Re: [Haskell-cafe] I Need a Better Functional Language!
10.04.2012, 02:00, Ryan Ingram ryani.s...@gmail.com: A concurring opinion here, and an example. iff :: Bol - a - a - a iff True x _ = x iff False _ x = x f, g :: Bool - Bool f x = x g x = iff x True False Are these two functions equal? I would say yes, they are. Yet once you can pattern match on functions, you can easily tell these functions apart, and create a function h :: (Bool - Bool) - Bool such that h f = True but h g = False. -- ryan I've just remembered an interesting statement that there is a language where each equivalence class of programs Dan Doel mentioned (f = g iff forall x. f x = g x) has a single program in it. That is there is a one-to-one correspondence between programs and functions. Though as far as I understood one cannot construct a translator from this language to another language. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] I Need a Better Functional Language!
Hello! I've just realized that Haskell is no good for working with functions! First, what are 'functions' we are interested at? It can't be the usual set-theoretic definition, since it is not constructive. The constructive definition should imply functions that can be constructed, computed. Thus these are computable functions that should be of our concern. But computable functions in essence are just a synonym for programs. One could expect from a language that bears 'functional' as its characteristic to be able to do everything imaginable with functions. However, the only thing Haskell can do with functions is to apply them to arguments and to feed them as arguments, run in parallel (run and concatenate programs). Obviously, that's not all of the imaginable possibilities. One also can rewrite programs. And write programs that rewrite programs. And write programs that rewrite programs that rewrite the first programs and so on. But there is no such possibility in Haskell, except for introducing a DSL. So now I wonder, what are the languages that are functional in the sense above? With a reasonable syntax and semantics, thus no assembler. I guess Lisp might be of this kind, but I'm not sure. In addition, I'm not a fan of parentheses. What else? Pure? Mathematica? Maxima? Note, that the reflectivity is important. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] How do you describe systems in general with Haskell?
If you are to describe a system, which consists of several subsystems, how do you approach the problem? What types, classes, functions whatever do you introduce? I guess it is a common problem, is there a general method? Just to describe, not to solve (though if the description implies the solution then it is wonderful). Obviously this is not just a haskell-specific problem, but I think there might be people who are aware of the best current solution (category theory?). For a dummy example, how would you describe the system from a fox, goose and bag of beans puzzle (wolf, goat and cabbage)? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Can't resolve class dependences (making Boolean class)
Hello! I'm trying to have a class for booleans called Boolean (the methods are not complete): class MyEq a where (===) :: (Boolean b) = a - a - b class (MyEq a) = Boolean a where (/\) :: a - a - a instance MyEq Bool where x === y = x==y instance Boolean Bool where (/\) = () However, to make Bool an instance of Boolean I need to make it an instance of MyEq first, which I can't, because to define === I need Bool to be in Boolean. Indeed the code above give the error: Could not deduce (b ~ Bool) from the context (Boolean b) bound by the type signature for === :: Boolean b = Bool - Bool - b at 1.hs:8:5-18 `b' is a rigid type variable bound by the type signature for === :: Boolean b = Bool - Bool - b at 1.hs:8:5 In the expression: x == y In an equation for `===': x === y = x == y In the instance declaration for `MyEq Bool' Failed, modules loaded: none. How can I overcome the issue? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Can't resolve class dependences (making Boolean class)
Thank you all guys, fromBool did the trick. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Question about type families
Is there a way to make the following code working?
{-# LANGUAGE TypeFamilies #-}
data family Foo a
data instance (Num a)= Foo a = A a deriving Show
data instance (Fractional a) = Foo a = B a deriving Show
I want to have different constructors for 'Foo a' depending on a class of 'a'.
Note also, that in the example above I also meant constructor A to be available
for (Fractional a) = Foo, since in that case 'a' has Num too. How can I
achieve it, maybe not with TypeFamilies? Current error is
Conflicting family instance declarations:
data instance Foo a -- Defined at 1.hs:7:33-35
data instance Foo a -- Defined at 1.hs:5:33-35
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[Haskell-cafe] TypeOperators and Unicode
I want to have Unicode symbols for type operator:
{-# LANGUAGE TypeOperators #-}
data a ── b = Foo a b
But it doesn't work. Any suggestions?
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Re: [Haskell-cafe] TypeOperators and Unicode
Still
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE UnicodeSyntax #-}
data a ── b = Foo a b
leads to
test.hs:4:6: Malformed head of type or class declaration: a ── b
Failed, modules loaded: none.
12.09.2011, 11:56, Maciej Marcin Piechotka uzytkown...@gmail.com:
On Mon, 2011-09-12 at 11:51 +0400, Grigory Sarnitskiy wrote:
I want to have Unicode symbols for type operator:
{-# LANGUAGE TypeOperators #-}
Add also:
{-# LANGUAGE UnicodeSyntax #-}
data a ── b = Foo a b
But it doesn't work. Any suggestions?
Regards
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[Haskell-cafe] Can I have a typeclass for topological spaces?
Hello! I just wonder whether it is possible to have a typeclass for topological spaces? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Can I have a typeclass for topological spaces?
Oh, I guess the class would look something like that: class TopologicalSpace a where ifOpen :: (Subset a) - Bool and Subset x is a type corresponding to subsets of x. 11.08.2011, 17:52, Grigory Sarnitskiy sargrig...@ya.ru: Hello! I just wonder whether it is possible to have a typeclass for topological spaces? ___ 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
[Haskell-cafe] Function returning the type of its argument.
It is not possible in Haskell, moreover it seems to be too alien to Haskell. Nevertheless, is there an extension which would allow to write a function that returns the type of its argument? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] GHC handles badly with math formulas
I've noted several times that GHC doesn't evaluate formulas for Double values during compilation. That is using 4.2326514735445615 instead of (512 / 0.844)**(1/3) or 0.906179845938664 instead of (1/3) * sqrt(5 + 2 * sqrt(10 / 7)) This can lead to significant slowdown if such values are called often. It's not always convenient to use where or let to reduce the number of calculations of such constants so I wonder how to force GHC to evaluate them during compilation? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Looking for n-body example with repa.
Hello! I'm studying repa package and trying to implement O(N^2) n-body code. I'm using Array DIM2 Double to represent the collection of particles. I've managed to write a function which calculates the energy of one particle in the field of others but I'm struggling to write a code to calculate the energy of the whole system. Maybe someone here has already written such code? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Accelerate package (CUDA). How to actually create an array?
Hello! I'm probing CUDA with Haskell, accelerate package to be exact. Sound stupid, but I couldn't find how to actually construct an array, for example Vector Float. There is quite a number of examples provided with the package, but they seem not simple enough for me just to start. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Accelerate package (CUDA). How to actually create an array?
There's fromIArray and fromList [1]. Does that answer your question? Huh, yes, thank you! But still I don't get it. Neither arr1 = fromList 3 [1,2,3] :: Array DIM1 Int nor arr1 = fromList (1,3) [1,2,3] :: Array DIM1 Int works ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] parMap doesn't work fine
Hello! I've just started using parallel computations in Haskell. parMap works fine, it is so easy to use. However, parMap fails with functions returning lazy structures, e.g. tuples. This code works as expected: (parMap rpar) bm tvalues bm :: Double - Double is some heavy function. But if I want to return list of pairs (t, bm t) it doesn't use cpu cores fine (only one is in use): (parMap rpar) (\t - (t, bm t)) tvalues The same is valid for functions returning lists. How do I use multiple cores with functions returning tuples? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Exception for NaN
How do I make my program stop whenever it gets somewhere NaN as a result during a calculation? If there is no appropriate flag for ghc maybe there exist flags for C to use in optc. I don't want NaN to propagate, it is merely stupid, it should be terminated. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Painless parallelization.
Hello, I'm searching a way to benefit from modern hardware in my programs. I consider parallel programing to be actually easier than sequential one. Parallel computation allows to avoid sophisticated algorithms that were developed to gain performance on sequential architecture. It should also allow to stop bothering about using immutable objects --- immutable parallel arrays should be as fast as mutable ones, right? (provided there is enough cores) So what are the options to write a pure functional parallel code with the level of abstraction I used in Haskell? So far I've found Data Parallel Haskell for multicore CPU's and Data.Array.Accelerate for GPU's. It would be nice to have something at the release state, rather than some beta. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Deciding equality of functions.
I guess that deciding whether two functions are equal in most cases is algorithmically impossible. However maybe there exists quite a large domain of decidable cases? If so, how can I employ that in Haskell? It is a common situation when one has two implementations of the same function, one being straightforward but slow, and the other being fast but complex. It would be nice to be able to check if these two versions are equal to catch bugs in the more complex implementation. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Data constructor synonyms
Hello! Assume I have a type MyType with the constructor GeneralConstructor: data MyType = GeneralConstructor [Double] but I also want to have a separate name for special case of this constructor: SpecialConstructor Double so SpecialConstructor a = GeneralConstructor (a:[]) that is SpecialConstructor 5 was exactly the same as GeneralConstructor [5]. And for example instead of writing GeneralConstructor [0] I would like to use constructor Zero. It's all just for convenience. How can I achieve this? Well, of course I always can use sed to replace SpecialConstructor 5 with GeneralConstructor [5] in program sources, but it's not convenient. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Data constructor synonyms
18.03.2011, 14:22, Roel van Dijk vandijk.r...@gmail.com;: Remember that constructors are functions, except that you can't pattern match against them. .. The downside is that you can't pattern-match against these functions. The thing is that I need pattern matching, just functions won't do. Anyway, a new question arose. If I have already declared a type, can I add new constructors to it from other modules? Maybe there are some GHC extensions to solve both these problems. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Effective function representation.
Hello! I need to deal with functions of type (Double - Double). I need Fourier transform, integration, + - * / operations, value of a function in a point, probably composition. However it is not very effective to use straightforwardly this type. Since functions in question are rather smooth (if not analytical), the best option would be to use some kind of pointwise representation (e.g. lists, arrays). But in this case the code wouldn't be so easy to understand and implement, compact and so on. Is there some libraries which allow me to work with functions as if their type was (Double - Double), but indeed it was something faster? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Equivalence of two expressions
I'm not very familiar with algebra and I have a question. Imagine we have ring K. We also have two expressions formed by elements from K and binary operations (+) (*) from K. Can we decide weather these two expressions are equivalent? If there is such an algorithm, where can I find something in Haskell about it? If there is no such algorithm for a ring, maybe there is for a field? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Friedberg numberings.
Hello! The question is not about Haskell, but I don't know where else to ask. In the book Computable functions by Vereshchagin and Shen it is said that it is possible to invent a programming language such that each programming problem has a unique solution in it. The author claims that this statement is a rewording of the theorem, that there is a universal computable function, such that any computable function has exactly one number. I wonder has such language been actually constructed? the book itself (look at the bottom of p 30 for the statement): http://books.google.ru/books?id=A6uvsks0abgCpg=PA30#v=onepageq=f=false ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Program with ByteStrings leads to memory exhaust.
I have a simple program that first generates a large (~ 500 mb) file of random numbers and then reads the numbers back to find their sum. It uses Data.Binary and Data.ByteString.Lazy. The problem is when the program tries to read the data back it quickly (really quickly) consumes all memory. The source: http://moonpatio.com/fastcgi/hpaste.fcgi/view?id=3607#a3607 or: module Main where import Data.Binary import Data.Int import System.Random import qualified Data.ByteString.Lazy as BL encodeFileAp f = BL.appendFile f . encode path = Results.data n = 20*1024*1024 :: Int getBlockSize :: BL.ByteString - Int64 getBlockSize bs = round $ (fromIntegral $ BL.length bs) / (fromIntegral n) fillFile :: StdGen - Int - IO () fillFile _ 0 =return () fillFile gen i = do let (x, gen') = random gen :: (Double, StdGen) encodeFileAp path x fillFile gen' (i-1) processFile :: BL.ByteString - Int64 - Int - Double - Double processFile bs blockSize 0 sum = sum processFile bs blockSize i sum = let tmpTuple = BL.splitAt blockSize bs x = decode $ fst $! tmpTuple in processFile (snd tmpTuple) blockSize (i-1) $! sum + x main = do fillFile (mkStdGen 42) n results - BL.readFile path putStrLn $ show $ processFile results (getBlockSize results) n 0 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Solved: [Was: Re: [Haskell-cafe] Program with ByteStrings leads to memory exhaust]
I have tweaked this program a few ways for you. The big mistake (and why it runs out of space) is that you take ByteString.Lazy.length to compute the block size. This forces the entire file into memory -- so no benefits of lazy IO. As a separate matter, calling 'appendFile . encode' incrementally for each element will be very slow. Much faster to encode an entire list in one go. Finally, using System.Random.Mersenne is significantly faster at Double generation that System.Random. Thank you! Just excellent! // I'm so happy :-) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] How to derive instance for type without exported constructor?
In System.Random StdGen is defined as data StdGen = StdGen Int32 Int32 but its constructor StdGen is not exported. How to make StdGen to be an instance of Binary? The following won't work: instance Data.Binary.Binary StdGen where put (StdGen aa ab) = do Data.Binary.put aa Data.Binary.put ab get = do aa - get ab - get return (StdGen aa ab) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to derive instance for type without exported constructor?
{-# OPTIONS_GHC -fglasgow-exts -XGenerics -package lang #-}
Got some problems:
Could not find module `Generics':
it is a member of package ghc-6.8.2, which is hidden
Failed, modules loaded: none.
and for ghci test.hs -fglasgow-exts -XGenerics -package lang
ghc-6.8.2: unknown package: lang
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Re: [Haskell-cafe] How to derive instance for type without exported constructor?
This time I've checked that it really compiles. Pretty much sure it works. But how?! I'can't compile it: test.hs:11:2: Conflicting definitions for `put'' Bound at: test.hs:11:2-5 test.hs:13:2-5 test.hs:20:2-5 In the default-methods for class Binary' test.hs:12:2: Conflicting definitions for `get'' Bound at: test.hs:12:2-5 test.hs:15:2-5 test.hs:21:2-5 In the default-methods for class Binary' ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to derive instance for type without exported constructor?
Well, I've managed to produce a solution, quite ugly and unefficient. Still it works (and I really need it). StdGen serialization occurs only once during computation that lasts several hours, so the speed is not vital for me. Here is my solution: module Main where import System.Random import Data.Binary import Data.Int data StdGen' = StdGen' Int32 Int32 deriving (Show) gen2gen' :: StdGen - StdGen' gen2gen' gen = let [g1, g2] = words $ show $ gen g1' = read g1 :: Int32 g2' = read g2 :: Int32 in StdGen' g1' g2' gen'2gen :: StdGen' - StdGen gen'2gen (StdGen' g1' g2') = let gen = read $ show g1' ++ ' ':(show g2') :: StdGen in gen instance Data.Binary.Binary StdGen' where put (StdGen' aa ab) = do Data.Binary.put aa Data.Binary.put ab get = do aa - get ab - get return (StdGen' aa ab) instance Data.Binary.Binary StdGen where put gen = put $ gen2gen' gen get = do gen' - get return (gen'2gen gen') ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Cabal install specific version of a package
How to install specific version of a package (derive 0.1.4)? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Can't derive Binary for StdGen
Hello! I'm trying to derive Binary for StdGen with DrIFT:
module Main where
import System.Random
import Data.Binary
{-!for StdGen derive : Binary !-}
data Foo = Foo StdGen StdGen deriving (Show) {-! derive : Binary !-}
but I got error DrIFT: can't find module System/Random
What shall I do?
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[Haskell-cafe] Got problems with classes
Hello! I can't understand why the following dummy example doesn't work.
{-# OPTIONS -XTypeSynonymInstances #-}
{-# OPTIONS -XFlexibleInstances #-}
module Main where
import Data.Array.Unboxed
class Particle p
type ParticleC = (Double, Double, Double)
instance Particle ParticleC
class Configuration c where
getParticleI :: (Particle p) = c - Int - p
type Collection p = UArray (Int,Int) Double
instance Configuration (Collection p) where
getParticleI config i = (1,1,1) :: ParticleC
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Re: [Haskell-cafe] Got problems with classes
Thank you all, and especially Bulat. I've folowed the links and solved the problem in a new way. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Program with profiling runs faster than without
14.07.09, 12:37, Grigory Sarnitskiy sargrig...@ya.ru: Hello! I can't understand why the following happens. ghc --make -fforce-recomp -O2 -fexcess-precision -fvia-C -optc-O2 Run.lhs -o Run -prof -auto-all and time ./Run TestSim seems to be much faster (I got ~4 times faster indeed) than just ghc --make -fforce-recomp -O2 -fexcess-precision -fvia-C -optc-O2 Run.lhs -o Run and time ./Run TestSim with ghc 6.8.2 on pentium 4 2.4 GHz under Ubuntu I was on my way to optimize the program when I've discovered this. The program is rather complicated and badly optimized but still I think it is quite strange to the profiled version to run faster. All necessary files I send with this letter (Tann.7z). Well, I've tested the code with ghc 6.10.3 under Windows --- the result is quite the same, however with the native binary compilier (not via C) the redult is even more drastic. I'm really interested how to obtain the same speed withput profiling compilation. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Program with profiling runs faster than without
14.07.09, 15:16, Malcolm Wallace malcolm.wall...@cs.york.ac.uk: This is only a guess, but maybe there is a context-qualified CAF-like value that is being re-evaluated multiple times in the non-profiling case, but is appropriately monomorphised in the profiling case, so it is only evaluated once? Regards, Malcolm And I guess you are quite right. I knew there is a poorly optimized place in my program, but I didn't touch it for some ideological reasons. But this morning I get how to optimize it in an ideological friendly manner, so now without profiling the program ~ 2 times faster. The speed of profiled version hasn't changed, hence I've manually done some work the compiler does during profiling. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Array Binary IO molecular simulation
To sum up here is the example that can write two arrays in one file and then read this two arrays back. To restore written data it just reads the file into bytestring, then splits the bytestring into equal parts. The parts are decoded. I suppose the method is suitable for decoding files with unboxed arrays of equal size. import Data.Array.Unboxed import Data.Binary import qualified Data.ByteString.Lazy as BL import IO a = listArray ((1,1),(3,2)) [3,4,5,6,7,8] :: UArray (Int, Int) Float b = listArray ((1,1),(3,2)) [9,10,11,12,13,14] :: UArray (Int, Int) Float encodeFile2 f = BL.appendFile f . encode encoder = do encodeFile Results.txt a encodeFile2 Results.txt b decoder = do contents - BL.readFile Results.txt print $ (show (decode (fst (BL.splitAt 118 contents)) :: UArray (Int, Int) Float)) print $ (show (decode (snd (BL.splitAt 118 contents)) :: UArray (Int, Int) Float)) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Array Binary IO molecular simulation
To sum up here is the example that can write two arrays in one file and then read this two arrays back. To restore written data it just reads the file into bytestring, then splits the bytestring into equal parts. The parts are decoded. I suppose the method is suitable for decoding files with unboxed arrays of equal size. import Data.Array.Unboxed import Data.Binary import qualified Data.ByteString.Lazy as BL import IO a = listArray ((1,1),(3,2)) [3,4,5,6,7,8] :: UArray (Int, Int) Float b = listArray ((1,1),(3,2)) [9,10,11,12,13,14] :: UArray (Int, Int) Float encodeFile2 f = BL.appendFile f . encode encoder = do encodeFile "Results.txt" a encodeFile2 "Results.txt" b decoder = do contents - BL.readFile "Results.txt" print $ (show (decode (fst (BL.splitAt 118 contents)) :: UArray (Int, Int) Float)) print $ (show (decode (snd (BL.splitAt 118 contents)) :: UArray (Int, Int) Float)) P.S. I've already sent this letter to mailist several ours ago, but it wasn't published :-/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Array Binary IO molecular simulation
2009/05/02 Jason Dusek :The original poster should try serializing a tuple of arrays instead of serializing each array individually.Maybe, but I have some doubts. I have to operate with thousands of arrays --- are tuples good in such case? Moreover it is desirable to write data as it is calculated to be sure it wont be lost if the program suddenly stops for some reason. Can tuple/array/list of arrays be serialized and written to the file without its whole computation, but just as new elements appear? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Array Binary IO molecular simulation
Hello!I'm interested in computer simulation of molecular systems, especially liquids. Maybe some would say Haskell is far from best choice in the case, but I really like the ease of writing programs in Haskell.So I wonder of existing projects of such type, both Molecular dynamics and Monte Carlo methods. I've got also some technical questions. Now I'm using 2D DiffUArray to represent particle positions during the simulation (when there are lots of array updates). Is this reasonably fast (I want to use pure external interface of DiffArray)?During the simulation each nth cycle the current position is stored for further processing. I haven't done this stage yet. To store the position I'm going to turn DiffUArray to UArray and write it in the file using tools of Data.Binary. Unfortunately I failed to produce the working code to write lots of 2D UArrays and then to read them. I know how to write several arrays in a file, but not how to read them back. Could someone please help me? Just to show how I've thought of storing several arrays in one file:import Data.Array.Unboxedimport Data.Binaryimport qualified Data.ByteString.Lazy as BLa = listArray ((1,1),(3,2)) [3,4,5,6,7,8] :: UArray (Int, Int) Floatb = listArray ((1,1),(3,2)) [9,10,11,12,13,14] :: UArray (Int, Int) FloatencodeFile2 f = BL.appendFile f . encoderun = do encodeFile "Results.txt" a encodeFile2 "Results.txt" b___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
