Re: [Haskell-cafe] A real Haskell Cookbook
On Fri, 2007-23-02 at 02:24 -0500, Albert Y. C. Lai wrote: Call me a technophile, but it saddens me that ASCII has already held us back for too many decades, and looks like it will still hold us back for another. OK. You're a technophile. But I agree with you. ASCII needs to die a slow, brutal death. Quickly. (And yes, I'm aware of the contradiction. ;)) -- Michael T. Richter [EMAIL PROTECTED] Disclaimer: Any people who think that opinions expressed from my private email account in any way, shape or form are those of my employer have more lawyers at their beck and call than they do brain cells. smiley-4.png Description: PNG image 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] Prime finding
I ran a few of the tests myself on my Mac Mini G4 with 512 Mb ram. I compiled the programs with ghc 6.6. I got different results however. 10^310^410^5 Reinke 0.7251 1.751 1m0.310s Runciman0.126 1.097 5m19.569s Zilibowitz 0.074.668 11m45.877s NaiveSeive 0.369 47.795 - The NaiveSeive program ran somewhat slower on my machine than it seemed to on yours. Also the Reinke program seemed to be faster than Runciman on my machine. It may be to do with not having enough ram. But I'm not too sure. Can you suggest any explanation for the different results? Ruben On 23/02/2007, at 4:46 PM, Melissa O'Neill wrote: Ruben Zilibowitz wrote: I see that there has been some discussion on the list about prime finding algorithms recently. I just wanted to contribute my own humble algorithm: Thanks! Comparing it to some of the algorithms in: http://www.haskell.org/pipermail/haskell-cafe/2007-February/ 022765.html It seems to perform reasonably well. It also has the advantage of being quite short. I've added it to my table. It's fun to find new ways to figure out primes, but I think the shortness advantage goes to the naive primes algorithm, which is faster and shorter. Melissa. -- Time (in seconds) for Number of Primes Algorithm 10^310^4 10^5 10^6 10^7 10^8 -- C-Sieve 0.00 0.00 0.01 0.29 5.1288.24 O'Neill (#2) 0.01 0.09 1.4522.41393.28 - O'Neill (#1) 0.01 0.14 2.9347.08 - - Bromage 0.02 0.39 6.50 142.85 - - sieve (#3) 0.01 0.25 7.28 213.19 - - Naive 0.32 0.6616.04 419.22 - - Runciman 0.02 0.7429.25- - - Reinke0.04 1.2141.00- - - Zilibowitz0.02 2.50 368.33- - - Gale (#1) 0.12 17.99-- - - sieve (#1) 0.16 32.59-- - - sieve (#2) 0.01 32.76-- - - Gale (#2) 1.36268.65-- - - -- ___ 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] Prime finding
*sigh* don't click send at 2:30am... I wrote: The algorithm named Naive in my table is called SimplePrimes in the zip file, and the example named sieve in my table is called NaivePrimes in the zip file. The algorithm named Naive in my table is called SimplePrimes in the zip file, and the example named sieve in my table is called NaiveSieve in the zip file. Melissa. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Code and Perf. Data for Prime Finders (was: Genuine Eratosthenes sieve)
G'day all.
Quoting Melissa O'Neill [EMAIL PROTECTED]:
Cool, thanks. When I ran your code trying to find the 10,000th
prime, I got
AtkinSieveTest: Ix{Integer}.index: Index (36213) out of range
((0,36212))
but that went away when I made your array one bigger.
Fixed, thanks.
Cheers,
Andrew Bromage
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[Haskell-cafe] Re: process
I have in mind something as connections via pipes to the chils's stdin, stdout and stderr, but the stream library just supports internal pipes, and posix require Unix. By this means it's not possible to request, receive and than respond,... with the process. Does there exist an alternative way? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: process
h._h._h._: I have in mind something as connections via pipes to the chils's stdin, stdout and stderr, but the stream library just supports internal pipes, and posix require Unix. By this means it's not possible to request, receive and than respond,... with the process. Does there exist an alternative way? I usually use System.Process for this kind of thing. http://haskell.org/ghc/docs/latest/html/libraries/base/System-Process.html -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] TFP 2007: Registration and Program
Dear Colleagues, You may now resgister for TFP 2007! TFP 2007 will be held April 2-4, 2007 in New York City, USA. April 2 is the first night of Passover. This is not one of those Your point is well taken. It is very unfortunate that the overlap you have pointed out exists. The organizing committee had to consider _many_ variables including, among others, the availability of a venue and of hotels for participants in NYC. Sometimes the logistics of a situation force your hand. Dr. Marco T. Morazan TFP 2007 Program Committee Chair http://cs.shu.edu/tfp2007/___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: process
This seemed like a handy thing to have an example of, so I added it to my growing repo of sample haskell programs and tried running it. But I was unsuccessful. Can anyone see what I'm doing wrong? In case it matters, I'm on a virtualized user-mode-linux shell. ** [EMAIL PROTECTED]:~/learning/haskell/inter-process-communication$ cat /proc/version Linux version 2.4.29-linode39-1um ([EMAIL PROTECTED]) (gcc version 3.3.3 20040412 (Red Hat Linux 3.3.3-7)) #1 Wed Jan 19 12:22:14 EST 2005 [EMAIL PROTECTED]:~/learning/haskell/inter-process-communication$ ghc -v 21 | head -n1 Glasgow Haskell Compiler, Version 6.6, for Haskell 98, compiled by GHC version 6.6 [EMAIL PROTECTED]:~/learning/haskell/inter-process-communication$ cat inter-process-communication.hs module Main where import System.Process import System.IO main :: IO () main = do putStrLn Running BC (inp,out,err,pid) - runInteractiveProcess bc [] Nothing Nothing hSetBuffering inp LineBuffering hSetBuffering out LineBuffering hSetBuffering err LineBuffering hPutStrLn inp 1+3 a - hGetLine out hPutStrLn inp a a - hGetLine out hPutStrLn inp quit waitForProcess pid putStrLn a [EMAIL PROTECTED]:~/learning/haskell/inter-process-communication$ runghc inter-process-communication.hs Running BC *** Exception: waitForProcess: does not exist (No child processes) [EMAIL PROTECTED]:~/learning/haskell/inter-process-communication$ 2007/2/23, Jules Bean [EMAIL PROTECTED]: h. wrote: If it basically works, what goes wrong in my programm? Well that depends entirely what your program is supposed to do. Your email doesn't tell us (a) what your program was supposed to do or (b) what goes wrong. Therefore we are forced to guess! The following slight variation of your program works fine for me. I don't have anything called 'prog1' on my system, so I used 'bc' which is a calculator program standard on unixes, which works by line-by-line interaction. I varied your program just a tiny bit to get some interesting output: module Main where import System.Process import System.IO main :: IO () main = do putStrLn Running BC (inp,out,err,pid) - runInteractiveProcess bc [] Nothing Nothing hSetBuffering inp LineBuffering hSetBuffering out LineBuffering hSetBuffering err LineBuffering hPutStrLn inp 1+3 a - hGetLine out hPutStrLn inp a a - hGetLine out hPutStrLn inp quit waitForProcess pid putStrLn a This program asks 'bc' to calculate 1+3. The reply is stored in 'a'. Then the program sends 'a' back to bc, effectively asking bc to calculate 4. Since the 4 evaluates just to 4, 'a' gets the value 4 once more. Then I have to send quit to bc. That is the command that bc interprets as an instruction to quit; without that command, 'waitForProcess pid' will wait forever (it's waiting for bc to quit). Finally my program outputs 4 the result of the last calculation. Is this close to what you're trying to do? Jules ___ 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] Re: process
On 23/02/07, Thomas Hartman [EMAIL PROTECTED] wrote: This seemed like a handy thing to have an example of, so I added it to my growing repo of sample haskell programs and tried running it. But I was unsuccessful. Your program works for me both compiled or using runghc: Linux lonlsd62 2.6.9-11.ELsmp #1 SMP Fri May 20 18:26:27 EDT 2005 i686 i686 i386 GNU/Linux Glasgow Haskell Compiler, Version 6.6, for Haskell 98, compiled by GHC version 6.6 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: process
Jules Bean jules at jellybean.co.uk writes: Well that depends entirely what your program is supposed to do. Your email doesn't tell us (a) what your program was supposed to do or (b) what goes wrong. Therefore we are forced to guess! The following slight variation of your program works fine for me. I don't have anything called 'prog1' on my system, so I used 'bc' which is a calculator program standard on unixes, which works by line-by-line interaction. I varied your program just a tiny bit to get some interesting output: module Main where import System.Process import System.IO main :: IO () main = do putStrLn Running BC (inp,out,err,pid) - runInteractiveProcess bc [] Nothing Nothing hSetBuffering inp LineBuffering hSetBuffering out LineBuffering hSetBuffering err LineBuffering hPutStrLn inp 1+3 a - hGetLine out hPutStrLn inp a a - hGetLine out hPutStrLn inp quit waitForProcess pid putStrLn a This program asks 'bc' to calculate 1+3. The reply is stored in 'a'. Then the program sends 'a' back to bc, effectively asking bc to calculate 4. Since the 4 evaluates just to 4, 'a' gets the value 4 once more. Then I have to send quit to bc. That is the command that bc interprets as an instruction to quit; without that command, 'waitForProcess pid' will wait forever (it's waiting for bc to quit). Finally my program outputs 4 the result of the last calculation. Is this close to what you're trying to do? Jules Thanks, but I still puzzle over the same problem. I wrote the following lines to test exactely your code: module Main where main :: IO () main = f where f = do a - getLine if a == quit then return () else putStrLn a f running the program in the console works without any problems (1+3 is the result :) ), but with runInteractiveProcess I do not get any output except Running BC, and every IO action after the first hPutStrLn inp 1+3 is never reached (the program hang-up there - no error is thrown) - thats my problem... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Illegal polymorphic or qualified type: forall l.
how can i fix this? Mmmh I really need some haskell type class traingings ;) = test file == module Main where import HList import HOccurs import Control.Monad.Reader class Get a b where get :: a - b data D1 = D1 Int -- dummy type type ActionMonad a l = forall l. (HOccurs D1 l) = ( ReaderT l IO a ) data CR = CR (ActionMonad Bool ()) instance Get CR (ActionMonad Bool ()) where get (CR a) = a main = do print test = error == || [1 of 1] Compiling Main ( uqt.hs, uqt.o ) || uqt.hs|16| 0: || Illegal polymorphic or qualified type: forall l. || (HOccurs D1 l) = || ReaderT l IO Bool || In the instance declaration for `Get CR (ActionMonad Bool ())' == Marc ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Map list of functions over a single argument
On 2/22/07, Gene A [EMAIL PROTECTED] wrote: The functions as I originally defined them are probably easier for someone new to Haskell to understand what was going on than the rather stark ($ a) in the final factoring of the function... Though the final resulting function is far the cleaner for that notation! This is what I came up with when I was experimenting: map (\f - f $ a) fs which then helped me to see it could be rewritten as just map ($ a) fs martin ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] EnumSet and EnumMap
I could not quickly find anyone else writing this boiler plate, so I have posted
this useful wrapper on the Haskell wiki at
http://haskell.org/haskellwiki/EnumSet_EnumMap
This uses a cheap newtype to wrap IntSet and IntMap so that you can store any
Enum in them. It saves either writing many toEnum/fromEnum functions or using
the slower and more generic Data.Set and Data.Map.
The original motivation was to go from Map Char to IntMap.
And as a bonus, the type signature of the newtype is the same kind as Data.Set
and Data.Map (which matters when declaring instances...)
newtype EnumSet e = EnumSet {unEnumSet :: S.IntSet}
deriving (Monoid,Eq,Read,Show,Ord)
newtype EnumMap k a = EnumMap {unEnumMap :: M.IntMap a}
deriving (Eq,Read,Show,Ord,Monoid,Foldable,Functor)
This has been quickly tested with GHC 6.6 and may contain typographical errors I
have not caught yet.
--
Chris
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Re: [Haskell-cafe] exists . a psuedo-standard non-empty list module
Hi Nick That sounds like a great option. Candidate numero uno as of now. What I have in mind right now should be pretty light weight, but it will mostly be a regurgitation of code I've seen floating around. Some of the code from the previous wiki link, type-level decimal numbers I saw in an Oleg paper (I think), etc. I am happy to accept a Safe list implementation much the same way as Oleg's implementation. The Safe library is a place to put code which allows the user to write code which ensures their are no pattern match errors, or to give better error messages when there are pattern match errors. Something like a type level implementation of decimals, if not directly concerned with this, might be better in a separate library for type level computation. Something like http://www.eecs.tufts.edu/~rdocki01/typenats.html Would you be open to such code in your library? Anyone have a better place for it? Yep, just send in a patch :) Thanks Neil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] exists . a psuedo-standard non-empty list module
Hi Incidentally, inserting NList into the existing Safe.List does not seem like a good match as NList critically relies on being in a separate module with a limited export. As mentioned before, Safe.List would be an entirely separate module in my package, so can export/not export whatever it chooses. * Catch: http://www-users.cs.york.ac.uk/~ndm/projects/catch.php * ESC-Haskell: http://www.cl.cam.ac.uk/~nx200/research/escH-hw.ps I would submit the approach of the lightweight static capabilities (cf above Wiki link) to be counted as the third project in that area. The latter has an advantage that it is available in Haskell right now and requires no extra tools. I've added a link to my web page, which is where I also paste from where someone asks this question :) Thanks Neil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: process
Dougal Stanton wrote: If it basically works, what goes wrong in my programm? Maybe something to do with compiler flags? No. This isn't even a Haskell-related problem, in all likelihood. Bidirectional interaction with another process over a pipe, particularly when the other process is using stdio or an equivalent (i.e. most programs), is a classic and fruitful source of deadlocks. Just because *your* end of each pipe is a line-buffered file handle has no bearing on the *other* process's management of its pair of endpoints. For example, on a Unix-like system, the other process's stdio will block-buffer stdin and stdout by default if it finds that they're not attached to tty-like file descriptors. There are really only two ways to deal with this. The first is to read from the subprocess in a separate thread, but this only works effectively if what you're sending to the other process doesn't depend on what you read back from it (because there's no way of forcing it to send you anything). The second is Unix-specific, and involves talking to the other process via a pseudotty instead of a pair of pipes. This convinces the other process's stdio that you're a terminal, and you get the line-buffering you desire. It's *still* highly deadlock-prone, and not something to do casually. So what you're trying to do looks easy if you've never tried it, but it's actually very fiddly in all but the most trivial of circumstances. The third, and best, way to deal with this problem is to completely avoid it unless you want to spend several hours or days scratching your head. b ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: process
Bryan O'Sullivan wrote: Just because *your* end of each pipe is a line-buffered file handle has no bearing on the *other* process's management of its pair of endpoints. For example, on a Unix-like system, the other process's stdio will block-buffer stdin and stdout by default if it finds that they're not attached to tty-like file descriptors. In case the implications of this aren't clear, let me expand a little. You've got a line-buffered stdout. You write 1+1\n, which sends 4 bytes to the other process. It's got a block-buffered stdin, so it's going to sit in its first read until it receives 512 bytes (or whatever the buffer size is) from you. And an oversized violin, you have a deadlock! The converse bites you, too. You want to read a line from the other process. It writes 1+1\n to you, but its stdio buffers up the 4 bytes because it hasn't reached the 512-byte watermark. It then tries to read from you, but you're still blocked trying to read the first line (that it hasn't actually sent) from it. Deadlock. b ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A real Haskell Cookbook
On Fri, 23 Feb 2007 18:09:15 +, you wrote: Well, actually, I never cited the non-breaking space character as a problem. Well, actually, you did: Symbols such as the 160 used liberally in the Haskell wikibook are totally invisible to screen readers. #160; = NO BREAK SPACE Which is why I asked specifically about that. Steve Schafer Fenestra Technologies Corp. http://www.fenestra.com/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: process
Albert Y. C. Lai trebla at vex.net writes: h. wrote: module Main where main :: IO () main = f where f = do a - getLine if a == quit then return () else putStrLn a f This one also needs to switch to line buffering. Add/Change: import System.IO(stdout, hSetBuffering, BufferMode(LineBuffering)) main = hSetBuffering stdout LineBuffering f Thanks a lot, now it does work! This means just the proc1 program has to be changed and everything will work properly (hopefully - at least the haskell part works :) ). ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A real Haskell Cookbook
So that's what it is! I wondered why alt-num-0160 only produced a space character. Still, as I said originally, it is totally invisible in the browse buffer. Anyway, are you one of the authors of the wikibook Or, are you just offering your assistance? All the best Paul At 19:03 23/02/2007, you wrote: On Fri, 23 Feb 2007 18:09:15 +, you wrote: Well, actually, I never cited the non-breaking space character as a problem. Well, actually, you did: Symbols such as the 160 used liberally in the Haskell wikibook are totally invisible to screen readers. #160; = NO BREAK SPACE Which is why I asked specifically about that. Steve Schafer Fenestra Technologies Corp. http://www.fenestra.com/ ___ 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] A real Haskell Cookbook
P. R. Stanley wrote: I'm referring to math symbols which do not get successfully translated into an intelligible symbol in the screen reader browse buffer. Is there a way to make the symbols both look right on a screen and sound right from a screen reader? E.g., span title=big sigmaΣ/span !-- there's a U+03A3 in there -- ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A real Haskell Cookbook
On 23/02/07, P. R. Stanley [EMAIL PROTECTED] wrote: As a tip for anyone involved in writing and publishing scientific materials on the web, unless the maths is either written without any funny symbols or, better still, typeset in latex, it is not accessible to a screen-reader. I was under the impression that modern screen readers could pronounce Unicode characters by looking up their name. I.e., your #160; would get read as 'Non-breaking space' (perhaps a bad example, this one wouldn't want to be read out due to its abuse as a layout tool, which would make reading old pages very awkward). I don't see how images are going to be much better? I suppose math images do, on MediaWiki, have an alt text which is their LaTeX, but I'd hate to have to have that read to me. If you're interested in talking to the authors of the wikibook, subscribe to the wikibook@haskell.org mailing list. -- -David House, [EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] How to build a generic spreadsheet?
I want to write a program where a user would update a bunch of variables, and everything that depends on those variables (and nothing else) are recalculated. Basically, a spreadsheet, but generalized for any computation. Could someone recommend an elegant way to do it or some good reading material? Thanks, Greg ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to build a generic spreadsheet?
On Fri, Feb 23, 2007 at 02:33:00PM -0800, Greg Fitzgerald wrote: I want to write a program where a user would update a bunch of variables, and everything that depends on those variables (and nothing else) are recalculated. Basically, a spreadsheet, but generalized for any computation. Could someone recommend an elegant way to do it or some good reading material? http://www.cse.ogi.edu/~magnus/Adaptive/ That might be a good place to start. -- the Edward Blevins [EMAIL PROTECTED](512) 796-6661 Today is Prickle-Prickle, the 54th day of Chaos in the YOLD 3173 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to build a generic spreadsheet?
On 2/23/07, Sebastian Sylvan [EMAIL PROTECTED] wrote: On 2/23/07, Greg Fitzgerald [EMAIL PROTECTED] wrote: I want to write a program where a user would update a bunch of variables, and everything that depends on those variables (and nothing else) are recalculated. Basically, a spreadsheet, but generalized for any computation. Could someone recommend an elegant way to do it or some good reading material? Off the top of my head, one cool way of doing it would be to have each variable be a separate thread (they're lightweight, so it's okay! :-)), and you would have a list of input connections and output connections, in the form of TVars. In its resting state you would have a transaction which simply reads all of the input variables, and returns the new list of inputs if and only if either of them are changed, something like: -- not compiled, consider it pseudocode :-) getInputs :: (Eq a ) = [( a, TVar a)] - STM [a] getInputs inp = do let (vals, vars) = unzip inp newVals - mapM readTVar vars when ( newVals /= vals ) retry -- at least one input must've been changed Bah, this should be: when ( newVals == vals ) retry Of course... -- Sebastian Sylvan +46(0)736-818655 UIN: 44640862 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to build a generic spreadsheet?
Greg Fitzgerald wrote: I want to write a program where a user would update a bunch of variables, and everything that depends on those variables (and nothing else) are recalculated. http://sigfpe.blogspot.com/2006/11/from-l-theorem-to-spreadsheet.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A real Haskell Cookbook
As a tip for anyone involved in writing and publishing scientific materials on the web, unless the maths is either written without any funny symbols or, better still, typeset in latex, it is not accessible to a screen-reader. I was under the impression that modern screen readers could pronounce Unicode characters by looking up their name. I.e., your #160; would get read as 'Non-breaking space' (perhaps a bad example, this one wouldn't want to be read out due to its abuse as a layout tool, which would make reading old pages very awkward). I don't see how images are going to be much better? I suppose math images do, on MediaWiki, have an alt text which is their LaTeX, but I'd hate to have to have that read to me. I think latex is the perfect solution to the problem. It is perhaps the only 100 percent accessible medium available right now. It doesn't require any special software to read. All it needs is a simple text editor. Latex is a well-established tool/medium in the world-wide scientific community and therefore its inclusion in the Haskell wikibook or any other scientific document along with the unicode characters and image files would be potentially beneficial to everyone. Paul If you're interested in talking to the authors of the wikibook, subscribe to the wikibook@haskell.org mailing list. -- -David House, [EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to build a generic spreadsheet?
Hi I want to write a program where a user would update a bunch of variables, and everything that depends on those variables (and nothing else) are recalculated. Basically, a spreadsheet, but generalized for any computation. Could someone recommend an elegant way to do it or some good reading material? PropLang already has the framework to do this: http://www.cs.york.ac.uk/fp/darcs/proplang/ Take a look at the samples, you can say something like: sb!text = (\x - Word count: ++ show (length $ words x)) =$$= txt!text The status bar's text is the word count, and its automatically updated if the user types. PropLang mainly operates with Gtk, but the framework is more general. What it does lack is much documentation :) Thanks Neil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A real Haskell Cookbook
Is there a way to make the symbols both look right on a screen and sound right from a screen reader? E.g., span title=big sigmaΣ/span !-- there's a U+03A3 in there -- In theory the title attribute should be the adequate yet simple solution we're after. Sadly, in reality this 'aint the case. The title attribute works beautifully in list and table elements. Having read some of the posts I've come to the conclusion that the addition of Latex source code along with the unicode stuff may be the best way forward. I am, however, still open to new ideas. So please don't hesitate to keep them coming. By the way guys, if we're straying off-topic here please feel free to drop me a line privately. Best wishes Paul ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] beginner question re example in Hutton's Programming in Haskell
I have been trying to work through Graham Hutton's Programming in Haskell, but have hit something of a snag in chapter 8.4. Hutton presents some sample code which I am trying to run, with no luck so far. Here is the code as I constructed it by gathering snippets presented across three pages. code module Main where -- as per Hutton page 75 type Parser a = String - [(a, String)] -- page 75 return :: a - Parser a return v = \inp - [(v,inp)] -- page 76 failure :: Parser a failure = \inp - [ ] item :: Parser Char item = \inp - case inp of [ ] - [ ] (x:xs)- [(x,xs)] parse :: Parser a - String - [(a,String)] parse p inp = p inp -- page 77 p :: Parser (Char, Char) p = do x - item item y - item return (x,y) /code When I tried to load this code, I got this error message: Ambiguous occurrence `return' It could refer to either `return', defined at /Users/joe/haskell/ parse2.hs:8:0 or `return', imported from Prelude OK. My reasoning was that Hutton took the trouble to define return, so I decided to use the local definition instead of the one in the Prelude. I changed the last line from return (x,y) to Main.return (x,y). The new error message is worse: Couldn't match expected type `Char' against inferred type `[(Char, String)]' In the expression: x In the first argument of `return', namely `(x, y)' In the expression: return (x, y)/blockquote Hutton provided explicit type signatures, so I did not expect type issues. I decided to take another approach. The book has a website that lists errata and provides code listings. The code for chapter eight is at http://www.cs.nott.ac.uk/~gmh/Parsing.lhs When I read Hutton's code, I noticed that he begins by importing Monad. The code I list above is from chapter 8, pages 75-77 of the book. Monads have not yet been mentioned. The book's index shows that monads aren't mentioned till page 113, in chapter 10. I also notice that in his code, Hutton makes repeated use of a symbol P whose meaning I do not know. What do I have to do to make this code work? I know I can use Hutton's code from the website, but I expected the code presented in the book to work, or the code on the website to restrict itself to what has been discussed in the book. Am I missing something here? Thanks, David Cabana ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] beginner question re example in Hutton's Programming in Haskelly
On Fri, Feb 23, 2007 at 11:18:46PM -0500, David Cabana wrote: I have been trying to work through Graham Hutton's Programming in Haskell, but have hit something of a snag in chapter 8.4. Hutton presents some sample code which I am trying to run, with no luck so far. Here is the code as I constructed it by gathering snippets presented across three pages. code module Main where -- as per Hutton page 75 type Parser a = String - [(a, String)] -- page 75 return :: a - Parser a return v = \inp - [(v,inp)] This return conflicts with the one in Prelude, and (while similar) they are not interchangable. -- page 76 failure :: Parser a failure = \inp - [ ] This is analogous to Prelude.fail. Fortunately Hutton didn't call it that :) item :: Parser Char item = \inp - case inp of [ ] - [ ] (x:xs)- [(x,xs)] Looks reasonable parse :: Parser a - String - [(a,String)] parse p inp = p inp Same here -- page 77 p :: Parser (Char, Char) p = do x - item item y - item return (x,y) /code Bad! Due to the Layout Rule that is parsed as a single long statement... I'm quite suprised you didn't get a parse error. It needs to be: p :: Parser (Char, Char) p = do x - item item y - item return (x,y) But, this still won't work. essentially the 'do' uses Prelude.return, Prelude.(), and Prelude.(=), which work on defined Monads; but your parser type is not properly declared as a monad. (and cannot be, because it is a type synonym.) You could define: () :: Parser x - Parser y - Parser y (p1 p2) l = [ (s,rs2) | (f,rs1) - p1 l , (s,rs2) - p2 rs1 ] (=) :: Parser x - (x - Parser y) - Parser y (p1 = fn) l = [ (s,rs2) | (f,rs1) - p1 l , (s,rs2) - fn f rs1 ] then use those (do-notation ignores scope so it must be desugared): p :: Parser (Char, Char) p = item Main.= \x - item Main. item Main.= \y - Main.return (x,y) This should work. Famous last words I know :) When I tried to load this code, I got this error message: Ambiguous occurrence `return' It could refer to either `return', defined at /Users/joe/haskell/ parse2.hs:8:0 or `return', imported from Prelude OK. My reasoning was that Hutton took the trouble to define return, so I decided to use the local definition instead of the one in the Prelude. I changed the last line from return (x,y) to Main.return (x,y). The new error message is worse: Couldn't match expected type `Char' against inferred type `[(Char, String)]' In the expression: x In the first argument of `return', namely `(x, y)' In the expression: return (x, y)/blockquote Hutton provided explicit type signatures, so I did not expect type issues. I decided to take another approach. The book has a website that lists errata and provides code listings. The code for chapter eight is at http://www.cs.nott.ac.uk/~gmh/Parsing.lhs When I read Hutton's code, I noticed that he begins by importing Monad. The code I list above is from chapter 8, pages 75-77 of the book. Monads have not yet been mentioned. The book's index shows that monads aren't mentioned till page 113, in chapter 10. I also notice that in his code, Hutton makes repeated use of a symbol P whose meaning I do not know. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Code and Perf. Data for Prime Finders
Perhaps you might want include in your test the following: http://www.haskell.org/pipermail/haskell-cafe/2007-February/022437.html It seems quite close to the genuine Eratosthenes sieve algorithm: it employs the idea of marks, it can cross composite numbers off several times, and it never tries to divide or examine prime numbers. In fact, the algorithm doesn't even use the full division or full comparison (let alone other arithmetic operations). ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
