Re: [Haskell-cafe] Re: (flawed?) benchmark : sort

2008-03-12 Thread Denis Bueno
On Tue, Mar 11, 2008 at 4:01 AM, Adrian Hey [EMAIL PROTECTED] wrote: and sorting is meant to be a permutation, so we happily have the situation where this has a correct answer: 2. Anything else is incorrect. Isn't 3 also a permutation? Why is it incorrect? Because it is not

Re: [Haskell-cafe] Constructing Data.Map from ByteString

2008-03-12 Thread Adam Langley
On Mon, Mar 10, 2008 at 4:33 PM, Dave Tapley [EMAIL PROTECTED] wrote: Concerning this minimal example: http://hpaste.org/6268 Change the Data.ByteString.Char8 to Data.ByteString.Lazy.Char8, also the takeWhile, dropWhile pair is better expressed using span. With those two changes, and a 150MB

Re: [Haskell-cafe] Constructing Data.Map from ByteString

2008-03-12 Thread Philip Armstrong
On Mon, Mar 10, 2008 at 11:33:58PM +, Dave Tapley wrote: I've been plugging away at this all day and some discussion in #haskell has been fruitless. Perhaps you have the inspiration to see what's happening! Concerning this minimal example: http://hpaste.org/6268 It works as required,

Re: [Haskell-cafe] Equality constraints in type families

2008-03-12 Thread Tom Schrijvers
On Tue, 11 Mar 2008, Hugo Pacheco wrote: Yes, I have tried both implementations at the start and solved it by choosing for the following: type family F a :: * - * type FList a x = Either () (a,x) type instance F [a] = FList a instance (Functor (F [a])) where fmap _ (Left _) = Left () fmap f

Re: [Haskell-cafe] Equality constraints in type families

2008-03-12 Thread Hugo Pacheco
That's simple Tom. Imagine the factorial function for Int written as a paramorphism: type instance F Int = Either One instance (Mu Int) where inn (Left _) = 0 inn (Right n) = succ n out 0 = Left () out n = Right (pred n) instance Functor (F Int) where fmap _ (Left ()) = Left

Re: [Haskell-cafe] Re: (flawed?) benchmark : sort

2008-03-12 Thread Adrian Hey
Denis Bueno wrote: On Tue, Mar 11, 2008 at 4:01 AM, Adrian Hey [EMAIL PROTECTED] wrote: and sorting is meant to be a permutation, so we happily have the situation where this has a correct answer: 2. Anything else is incorrect. Isn't 3 also a permutation? Why is it incorrect?

Re: [Haskell-cafe] Exception handling when using STUArray

2008-03-12 Thread Donn Cave
On Mar 10, 2008, at 5:48 PM, Jonathan Cast wrote: On 10 Mar 2008, at 12:37 AM, Donn Cave wrote: ... An exception is, for me, any state that isn't properly accounted for in its immediate context. openFile could return 'Maybe Handle', but it doesn't, so the context demands a Handle or

Re: [Haskell-cafe] Re: [GSoC] A data parallel physics engine

2008-03-12 Thread Sebastian Sylvan
On Mon, Mar 10, 2008 at 11:48 PM, Manuel M T Chakravarty [EMAIL PROTECTED] wrote: Roman Cheplyaka: I'm looking for interesting project to work on during Google Summer of Code. So I found [1]A data parallel physics engine ticket and got excited about it. I'd like to know interested mentors

Re: [Haskell-cafe] Re: (flawed?) benchmark : sort

2008-03-12 Thread Derek Gladding
Speaking as someone who often has to answer questions along the lines of why isn't my code generating the results I want on your system?, I wouldn't call it evil, just commonly mistaken for Real. NaN breaks most assumptions about ordering: (NaN = _) == false (NaN == _) == false (NaN = _) ==

Re: [Haskell-cafe] Re: (flawed?) benchmark : sort

2008-03-12 Thread Remi Turk
On Tue, Mar 11, 2008 at 01:43:36AM -0400, Brandon S. Allbery KF8NH wrote: On Mar 11, 2008, at 0:20 , Chaddaï Fouché wrote: 2008/3/11, David Menendez [EMAIL PROTECTED]: I think Adrian is just arguing that a == b should imply f a == f b, for all definable f, in which case it doesn't *matter*

[Haskell-cafe] An offer to any haskell projects out there.

2008-03-12 Thread michael
Hello, My name is Michael Litchard. I'm a techie living in silicon valley, and I want to move into tech writing. I've got the background, now I need a portfolio. I figured the best way to go is to attach myself to some open source projects, and haskell has

Re: [Haskell-cafe] Re: Constructing Data.Map from ByteString

2008-03-12 Thread Adam Langley
On Tue, Mar 11, 2008 at 4:13 AM, Dave Tapley [EMAIL PROTECTED] wrote: I've upgraded to bytestring-0.9.0.5 from Darcs, no improvement. Also this morning I tried using Data.HashMap with Bytestring's readInt and HashMap's hashInt.. The result was a Stack space overflow :( Map is probably a

Re: [Haskell-cafe] A question about monad laws

2008-03-12 Thread askyle
My favorite presentation of the monad laws is associativity of Kliesli composition: (a1 = a2) x = a1 x = a2 -- predefined in 6.8 control.monad -- The laws return = a= a a = return= a a = (b = c) = (a = b) = c If you use this presentation you also need the following law:

Re: Re: [Haskell-cafe] A question about monad laws

2008-03-12 Thread askyle
I'm not sure whether this is the right branch of the thread for this post. Maybe it belongs to a different thread altogether. But here goes: Maybe most of our gripes with floating point arithmetic (besides broken implementations) is that we expect it to behave like Real arithmetic, and when it

Re: [Haskell-cafe] Constructing Data.Map from ByteString

2008-03-12 Thread Don Stewart
dave.a.tapley: Hi all, I've been plugging away at this all day and some discussion in #haskell has been fruitless. Perhaps you have the inspiration to see what's happening! Concerning this minimal example: http://hpaste.org/6268 It works as required, loading K/V pairs into a Data.Map,

Re: [Haskell-cafe] Re: Constructing Data.Map from ByteString

2008-03-12 Thread Duncan Coutts
On Tue, 2008-03-11 at 11:13 +, Dave Tapley wrote: Just a few updates on this one: I've upgraded to bytestring-0.9.0.5 from Darcs, no improvement. Also this morning I tried using Data.HashMap with Bytestring's readInt and HashMap's hashInt.. The result was a Stack space overflow :(

[Haskell-cafe] Re: (flawed?) benchmark : sort

2008-03-12 Thread Aaron Denney
On 2008-03-11, Adrian Hey [EMAIL PROTECTED] wrote: Neil Mitchell wrote: Hi (sort [a,b]) in the case we have: (compare a b = EQ) Which of the following 4 possible results are correct/incorrect? 1- [a,a] 2- [a,b] 3- [b,a] 4- [b,b] Fortunately the Haskell sort is meant to be

[Haskell-cafe] Bug with GADT in function Patterns?

2008-03-12 Thread Hugo Pacheco
Hi guys, I have found a bug on the compiler (at least ghc 6.8.2). For some module (yes, the example does nothing at all): *module Test where data Type a where Func :: Type a - Type b - Type (a - b) PF :: Type a - Type (PF a) data PF a where ID :: PF (a - a) test :: Type a - a - a

Re: [Haskell-cafe] Reflective capabilities of Haskell (cont'd)

2008-03-12 Thread jeff p
Hello, Data.Typeable gives you most of what you want except for access to function bodies. -Jeff On Tue, Mar 11, 2008 at 6:17 AM, Martin Hofmann [EMAIL PROTECTED] wrote: I am trying to port a programme written in Maude, which is a reflective language based on rewriting logic (

Re: [Haskell-cafe] IO () and IO [()]

2008-03-12 Thread Jules Bean
Henning Thielemann wrote: On Mon, 10 Mar 2008, Neil Mitchell wrote: I would like to know if in fact there's any difference in practice between (), [()], i.e. if in practice the difference matters. Usually, not so much. A lot of Monad functions have _ variants, i.e. mapM and mapM_. If you

[Haskell-cafe] Re: Re: Reflective capabilities of Haskell (cont'd)

2008-03-12 Thread Martin Hofmann
Data.Typeable gives you most of what you want except for access to function bodies. Thanks a lot, this helps a bit, but access to function bodies is exactly what I need. Or being more precise, I need the functionality of ghci's command ':t'. So functions that behave as follows, where

Re: [Haskell-cafe] Re: Constructing Data.Map from ByteString

2008-03-12 Thread Ketil Malde
Dave Tapley [EMAIL PROTECTED] writes: I've upgraded to bytestring-0.9.0.5 from Darcs, no improvement. Also this morning I tried using Data.HashMap with Bytestring's readInt and HashMap's hashInt.. The result was a Stack space overflow :( That's not so good. It works as required, loading

Re: [Haskell-cafe] Re: (flawed?) benchmark : sort

2008-03-12 Thread Ketil Malde
Adrian Hey [EMAIL PROTECTED] writes: So really I think the docs have this backwards. It's sortBy that implements a stable sort (assuming a suitably sane comparison function I guess) and apparently sort is whatever you get from (sortBy compare). But this is unduly restrictive on possible

[Haskell-cafe] ANNOUNCE: wxHaskell 0.10.3 rc1

2008-03-12 Thread Jeremy O'Donoghue
We are pleased to announce the first release candidate of wxHaskell 0.10.3. This is the first update with binary packages available since June 2005, and is the result of a great deal of work by a new team of contributors. We are hoping to make a full release shortly, and issues and bug reports

Re: [Haskell-cafe] simple Haskell question - List comprehensions

2008-03-12 Thread Philip Müller
Dan Licata schrieb: Does that help? Yeah, it did - Thanks! - Philip ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

Re: [Haskell-cafe] Exception handling when using STUArray

2008-03-12 Thread Henning Thielemann
On Tue, 11 Mar 2008, Donn Cave wrote: On Mar 10, 2008, at 5:48 PM, Jonathan Cast wrote: On 10 Mar 2008, at 12:37 AM, Donn Cave wrote: ... An exception is, for me, any state that isn't properly accounted for in its immediate context. openFile could return 'Maybe Handle', but it doesn't,

Re: [Haskell-cafe] [GSoC] A data parallel physics engine

2008-03-12 Thread Neil Mitchell
Hi I'm looking for interesting project to work on during Google Summer of Code. So I found [1]A data parallel physics engine ticket and got excited about it. I'd like to know interested mentors and community opinion about the complexity of such project. I don't think there are a great

Re: [Haskell-cafe] Exception handling when using STUArray

2008-03-12 Thread Brandon S. Allbery KF8NH
On Mar 11, 2008, at 14:27 , Donn Cave wrote: readLDAPMessage s = let [(_, msgID), (tag, body)] = berList s in LDAPMessage (berInt msgID) (readResponse tag body) I go on to account for all the LDAP stuff I need in about 60 lines of that kind of thing, 1/3 of it devoted to

Re: [Haskell-cafe] Re: (flawed?) benchmark : sort

2008-03-12 Thread Jules Bean
Adrian Hey wrote: Denis Bueno wrote: On Tue, Mar 11, 2008 at 4:01 AM, Adrian Hey [EMAIL PROTECTED] wrote: and sorting is meant to be a permutation, so we happily have the situation where this has a correct answer: 2. Anything else is incorrect. Isn't 3 also a permutation? Why is

Re: [Haskell-cafe] Re: (flawed?) benchmark : sort

2008-03-12 Thread Jules Bean
Derek Gladding wrote: Speaking as someone who often has to answer questions along the lines of why isn't my code generating the results I want on your system?, I wouldn't call it evil, just commonly mistaken for Real. Yes, of course. Double is an excellent example since it indicates that

Re: [Haskell-cafe] Re: (flawed?) benchmark : sort

2008-03-12 Thread Adrian Hey
Ketil Malde wrote: Adrian Hey [EMAIL PROTECTED] writes: So really I think the docs have this backwards. It's sortBy that implements a stable sort (assuming a suitably sane comparison function I guess) and apparently sort is whatever you get from (sortBy compare). But this is unduly restrictive

[Haskell-cafe] Reminder: 4th Haskell Hackathon, April 11-13 in Gothenburg

2008-03-12 Thread Bjorn Bringert
Hac4 4th Haskell Hackathon April 11-13, 2008 Gothenburg, Sweden http://haskell.org/haskellwiki/Hac4 Sponsored by Credit Suisse and Galois. This is a

Re: [Haskell-cafe] Exception handling when using STUArray

2008-03-12 Thread Donn Cave
On Mar 12, 2008, at 6:34 AM, Brandon S. Allbery KF8NH wrote: On Mar 11, 2008, at 14:27 , Donn Cave wrote: readLDAPMessage s = let [(_, msgID), (tag, body)] = berList s in LDAPMessage (berInt msgID) (readResponse tag body) I go on to account for all the LDAP stuff I need in about

Re: [Haskell-cafe] Re: (flawed?) benchmark : sort

2008-03-12 Thread Lennart Augustsson
I agree, I view == as some kind of equivalence relation in Haskell, and not a congruence relation (which would force x==y = f x == f y). Of course, the Haskell type system isn't strong enough to enforce anything more than it being a function returning a boolean. -- Lennart On Wed, Mar 12, 2008

[Haskell-cafe] File I/O question

2008-03-12 Thread Andrew Coppin
Hi Cafe. There's good news and there's bad news. The bad news is... I'm back. [Did I miss anything good?] The good news is... I have an actual question to ask as well. When I write to a file using System.IO, the file is locked for exclusive access. I gather this is as specified in the

Re: [Haskell-cafe] Space leak - help needed

2008-03-12 Thread Krzysztof Kościuszkiewicz
On Mon, Mar 03, 2008 at 05:20:09AM +0100, Bertram Felgenhauer wrote: Another story from an (almost) happy Haskell user that finds himself overwhelmed by laziness/space leaks. I'm trying to parse a large file (600MB) with a single S-expression like structure. With the help of

Re: [Haskell-cafe] Re: Re: Reflective capabilities of Haskell (cont'd)

2008-03-12 Thread Jeff Polakow
Hello, Thanks a lot, this helps a bit, but access to function bodies is exactly what I need. Or being more precise, I need the functionality of ghci's command ':t'. So functions that behave as follows, where everything is of course meta-represented in some way as ADT: Prelude

Re: [Haskell-cafe] Re: (flawed?) benchmark : sort

2008-03-12 Thread Adrian Hey
Jules Bean wrote: Adrian Hey wrote: This might be a reasonable thing to say about *sortBy*, but not sort as the ordering of equal elements should not be observable (for any correct instance of Ord). It should be impossible to implement a function which can discriminate between

Re: [Haskell-cafe] Re: (flawed?) benchmark : sort

2008-03-12 Thread Adrian Hey
Remi Turk wrote: I wouldn't bet on it either: Prelude 0.0 == -0.0 True Prelude isNegativeZero 0.0 == isNegativeZero (-0.0) False Although isNegativeZero might be considered a ``private, internal interface that exposes implementation details.'' Interesting example. So is the correct

Re: [Haskell-cafe] [GSoC] A data parallel physics engine

2008-03-12 Thread Jed Brown
On 12 Mar 2008, [EMAIL PROTECTED] wrote: I'm looking for interesting project to work on during Google Summer of Code. So I found [1]A data parallel physics engine ticket and got excited about it. I'd like to know interested mentors and community opinion about the complexity of such project.

Re: [Haskell-cafe] Re: (flawed?) benchmark : sort

2008-03-12 Thread Adrian Hey
Aaron Denney wrote: On 2008-03-11, Adrian Hey [EMAIL PROTECTED] wrote: Having tried this approach myself too (with the clone) I can confirm that *this way lies madness*, so in future I will not be making any effort to define or respect sane, unambiguous and stable behaviour for insane Eq/Ord

Re: [Haskell-cafe] Re: Re: Reflective capabilities of Haskell (cont'd)

2008-03-12 Thread Jeff Polakow
Hello, Prelude Data.Typeable typeOf (\a - (Just (a:))) (\a - (Just (a:))) :: Char - Maybe [Char] Prelude Data.Typeable getDomain $ typeOf (\a - (Just (a:))) [Char] Prelude Data.TypeablegetCodomain $ typeOf (\a - (Just (a:))) (Maybe [Char]) Data.Typeable

Re: [Haskell-cafe] Re: (flawed?) benchmark : sort

2008-03-12 Thread Lennart Augustsson
I'd say that any polymorphic code that assumes that x==y implies x=y is broken. But apart from that, floating point numbers break all kinds of laws that we might expect to hold. Even so, they are convenient to have instances of various classes. On Wed, Mar 12, 2008 at 7:31 PM, Adrian Hey [EMAIL

Re: [Haskell-cafe] Re: Constructing Data.Map from ByteString

2008-03-12 Thread Ketil Malde
Duncan Coutts [EMAIL PROTECTED] writes: To get something really compact we could use an index composed of three unboxed Int arrays. To get something *really* compact, we could build a (kind of) suffix array. That is, we do a lexical sort of the lines, and store the sorted offsets of the

Re: [Haskell-cafe] Space leak - help needed

2008-03-12 Thread Justin Bailey
On Wed, Mar 12, 2008 at 12:12 PM, Krzysztof Kościuszkiewicz [EMAIL PROTECTED] wrote: I have tried both Poly.StateLazy and Poly.State and they work quite well - at least the space leak is eliminated. Now evaluation of the parser state blows the stack... The code is at

Re: [Haskell-cafe] Exception handling when using STUArray

2008-03-12 Thread Brandon S. Allbery KF8NH
On Mar 12, 2008, at 14:17 , Donn Cave wrote: Sure. It isn't a lot of code, so I subjected it to Either-ization as an experiment, and I did indeed take the monad procedural route. Monad != procedural, unless you insist on do notation. Think of it as composition (it may be easier to use

Re: [Haskell-cafe] Exception handling when using STUArray

2008-03-12 Thread Donn Cave
On Mar 12, 2008, at 12:32 PM, Brandon S. Allbery KF8NH wrote: On Mar 12, 2008, at 14:17 , Donn Cave wrote: Sure. It isn't a lot of code, so I subjected it to Either-ization as an experiment, and I did indeed take the monad procedural route. Monad != procedural, unless you insist on do

Re: [Haskell-cafe] IO () and IO [()]

2008-03-12 Thread Lennart Augustsson
Yes, I wish Haskell had a 1-tuple. The obvious syntax is already taken, but I could accept something different, like 'One a'. On Mon, Mar 10, 2008 at 11:17 PM, Dan Weston [EMAIL PROTECTED] wrote: I understand the lack of distinction between a unit type and a 0-tuple, since they are

Re: [Haskell-cafe] [GSoC] A data parallel physics engine

2008-03-12 Thread Bas van Dijk
2008/3/10 Roman Cheplyaka [EMAIL PROTECTED]: I'm looking for interesting project to work on during Google Summer of Code. So I found [1]A data parallel physics engine ticket and got excited about it. I'd like to know interested mentors and community opinion about the complexity of such

Re: [Haskell-cafe] [GSoC] A data parallel physics engine

2008-03-12 Thread Andrew Coppin
Bas van Dijk wrote: A bit offtopic but slightly related: I just added a GSoC project proposal about adding a nVidia CUDA backend to Data Parallel Haskell: http://hackage.haskell.org/trac/summer-of-code/ticket/1537 It would be great if this physics engine or matrix library could run on a CUDA

[Haskell-cafe] Re: (flawed?) benchmark : sort

2008-03-12 Thread Aaron Denney
On 2008-03-12, Adrian Hey [EMAIL PROTECTED] wrote: Aaron Denney wrote: On 2008-03-11, Adrian Hey [EMAIL PROTECTED] wrote: Having tried this approach myself too (with the clone) I can confirm that *this way lies madness*, so in future I will not be making any effort to define or respect sane,

Re: [Haskell-cafe] File I/O question

2008-03-12 Thread Don Stewart
andrewcoppin: Hi Cafe. There's good news and there's bad news. The bad news is... I'm back. [Did I miss anything good?] The good news is... I have an actual question to ask as well. When I write to a file using System.IO, the file is locked for exclusive access. I gather this is as

Re: [Haskell-cafe] An offer to any haskell projects out there.

2008-03-12 Thread Don Stewart
michael: Hello, My name is Michael Litchard. I'm a techie living in silicon valley, and I want to move into tech writing. I've got the background, now I need a portfolio. I figured the best way to go is to attach myself to some open source projects, and haskell

Re: [Haskell-cafe] File I/O question

2008-03-12 Thread Andrew Coppin
Don Stewart wrote: Hey Andrew, What are you trying to do? Read and write to the same file (if so, you need to use strict IO), or are you trying something sneakier? I have a long-running Haskell program that writes status information to a log file. I'd like to be able to open and read that

[Haskell-cafe] Java interfacing and ghc-6.8?

2008-03-12 Thread Marc Weber
Hi, I've read on haskell org about gcjni Haskel/Java VM bridge Lambada ( ghc 6.6.1) Do you know wether any of them can be compiled with ghc-6.8 ? If not does it need much effort to patch them? Sincerly Marc Weber ___ Haskell-Cafe mailing list

Re: [Haskell-cafe] File I/O question

2008-03-12 Thread Don Stewart
andrewcoppin: Don Stewart wrote: Hey Andrew, What are you trying to do? Read and write to the same file (if so, you need to use strict IO), or are you trying something sneakier? I have a long-running Haskell program that writes status information to a log file. I'd like to be able

[Haskell-cafe] Termination of substitution

2008-03-12 Thread Neil Mitchell
Hi I'm trying to show that a system of rules for manipulating Haskell expressions is terminating. The rules can be applied in any order, to any subexpression - and there is a problem if there is any possible infinite sequence. The rule that is giving me particular problems is: (\v - x) y =

Re: [Haskell-cafe] Java interfacing and ghc-6.8?

2008-03-12 Thread Don Stewart
marco-oweber: Hi, I've read on haskell org about gcjni Haskel/Java VM bridge Lambada ( ghc 6.6.1) Do you know wether any of them can be compiled with ghc-6.8 ? If not does it need much effort to patch them? None of these are maintained, as far as I'm aware, but the Java FFI

Re: [Haskell-cafe] File I/O question

2008-03-12 Thread Andrew Coppin
Don Stewart wrote: andrewcoppin: Don Stewart wrote: Hey Andrew, What are you trying to do? Read and write to the same file (if so, you need to use strict IO), or are you trying something sneakier? I have a long-running Haskell program that writes status information to a log

Re: [Haskell-cafe] [GSoC] A data parallel physics engine

2008-03-12 Thread Dan Piponi
2008/3/12 Jed Brown [EMAIL PROTECTED]: It would be a shame to ...miss the very important point that a matrix is nothing more than a linear transformation between finite dimensional spaces. I rate this obvious seeming fact as one of the most important things I've learnt about numerical

Re: [Haskell-cafe] Exception handling when using STUArray

2008-03-12 Thread Henning Thielemann
On Wed, 12 Mar 2008, Donn Cave wrote: On Mar 12, 2008, at 12:32 PM, Brandon S. Allbery KF8NH wrote: On Mar 12, 2008, at 14:17 , Donn Cave wrote: Sure. It isn't a lot of code, so I subjected it to Either-ization as an experiment, and I did indeed take the monad procedural route. Monad !=

Re: [Haskell-cafe] IO () and IO [()]

2008-03-12 Thread Bryan O'Sullivan
Lennart Augustsson wrote: Yes, I wish Haskell had a 1-tuple. The obvious syntax is already taken, but I could accept something different, like 'One a'. Python's one-tuple syntax is (1,). The obvious difficulty with adapting this notation to Haskell lies in how one might write the constructor

Re: [Haskell-cafe] File I/O question

2008-03-12 Thread Don Stewart
andrewcoppin: Nope. Just WriteMode. I'm trying to read the file from Notepad.exe while my Haskell program is still running - which takes about an hour. Oh, you want another process in the system to read the file while GHC is writing to it? This works fine on unix systems -- and perhaps

Re: [Haskell-cafe] File I/O question

2008-03-12 Thread Andrew Coppin
Don Stewart wrote: Oh, you want another process in the system to read the file while GHC is writing to it? That's the one. ;-) [Well, not GHC but my GHC-compiled binary, but anyway...] This works fine on unix systems -- and perhaps Neil, or one of the other windows experts, can explain what

Re: [Haskell-cafe] [GSoC] A data parallel physics engine

2008-03-12 Thread Don Stewart
ndmitchell: Hi I'm looking for interesting project to work on during Google Summer of Code. So I found [1]A data parallel physics engine ticket and got excited about it. I'd like to know interested mentors and community opinion about the complexity of such project. I don't think

Re: [Haskell-cafe] [GSoC] A data parallel physics engine

2008-03-12 Thread Don Stewart
v.dijk.bas: 2008/3/10 Roman Cheplyaka [EMAIL PROTECTED]: I'm looking for interesting project to work on during Google Summer of Code. So I found [1]A data parallel physics engine ticket and got excited about it. I'd like to know interested mentors and community opinion about the

Re: [Haskell-cafe] Termination of substitution

2008-03-12 Thread Taral
On 3/12/08, Neil Mitchell [EMAIL PROTECTED] wrote: However, I don't believe this expression is type safe in Haskell. Using higher-order polymorphism: f (x :: forall a. a - a) = x x -- Taral [EMAIL PROTECTED] Please let me know if there's any further trouble I can give you. -- Unknown

Re: [Haskell-cafe] [GSoC] A data parallel physics engine

2008-03-12 Thread Andrew Coppin
Don Stewart wrote: Note there's already a project at UNSW, with a PhD student attached, doing an nvidia CUDA backend to Data Parallel Haskell. Perhaps this could be factored in somehow? At least there's a source of mentors here. Aa... I'd forgotten what an exciting place the Haskell

Re: [Haskell-cafe] Termination of substitution

2008-03-12 Thread Stefan O'Rear
On Wed, Mar 12, 2008 at 09:05:03PM +, Neil Mitchell wrote: Hi I'm trying to show that a system of rules for manipulating Haskell expressions is terminating. The rules can be applied in any order, to any subexpression - and there is a problem if there is any possible infinite sequence.

Re: [Haskell-cafe] Termination of substitution

2008-03-12 Thread Stefan O'Rear
On Wed, Mar 12, 2008 at 02:30:41PM -0700, Taral wrote: On 3/12/08, Neil Mitchell [EMAIL PROTECTED] wrote: However, I don't believe this expression is type safe in Haskell. Using higher-order polymorphism: f (x :: forall a. a - a) = x x Interestingly, this doesn't work - f is a

Re: [Haskell-cafe] [GSoC] A data parallel physics engine

2008-03-12 Thread Bas van Dijk
On Wed, Mar 12, 2008 at 10:27 PM, Don Stewart [EMAIL PROTECTED] wrote: Note there's already a project at UNSW, with a PhD student attached, doing an nvidia CUDA backend to Data Parallel Haskell. Great, do you perhaps have a link to a page describing that project? Then I can link to it from

Re: [Haskell-cafe] [GSoC] A data parallel physics engine

2008-03-12 Thread Dan Piponi
On Wed, Mar 12, 2008 at 2:33 PM, Andrew Coppin [EMAIL PROTECTED] wrote: Hanging around here, you really feel like you're at the cutting edge of... something... heh. Another approach isn't to target a CUDA back end for Haskell but to write an array library that builds computations that can

Re: [Haskell-cafe] Exception handling when using STUArray

2008-03-12 Thread Donn Cave
On Mar 12, 2008, at 2:10 PM, Henning Thielemann wrote: On Wed, 12 Mar 2008, Donn Cave wrote: On Mar 12, 2008, at 12:32 PM, Brandon S. Allbery KF8NH wrote: On Mar 12, 2008, at 14:17 , Donn Cave wrote: Sure. It isn't a lot of code, so I subjected it to Either-ization as an experiment, and

Re: [Haskell-cafe] An offer to any haskell projects out there.

2008-03-12 Thread Tim Chevalier
On 3/12/08, Don Stewart [EMAIL PROTECTED] wrote: One of the best things you could do would be to submit patches against the core library set where documentation is missing. Starting with things in base, array, containers, directory, filepath, pretty, time etc. That would likely help the

Re: [Haskell-cafe] Starting Haskell with a web application

2008-03-12 Thread Adam Langley
On Wed, Mar 5, 2008 at 12:25 PM, Adam Langley [EMAIL PROTECTED] wrote: I'm working towards, is an OpenID consumer. Once I have that working, I'll do a second release. It's not that far off, it's just a question of time. The darcs release of minihttp[1] can now do this. It's not a Hackage

Re: [Haskell-cafe] Starting Haskell with a web application

2008-03-12 Thread Adam Langley
On Wed, Mar 12, 2008 at 3:49 PM, Adam Langley [EMAIL PROTECTED] wrote: The OpenID example is running in EC2[4] at the moment if anyone wants to play. Well, thanks to all the people who hit it, there's nothing like users to find the stupid bugs ;) * Caching was wrong on the front page, so

Re: [Haskell-cafe] [GSoC] A data parallel physics engine

2008-03-12 Thread Roman Leshchinskiy
Neil Mitchell wrote: Hi I'm looking for interesting project to work on during Google Summer of Code. So I found [1]A data parallel physics engine ticket and got excited about it. I'd like to know interested mentors and community opinion about the complexity of such project. I don't think

Re: [Haskell-cafe] [GSoC] A data parallel physics engine

2008-03-12 Thread Roman Leshchinskiy
Bas van Dijk wrote: A bit offtopic but slightly related: I just added a GSoC project proposal about adding a nVidia CUDA backend to Data Parallel Haskell: http://hackage.haskell.org/trac/summer-of-code/ticket/1537 It would be great if this physics engine or matrix library could run on a CUDA

Re: [Haskell-cafe] Re: (flawed?) benchmark : sort

2008-03-12 Thread ajb
G'day all. Adrian Hey wrote: This might be a reasonable thing to say about *sortBy*, but not sort as the ordering of equal elements should not be observable (for any correct instance of Ord). It should be impossible to implement a function which can discriminate between [a,a],[a,b],[b,a],[b,b]

Re: [Haskell-cafe] Re: (flawed?) benchmark : sort

2008-03-12 Thread Krzysztof Skrzętnicki
In OCaml you have sort and fastsort - the latter doesn't have to be stable. It currently is, because fastsort = sort. I think it is a good thing to leave people an option, if there is something important to choose. On Thu, Mar 13, 2008 at 12:48 AM, [EMAIL PROTECTED] wrote: G'day all. Adrian

Re: [Haskell-cafe] [GSoC] A data parallel physics engine

2008-03-12 Thread Thomas Schilling
There's an effort going on to use techniques from Lava (the Haskell- based hardware description language) to target GPUs. Joel Svensson [1] has written his Master's thesis on this and is now working on this for his PhD, so if you ask kindly he might tell you more about this or send you the

[Haskell-cafe] floating point operations and representation

2008-03-12 Thread Jacob Schwartz
I have two questions about using the Double data type and the operations in the Floating typeclass on a computer that uses IEEE floating point numbers. I notice that the Floating class only provides log (presumably log base 'e') and logBase (which, in the latest source that I see for GHC is

Re: [Haskell-cafe] A question about monad laws

2008-03-12 Thread ajb
G'day all. Quoting askyle [EMAIL PROTECTED]: If you use this presentation you also need the following law: (a . b) = c = (a = c) . b that is, compatibility with ordinary function composition. I like to call this naturality, since it's instrumental in proving return and bind to be natural

Re: [Haskell-cafe] Bug with GADT in function Patterns?

2008-03-12 Thread Manuel M T Chakravarty
Hi Hugo, I have found a bug on the compiler (at least ghc 6.8.2). For some module (yes, the example does nothing at all): module Test where data Type a where Func :: Type a - Type b - Type (a - b) PF :: Type a - Type (PF a) data PF a where ID :: PF (a - a) test :: Type a - a -

Re: [Haskell-cafe] [GSoC] A data parallel physics engine

2008-03-12 Thread Manuel M T Chakravarty
Don Stewart: I'd chime in here -- actually getting arrays and parallel arrays with list-like interfaces, and then onto matrices, will impact a lot of people's work, in a good way. I am not quite sure what you mean with a list-like interface. NDP/DPH- style arrays are exactly like Haskell

Re: [Haskell-cafe] Bug with GADT in function Patterns?

2008-03-12 Thread Hugo Pacheco
Hi have tried with all versions until ghci-6.9.20080303 (from the nightly builds), is that the one? I'm sorry but where in the darcs repo can I find it? I cannot find a ghc-6.9branch. Thanks, hugo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org

Re: [Haskell-cafe] floating point operations and representation

2008-03-12 Thread Don Stewart
quark: I have two questions about using the Double data type and the operations in the Floating typeclass on a computer that uses IEEE floating point numbers. I notice that the Floating class only provides log (presumably log base 'e') and logBase (which, in the latest source that I see for

Re: [Haskell-cafe] [GSoC] A data parallel physics engine

2008-03-12 Thread Don Stewart
chak: Don Stewart: I'd chime in here -- actually getting arrays and parallel arrays with list-like interfaces, and then onto matrices, will impact a lot of people's work, in a good way. I am not quite sure what you mean with a list-like interface. NDP/DPH- style arrays are exactly like

Re: [Haskell-cafe] [GSoC] A data parallel physics engine

2008-03-12 Thread Manuel M T Chakravarty
Jed Brown: On 12 Mar 2008, [EMAIL PROTECTED] wrote: I don't think there are a great deal of Haskell users who _really_ need a physics engine right now. However, there seem to be a massive number who are working with matrices. I am informed that a lot of physics is just matrix stuff underneath

Re: [Haskell-cafe] [GSoC] A data parallel physics engine

2008-03-12 Thread Manuel M T Chakravarty
Roman Leshchinskiy: Bas van Dijk wrote: A bit offtopic but slightly related: I just added a GSoC project proposal about adding a nVidia CUDA backend to Data Parallel Haskell: http://hackage.haskell.org/trac/summer-of-code/ticket/1537 It would be great if this physics engine or matrix library

Re: [Haskell-cafe] Re: (flawed?) benchmark : sort

2008-03-12 Thread David Menendez
On Wed, Mar 12, 2008 at 7:48 PM, [EMAIL PROTECTED] wrote: Adrian Hey wrote: This might be a reasonable thing to say about *sortBy*, but not sort as the ordering of equal elements should not be observable (for any correct instance of Ord). It should be impossible to implement a

Re: [Haskell-cafe] Re: (flawed?) benchmark : sort

2008-03-12 Thread ajb
G'day all. Quoting David Menendez [EMAIL PROTECTED]: Adrian is arguing that compare a b == EQ should imply compare (f a) (f b) == EQ for all functions f (excluding odd stuff). Thus, the problem with your example would be in the Ord instance, not the sort function. Understood, and the

Re: [Haskell-cafe] Bug with GADT in function Patterns?

2008-03-12 Thread Manuel M T Chakravarty
Hugo Pacheco: Hi have tried with all versions until ghci-6.9.20080303 (from the nightly builds), is that the one? Yep, that one is fine. I'm sorry but where in the darcs repo can I find it? I cannot find a ghc-6.9 branch. 6.9 is not a branch, it is the main repository; ie,

Re: [Haskell-cafe] Re: (flawed?) benchmark : sort

2008-03-12 Thread Dan Licata
On Mar12, [EMAIL PROTECTED] wrote: G'day all. Quoting David Menendez [EMAIL PROTECTED]: Adrian is arguing that compare a b == EQ should imply compare (f a) (f b) == EQ for all functions f (excluding odd stuff). Thus, the problem with your example would be in the Ord instance, not the sort

[Haskell-cafe] floating point operations and representation

2008-03-12 Thread Don Stewart
I am under the restriction that I need to write Haskell programs using Double which mimic existing C/C++ programs or generated data sets, and get the same answers. (It's silly, but take it as a given requirement.) If the C programs are using log2, then I need log2 in the Haskell, or else I

[Haskell-cafe] linker question

2008-03-12 Thread Galchin Vasili
Hello, I have made modifications against an existing Haskell library and installed in my --prefix=$HOME. How do I specify to link against this test .a and not the global archive? Regards, vasili ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org

Re: [Haskell-cafe] linker question

2008-03-12 Thread Don Stewart
vigalchin: Hello, I have made modifications against an existing Haskell library and installed in my --prefix=$HOME. How do I specify to link against this test .a and not the global archive? Regards, vasili Install with cabal and use the --user flag