Re: [Haskell-cafe] What do you call Applicative Functor Morphism?
Hello, I'm curious and go a bit off topic triggered by your statement: On Nov 6, 2010, at 12:49 PM, rocon...@theorem.ca wrote: An applicative functor morphism is a polymorphic function, eta : forall a. A1 a - A2 a between two applicative functors A1 and A2 that preserve pure and * I recently wondered: why morphism and not homomorphism? Wikipedia says: In abstract algebra, a homomorphism is a structure-preserving map between two algebraic structures and In mathematics, a morphism is an abstraction derived from structure- preserving mappings between two mathematical structures. One difference is absract algebra ... algebraic structures vs mathematics ... mathematic structures another difference is the abstraction derived from part in the second phrase. So for the `Monoid` class, I'd say monoid homomorphism but I'm unsure whether `Applicative` counts as an algebraic structure or calls for using morphism instead. Is there a deeper reason why people use morphism and not homomorphism or is it just because it's shorter? Sebastian ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] What do you call Applicative Functor Morphism?
On Saturday 06 November 2010 2:09:13 am Sebastian Fischer wrote: Is there a deeper reason why people use morphism and not homomorphism or is it just because it's shorter? I don't really know. But that's (one) standard terminology in category theory. Objects and morphisms. It may be due to there being multiple prefixes in category theory that you can add to that: isomorphism epimorphism monomorphism ... In that light, it makes some sense to have the default be just morphism, rather than the additional homo- prefix. -- Dan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Compiler constraints in cabal
Ah, I hadn't thought of that. But doesn't the version of GHC change much more often than the version of base does? Reiner On 6 November 2010 03:49, Ozgur Akgun ozgurak...@gmail.com wrote: AFAIK, the way to do this is putting constraints on the base package. On 5 November 2010 14:59, Reiner Pope reiner.p...@gmail.com wrote: Hi, I have a library, hmatrix-static, on Hackage. Version 0.3 (the current version) compiles with ghc-6.12. Let's say I want to upgrade my library using new features in ghc-7.0, and then release these upgrades as version 0.4. Is there any way to state in my cabal file that this new version will no longer compile under ghc-6.12? The reason I would like to state this is so that a user with ghc-6.12 can do 'cabal install hmatrix-static' (or do a cabal install of a program depending on hmatrix-static) and see that cabal will install version 0.3 rather than attempt to install version 0.4 and fail. Thanks for your help. Reiner ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Compiler constraints in cabal
On 6 November 2010 17:52, Reiner Pope reiner.p...@gmail.com wrote: Ah, I hadn't thought of that. But doesn't the version of GHC change much more often than the version of base does? Each major version of GHC has a different (major) version of base. I think you can also say stuff like ghc = 6.10, but I'm not sure. -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] vector-space and standard API for vectors
On 11/5/10 7:54 AM, Alexey Khudyakov wrote:
We already know that there are noncommutative modules/vectorspaces of
interest (e.g., modules over quaternions and modules over graph paths),
why not support them from the beginning? It seems like you're going out
of your way to exclude things that would be trivial to include. This is
exactly why this is my standard complaint against the various proposals
out there for new numeric hierarchies. People who are used to only using
R^n think the proposals are just fine, but none of the proposals capture
the structures I work with daily. Which means the new proposals are no
better than the Prelude for me.
Could you tell what data structures do you use? It's difficult to think
about them without concrete examples.
Data structures? That varies a lot depending on the task: Data.Map,
Data.Set, Data.IntMap, Data.IntSet, Data.Trie, Data.ByteString...
A lot of my concrete examples of semirings and modules come from natural
language processing tasks. One example I already mentioned is the
semiring of a collection of paths over a graph (so something like
Data.Set (Data.Seq Arc)). Path collections show up, for example, when
dealing with Markov chains and HMMs where the goal is to maximize or sum
the weights over all paths.
To make it clearer, a Markov chain is a probabilistic version of a
finite state automaton, so you have some set of nodes, and the arcs for
transitioning from one node to another have probabilistic weights on
them. An HMM is an extension of a Markov chain into a probabilistic
version of a Moore machine, so in addition to the probabilistic
transitions from state to state, we also have for each state a
probability distribution over emitted symbols.
An interesting problem for HMMs is this: given some observed sequence of
emitted symbols, reconstruct the most likely path of states which would
cause the symbol sequence to be emitted. A nearly identical problem is:
given some observed sequence of symbols, determine the total probability
of all state sequences which could have generated it.
In addition to the perspective of HMMs as probabilistic Moore machines,
there are two other perspectives which are helpful. One is the graphical
model perspective where we have something that looks a bit like this (in
fixed-width font):
Q0 - Q1 - Q2 - ... - Qn
| ||
v vv
S1S2 Sn
Each Sk and Qk are random variables. The random variables Qk represent
being in some particular state q at time k, and the choice of which
state is drawn from a probability distribution based on the state
Q(k-1). The random variables Sk represent emitting some particular
symbol s at time k, and the choice of which symbol is drawn from a
distribution based on the state Qk.
The third perspective, which is the most helpful one for solving our two
problems, is if we take this graphical model and unfold it into a
trellis graph (ignoring the Sk variables for now). Each node in the
trellis represents an assignment of particular values to each of the
random variables. So if Q1 could take on values qA, qB, and qC then we'd
have three nodes for each of Q1=qA, Q1=qB, and Q1=qC. The arcs in the
trellis are weighted with the probability of transitioning from one node
to the next; so an arc Q1=q1 - Q2=q2 has weight Pr(Q2=q2 | Q1=q1). A
path through the trellis represents a variable assignment, which is to
say a sequence of states in the Markov chain; and the weight of the path
is the probability of the Markov chain taking that path.
There is a general algorithm for solving the two problems I mentioned,
and ultimately they're the same algorithm except with different
semirings. Note that a collection of paths between two points on a graph
forms a semiring[1] where sum is the union of path collections and
product is the extension of paths[2], so the answers we want can be
gotten by semiring homomorphisms from the collection of paths to some
other domain. To get the probability of all state sequences which could
give rise to a given symbol sequence we can use the probability
semiring[3] ---which we can simplify to the metric space [0..1] with (+)
and (*), since the algorithm ensures that all events are disjoint. This
version is called the forward algorithm. To get the probability the
most likely state sequence we can use the semiring [0..1] with max and
(+), which is called the Viterbi algorithm. In practice we tend to use
the log version of these semirings in order to prevent underflow.
There's also a variant of the Viterbi algorithm which stores
backpointers to the most likely previous state, which makes it easier to
recover the most likely state sequence instead of just the
(log)probability of the sequence. The Viterbi algorithm with back
pointers is also a semiring: Maybe(Prob, Maybe State) with Nothing as
zero, Just(1,Nothing) as one, argmax as sum: mx+my = do {
Re: Re[2]: [Haskell-cafe] Most popular haskell applications
Hi Bulat Doesn't your own FreeArc do pretty well? Its appealing to an audience beyond programmers. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Most popular haskell applications
Ivan Lazar Miljenovic wrote: Bulat Ziganshin wrote: people, are you know haskell apps that has more than 50k downloads per month (or more than 25k users) ? Possible candidates: * GHC * XMonad * Darcs * Pandoc I have no idea how to measure number of downloads or users, but pandoc is used outside of the Haskell community. (And it can process this email). Tillmann ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] What do you call Applicative Functor Morphism?
On 11/6/10 2:09 AM, Sebastian Fischer wrote: Hello, I'm curious and go a bit off topic triggered by your statement: On Nov 6, 2010, at 12:49 PM, rocon...@theorem.ca wrote: An applicative functor morphism is a polymorphic function, eta : forall a. A1 a - A2 a between two applicative functors A1 and A2 that preserve pure and * I recently wondered: why morphism and not homomorphism? Indeed, for the present example I'd call eta an applicative-functor homomorphism[1]. The use of morphism in category theory originated as a shortening of homomorphism[2], though there is a semantic difference between them as the two terms are used today. A morphism is an arrow in any particular category. What it takes to be morphism in category, C, depends on which category C happens to be. It turns out that many of the algebraic constructs studied outside of category theory form categories where the objects are particular constructs (e.g., specific rings, groups,...) and the morphisms are the appropriate homomorphisms (e.g., ring homomorphisms, group homomorphisms,...). Thus, the term homomorphism has to do with particular kinds of structure preserving transformations that are discussed in the underlying theories, whereas morphism is a general term in category theory used as a metatheory. [1] Assuming the context presented in the original email. In other contexts I may refer to eta as an Applicative morphism (i.e., a morphism in the category whose objects are Applicative instances) or as an Applicative transformation (i.e., a natural transformation between Applicative instances viewed as functors). [2] Whence the use of Hom(A,B) to refer to the collection of morphisms from A to B, and related terms like hom-set and hom-functor. -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Compiler constraints in cabal
On 11/6/10 3:13 AM, Ivan Lazar Miljenovic wrote: On 6 November 2010 17:52, Reiner Popereiner.p...@gmail.com wrote: Ah, I hadn't thought of that. But doesn't the version of GHC change much more often than the version of base does? Each major version of GHC has a different (major) version of base. I think you can also say stuff like ghc= 6.10, but I'm not sure. The correct condition notation is: impl(ghc = 6.10) -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Finding the contents of haskell platform?
On 05/11/2010 09:05 PM, Stephen Tetley wrote: On 5 November 2010 20:08, Andrew Coppinandrewcop...@btinternet.com wrote: Would it be hard to replace - with a real Unicode arrow character? It should be quite easy - whether a given font has an arrow readily available is a different matter. I can't remember the last time I saw a browser that couldn't do this. There /are/ symbols that don't work reliably, but the basic arrow symbols seem to be pretty well supported. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Compiler constraints in cabal
I was aware of this condition, but I'm not precisely sure it addresses my requirements. When you run cabal install some-package, cabal reads all version constraints listed in the build-depends field, and chooses which versions of which packages to download from Hackage in order to satisfy these constraints. I want to expose my dependency on a particular version of ghc to cabal's constraint satisfier. The end result I want is that when you type cabal install hmatrix-static with ghc-6.12 installed, then cabal chooses hmatrix-static-0.3; and when you type cabal install hmatrix-static with ghc-7.0 installed, then cabal chooses hmatrix-static-0.4. As I understand it, using impl(ghc = 7.0) won't achieve this. The closest thing I can think of is to write my hmatrix-static.cabal file for version 0.4 as: ... if impl(ghc 7.0) build-depends: nonexistant-package ... so that cabal cannot satisfy the constraints for hmatrix-static-0.4 unless I have ghc = 7.0. This seems a little hacky, and I'm also not sure if it works. (I'm finding it rather hard to test these ideas, because I don't want to upload a new package to Hackage every time...) All the best, Reiner On 6 November 2010 19:24, wren ng thornton w...@freegeek.org wrote: On 11/6/10 3:13 AM, Ivan Lazar Miljenovic wrote: On 6 November 2010 17:52, Reiner Popereiner.p...@gmail.com wrote: Ah, I hadn't thought of that. But doesn't the version of GHC change much more often than the version of base does? Each major version of GHC has a different (major) version of base. I think you can also say stuff like ghc= 6.10, but I'm not sure. The correct condition notation is: impl(ghc = 6.10) -- Live well, ~wren ___ 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] Finding the contents of haskell platform?
On 6 November 2010 09:52, Andrew Coppin andrewcop...@btinternet.com wrote: I can't remember the last time I saw a browser that couldn't do this. There /are/ symbols that don't work reliably, but the basic arrow symbols seem to be pretty well supported. Okay I'll shift my position a bit... Arrows are likely present in a modern system font. Outside the Symbol font, they aren't a standard symbol in PostScript and the font standards are based on PostScript - OpenType being the latest though it has less PostScript than its predecessors. But fonts are still quite a different beast to Unicode. So fonts are completely free not to define arrows or most other symbols, however it seems that standard system fonts e.g Arial, Times New Roman on Windows define them. There's no guarantee they will be present in the standard system fonts on old systems or in non-system fonts that define whichever symbols the font designer feels necessary. Modern browsers might add in arrow from a different font if it is not present in the one chosen by the web page author - I suspect this is happening on this page where the arrow looks wrong typographically: http://conal.net/blog/posts/adding-numbers/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Flagstone problem
On Thu, Nov 04, 2010 at 10:50:06AM -0700, michael rice wrote: Hi, I've been looking at a flagstone problem, where no two adjacent n-tuples can be identical. I solved the problem with Icon using Interesting stuff! = Here's my Haskell code import Data.Bits import Data.List flagstone n = foldl (++) (take n (map show (f $ group [if even y then 0 else 1 | y - [bitcount x | x - [20..]]]))) By the way, I would write this as flagstone n = concat . take n . map show . f . group . map (fromEnum . odd . bitcount) $ [20..] You should never use foldl (++) as it is rather inefficient: you get things like (((a ++ b) ++ c) ++ d) ... which ends up traversing the left part of the list repeatedly. And list comprehensions can be nice at times, but personally using map seems clearer in this case. = My question A further exercise in the text: Exercise 5.-(a) Define a(n) as the sum of the binary digits in the binary representation of n. Define b(i) as the number of a's between successive zeros as before. Then T = b(1) b(2) b(3) b(4) ... gives an infinite sequence of *seven* symbols with no repeats. (b) Write a routine to generate a sequence for seven colors of beads on a string with no repeats. I may be misreading, but does this make any sense? Doesn't make much sense to me. The sum of binary digits in the binary representation of n will not be zero very often... -Brent ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] What do you call Applicative Functor Morphism?
On Fri, Nov 05, 2010 at 11:49:27PM -0400, rocon...@theorem.ca wrote: An applicative functor morphism is a polymorphic function, eta : forall a. A1 a - A2 a between two applicative functors A1 and A2 that preserve pure and *: eta (pure c) = pure c eta (f * x) = eta f * eta x What do you guys call such a thing? My leading candidate is idomatic transformation. An applicative functor is a functor with some extra structure. Such a function is a natural transformation between the underlying functors that preserves the extra structure. So applicative transformation seems a logical name. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] hmatrix's fitModel function crashes ghc(i)
Hello, I would like to use hmatrix to do some function fitting with the Levenberg Marquardt algorithm. As an example I would like to fit the very simple function f x = a*x + b on some data points. The problem is that executing the 'fitModel' function crashes GHC(i) with a segmentation fault. This makes debugging difficult. Can anyone spot what I am doing wrong? Given all the lists of Double's it seems very easy to make an error regarding the number of arguments with the model function or the derivative. Try to evaluate the 'test' function in the small program listed below. I would expect an output of [1, 0] (y = 1*x + 0) instead of a segmentation fault. Relevant versions: - hmatrix-0.10.0.0 - gsl-1.14 - ghc-6.12.3 (64 bit) Small program: module Test where -- from base: import Control.Arrow ( second ) import Control.Applicative ( pure ) -- from hmatrix: import Data.Packed.Matrix( Matrix ) import Numeric.GSL.Fitting ( FittingMethod(LevenbergMarquardt), fitModel ) -- input list of (x, y) pairs, output coefficients of f x = a x * b fitLinear :: [(Double, Double)] - ([Double], Matrix Double) fitLinear samples = fitModel 1 1 10 (linearModel, linearDer) (map (second pure) samples) [0, 0] linearModel :: [Double] - Double - [Double] linearModel [a, b] x = [a*x + b, 0] linearModel _ x = error wrong arguments linearDer :: [Double] - Double - [[Double]] linearDer [_, _] x = [[x, 0]] linearDer _ _ = error wrong arguments test = fitLinear [(0,0), (1,1), (2,2)] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] How to put a string into Data.Binary.Put
Hi, I was trying to put a String in a ByteString import qualified Data.ByteString.Lazy as BS message :: BS.ByteString message = runPut $ do let string=SOME STRING map (putWord8.fromIntegral.ord) string -- this ofcourse generates [Put] How can I convert the list of Put's such that it could be used in the Put monad? For now I used the workaround of first converting the string to ByteString like this - stringToByteString :: String - BS.ByteString stringToByteString str = BS.pack (map (fromIntegral.ord) str) and then using putLazyByteString inside the Put monad. -- Regards, Kashyap ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Review request for my baby steps towards a platform independent interactive graphics using VNC
I've progressed further - now the VNC client opens up a window with
the dimensions set in the code!
https://github.com/ckkashyap/LearningPrograms/blob/master/Haskell/vnc/vnc.hs
I've pasted the code here for quick reference - would really
appreciate some feedback.
module Main where
import Network.Server
import Network.Socket
import Control.Monad
import System.IO
import qualified Data.ByteString.Lazy as BS
import Data.Char
import Data.Binary.Get
import Data.Binary.Put
import Data.Word
main :: IO ()
main = do
running - serveOne (Just $ UserWithDefaultGroup ckk) server
putStrLn server is accepting connections!!!
waitFor running
where server = Server (SockAddrInet 5901 iNADDR_ANY) Stream doVNC
doVNC :: ServerRoutine
doVNC (h,n,p) = do startRFB h
startRFB :: Handle - IO ()
startRFB h = do
hPutStr h RFB 003.003\n
hFlush h
clientHeaderByteStream - BS.hGet h 12
putStrLn (show clientHeaderByteStream)
let (m,n) = ( runGet readClientHeader clientHeaderByteStream)
-- Send 1 to the client, meaning, no auth required
BS.hPutStr h (BS.pack [0,0,0,1])
hFlush h
clientInitMessage - BS.hGet h 1
let sharedOrNot = runGet (do {x-getWord8;return(x);})
clientInitMessage
putStrLn (show sharedOrNot)
BS.hPutStr h serverInitMessage
hFlush h
serverInitMessage :: BS.ByteString
serverInitMessage = runPut $ do
putWord16be (300::Word16) -- width
putWord16be (300::Word16) -- height
--pixel format
putWord8 (32::Word8) -- bits per pixl
putWord8 (24::Word8) -- depth
putWord8 (1::Word8) -- big endian
putWord8 (1::Word8) -- true color
putWord16be (255::Word16) -- red max
putWord16be (255::Word16) -- green max
putWord16be (255::Word16) -- blue max
putWord8 (24::Word8) -- red shift
putWord8 (1::Word8) -- green shift
putWord8 (1::Word8) -- blue shift
--padding
putWord8 (0::Word8)
putWord8 (0::Word8)
putWord8 (0::Word8)
--name length
let name = Haskell Framebuffer
putWord32be (((fromIntegral.length)
name)::Word32)
putLazyByteString (stringToByteString name)
byteString2Number :: BS.ByteString - Int
byteString2Number bs = _byteString2Number 1 (digits bs)
where
_byteString2Number _ [] = 0
_byteString2Number n (x:xs) = (n*x) + (_byteString2Number
(n*10) xs)
digits bs = map ((+(-48)).fromIntegral) (BS.unpack(BS.reverse
bs))
readClientHeader = do
getLazyByteString 4
m - getLazyByteString 3
getWord8
n - getLazyByteString 3
getWord8
let majorVersionNumber = byteString2Number m
let minorVersionNumber = byteString2Number n
if (majorVersionNumber /= 3) then
fail (ERROR: Unsupported version ++ (show
majorVersionNumber))
else
return (byteString2Number m,byteString2Number n)
word8ToByteString :: Word8 - BS.ByteString
word8ToByteString n = runPut $ putWord8 n
word16ToByteString :: Word16 - BS.ByteString
word16ToByteString n = runPut $ putWord16be n
word32ToByteString :: Word32 - BS.ByteString
word32ToByteString n = runPut $ putWord32be n
stringToByteString :: String - BS.ByteString
stringToByteString str = BS.pack (map (fromIntegral.ord) str)
On Thu, Nov 4, 2010 at 12:18 PM, C K Kashyap ckkash...@gmail.com wrote:
Hi,
I started with the implementation of a VNC server library intended to
be used as a library for rendering graphics and interacting with the
user(mouse/keyboard). I'd appreciate it very much if I could get some
feedback on my approach to binary parsing and Haskellism.
Also, any reference/suggestion on how I could go about using a state
machine to deal with the RFB protocol.
http://hpaste.org/41131/vnc_server
It's really early - but just wanted to get some advice on the approach.
--
Regards,
Kashyap
--
Regards,
Kashyap
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to put a string into Data.Binary.Put
On Saturday 06 November 2010 13:30:45, C K Kashyap wrote: Hi, I was trying to put a String in a ByteString import qualified Data.ByteString.Lazy as BS message :: BS.ByteString message = runPut $ do let string=SOME STRING map (putWord8.fromIntegral.ord) string -- this ofcourse generates [Put] You'd want mapM_ (putWord8 . fromIntegral . ord) How can I convert the list of Put's such that it could be used in the Put monad? sequence_ :: Monad m = [m a] - m () if you want to use the results of the monadic actions, sequence :: Monad m = [m a] - m [a] Often sequence and sequence_ are used for list resulting from a map, so there's mapM_ :: Monad m = (a - m b) - [a] - m () mapM_ f xs = sequence_ (map f xs) mapM :: Monad m = (a - m b) - [a] - m [b] mapM f xs = sequence (map f xs) For now I used the workaround of first converting the string to ByteString like this - stringToByteString :: String - BS.ByteString stringToByteString str = BS.pack (map (fromIntegral.ord) str) and then using putLazyByteString inside the Put monad. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANNOUNCE: arrow-list. List arrows for Haskell.
Hi all, Live from the Hackaton in Ghent, Belgium, I present the first release of the arrow-list[1,2] package. List arrows are a powerful tool when processing XML, building query languages and lots of other domains that build on functions that might return more than one value as their output. This package is inspired by the arrow combinators provided by the HXT package, but in my opinion list arrows deserve to be on Hackage on their own. Cheers, Sebastiaan [1] http://hackage.haskell.org/package/arrow-list [2] https://github.com/sebastiaanvisser/arrow-list (package description) List arrows for Haskell. This small Haskell library provides some type class, types and functions to work with list arrows. List arrows represent computations that may return multiple outputs. Making functions that return lists an instance of both the `Category` and `Arrow` type classes allow you to easily compose multiple computations into one with standard building blocks. This package provides: - A type class `ArrowList` for embedding functions that produce a list of outputs into _some_ list arrow. - A list of utility functions for working with list-arrows, these functions are based on the `ArrowList` type class so they are not tied one specific instance. - A concrete list arrow type that is implemented as a `Kleisli` arrow over the `ListT` list monad transformer. In short, you can both build pure list arrows and list arrows that produce tributary effects. - Not list arrow specific: A type class `ArrowKleisli` for embedding monadic computations into an arrow. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to put a string into Data.Binary.Put
Thanks a lot Gregory and Daniel, I think I'll go with the mapM_ (putWord8 . fromIntegral . ord) approach. -- Regards, Kashyap ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Packagse for a simple database application
Hello Cafe, More as an exercice than anything else I would like to write a small database application which would allow a user to read/write data from/to a DB. The user would interact with the application via a web browser. Which (reliable/stable/workable) packages are the best for this task? I was thinking of Happstack and HaskellDB. Any others? Thank you Regards J-C ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] What do you call Applicative Functor Morphism?
On Sat, 6 Nov 2010, Sebastian Fischer wrote: Hello, I'm curious and go a bit off topic triggered by your statement: On Nov 6, 2010, at 12:49 PM, rocon...@theorem.ca wrote: An applicative functor morphism is a polymorphic function, eta : forall a. A1 a - A2 a between two applicative functors A1 and A2 that preserve pure and * I recently wondered: why morphism and not homomorphism? Morphisms can be more general than homomorphisms. But in this case I mean the morphisms which are homomorphisms. I was too lazy to write out the whole word. -- Russell O'Connor http://r6.ca/ ``All talk about `theft,''' the general counsel of the American Graphophone Company wrote, ``is the merest claptrap, for there exists no property in ideas musical, literary or artistic, except as defined by statute.'' ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to put a string into Data.Binary.Put
Use one of the Char8 modules, depending on whether you want a strict or lazy bytestring: --- import qualified Data.ByteString.Lazy.Char8 as BS message :: BS.ByteString message = BS.pack SOME STRING --- See the docs at: http://hackage.haskell.org/packages/archive/bytestring/0.9.1.7/doc/html/Data-ByteString-Char8.html http://hackage.haskell.org/packages/archive/bytestring/0.9.1.7/doc/html/Data-ByteString-Lazy-Char8.html mapping over putWord8 is much slower than putting a single bytestring; if you want to put a string, pack it first: --- putString :: String - Put putString str = putLazyByteString (BS.pack str) -- alternative: probably faster import qualified Data.ByteString.Char8 as B putString :: String - Put putString str = putByteString (B.pack str) --- On Sat, Nov 6, 2010 at 05:30, C K Kashyap ckkash...@gmail.com wrote: Hi, I was trying to put a String in a ByteString import qualified Data.ByteString.Lazy as BS message :: BS.ByteString message = runPut $ do let string=SOME STRING map (putWord8.fromIntegral.ord) string -- this ofcourse generates [Put] How can I convert the list of Put's such that it could be used in the Put monad? For now I used the workaround of first converting the string to ByteString like this - stringToByteString :: String - BS.ByteString stringToByteString str = BS.pack (map (fromIntegral.ord) str) and then using putLazyByteString inside the Put monad. -- Regards, Kashyap ___ 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] Flagstone problem
Hi Brent, Efficiency aside, your code is definitely more readable. I flubbed that step from True/False to 0/1 using fromEnum. Haskell's grab bag has so many tools it's easy to omit one. Thanks, Michael --- On Sat, 11/6/10, Brent Yorgey byor...@seas.upenn.edu wrote: From: Brent Yorgey byor...@seas.upenn.edu Subject: Re: [Haskell-cafe] Flagstone problem To: haskell-cafe@haskell.org Date: Saturday, November 6, 2010, 7:03 AM On Thu, Nov 04, 2010 at 10:50:06AM -0700, michael rice wrote: Hi, I've been looking at a flagstone problem, where no two adjacent n-tuples can be identical. I solved the problem with Icon using Interesting stuff! = Here's my Haskell code import Data.Bits import Data.List flagstone n = foldl (++) (take n (map show (f $ group [if even y then 0 else 1 | y - [bitcount x | x - [20..]]]))) By the way, I would write this as flagstone n = concat . take n . map show . f . group . map (fromEnum . odd . bitcount) $ [20..] You should never use foldl (++) as it is rather inefficient: you get things like (((a ++ b) ++ c) ++ d) ... which ends up traversing the left part of the list repeatedly. And list comprehensions can be nice at times, but personally using map seems clearer in this case. = My question A further exercise in the text: Exercise 5.-(a) Define a(n) as the sum of the binary digits in the binary representation of n. Define b(i) as the number of a's between successive zeros as before. Then T = b(1) b(2) b(3) b(4) ... gives an infinite sequence of *seven* symbols with no repeats. (b) Write a routine to generate a sequence for seven colors of beads on a string with no repeats. I may be misreading, but does this make any sense? Doesn't make much sense to me. The sum of binary digits in the binary representation of n will not be zero very often... -Brent ___ 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] http://functionalley.eu
I've just written a few packages which I think may be useful, and have made them available as free opensource on a personal website http://functionalley.eu. I opted to host them there rather than uploading them to Hackage, because they're part of a wider project. The main offerings are; a regex-engine which is polymorphic in terms of the type of the input-data, a traditional character-based regex-engine derived from it, and an application to determine the most efficient order in which to pack files into a given storage-space. I understand this isn't the ideal venue in which announce new packages, but having looked briefly at the hask...@haskell.org mail-group and the cerebral offerings there, I'm rather concerned that my meagre offerings may resemble germs in a Dettol factory. Is there a more appropriate forum ? If anyone has the time, I'd also greatly appreciate any feedback on this s/w. Regards, Alistair Ward P.S. This is my first posting. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] http://functionalley.eu
haskellcafe: I've just written a few packages which I think may be useful, and have made them available as free opensource on a personal website http://functionalley.eu Wonderful, thank you! I opted to host them there rather than uploading them to Hackage, because they're part of a wider project. Note that this means they won't be cabal installable or searchable. Was that your intention? -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] http://functionalley.eu
Black letters over dark blue background hurt my eyes. On 6 Nov 2010, at 18:10, Alistair Ward wrote: I've just written a few packages which I think may be useful, and have made them available as free opensource on a personal website http://functionalley.eu. I opted to host them there rather than uploading them to Hackage, because they're part of a wider project. The main offerings are; a regex-engine which is polymorphic in terms of the type of the input-data, a traditional character-based regex-engine derived from it, and an application to determine the most efficient order in which to pack files into a given storage-space. I understand this isn't the ideal venue in which announce new packages, but having looked briefly at the hask...@haskell.org mail-group and the cerebral offerings there, I'm rather concerned that my meagre offerings may resemble germs in a Dettol factory. Is there a more appropriate forum ? If anyone has the time, I'd also greatly appreciate any feedback on this s/w. Regards, Alistair Ward P.S. This is my first posting. ___ 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] http://functionalley.eu
I opted to host them there rather than uploading them to Hackage, because they're part of a wider project. Note that this means they won't be cabal installable or searchable. Was that your intention? I am curious about this: wasn't cabal designed with the option of having several package repos in mind? please clarify/document --remote-repo http://hackage.haskell.org/trac/hackage/ticket/759 Claus ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] http://functionalley.eu
claus.reinke: I opted to host them there rather than uploading them to Hackage, because they're part of a wider project. Note that this means they won't be cabal installable or searchable. Was that your intention? I am curious about this: wasn't cabal designed with the option of having several package repos in mind? please clarify/document --remote-repo http://hackage.haskell.org/trac/hackage/ticket/759 It supports remote Hackage repositories -- not arbitrary URLs (though that is planned). Search won't work though. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to put a string into Data.Binary.Put
On 11/6/10 6:38 AM, C K Kashyap wrote: Thanks a lot Gregory and Daniel, I think I'll go with the mapM_ (putWord8 . fromIntegral . ord) approach. If your string has any chance of containing Unicode characters then you will want to use the encode function in the module Codec.Binary.UTF8.String in the package utf8-string, so that the code becomes mapM_ putWord8 . encode Cheers, Greg ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Flagstone problem
On Nov 6, 2010, at 4:03 AM, Brent Yorgey wrote: Doesn't make much sense to me. The sum of binary digits in the binary representation of n will not be zero very often... I think they mean the sum (mod 2) when they say the sum of binary digits. That should be zero half the time. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Finding the contents of haskell platform?
On Nov 6, 2010, at 3:56 AM, Stephen Tetley wrote: Modern browsers might add in arrow from a different font if it is not present in the one chosen by the web page author - I suspect this is happening on this page where the arrow looks wrong typographically: I don't think that's what's going on. Notice that the font used in that page is fixed width. The arrow looks wrong because it has to fit in a fixed width space. Fixed width arrows all look stubby, even if they are styled like the rest of the font. Very few programming fonts have arrows or other symbols. When I played around with UnicodeSyntax, I tried lots of different fonts. The only one I found that is halfway readable is GNU Unifont (at unifoundry.com) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Finding the contents of haskell platform?
On 6 November 2010 18:01, Alexander Solla a...@2piix.com wrote: On Nov 6, 2010, at 3:56 AM, Stephen Tetley wrote: Modern browsers might add in arrow from a different font if it is not present in the one chosen by the web page author - I suspect this is happening on this page where the arrow looks wrong typographically: I don't think that's what's going on. Notice that the font used in that page is fixed width. The arrow looks wrong because it has to fit in a fixed width space. Fixed width arrows all look stubby, even if they are styled like the rest of the font. Yes - I expect I'm wrong on that, although I'd say the arrow looks wrong because its too low. I thought I read that Firefox does a font swap if it can't find a glyph, but thinking about it myself I can't see that this would make sense - Firefox would have to know an awful lot about the OSes fonts to know if they have missing glyphs. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: http://functionalley.eu
On Sat, 2010-11-06 at 15:10 +, Alistair Ward wrote: I opted to host them there rather than uploading them to Hackage, because they're part of a wider project. You can upload to hackage packages hosted (like webpage, code repo, bug tracker...) elsewhere - it similar to Ubuntu (or insert your favourite distro here) containing packages for KDE while not hosting KDE. 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: http://functionalley.eu
Thanks for the feedback. That sounds interesting. I've not uploaded anything to hackage before, so perhaps such features will become more obvious after I've had a go. On Sat, 2010-11-06 at 18:19 +, Maciej Piechotka wrote: On Sat, 2010-11-06 at 15:10 +, Alistair Ward wrote: I opted to host them there rather than uploading them to Hackage, because they're part of a wider project. You can upload to hackage packages hosted (like webpage, code repo, bug tracker...) elsewhere - it similar to Ubuntu (or insert your favourite distro here) containing packages for KDE while not hosting KDE. 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] Flagstone problem
Hi, Alexander Your change produces the same sequence of 0s, 1s, and 2s. mod n 2 == fromEnum (even n) Michael --- On Sat, 11/6/10, Alexander Solla a...@2piix.com wrote: From: Alexander Solla a...@2piix.com Subject: Re: [Haskell-cafe] Flagstone problem To: Cc: haskell-cafe Cafe haskell-cafe@haskell.org Date: Saturday, November 6, 2010, 1:40 PM On Nov 6, 2010, at 4:03 AM, Brent Yorgey wrote: Doesn't make much sense to me. The sum of binary digits in the binary representation of n will not be zero very often... I think they mean the sum (mod 2) when they say the sum of binary digits. That should be zero half the time. ___ 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] internship opportunities in France
Hello folks ! I am a Computer Science student looking for an internship of 6 months here in France. Does anybody know of any company working with Haskell ? Thanks in advance :D, Lorenzo Fundaró García ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: hmatrix's fitModel function crashes ghc(i)
Hello Roel, Roel van Dijk wrote: Hello, I would like to use hmatrix to do some function fitting with the Levenberg Marquardt algorithm. As an example I would like to fit the very simple function f x = a*x + b on some data points. The problem is that executing the 'fitModel' function crashes GHC(i) with a segmentation fault. Can you reproduce it on a 32 bit machine? There is a known problem with some hmatrix GSL wrappers on 64 bit in interpreted mode. This is mentioned at the end of the install page: http://code.haskell.org/hmatrix/install.html In this case the segmentation fault happens inside a foreign GSL function, only in interpreted code, and only in 64 bit. It does not happen in compiled code. (Although I have a report of a similar segmentation fault with compiled code if the output is redirected). I don't really know how to debug this kind of problem. As a first step I will try to obtain a minimal test case without any package dependencies. This makes debugging difficult. Can anyone spot what I am doing wrong? Your are doing nothing wrong. I will create a new, more visible page for the known problems. Given all the lists of Double's it seems very easy to make an error regarding the number of arguments with the model function or the derivative. Static argument checking would be ideal, but at least they are normal runtime errors and should never crash the program. Try to evaluate the 'test' function in the small program listed below. I would expect an output of [1, 0] (y = 1*x + 0) instead of a segmentation fault. It works for me in 32 bit: $ ghci Test.hs GHCi, version 6.12.3: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Loading package ffi-1.0 ... linking ... done. [1 of 1] Compiling Test ( Test.hs, interpreted ) Ok, modules loaded: Test. *Test test Loading package filepath-1.1.0.4 ... linking ... done. Loading package old-locale-1.0.0.2 ... linking ... done. Loading package old-time-1.0.0.5 ... linking ... done. Loading package unix-2.4.0.2 ... linking ... done. Loading package directory-1.0.1.1 ... linking ... done. Loading package process-1.0.1.3 ... linking ... done. Loading package array-0.3.0.1 ... linking ... done. Loading package storable-complex-0.2.1 ... linking ... done. Loading package hmatrix-0.10.0.1 ... linking ... done. ([1.0,0.0],(14) [ 1.0, 0.0, 1.0, 0.0 ]) Relevant versions: - hmatrix-0.10.0.0 - gsl-1.14 - ghc-6.12.3 (64 bit) Small program: module Test where -- from base: import Control.Arrow ( second ) import Control.Applicative ( pure ) -- from hmatrix: import Data.Packed.Matrix( Matrix ) import Numeric.GSL.Fitting ( FittingMethod(LevenbergMarquardt), fitModel ) -- input list of (x, y) pairs, output coefficients of f x = a x * b fitLinear :: [(Double, Double)] - ([Double], Matrix Double) fitLinear samples = fitModel 1 1 10 (linearModel, linearDer) (map (second pure) samples) [0, 0] linearModel :: [Double] - Double - [Double] linearModel [a, b] x = [a*x + b, 0] linearModel _ x = error wrong arguments linearDer :: [Double] - Double - [[Double]] linearDer [_, _] x = [[x, 0]] linearDer _ _ = error wrong arguments test = fitLinear [(0,0), (1,1), (2,2)] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] internship opportunities in France
Hello, as well as I know, there is very few, if no, jobs in Haskell in France. They are much more on CAML. Corentin On Sat, Nov 6, 2010 at 9:00 PM, Lorenzo Fundaró lfund...@etu.utc.fr wrote: Hello folks ! I am a Computer Science student looking for an internship of 6 months here in France. Does anybody know of any company working with Haskell ? Thanks in advance :D, Lorenzo Fundaró García ___ 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] What do you call Applicative Functor Morphism?
category theory encompasses more than just algebra. so there are homomorphisms, but also diffeomorphisms, symplectomorphisms, et cetera (in addition to things which don't have the -morphism suffix in normal usage, like continuous maps, natural transformations.) b On Nov 6, 2010, at 7:19 AM, rocon...@theorem.ca wrote: On Sat, 6 Nov 2010, Sebastian Fischer wrote: Hello, I'm curious and go a bit off topic triggered by your statement: On Nov 6, 2010, at 12:49 PM, rocon...@theorem.ca wrote: An applicative functor morphism is a polymorphic function, eta : forall a. A1 a - A2 a between two applicative functors A1 and A2 that preserve pure and * I recently wondered: why morphism and not homomorphism? Morphisms can be more general than homomorphisms. But in this case I mean the morphisms which are homomorphisms. I was too lazy to write out the whole word. -- Russell O'Connor http://r6.ca/ ``All talk about `theft,''' the general counsel of the American Graphophone Company wrote, ``is the merest claptrap, for there exists no property in ideas musical, literary or artistic, except as defined by statute.'' ___ 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] internship opportunities in France
Hi, There is for instance http://gamr7.com/ They are listed in http://www.haskell.org/haskellwiki/Haskell_in_industry Cheers, Thu 2010/11/6 Corentin Dupont corentin.dup...@gmail.com: Hello, as well as I know, there is very few, if no, jobs in Haskell in France. They are much more on CAML. Corentin On Sat, Nov 6, 2010 at 9:00 PM, Lorenzo Fundaró lfund...@etu.utc.fr wrote: Hello folks ! I am a Computer Science student looking for an internship of 6 months here in France. Does anybody know of any company working with Haskell ? Thanks in advance :D, Lorenzo Fundaró García ___ 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 mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Most popular haskell applications
On 6 November 2010 19:14, Tillmann Rendel ren...@mathematik.uni-marburg.de wrote: Ivan Lazar Miljenovic wrote: Bulat Ziganshin wrote: people, are you know haskell apps that has more than 50k downloads per month (or more than 25k users) ? Possible candidates: * GHC * XMonad * Darcs * Pandoc I have no idea how to measure number of downloads or users, but pandoc is used outside of the Haskell community. (And it can process this email). I _knew_ I was missing something... And seeing as how some ruby developers have developed bindings to pandoc, it _must_ be popular ;-) -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] internship opportunities in France
Nope, the page is outdated. Gamr7 doesn't use Haskell currently. They used it before, but now Haskell is sort of in standby. Currently they mostly use Python and C/C++. I don't work here, I know it since I have applied for this intership proposal (I'm french too) and been accepted. 2010/11/6 Vo Minh Thu not...@gmail.com Hi, There is for instance http://gamr7.com/ They are listed in http://www.haskell.org/haskellwiki/Haskell_in_industry Cheers, Thu 2010/11/6 Corentin Dupont corentin.dup...@gmail.com: Hello, as well as I know, there is very few, if no, jobs in Haskell in France. They are much more on CAML. Corentin On Sat, Nov 6, 2010 at 9:00 PM, Lorenzo Fundaró lfund...@etu.utc.fr wrote: Hello folks ! I am a Computer Science student looking for an internship of 6 months here in France. Does anybody know of any company working with Haskell ? Thanks in advance :D, Lorenzo Fundaró García ___ 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 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] internship opportunities in France
But (and sorry for the double mail), Lorenzo, you may want to take a look abroad. It looks like you are looking for the same thing I was. But I kind of gave up since I found 2 interesting internships in France (nothing to do with Haskell). You're looking for a 6-month intership. I guess you're in M2 or in 5th year in a school of engineering, right? (I'm in the INSA of Rouen) In France, I think it's a dead-end: I only know in France one university that teaches Haskell, that of Caen, and they're not proposing internships (I searched), and I know no company that uses Haskell. But there might be some company or university in Europe that could offer such an intership. 2010/11/6 Yves Parès limestr...@gmail.com Nope, the page is outdated. Gamr7 doesn't use Haskell currently. They used it before, but now Haskell is sort of in standby. Currently they mostly use Python and C/C++. I don't work here, I know it since I have applied for this intership proposal (I'm french too) and been accepted. 2010/11/6 Vo Minh Thu not...@gmail.com Hi, There is for instance http://gamr7.com/ They are listed in http://www.haskell.org/haskellwiki/Haskell_in_industry Cheers, Thu 2010/11/6 Corentin Dupont corentin.dup...@gmail.com: Hello, as well as I know, there is very few, if no, jobs in Haskell in France. They are much more on CAML. Corentin On Sat, Nov 6, 2010 at 9:00 PM, Lorenzo Fundaró lfund...@etu.utc.fr wrote: Hello folks ! I am a Computer Science student looking for an internship of 6 months here in France. Does anybody know of any company working with Haskell ? Thanks in advance :D, Lorenzo Fundaró García ___ 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 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] Review request for my baby steps towards a platform independent interactive graphics using VNC
On Nov 4, 2010, at 3:48 PM, C K Kashyap wrote: Also, any reference/suggestion on how I could go about using a state machine to deal with the RFB protocol. A simple way to model state machines is to use one function for each state. Each function calls the functions corresponding to successor states. (Not sure whether this answers you question, though). Sebastian ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANNOUNCE: arrow-list. List arrows for Haskell.
On Nov 6, 2010, at 10:00 PM, Sebastiaan Visser wrote: List arrows are a powerful tool when processing XML, building query languages and lots of other domains that build on functions that might return more than one value as their output. Interesting. Do you plan to write some examples that show * how to use ListArrows, * differences to using the list monad, and * when using ListArrow is preferrable? I'm interested to see something like this worked out although I have some rough ideas like monads are more powerful and arrows may allow stronger reasoning and more efficient implementations. Can you substantiate these general points for the concrete case of ListArrow vs list monad? I assume your implementation is *not* more efficient than the list monad as it builds on ListT. Sebastian ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] hmatrix's fitModel function crashes ghc(i)
Message: 29 Date: Sat, 6 Nov 2010 13:22:10 +0100 From: Roel van Dijk vandijk.r...@gmail.com Subject: [Haskell-cafe] hmatrix's fitModel function crashes ghc(i) To: Haskell Caf? haskell-cafe@haskell.org Message-ID: aanlktim5egsl_bz+ruv-=d-z3db65sc8o=ckqltcy...@mail.gmail.com Content-Type: text/plain; charset=UTF-8 Hello, I would like to use hmatrix to do some function fitting with the Levenberg Marquardt algorithm. As an example I would like to fit the very simple function f x = a*x + b on some data points. The problem is that executing the 'fitModel' function crashes GHC(i) with a segmentation fault. This makes debugging difficult. Can anyone spot what I am doing wrong? Given all the lists of Double's it seems very easy to make an error regarding the number of arguments with the model function or the derivative. Try to evaluate the 'test' function in the small program listed below. I would expect an output of [1, 0] (y = 1*x + 0) instead of a segmentation fault. Relevant versions: - hmatrix-0.10.0.0 - gsl-1.14 - ghc-6.12.3 (64 bit) Is that the 64 bit Linux ghc? I think the problem is with the GSL random number generation through GHCi. Try: module Test where Import Numeric.Container(RandDist,randomVector) seed = 0 size = 100 main = putStrLn $ show $ randomVector seed Gaussian size This should work when compiled with `ghc --make` and crash when invoked in `ghci`. I think the problem is with linking static data in GHCi on x86_64. Hope this helps. I seem to recall there might be a ghc trac ticket related to this but a quick search turned up nothing. Cheers, Vivian ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Compiler constraints in cabal
On 11/6/10 6:20 AM, Reiner Pope wrote: I was aware of this condition, but I'm not precisely sure it addresses my requirements. When you run cabal install some-package, cabal reads all version constraints listed in the build-depends field, and chooses which versions of which packages to download from Hackage in order to satisfy these constraints. I want to expose my dependency on a particular version of ghc to cabal's constraint satisfier. The end result I want is that when you type cabal install hmatrix-static with ghc-6.12 installed, then cabal chooses hmatrix-static-0.3; and when you type cabal install hmatrix-static with ghc-7.0 installed, then cabal chooses hmatrix-static-0.4. Clients of hmatrix-static would have to say if impl(ghc = 7.0) Build-Depends: hmatrix-static == 0.4.* else Build-Depends: hmatrix-static == 0.3.* in order to pull in the right dependency for themselves. In order to get the behavior you're after, though, is trickier business. Since every version of GHC ships with a different version of base, you'll have to make use of that knowledge such that users of ghc-7.0 with base-5 will get hmatrix-static-0.4 whereas users of ghc-6.12 with base-4 will get hmatrix-static-0.3 -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
