Re: [Haskell-cafe] Re: ANNOUNCE: haskell-src-exts 0.4.4

2008-12-08 Thread Neil Mitchell
Hi Niklas, Apart from this, HSE now also parses any unrecognized pragma in option (e.g. LANGUAGE), declaration (e.g. RULES) or expression (e.g. SCC) position, allowing user-customized pragmas. Unrecognized pragmas in other positions will (unfortunately) give a parse error. If this ever means

[Haskell-cafe] Why does instance Ord Pat causes loop

2008-12-08 Thread Martin Hofmann
I am storing the TH data types 'Exp' and 'Pat' in Maps and Sets. As a first attempt to quickly get rid of typechecker's complaints I defined some naive instances of Ord for Exp and Pat. Now it took me about a week to realise, that 'instance Ord Pat' causes ghc to loop. Apparently, there is a

Re: [Haskell-cafe] Why does instance Ord Pat causes loop

2008-12-08 Thread Luke Palmer
On Mon, Dec 8, 2008 at 2:04 AM, Martin Hofmann [EMAIL PROTECTED] wrote: I am storing the TH data types 'Exp' and 'Pat' in Maps and Sets. As a first attempt to quickly get rid of typechecker's complaints I defined some naive instances of Ord for Exp and Pat. Now it took me about a week to

Re: [Haskell-cafe] Why does instance Ord Pat causes loop

2008-12-08 Thread Luke Palmer
On Mon, Dec 8, 2008 at 2:04 AM, Martin Hofmann [EMAIL PROTECTED] wrote: I am storing the TH data types 'Exp' and 'Pat' in Maps and Sets. As a first attempt to quickly get rid of typechecker's complaints I defined some naive instances of Ord for Exp and Pat. Now it took me about a week to

Re: [Haskell-cafe] Why does instance Ord Pat causes loop

2008-12-08 Thread Bulat Ziganshin
Hello Martin, Monday, December 8, 2008, 12:04:06 PM, you wrote: Now it took me about a week to realise, that 'instance Ord Pat' causes ghc to loop. naive Ord instance Ord Exp instance Ord Pat i think you just don't learned this part of Haskell. empty instance declarations like these

Re: [Haskell-cafe] Why does instance Ord Pat causes loop

2008-12-08 Thread Martin Hofmann
Thanks a lot for the quick replies. Indeed that was not clear to me. Cheers, Martin ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

[Haskell-cafe] Pragmas (was: ANNOUNCE: haskell-src-exts 0.4.4)

2008-12-08 Thread Roman Cheplyaka
* Neil Mitchell [EMAIL PROTECTED] [2008-12-08 08:29:03+] Apart from this, HSE now also parses any unrecognized pragma in option (e.g. LANGUAGE), declaration (e.g. RULES) or expression (e.g. SCC) position, allowing user-customized pragmas. Unrecognized pragmas in other positions will

[Haskell-cafe] Deriving something else?

2008-12-08 Thread John Ky
Hi, I've defined a class and some instances, which I'm hoping would help me show values of types that may include transactional elements. class TShow a where tshow :: a - IO String instance Show (TVar a) where show = % instance (Show a) = TShow a where tshow a = return $ show a

[Haskell-cafe] Overlapping instances

2008-12-08 Thread John Ky
Hi, I've got the following code which tries to implement a TShow class, which is equivalent to Show, except it is supposed to work on TVar types as well. import GHC.Conc createEngine :: String - Int - Int - IO Engine createEngine name major minor = do tUsers - newTVarIO [] return $ Engine

Re: [Haskell-cafe] Animated line art

2008-12-08 Thread Tim Docker
On 06/12/2008, at 6:32 AM, Andrew Coppin wrote: Tim Docker wrote: If you implement your drawing logic as a function from time to the appropriate render actions, ie | import qualified Graphics.Rendering.Cairo as C | | type Animation = Time - C.Render () then you just need to call this

Re: [Haskell-cafe] Deriving something else?

2008-12-08 Thread Janis Voigtlaender
John Ky wrote: Having created a new class is it possible to do some magic so that it can be put it into a deriving clause? http://hackage.haskell.org/cgi-bin/hackage-scripts/package/derive -- Dr. Janis Voigtlaender http://wwwtcs.inf.tu-dresden.de/~voigt/ mailto:[EMAIL PROTECTED]

[Haskell-cafe] Re: Problem with System.Random.randoms

2008-12-08 Thread Mauricio
Hi, I have a small problem with System.Random.randoms. I need a rather large number of random numbers but the following program consumes a huge amount of memory. I terminated it when it used up more than 2 Gb: Interesting. Well, if you don't solve this problem, I recently needed random

[Haskell-cafe] Cabal: defaultMainNoRead and source file location

2008-12-08 Thread Mauricio
Hi, I've just seen this from Distribution.ModuleName (ghc 6.10): toFilePath $ ( simple A.B.C ) to which ghci answers: A.B.C. Shouldn't it say A/B/C? The reason why I'm asking is that I've just created a Setup.hs with 'defaultMainNoRead', and 'Setup build' complains it can't find

[Haskell-cafe] Re: Dr Dobbs: Time to get good at functional programming

2008-12-08 Thread Stefan Monnier
http://www.ddj.com/development-tools/212201710;jsessionid=3MQLTTYJRPL3CQSNDLRSKH0CJUNN2JVN Do they purposefully obfuscate names? I mean who are those Martin Obersky and Don Sype? Stefan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org

Re: [Haskell-cafe] Origins of '$'

2008-12-08 Thread Mark P. Jones
Don Stewart wrote: Which suggests that $ was already in the 1.0 report going to SIGPLAN. Perhaps Paul or Simon could shed light on it? Anyone have the 1.0 report lying around to check if it was in earlier? As far as Haskell is concerned, the first report-ed occurrence of the $ operator was in

Re: [Haskell-cafe] Origins of '$'

2008-12-08 Thread Jonathan Cast
On Mon, 2008-12-08 at 09:58 -0800, Mark P. Jones wrote: Don Stewart wrote: Which suggests that $ was already in the 1.0 report going to SIGPLAN. Perhaps Paul or Simon could shed light on it? Anyone have the 1.0 report lying around to check if it was in earlier? As far as Haskell is

Re: [Haskell-cafe] How to define Show [MyType] ?

2008-12-08 Thread Ryan Ingram
On Sun, Dec 7, 2008 at 1:51 AM, Fraser Wilson [EMAIL PROTECTED] wrote: (I know you know this, I just have this weird fascination with the showList wart, although for the life of me I can't think of a better way of doing it) Well, if you extend the compiler's core language with typecase, you can

Re: [Haskell-cafe] Overlapping instances

2008-12-08 Thread Ryan Ingram
On Mon, Dec 8, 2008 at 4:43 AM, Tobias Bexelius [EMAIL PROTECTED] wrote: {-# LANGUAGE OverlappingInstances #-} With this extension, the most specific instance will be used, i.e. instance TShow Engine for Engine's, no matter if it is an instance of Show. Of course, down this way madness lies

Re: [Haskell-cafe] Origins of '$'

2008-12-08 Thread Dan Piponi
On Sun, Dec 7, 2008 at 2:05 AM, Hans Aberg [EMAIL PROTECTED] wrote: As for the operator itself, it appears in Alonzo Church, The Calculi of Lambda-Conversion, where it is written as exponentiation, like x^f That's reminiscent of the notation in Lambek and Scott where (roughly speaking) the

[Haskell-cafe] Re: Cabal: defaultMainNoRead and source file location

2008-12-08 Thread Mauricio
(...) The reason why I'm asking is that I've just created a Setup.hs with 'defaultMainNoRead', and 'Setup build' complains it can't find A.B.C. When I copy (move doesn't work) C.hs from src_dir/A/B to src_dir/A.B.C.hs, it doesn't complain, although it fails to generate my

Re: [Haskell-cafe] Origins of '$'

2008-12-08 Thread Nathan Bloomfield
In set theory, and sometimes in category theory, A^B is just another notation for Hom(B, A), and the latter might be given the alternate notation B - A. And th reason is that for finite sets, computing cardinalities result in the usual power function of natural numbers - same as Church,

Re: [Haskell-cafe] Origins of '$'

2008-12-08 Thread Joachim Breitner
Hi, Am Montag, den 08.12.2008, 15:59 -0600 schrieb Nathan Bloomfield: Slightly off topic, but the A^B notation for hom-sets also makes the natural isomorphism we call currying expressable as A^(BxC) = (A^B)^C. So A^(B+C) = A^B × A^C ? Oh, right, I guess that’s actually true: uncurry either

Re: [Haskell-cafe] Re: Dr Dobbs: Time to get good at functional programming

2008-12-08 Thread Thomas Schilling
That article is an incredibly half-assed job. It reads like a high-school essay, thrown together in a hurry before a 1 hour deadline. Maybe it's a good sign that people think they have to do this, but it really doesn't help anyone who wants to know why FP might be worth learing. 2008/12/8

Re: [Haskell-cafe] Re: Dr Dobbs: Time to get good at functional programming

2008-12-08 Thread Jason Dusek
It's just there so you can show your boss it was in Dr. Dobbs, and so your boss can think Wow, I know what FP is -- thank you, Dr. Dobbs!. For this purpose, the only thing better is if we could somehow get them to mention Microsoft everywhere they mention Haskell. Any actual

Re: [Haskell-cafe] Origins of '$'

2008-12-08 Thread Dan Piponi
2008/12/8 Joachim Breitner [EMAIL PROTECTED]: So A^(B+C) = A^B × A^C ? That's part of the basis for Hinze's paper on memoization: http://www.informatik.uni-bonn.de/~ralf/publications/WGP00b.ps.gz It's always nice to see that I havn't learned the elementary power calculation rules for nothing

Re: [Haskell-cafe] Building plugins from Hackage

2008-12-08 Thread Don Stewart
solistic: Hello List, when I try to install the package plugins with cabal i get the following error. cabal: dependencies conflict: ghc-6.8.3 requires Cabal ==1.2.4.0 however Cabal-1.2.4.0 was excluded because plugins-1.3.1 requires Cabal ==1.4.* Is there a way to resolve this? Any

Re: [Haskell-cafe] Re: Dr Dobbs: Time to get good at functionalprogramming

2008-12-08 Thread Claus Reinke
For this purpose, the only thing better is if we could somehow get them to mention Microsoft everywhere they mention Haskell. Any actual explaining would just get in the way :) Doesn't quite work without explaining, because one would have to be very careful not to mis-represent financial

Re: [Haskell-cafe] Re: Dr Dobbs: Time to get good at functionalprogramming

2008-12-08 Thread Don Stewart
claus.reinke: For this purpose, the only thing better is if we could somehow get them to mention Microsoft everywhere they mention Haskell. Any actual explaining would just get in the way :) Doesn't quite work without explaining, because one would have to be very careful not to

Re: [Haskell-cafe] Reading showables

2008-12-08 Thread Daniel Yokomizo
2008/12/7 John Ky [EMAIL PROTECTED]: Thanks for the clarification. They're all the same, as you've explained: Prelude putStrLn $ (show . read) 123 *** Exception: Prelude.read: no parse Prelude putStrLn $ show $ read 123 *** Exception: Prelude.read: no parse Prelude putStrLn $ (\x - show

Re: [Haskell-cafe] Why does instance Ord Pat causes loop

2008-12-08 Thread wren ng thornton
Luke Palmer wrote: It would be nice if typeclass authors could somehow declare the minimal complete definition, so we could get a warning in this case. Or the minimal complete definitions. Since there can be more than one covering set. -- Live well, ~wren