Re: [Haskell-cafe] Haskell Weekly News: Issue 85 - September 13, 2008
On 2008 Sep 14, at 1:24, Daryoush Mehrtash wrote: What I am trying to figure out is that say on the code for the IRC bot that is show here http://www.haskell.org/haskellwiki/Roll_your_own_IRC_bot/Source What would theorem proofs do for me? Assurance of correct operation; for example, a mathematically provable lack of security holes, assuming you can describe its proper operation in terms of suitable theorems (which, for a simple bot like that, is not so difficult). -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] [EMAIL PROTECTED] system administrator [openafs,heimdal,too many hats] [EMAIL PROTECTED] electrical and computer engineering, carnegie mellon universityKF8NH ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] static linking failure -- can't find crt0
I'm building a really static executable on OS X with options `-optl-static -static` and, while the libraries seem to link fine, the executable itself does not -- it can't find the C runtime. This is actually by design -- Apple does not support static binaries. There is a work around -- just symlink stuff till the errors go away -- but it might be better if I could statically link only those C libraries that I knew were not on stock Macs. Are there GHC options for that? I assume this all works fine on Linux and Windows, but I'll know soon enough... -- _jsn |...can't find the C runtime.| ld_classic: can't locate file for: -lcrt0.o collect2: ld returned 1 exit status |does not support| http://developer.apple.com/qa/qa2001/qa1118.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Hugs on the iphone
Hi, is there any chance of having hugs compile for the iPhone? Cross-compiling? Compiling directly on the iPhone? Greets, Alberto ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell Weekly News: Issue 85 - September 13, 2008
On Sun, Sep 14, 2008 at 5:56 AM, Thomas M. DuBuisson [EMAIL PROTECTED] wrote: What would theorem proofs do for me? Imagine if you used SmallCheck to exhastively test the ENTIRE problem space for a given property. Now imagine you used your brain to show the programs correctness before the heat death of the universe... Proofs are not features, nor are they code. What you prove is entirely up to you and might not be what you think. Take, for example, the issue of proving a sort function works correctly [1]. I'm not saying this to discourage complete proofs, but just cautioning you that proving something as unimportant and IO laden as an IRC bot probably isn't the best example. Do see the linked PDF, and [2] as well. Oh, and for examples where people should have used FM, search for 'ariane 1996' or the gulf war patriot missle failure TomMD [1] http://www.cl.cam.ac.uk/~mjcg/Teaching/SpecVer1/Lectures/pslides07x4.pdf [2] http://users.lava.net/~newsham/formal/reverse/ One thing have always bugged me: how do you prove that you have correctly proven something? I mean, when I write a code I'm formaly stating what I want to happen and bugs happen. If I try to prove some part of the code I write more formal text (which generally isn't even checked by a compiler); how can I be sure that my proof doesn't contain bugs? Why would it make my program less error-prone? Is there any article that tries to compare heavy testing with FM? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: pandoc 1.0.0.1
2008/9/14 John Goerzen [EMAIL PROTECTED]: 2) Variable x defined but not used I most often ignore this when it occurs in a function definition. Sometimes I may have a function that could be written foo _ (x, _) _ = bar (x + 5) But for clarity's sake on what all the unused args are, which really helps for future maintainability, I'll usually use a descriptive -- but unused -- variable name. This doesn't appear to be commonly known, but actually any identifier that /starts/ with an _ will not trigger the unused-arg warning. So if you wrote your example like this: foo _stuff (x, _y) _more = bar (x + 5) It would satisfy both the compiler and your desire for descriptive variable names. Cheers, Max ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell Weekly News: Issue 85 - September 13, 2008
2008/9/14 Rafael Almeida [EMAIL PROTECTED]: One thing have always bugged me: how do you prove that you have correctly proven something? I mean, when I write a code I'm formaly stating what I want to happen and bugs happen. If I try to prove some part of the code I write more formal text (which generally isn't even checked by a compiler); how can I be sure that my proof doesn't contain bugs? Why would it make my program less error-prone? Is there any article that tries to compare heavy testing with FM? Well, that's where formal prover enter the picture : when you prove something with Coq, you can be reasonably sure that your proof is correct. And FM brings absolute certitude a propriety is verified by your program whereas testing however heavy can only check this property on a finite set of inputs (using randomly generated input help alleviate the risk of blind spot but is still limited). -- Jedaï ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Views
I think the crux of the matter was that a monad is too general. Either there is a result or there is not. That's precisely the intended use of a Maybe. Indeed Monad m = is dangerous here because not every Monad has a reasonable definition of fail. But that seems to be a problem in the (current) definition of Monad, and its solution was MonadZero, no? J.W. signature.asc Description: OpenPGP digital signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Views
Johannes Waldmann wrote:
a) ... to use Maybe
b) ... to provide my own Data.Heap.View type
leave the choice up to the programmer,
and provide a generic interface,
accepting any MonadZero (*) instance.
cf. Data.Set.maxView
AFAIK there has been a vivid discussion about that. I think the crux of
the matter was that a monad is too general. Either there is a result or
there is not. That's precisely the intended use of a Maybe.
Besides, I just learned that Data.Map.{lookup,minView,maxView} and the
like have been modified to return a Maybe in the current GHC head
branch, see [1]. This suggests using Maybe in my case as well.
[...]
[1]
http://www.haskell.org/ghc/dist/current/docs/libraries/containers/Data-Map.html
--
Früher hieß es ja: Ich denke, also bin ich.
Heute weiß man: Es geht auch so.
- Dieter Nuhr
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Re: [Haskell-cafe] Re: [Haskell] Heads Up: code.haskell.org is upgrading to darcs 2
Hi Ignore the previous email message, as soon as I sent the email it started working - I guess it was just code.haskell.org server issues. Thanks Neil On 9/14/08, Neil Mitchell [EMAIL PROTECTED] wrote: Hi I'm currently unable to push to [EMAIL PROTECTED]:/srv/code/hoogle using darcs 1.0.9 on Windows Vista, and wasn't able to yesterday either. Is code.haskell.org just being slow, or is there a chance that Hoogle suffered as a result of the upgrade? Thanks Neil On 9/11/08, Eric Y. Kow [EMAIL PROTECTED] wrote: We are upgrading /usr/bin/darcs to version 2 on the machine that hosts code.haskell.org. That means it will be used by everyone who uses ssh to push or pull from a darcs repository on code.haskell.org. Pulling via http is completely unaffected. Thanks Duncan! Now my hope is that we can encourage the good folk at Galois to make a similar upgrade for darcs.haskell.org -- Eric Kow http://www.nltg.brighton.ac.uk/home/Eric.Kow PGP Key ID: 08AC04F9 ___ 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] Views
Johannes Waldmann wrote: I think the crux of the matter was that a monad is too general. Either there is a result or there is not. That's precisely the intended use of a Maybe. Indeed Monad m = is dangerous here because not every Monad has a reasonable definition of fail. But that seems to be a problem in the (current) definition of Monad, and its solution was MonadZero, no? I agree that the MonadZero class with a useful 'zero' :: m a would be the right abstraction for views. But MonadZero is not part of base, mtl or any other common package, or am I missing something? Changing this is beyond a simple heap package ;) -- Früher hieß es ja: Ich denke, also bin ich. Heute weiß man: Es geht auch so. - Dieter Nuhr ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Hugs on the iphone
Alberto R. Galdo wrote: Hi, is there any chance of having hugs compile for the iPhone? Cross-compiling? Compiling directly on the iPhone? Greets, Alberto The iPhone, like most modern mobile devices, is based on the ARM processor, for which there is currently no GHC port. However, jhc outputs portable C code which can be (cross) compiled for ARM. I have succeeded in building Haskell code with jhc on my desktop (x86 Linux), then cross-compiling the resulting C code in a scratchbox environment for my Nokia N810. In short, if you can compile C code for the iPhone (cross-compiled or native), you can probably use jhc to turn Haskell into suitable C. jhc is not self-hosting, and it requires gcc as a back-end, so it isn't suitable for running on the device. See also the GHC-on-ARM project[1], an attempt to port GHC to ARM Linux devices. Braden Shepherdson shepheb [1] http://hackage.haskell.org/trac/ghc/wiki/ArmLinuxGhc ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Hugs on the iphone
Braden Shepherdson wrote: Alberto R. Galdo wrote: Hi, is there any chance of having hugs compile for the iPhone? Cross-compiling? Compiling directly on the iPhone? Greets, Alberto The iPhone, like most modern mobile devices, is based on the ARM processor, for which there is currently no GHC port. However, jhc outputs portable C code which can be (cross) compiled for ARM. I have succeeded in building Haskell code with jhc on my desktop (x86 Linux), then cross-compiling the resulting C code in a scratchbox environment for my Nokia N810. In short, if you can compile C code for the iPhone (cross-compiled or native), you can probably use jhc to turn Haskell into suitable C. jhc is not self-hosting, and it requires gcc as a back-end, so it isn't suitable for running on the device. See also the GHC-on-ARM project[1], an attempt to port GHC to ARM Linux devices. Braden Shepherdson shepheb [1] http://hackage.haskell.org/trac/ghc/wiki/ArmLinuxGhc I failed completely to mention Hugs: I don't think it exists, but I think someone managed to port it to the Nintendo DS a while back, so it should be possible. Braden Shepherdson shepheb ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: [Haskell] Heads Up: code.haskell.org is upgrading to darcs 2
On Sun, 2008-09-14 at 14:41 +0100, Neil Mitchell wrote: Hi Ignore the previous email message, as soon as I sent the email it started working - I guess it was just code.haskell.org server issues. Yes it was unavailable for a short time yesterday. It got rebooted by the hosting company, we're not exactly sure why. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell Weekly News: Issue 85 - September 13, 2008
On Sunday 14 September 2008 6:59:06 am Rafael Almeida wrote: One thing have always bugged me: how do you prove that you have correctly proven something? I mean, when I write a code I'm formaly stating what I want to happen and bugs happen. If I try to prove some part of the code I write more formal text (which generally isn't even checked by a compiler); how can I be sure that my proof doesn't contain bugs? Why would it make my program less error-prone? Is there any article that tries to compare heavy testing with FM? This isn't really a problem if you're programming in a language in which the proofs of program correctness are checked by the compiler/what have you, as Chaddaï has already said. In that case, it's similar to asking, how do I know my Haskell programs are actually type correct? Barring bugs in the tools (which, in the ideal case, are built on a simple enough foundation to be confidently proven correct by hand), it's not so much a concern. A more difficult question is: how do I know that the formal specification I've written for my program is the right one? Tools can fairly easily check that your programs conform to a given specification, but they cannot (to my knowledge) check that your specification says exactly what you want it to say. Of course, this is no worse than the case with test suites, since one can similarly ask, how can I be sure the tests check for the properties/behavior that I actually want? -- Dan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] system in forkIO
Hello. import System.Cmd import GHC.Conc main :: IO () main = forkIO ( do putStrLn fork system ls return ()) getChar return () When I run this code, I get fork and the result of ls only after I press a key. Does getChar blocks the other threads? Greetings. -- marcot Página: http://marcotmarcot.iaaeee.org/ Blog: http://marcotmarcot.blogspot.com/ Correio: [EMAIL PROTECTED] XMPP: [EMAIL PROTECTED] IRC: [EMAIL PROTECTED] Telefone: 25151920 Celular: 98116720 Endereço: Rua Turfa, 639/701 Prado 30410-370 Belo Horizonte/MG Brasil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] system in forkIO
On Sun, Sep 14, 2008 at 02:24:23PM -0300, Marco Túlio Gontijo e Silva wrote: and the result of ls only after I press a key. Does getChar blocks the other threads? yes, but you can use forkOS from Control.Concurrent and compile with -threaded. See the relevant documentation for the details. Hope this helps, Andrea ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] system in forkIO
On Sun, Sep 14, 2008 at 10:24 AM, Marco Túlio Gontijo e Silva [EMAIL PROTECTED] wrote: When I run this code, I get fork and the result of ls only after I press a key. Does getChar blocks the other threads? I think this behavior is caused by (or at least related to) the following GHC bug: http://hackage.haskell.org/trac/ghc/ticket/2363 That bug has been fixed for the 6.10 release; my testing indicated that your program behaves correctly in that version. See the above bug report for some suggestions on how to work around the 6.8 getChar blocking. Hope that helps, -Judah ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] message passing style in Monad
jinjing wrote: I found that as I can do xs.map(+1).sort by redefine . to be a . f = f a infixl 9 . This looks rather like ($), but backwards. I believe the F# name for this operator is (|), which is also a legal name for it in Haskell. Odd, since (|) alone isn't legal. Calling it (.) will confuse the heck out of anyone who maintains your code though, and make any transfer of code between your projects and other people's liable to introduce bugs. I can also do readFile readme.markdown . lines . length by making a . b = a .liftM b infixl 9 . Kinda annoying, but the option is there. Now that looks more interesting. Another name for it is (=^), since it is like (=) but lifts its right argument. I know the Fudgets library uses ^ in operators for a similar lifting meaning. -- src/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Semantic Domain, Function, and denotational model.....
I have been told that for a Haskell/Functional programmer the process of design starts with defining Semantic Domain, Function, and denotational model of the problem. I have done some googling on the topic but haven't found a good reference on it.I would appreciate any good references on the topic. thanks, daryoush ps. I have found referneces like http://en.wikibooks.org/wiki/Haskell/Denotational_semantics which talks about semantic domain for the Haskell programs 10, 9+1, 2*5 which doesn't do any good for me.I need something with a more real examples. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Semantic Domain, Function, and denotational model.....
Daryoush Mehrtash dmehrtash at gmail.com writes: I have been told that for a Haskell/Functional programmer the process of design starts with defining Semantic Domain, Function, and denotational model of the problem. I have done some googling on the topic but haven't found a good reference on it.I would appreciate any good references on the topic. http://www.cs.chalmers.se/Cs/Grundutb/Kurser/afp/lectures.html The whole course is interesting but lectures 23 are more specifically about your concern. -- JP ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Views
Hi, On Sun, Sep 14, 2008 at 7:01 AM, Stephan Friedrichs [EMAIL PROTECTED] wrote: I agree that the MonadZero class with a useful 'zero' :: m a would be the right abstraction for views. But MonadZero is not part of base, mtl or any other common package, or am I missing something? Changing this is beyond a simple heap package ;) The class ExceptionM from monadLib captures this functionality. However, for this simple case 'Maybe' seems quite enough because it is what you need most of the time. Furthermore, it does not loose any generality because you can use a function of type :: MonadZero m = Maybe a - m a, to convert to other monads, if it is necessary. -Iavor ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] system in forkIO
Em Dom, 2008-09-14 às 11:08 -0700, Judah Jacobson escreveu: On Sun, Sep 14, 2008 at 10:24 AM, Marco Túlio Gontijo e Silva [EMAIL PROTECTED] wrote: When I run this code, I get fork and the result of ls only after I press a key. Does getChar blocks the other threads? I think this behavior is caused by (or at least related to) the following GHC bug: http://hackage.haskell.org/trac/ghc/ticket/2363 Thanks, I got it to work running threadWaitRead stdInput before getChar. Only changing forkIO for forkOS gave me the same result. Greetings. -- marcot Página: http://marcotmarcot.iaaeee.org/ Blog: http://marcotmarcot.blogspot.com/ Correio: [EMAIL PROTECTED] XMPP: [EMAIL PROTECTED] IRC: [EMAIL PROTECTED] Telefone: 25151920 Celular: 98116720 Endereço: Rua Turfa, 639/701 Prado 30410-370 Belo Horizonte/MG Brasil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] system in forkIO
Andrea Rossato wrote: On Sun, Sep 14, 2008 at 02:24:23PM -0300, Marco Túlio Gontijo e Silva wrote: and the result of ls only after I press a key. Does getChar blocks the other threads? yes, but you can use forkOS from Control.Concurrent and compile with -threaded. See the relevant documentation for the details. forkOS not relevant here. -threaded is necessary to allow haskell code to run whilst FFI calls are blocked. getChar doesn't count as an FFI call (the RTS does its own IO multiplexing) but system does. forkOS is to do with bound threads, that's something else. Jules ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] message passing style in Monad
Simon Richard Clarkstone [EMAIL PROTECTED] writes: I can also do readFile readme.markdown . lines . length by making (.) = flip fmap ? -k -- If I haven't seen further, it is by standing in the footprints of giants ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] system in forkIO
Em Dom, 2008-09-14 às 16:07 -0300, Marco Túlio Gontijo e Silva escreveu: Thanks, I got it to work running threadWaitRead stdInput before getChar. Now I've got another problem: import Control.Concurrent import System.IO import System.Process main :: IO () main = do process - runCommand wget http://ftp.br.debian.org/debian/pool/main/g/ghc6/ghc6_6.8.2-6_amd64.deb; forkIO $ putStrLn fork getChar = putChar terminateProcess process waitForProcess process return () Not even fork is shown. Any hints? Greetings. -- marcot Página: http://marcotmarcot.iaaeee.org/ Blog: http://marcotmarcot.blogspot.com/ Correio: [EMAIL PROTECTED] XMPP: [EMAIL PROTECTED] IRC: [EMAIL PROTECTED] Telefone: 25151920 Celular: 98116720 Endereço: Rua Turfa, 639/701 Prado 30410-370 Belo Horizonte/MG Brasil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] system in forkIO
marcot: Em Dom, 2008-09-14 às 16:07 -0300, Marco Túlio Gontijo e Silva escreveu: Thanks, I got it to work running threadWaitRead stdInput before getChar. Now I've got another problem: import Control.Concurrent import System.IO import System.Process main :: IO () main = do process - runCommand wget http://ftp.br.debian.org/debian/pool/main/g/ghc6/ghc6_6.8.2-6_amd64.deb; forkIO $ putStrLn fork getChar = putChar terminateProcess process waitForProcess process return () Not even fork is shown. Any hints? Daemonic threads. When the main thread exits, everything exits. Check the docs for Control.Concurrent. You better use an MVar to ensure the main thread waits on its child. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ask
Hello, If we look at these two examples, it appears that the results are reversed: Prelude let n o = (-1 `o` 1) in n (-) 0 Prelude let n o = (-1 `o` 1) in n (+) -2 Prelude we expect (-1 - 1) = -2 and (-1 + 1) = 0, but we get the opposite. Due to operator precedence, the equations are being interpreted as: Prelude let n o = (-(1 `o` 1)) in n (-) 0 Prelude let n o = (-(1 `o` 1)) in n (+) -2 The fix is to use parens around a negative term: Prelude let n o = ((-1) `o` 1) in n (-) -2 Prelude let n o = ((-1) `o` 1) in n (+) 0 Prelude I have heard complaints about the negation sign in Haskell before, I suppose this is why. Hopefully someone else can provide more details. j. ps. You could probably also fix it by changing the precedence of the `o` operator. I believe that is possible. But parens around (-b) is the more standard solution. At Mon, 15 Sep 2008 02:24:14 +0200, Cetin Sert wrote: Hi why do I get? [EMAIL PROTECTED]:~/lab/exp/1 ./eq 23 23 3 a = b = c = n1-0.8457820374040622n2-0.1542179625959377 when I run import System.IO main :: IO () main = do a ← ask a b ← ask b c ← ask c eval a b c ask v = do putStr (v ++ = ) readLn eval a b c = do case delta 0 of True → putStr neg False → putStr (n1 ++ show n1 ++ n2 ++ show n2) where delta = b*b - 4*c*a n o = (-b `o` sqrt(delta))/(2*a) n1= n (+) n2= n (-) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ask
Am Montag, 15. September 2008 02:24 schrieb Cetin Sert: Hi why do I get? Buffering. For compiled programmes, stdin and stdout are line-buffered by default, so the output doesn't appear until the program finishes. Either put hSetBuffering stdout NoBuffering at the top of main or, better IMO, insert a hFlush stdout into ask before the readLn. And in eval, putStrLn would be better, I think. HTH, Daniel [EMAIL PROTECTED]:~/lab/exp/1 ./eq 23 23 3 a = b = c = n1-0.8457820374040622n2-0.1542179625959377 when I run import System.IO main :: IO () main = do a ← ask a b ← ask b c ← ask c eval a b c ask v = do putStr (v ++ = ) readLn eval a b c = do case delta 0 of True → putStr neg False → putStr (n1 ++ show n1 ++ n2 ++ show n2) where delta = b*b - 4*c*a n o = (-b `o` sqrt(delta))/(2*a) n1= n (+) n2= n (-) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ask
On 2008 Sep 14, at 20:47, Brandon S. Allbery KF8NH wrote: On 2008 Sep 14, at 20:24, Cetin Sert wrote: Hi why do I get? [EMAIL PROTECTED]:~/lab/exp/1 ./eq 23 23 3 a = b = c = n1-0.8457820374040622n2-0.1542179625959377 As is typical for Unix, filehandles including standard input and standard output are line buffered. See hSetBuffering ( http://www.haskell.org/ghc/docs/latest/html/libraries/base/System-IO.html#v%3AhSetBuffering ). Also, looking at that path, I'm tempted to point you to http://www.haskell.org/haskellwiki/Homework_help . -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] [EMAIL PROTECTED] system administrator [openafs,heimdal,too many hats] [EMAIL PROTECTED] electrical and computer engineering, carnegie mellon universityKF8NH ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hugs on the iphone
As pie. Just downloaded the source and compiled it on iPhone itself (no cross-compiling). On 15 Sep 2008, at 09:25, Don Stewart wrote: Very nice. Easy? miguelimo38: Did that. http://migmit.vox.com/library/photo/6a00e398c5c26f000500fa9696d8c40002.html On 14 Sep 2008, at 14:17, Alberto R. Galdo wrote: Hi, is there any chance of having hugs compile for the iPhone? Cross-compiling? Compiling directly on the iPhone? ___ 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] Hugs on the iphone
Very nice. Easy? miguelimo38: Did that. http://migmit.vox.com/library/photo/6a00e398c5c26f000500fa9696d8c40002.html On 14 Sep 2008, at 14:17, Alberto R. Galdo wrote: Hi, is there any chance of having hugs compile for the iPhone? Cross-compiling? Compiling directly on the iPhone? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hugs on the iphone
Did that. http://migmit.vox.com/library/photo/6a00e398c5c26f000500fa9696d8c40002.html On 14 Sep 2008, at 14:17, Alberto R. Galdo wrote: Hi, is there any chance of having hugs compile for the iPhone? Cross-compiling? Compiling directly on the iPhone? Greets, Alberto ___ 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] ask
Hi why do I get? [EMAIL PROTECTED]:~/lab/exp/1 ./eq 23 23 3 a = b = c = n1-0.8457820374040622n2-0.1542179625959377 when I run import System.IO main :: IO () main = do a ← ask a b ← ask b c ← ask c eval a b c ask v = do putStr (v ++ = ) readLn eval a b c = do case delta 0 of True → putStr neg False → putStr (n1 ++ show n1 ++ n2 ++ show n2) where delta = b*b - 4*c*a n o = (-b `o` sqrt(delta))/(2*a) n1= n (+) n2= n (-) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] system in forkIO
Em Dom, 2008-09-14 às 14:52 -0700, Don Stewart escreveu: marcot: Em Dom, 2008-09-14 às 16:07 -0300, Marco Túlio Gontijo e Silva escreveu: Thanks, I got it to work running threadWaitRead stdInput before getChar. Now I've got another problem: import Control.Concurrent import System.IO import System.Process main :: IO () main = do process - runCommand wget http://ftp.br.debian.org/debian/pool/main/g/ghc6/ghc6_6.8.2-6_amd64.deb; forkIO $ putStrLn fork getChar = putChar terminateProcess process waitForProcess process return () Not even fork is shown. Any hints? Daemonic threads. When the main thread exits, everything exits. Check the docs for Control.Concurrent. You better use an MVar to ensure the main thread waits on its child. I don't think this is the problem because the mais thread is not exiting. wget takes a lot of time to end, and I never really wait it to finish. I wanted to enable the user to interrupt it, but if it's finished, I don't want to wait for the user input anymore, so the child thread can exit with the main one. I just noticed that if I add a putStrLn wait before waitForProcess, it'll print wait and then fork. I couldn't understand why this happened, but I can't still pass through getChar to get to terminateProcess. Is it right to call getChar inside a forkIO? Greetings. -- marcot Página: http://marcotmarcot.iaaeee.org/ Blog: http://marcotmarcot.blogspot.com/ Correio: [EMAIL PROTECTED] XMPP: [EMAIL PROTECTED] IRC: [EMAIL PROTECTED] Telefone: 25151920 Celular: 98116720 Endereço: Rua Turfa, 639/701 Prado 30410-370 Belo Horizonte/MG Brasil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ask
On 2008 Sep 14, at 20:24, Cetin Sert wrote: Hi why do I get? [EMAIL PROTECTED]:~/lab/exp/1 ./eq 23 23 3 a = b = c = n1-0.8457820374040622n2-0.1542179625959377 As is typical for Unix, filehandles including standard input and standard output are line buffered. See hSetBuffering ( http://www.haskell.org/ghc/docs/latest/html/libraries/base/System-IO.html#v%3AhSetBuffering ). -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] [EMAIL PROTECTED] system administrator [openafs,heimdal,too many hats] [EMAIL PROTECTED] electrical and computer engineering, carnegie mellon universityKF8NH ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ask
On 15 Sep 2008, at 12:51 pm, Daniel Fischer wrote: Am Montag, 15. September 2008 02:24 schrieb Cetin Sert: Hi why do I get? Buffering. For compiled programmes, stdin and stdout are line- buffered by default, so the output doesn't appear until the program finishes. Either put hSetBuffering stdout NoBuffering at the top of main or, better IMO, insert a hFlush stdout into ask before the readLn. And in eval, putStrLn would be better, I think. Is this the problem we've had before, where the example in the Haskell 98 Report could not possibly work unless Haskell followed the same rule as C (read from stdin *automatically* flushes stdout), and the example works in several other Haskell systems, but not in GHC? Or is this a different problem? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hugs on the iphone
Cool! That's such a proof that it can be done... I had lots of problems trying to cross compile hugs from my mac to arm architecture ( seems that hugs codebase is not capable of cross compiling ) And when compiling directly on the iPhone, first there where problems with code signing, now with the configure script and C preprocessor sanity check... Any light on the topic from your experience? On 15/09/2008, at 7:24, Miguel Mitrofanov [EMAIL PROTECTED] wrote: Did that. http://migmit.vox.com/library/photo/6a00e398c5c26f000500fa9696d8c40002.html On 14 Sep 2008, at 14:17, Alberto R. Galdo wrote: Hi, is there any chance of having hugs compile for the iPhone? Cross-compiling? Compiling directly on the iPhone? Greets, Alberto ___ 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
