToFunc u) treeToFunc V = id I already create another datatype to represent a polymorphic program (using GADT or existentials), but doesn't see a way to convert this kind of tree to a function. Anyone has any idea? Thanks, Edgar Hmm. What GDAT/existential do you use (for lazy people who do not want to read paper)? How is it programmed in Lisp? data Tree a where Bin :: String - (c - (a, b)) - (a - b - c) - Tree a - Tree b - Tree c Un :: String - (a - a) - Tree a V :: Tree a treeToFunc :: Tree a - a - a treeToFunc (Bin _ f g l r) v = let ~(x, y) = f v in g (treeToFunc l x) (treeToFunc r y) treeToFunc (Un _ f)v = f v treeToFunc V v = v Or data Tree a where Bin :: String - Tree a - Tree b - Tree (a, b) Un :: String - (a - a) - Tree a V :: Tree a treeToFunc :: Tree a - a - a treeToFunc (Bin _ l r) (a, b) = (treeToFunc l a, treeToFunc r b) treeToFunc (Un _ f)v = f v treeToFunc V v = v Both compiles but I'm not sure if they are what you want. Regards signature.asc Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Ideas of a polymorphic Tree in Haskell
On Thu, 13/May/2010 at 18:57 +0100, Maciej Piechotka wrote: Hmm. What GDAT/existential do you use (for lazy people who do not want to read paper)? The GADT that I refered was from my faileds attempts. How is it programmed in Lisp? The paper don't give much details, but by what I undertood, if a random generated program don't compile it's discarted. [...] Both compiles but I'm not sure if they are what you want. What I want is to can create trees like: U (a - b) (U (c - a) V) Or: B (a - b - c) (U (c - a) V) (U (c - b) V) And convert this to a function c - b. I think I have achieved this now, but really don't understand exactly how it works. Look at this: data Tree a b c where B :: (a - d - b) - Tree e a c - Tree g d c - Tree a b c U :: (a - b) - Tree d a c - Tree a b c V :: (c - d) - Tree c d c treeToFunc :: Tree a b c - c - b treeToFunc (B f l r) = f $ (treeToFunc l) * (treeToFunc r) treeToFunc (U f u) = f.(treeToFunc u) treeToFunc (V f) = f The only problem is that I need to create (V id) in the last leaf everytime: *Main let r = B (\x y - (fromInteger x) + y) (U floor (V id)) (U (**2) (V id)) *Main (treeToFunc r) 3 12.0 Do you see any way to simplify this solution? Thanks, Edgar Regards ___ 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] Re: Ideas of a polymorphic Tree in Haskell
On Thu, May 13, 2010 at 3:01 PM, Edgar Z. Alvarenga ed...@ymonad.comwrote: On Thu, 13/May/2010 at 18:57 +0100, Maciej Piechotka wrote: Hmm. What GDAT/existential do you use (for lazy people who do not want to read paper)? The GADT that I refered was from my faileds attempts. How is it programmed in Lisp? The paper don't give much details, but by what I undertood, if a random generated program don't compile it's discarted. The impression I had from your first email is that your GADT approach worked but you didn't want to use it here. Have you seen the research on higher-order abstract syntax (HOAS)? What you're doing looks fairly similar to my naive eyes. I didn't speak up because I thought you had already been down that road. I was just trying to find a paper on the subject (I think there was an ICFP paper that explained them in GADTs), and I found this: http://www.haskell.org/pipermail/haskell/2007-January/019012.html I think this is the paper I had in mind: http://adam.chlipala.net/papers/PhoasICFP08/ I hope you find those resources helpful! Jason ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Ideas
+++ Andrew Coppin [Aug 25 07 12:50 ]: How easy would it be to make / would anybody care / has somebody already made ... in Haskell? - A wiki program. (Ditto.) I wrote a simple wiki using HAppS and pandoc. See demonstration #15 on the pandoc web page: http://sophos.berkeley.edu/macfarlane/pandoc/examples.html It's by no means a finished product, but might serve as a good base if you decide to work on a wiki. John ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Ideas
may i ask you what did you had in mind as an application when you started that ? This was just recreational programming: I wanted to see what writing a web application in Haskell would be like. I think it would be great to have a fully featured wiki program in Haskell, but I don't have time to do it myself. Your idea sounds very interesting. Feel free to extend pandocwiki if that works for you; it's GPL. John ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Ideas
thanks John for replying... when building , i cannot find the lcs mentionned in the cabal file not on hasckage nor on goggle. could you help? ( your papers on philosophy looks quite serious .. impressive you are in haskell too .. math backgroud ? logics ?) 2007/8/26, John MacFarlane [EMAIL PROTECTED]: may i ask you what did you had in mind as an application when you started that ? This was just recreational programming: I wanted to see what writing a web application in Haskell would be like. I think it would be great to have a fully featured wiki program in Haskell, but I don't have time to do it myself. Your idea sounds very interesting. Feel free to extend pandocwiki if that works for you; it's GPL. John ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Ideas
lcs can be found at http://urchin.earth.li/darcs/igloo/lcs/ +++ Luc TAESCH [Aug 26 07 23:45 ]: when building , i cannot find the lcs mentionned in the cabal file not on hasckage nor on goggle. could you help? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
