Re: [Haskell-cafe] split string into n parts
Hello jim, Monday, October 23, 2006, 11:29:07 PM, you wrote: I want to split a string into 5 parts of equal length, with the last fifth padded if necessary, but can't get it right - here's what I've got - fifths :: String - String fifths s = unwords [a1,a2,a3,a4,a5] where l = (length s) `div` 5 s0 = s++ (a1,s1) = splitAt l s0 (a2,s2) = splitAt l s1 ... you can also use the following func: splitByLen (len:lens) list = (x:splitByLens lens xs)where (x,xs) = splitAt len list splitByLen [] []= [] -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re[2]: [Haskell-cafe] Exception: Too many open files
Hello Bas, Tuesday, October 24, 2006, 1:03:55 AM, you wrote: Great it works! I didn't know about unsafeInterleaveIO [1]. Why is it called 'unsafe'? And how does the laziness work? Is it because of the 'let r = ... in (s, r)'? read either http://haskell.org/haskellwiki/IO_inside or Simon's paper awkward squad mentioned there in your original program, parseFile don't parsed file. it just returned thunk (computation) that will parse file when data from this thunk will be requested. so, your mapM returned 18k of such thunks, each with its own file open. Tomasz's solution postpone not only parsing, but the whole parseFile call (including file open) until the data from this parsing will be really requested. because your next code uses results of each parsing before using results of next one, this allows garbage collector to close files of already used parsings before you go to consume next one. smart solution -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Guards with do notation?
Hi, Am Dienstag, den 24.10.2006, 00:44 +0300 schrieb Misha Aizatulin: hello all, why is it not possible to use guards in do-expressions like do (a, b) | a == b - getPair return a and b are equal Probably because it is not well-defined for all Monad what a failure is, i.e. what to do in the other case. or something. Just my guess. Greetings, Joachim -- Joachim nomeata Breitner mail: [EMAIL PROTECTED] | ICQ# 74513189 | GPG-Key: 4743206C JID: [EMAIL PROTECTED] | http://www.joachim-breitner.de/ Debian Developer: [EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Guards with do notation?
On 24/10/06, Joachim Breitner [EMAIL PROTECTED] wrote: Am Dienstag, den 24.10.2006, 00:44 +0300 schrieb Misha Aizatulin: hello all, why is it not possible to use guards in do-expressions like do (a, b) | a == b - getPair return a and b are equal Probably because it is not well-defined for all Monad what a failure is, i.e. what to do in the other case. or something. Just my guess. Exactly the same thing that guards do elsewhere? Count the falsity of the guard as a pattern match failure. It's precisely the same as doing, e.g.: do Just (a, b) - Nothing return a and b were Just Pattern-match failure in a do-block invokes fail in that monad. -- -David House, [EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Guards with do notation?
Joachim Breitner wrote: Hi, Am Dienstag, den 24.10.2006, 00:44 +0300 schrieb Misha Aizatulin: hello all, why is it not possible to use guards in do-expressions like do (a, b) | a == b - getPair return a and b are equal Probably because it is not well-defined for all Monad what a failure is, i.e. what to do in the other case. or something. Just my guess. No, fail is indeed a method of class Monad, and it is there exactly for this reason, i.e. because pattern matching may fail (even without guards, think of do Just a - ... ) The restriction is there because guards are not allowed in lambda expressions, for which do-notation is merely syntactic sugar. (Some people have argued for lifting this restriction in Haskell', see http://thread.gmane.org/gmane.comp.lang.haskell.prime/1750/focus=1750) HTH Ben ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Exception: Too many open files
I don't know why these unsafe* functions are suggested so easily. Their name is chosen for good reason. On Mon, 23 Oct 2006, Bas van Dijk wrote: -- module Main where import Text.ParserCombinators.Parsec data T = ... test = print . take 3 = parseFiles parseFiles :: IO [T] parseFiles = mapM parseFile = getFileFPs Is it possible to turn it into parseFiles :: [IO T] ? Then you can easily do sequence (take 3 parseFiles) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: split string into n parts
I wrote: jim burton [EMAIL PROTECTED] wrote: Thankyou! It's http://www.rubyquiz.com - They are mostly well suited to haskell, lot of mazes etc. I've done 5 or 6 with varying degrees of success but have learned a lot. This thing about strings in fifths is from #1, the solitaire cipher. At a quick glance I can't see which bit needs it. The only mention of five is where it asks to split the string into groups of five characters (not into five equal parts), padded with Xs. You can do that like this: splitAtMb n l = let p = splitAt n l in if null $ fst p then Nothing else Just p Gah! Brain AWOL. I'm surprised no-one picked me up on that. Why didn't I use: splitAtMb n [] = Nothing splitAtMb n l = Just $ splitAt n l ? in_fives l = unfoldr (splitAtMb 5) (l ++ replicate (length l `mod` 5) 'X') And using length makes this over-strict. maybe something like groups_of n = unfoldr (splitPad 5) where splitPad [] = Nothing splitPad l = Just $ mapFst (padwith 'X') (splitAt n l) padwith c l = take n $ l ++ replicate n c mapFst f (a,b) = (f a, b) -- in Data.Graph.Inductive.Query.Monad which is a little bit inefficient, but less clunky than checking for the end of list in order to apply padwith just once. -- Jón Fairbairn [EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Guards with do notation?
Hi, Am Dienstag, den 24.10.2006, 12:48 +0200 schrieb Benjamin Franksen: Am Dienstag, den 24.10.2006, 00:44 +0300 schrieb Misha Aizatulin: hello all, why is it not possible to use guards in do-expressions like do (a, b) | a == b - getPair return a and b are equal Probably because it is not well-defined for all Monad what a failure is, i.e. what to do in the other case. or something. Just my guess. No, fail is indeed a method of class Monad, and it is there exactly for this reason, i.e. because pattern matching may fail (even without guards, think of do Just a - ... ) The restriction is there because guards are not allowed in lambda expressions, for which do-notation is merely syntactic sugar. (Some people have argued for lifting this restriction in Haskell', see http://thread.gmane.org/gmane.comp.lang.haskell.prime/1750/focus=1750) Then why is the “guard” function, which can be used in a way to implement what Misha wants, only available in MonadPlus, and not in Monad? Greetings, Joachim -- Joachim Breitner e-Mail: [EMAIL PROTECTED] Homepage: http://www.joachim-breitner.de ICQ#: 74513189 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Exception: Too many open files
Bas van Dijk wrote: On Monday 23 October 2006 21:50, Tomasz Zielonka wrote: unsafeInterleaveMapIO f (x:xs) = unsafeInterleaveIO $ do y - f x ys - unsafeInterleaveMapIO f xs return (y : ys) unsafeInterleaveMapIO _ [] = return [] Great it works! I didn't know about unsafeInterleaveIO [1]. Why is it called 'unsafe'? Because it causes pure code to perform side-effects (=IO), albeit in a controlled manner, so it's not as bad as unsafePerformIO. For instance, using getContents you get a string (list of chars) with the property that evaluating subsequent elements of the list causes IO to happen (in this case reading another character from stdin). Thus, unsafeInterleaveIO is safe only if it is not observable (from inside the program) when exactly the IO gets performed. Ben ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Solitaire cipher
I'm a beginner having a go at implementing the Solitaire cipher (http://www.rubyquiz.com/quiz1.html as mentioned in another post) and I'd be really grateful if you could help me improve the code to be neater use more functions from the Prelude etc, or errors (eg at the moment I can't work out why padding accumulates after encrypting, decrypting?)...Thanks. *Main decrypt $ encrypt haskell is better by miles HASKE LLISB ETTER BYMIL ESAYP X *Main decrypt $ encrypt $ decrypt $ encrypt haskell is better by miles HASKE LLISB ETTER BYMIL ESAYP X BFCRK X *Main --- import Char import Random import List import Foreign import Maybe data Card = Clubs Int | Spades Int | Diamonds Int | Hearts Int | JokerA | JokerB deriving (Show, Eq) type Deck = [Card] --cardval - clubs are face value, diamonds plus 13, and so on - Jokers are both 53 cardval :: Card - Int cardval (Clubs i)= i cardval (Diamonds i) = i+13 cardval (Hearts i) = i+26 cardval (Spades i) = i+39 cardval _= 53 isJoker:: Card - Bool isJoker JokerA = True isJoker JokerB = True isJoker _ = False --take a card to a letter card2char :: Card - Char card2char c = case c of (Clubs i)- int2alpha $ cardval c --can case fall through in haskell? (Diamonds i) - int2alpha $ cardval c (Hearts i) - int2alpha $ (cardval c-26) (Spades i) - int2alpha $ (cardval c-26) _- error (Can't make ++ show c ++ into alpha) --take a letter to int, A=1, Z=26 char2int :: Char - Int char2int = (64 `subtract`) . (ord) --take a letter to int, 1=A, Z=26 int2alpha :: Int - Char int2alpha = (chr) . (+64) splitAtMb n l = let p = splitAt n l in if null $ fst p then Nothing else Just p in_fives l = foldr (\x y - x++ ++y) [] $ unfoldr (splitAtMb 5) (l ++ replicate (5 - length l `mod` 5) 'X') --get an ordered deck newdeck :: Deck newdeck = suit 'c' ++ suit 'd' ++ suit 'h' ++ suit 's' ++ JokerA : JokerB : [] where suit s = case s of 'c' - [Clubs i | i - [1..13]] 's' - [Spades i | i - [1..13]] 'd' - [Diamonds i | i - [1..13]] 'h' - [Hearts i | i - [1..13]] --key the deck ready to provide a keystream - move JokerA down one place, --JokerB down 2 places, perform a triplecut then a countcut keydeck :: Deck - Deck keydeck = countcut. triplecut . (movedown JokerB) . (movedown JokerB) . (movedown JokerA) --bump a card down by one place in a deck, treating the deck as circular so if the card is -- last in the deck it becomes 2nd to front not 1st movedown :: Eq a = a - [a] - [a] movedown c d = if c == last d then head d : c : init (tail d) else top ++ bot!!1 : c : (tail (tail bot)) where splt = splitAt (locate c d) d top = fst splt bot = snd splt --substitute the cards above the first joker for those below the 2nd one triplecut :: Deck - Deck triplecut d = afterLastJoker d ++ center d ++ beforeFirstJoker d where beforeFirstJoker = takeWhile (not . isJoker) afterLastJoker = reverse . beforeFirstJoker . reverse center = reverse . dropWhile (not . isJoker) . reverse . dropWhile (not . isJoker) --get the value of the last card and move that many cards from the top of deck to above the last card countcut :: Deck - Deck countcut d = init (drop n d) ++ take n d ++ [last d] where n = cardval (last d) --key the deck, read the value of the top card as n, add the nth card to stream, repeat keystream :: Deck - String keystream d = if isJoker c then keystream d' else card2char c : keystream d' where d' = keydeck d c = d'!!(cardval $ d'!!0) locate :: Eq a = a - [a] - Int locate x xs = fromJust (elemIndex x xs) clean :: String - String clean = map toUpper . filter isAlpha encrypt, decrypt :: String - String --encrypt a string using an unshuffled deck to start encrypt = process (\x y - max26 (x+y)) where max26 x = if x 26 then x-26 else x --decrypt a string using an unshuffled deck to start decrypt = process (\x y - if x = y then (x+26)-y else x-y) process :: (Int - Int - Int) - String - String process f s = in_fives $ map int2alpha $ zipWith f ints1 ints2 where str1 = clean s str2 = take (length str1) (keystream newdeck) ints1 = map char2int str1 ints2 = map char2int str2 -- View this message in context: http://www.nabble.com/Solitaire-cipher-tf2500700.html#a6971077 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org
Re: [Haskell-cafe] Haskell beginner questions
Cybertronic wrote: Hi all, I'm pretty much new to Haskell however I'm stuck on something which is that I'm trying to create a function called display where I type in a DVD name, e.g. dvd1, it returns d (String) and the multiplication of q (Int) and i (Double) Here's what I've done so far: type Film = (Int,String,Int,Double) dvd1 :: Film dvd1 = (1, Space, 5, 9.99) display :: Product - String display (c,d,q,i) = d My display function only shows the string but unfortunately I'm stuck on how to get the display function to multiply q (Int) and i (Double) together and display it next to d. Can someone help me out please? :) I'd recommend a tutorial like http://www.cs.utah.edu/~hal/docs/daume02yaht.pdf display :: Film - String display (c,d,q,i) = d ++ ++ show (fromIntegral q * i) q needs to be converted first and show will convert the result to a string. -- View this message in context: http://www.nabble.com/Haskell-beginner-questions-tf2500050.html#a6971248 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Solitaire cipher
There are several problems with the behavior: *Main encrypt X *Main decrypt $ encrypt TANZP X So fixing this case would be the first thing to do, followed by: *Main encrypt hello LBVJW X *Main decrypt $ encrypt hello HELLO YFRTQ X ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: split string into n parts
Gah! Brain AWOL. I'm surprised no-one picked me up on that. Why didn't I use: splitAtMb n [] = Nothing splitAtMb n l = Just $ splitAt n l Actually, I've some code lying around doing exactly this (but without the padding ;)), written with the coalgebra inlined: split n = unfoldr $ \xs - case xs of [] - Nothing _ - Just (splitAt n xs) Cheers, Stefan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Solitaire cipher
Chris Kuklewicz wrote: There are several problems with the behavior: *Main encrypt X *Main decrypt $ encrypt TANZP X So fixing this case would be the first thing to do, followed by: *Main encrypt hello LBVJW X *Main decrypt $ encrypt hello HELLO YFRTQ X Thanks a lot, I think these are all related...some changes in_fives l = trim $ foldr (\x y - x++ ++y) [] $ unfoldr (splitAtMb 5) (l ++ replicate n 'X') where n = if m5 == 0 then 0 else 5 - m5 m5 = length l `mod` 5 trim :: String - String trim = reverse . dropWhile isSpace . reverse . dropWhile isSpace process :: (Int - Int - Int) - String - String process f s = if null str1 then else in_fives $ map int2alpha $ zipWith f ints1 ints2 where str1 = trim $ clean s str2 = take (length str1) (keystream newdeck) ints1 = map char2int str1 ints2 = map char2int str2 *Main decrypt $ encrypt $ decrypt $ encrypt hello HELLO *Main decrypt $ encrypt $ decrypt $ encrypt haskell is miles better HASKE LLISM ILESB ETTER *Main -- View this message in context: http://www.nabble.com/Solitaire-cipher-tf2500700.html#a6971503 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Read a single Char
Hello, I have a similar question. When I use getChar with Hugs the newline (caused by pressing 'Enter') seems to be carried over into the next call of main, where it is treated as a single input character. The workaround is getLine and head, but it would be nice to drop the newline right away. I suppose the solution offered here: hSetBuffering stdin NoBuffering will have the desired effect, but is there another way? Thanks, Hans van Thiel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Read a single Char
Hi I have a similar question. When I use getChar with Hugs the newline (caused by pressing 'Enter') seems to be carried over into the next call of main, where it is treated as a single input character. The workaround is getLine and head, but it would be nice to drop the newline right away. I suppose the solution offered here: Hmm, sounds like a bug in WinHugs, I'll check it out. Thanks Neil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Exception: Too many open files
On Tuesday 24 October 2006 13:03, Henning Thielemann wrote: Is it possible to turn it into parseFiles :: [IO T] ? Then you can easily do sequence (take 3 parseFiles) Thanks, I think I go for this sollution: parseFiles :: IO [IO a] parseFiles = liftM (map parseFile) getFileFPs test = print = sequence . take 3 = parseFiles Bas van Dijk ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Solitaire cipher
jim burton [EMAIL PROTECTED] writes: In addition to Chris's comments, here are some more: data Card = Clubs Int | Spades Int | Diamonds Int | Hearts Int | JokerA | JokerB They aren't really Ints; better to define something like data FaceValue = Ace | F2 | F3 | F4 | F5 | F6 | F7 | F8 | F9 | F10 | Jack | Queen | King and possibly derive Enum (which unfortunately would give the the wrong values, but that can be got around). deriving (Show, Eq) type Deck = [Card] --cardval - clubs are face value, diamonds plus 13, and so on - Jokers are both 53 I'd be inclined to define an Enum instance rather than cardval directly, but define cardval as an auxilliary function that scrunches both jokers to the same value. isJoker:: Card - Bool isJoker JokerA = True isJoker JokerB = True isJoker _ = False Since you've defined an instance of Eq, you can use isJoker c = c == JokerA || c == JokerB --take a card to a letter card2char :: Card - Char card2char c = case c of (Clubs i)- int2alpha $ cardval c --can case fall through in haskell? It's defined to, but you don't need a case clause as you can use cardval and mod. --take a letter to int, A=1, Z=26 char2int :: Char - Int char2int = (64 `subtract`) . (ord) Better to use (ord 'A' - 1) if you are going to do it this way. --take a letter to int, 1=A, Z=26 int2alpha :: Int - Char int2alpha = (chr) . (+64) and again splitAtMb n l = let p = splitAt n l in if null $ fst p then Nothing else Just p That was my mistake! Use the shorter, cleaner version I posted after that one. in_fives l = foldr (\x y - x++ ++y) [] $ unfoldr (splitAtMb 5) (l ++ replicate (5 - length l `mod` 5) 'X') Putting the spaces in at this point is a mistake! Also see what I said about length. --get an ordered deck newdeck :: Deck newdeck = suit 'c' ++ suit 'd' ++ suit 'h' ++ suit 's' ++ JokerA : JokerB : [] where suit s = case s of 'c' - [Clubs i | i - [1..13]] 's' - [Spades i | i - [1..13]] 'd' - [Diamonds i | i - [1..13]] 'h' - [Hearts i | i - [1..13]] That seems overly complicated. With an Enum instance, you'd just do newdeck = [Club Ace .. JokerB] or better, with an instance of Bounded too, newdeck = [minBound .. maxBound] Of course, you'd have to write toEnum to do the work, but I'd do it something like toEnum 54 = JokerB toEnum 53 = JokerA toEnum n = [Club, Diamond, Heart, Spade]!!suit $ (toEnum (val+1)) where (suit, val) = (n-1) `divMod` 13 Comments from now on are a bit less thought through... I think there are better ways to do some of these operations, but I'm not going to present them, just nitpick a bit instead. --key the deck ready to provide a keystream - move JokerA down one place, --JokerB down 2 places, perform a triplecut then a countcut keydeck :: Deck - Deck keydeck = countcut. triplecut . (movedown JokerB) . (movedown JokerB) . (movedown JokerA) --bump a card down by one place in a deck, treating the deck as circular so if the card is -- last in the deck it becomes 2nd to front not 1st movedown :: Eq a = a - [a] - [a] movedown c d = if c == last d that looks like an unnecessary pass over the list then head d : c : init (tail d) else top ++ bot!!1 : c : (tail (tail bot)) where splt = splitAt (locate c d) d top = fst splt bot = snd splt you can write where (top,bot) = splitAt ... But how about List.break? And if you know that bot is going to have enough elements where (top, card1:card2:rest) = break ... -- Jón Fairbairn [EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Re: Guards with do notation?
Joachim Breitner wrote: Am Dienstag, den 24.10.2006, 12:48 +0200 schrieb Benjamin Franksen: Am Dienstag, den 24.10.2006, 00:44 +0300 schrieb Misha Aizatulin: hello all, why is it not possible to use guards in do-expressions like do (a, b) | a == b - getPair return a and b are equal Probably because it is not well-defined for all Monad what a failure is, i.e. what to do in the other case. or something. Just my guess. No, fail is indeed a method of class Monad, and it is there exactly for this reason, i.e. because pattern matching may fail (even without guards, think of do Just a - ... ) The restriction is there because guards are not allowed in lambda expressions, for which do-notation is merely syntactic sugar. (Some people have argued for lifting this restriction in Haskell', see http://thread.gmane.org/gmane.comp.lang.haskell.prime/1750/focus=1750) Then why is the ?guard? function, which can be used in a way to implement what Misha wants, only available in MonadPlus, and not in Monad? This seems to be inconsistent. Anyway, the decision to include fail in class Monad (instead of using MonadZero) has been criticized by far more competent people than me, see this thread http://thread.gmane.org/gmane.comp.lang.haskell.cafe/15656/focus=15666 Ben ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Solitaire cipher
Jón Fairbairn-2 wrote: jim burton [EMAIL PROTECTED] writes: In addition to Chris's comments, here are some more: [snip] Thanks for your comments Jon. I thought about making Cards an instance of Enum but didn't realise how helpful it would be in various places. I will use the shorter version of your function - I need to get a chance to think about how it works first to be honest. Haven't noticed divMod before - handy! -- View this message in context: http://www.nabble.com/Solitaire-cipher-tf2500700.html#a6979284 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Read a single Char
No, it happens with Hugs on Fedora Core 5 (the fc5 Hugs package), not WinHugs. Thanks, Hans On Tue, 2006-10-24 at 17:27 +0100, Neil Mitchell wrote: Hi I have a similar question. When I use getChar with Hugs the newline (caused by pressing 'Enter') seems to be carried over into the next call of main, where it is treated as a single input character. The workaround is getLine and head, but it would be nice to drop the newline right away. I suppose the solution offered here: Hmm, sounds like a bug in WinHugs, I'll check it out Thanks Neil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Read a single char
Hi getChar doesn't return until I press Enter. I need something that returns immediately after I press any key. It's a problem with buffering: hSetBuffering stdin NoBuffering This usually doesn't work on Windows: GHC 6.4.2 and 6.6: requires enter Hugs (console) Sept. 2006: requires enter WinHugs (GUI) Sept. 2006: works as expected But it seems to work on Linux: GHC 6.4.1 on Ubuntu 6.06: works as expected GHC 6.6 on Ubuntu 6.06: works as expected I am really interested in hearing of a solution that works on all platforms. Does 'readKey', from System.Console.Readline, works on Windows? It works on Linux with the buffering advice applied. Maurício ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Read a single Char
No, it happens with Hugs on Fedora Core 5 (the fc5 Hugs package), not WinHugs. Woops, the previous post in a different thread was talking about WinHugs, and I forgot to context-switch :) Does GHCi give the different behaviour? If so, one of them is probably a bug. Thanks Neil Thanks, Hans On Tue, 2006-10-24 at 17:27 +0100, Neil Mitchell wrote: Hi I have a similar question. When I use getChar with Hugs the newline (caused by pressing 'Enter') seems to be carried over into the next call of main, where it is treated as a single input character. The workaround is getLine and head, but it would be nice to drop the newline right away. I suppose the solution offered here: Hmm, sounds like a bug in WinHugs, I'll check it out Thanks Neil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Read a single char
Hi!Sorry if it is a bit off-topic in this thread.How can I input EOF symbol in WinHugs? Ctrl-Z and Ctrl-D don't work for me,so I can't use getContents function. Maybe there is a piece of documentationthat I should read? Thanks!-- Dimitri ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Read a single char
H How can I input EOF symbol in WinHugs? No possible way. If you could type the NUL character that might possibly work, but even then 1) you can't, 2) it might not. Do you have a particular need for typing the end of getContents in WinHugs? If so, I can open a bug and might be able to fix it for the next release. Thanks Neil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Read a single Char
On Tue, Oct 24, 2006 at 06:14:14PM +0200, Hans van Thiel wrote: I have a similar question. When I use getChar with Hugs the newline (caused by pressing 'Enter') seems to be carried over into the next call of main, where it is treated as a single input character. The workaround is getLine and head, but it would be nice to drop the newline right away. I suppose the solution offered here: that is the correct behavior, input is never discarded, it is just saved up until you press enter for the first time. if you type fooenter, your next four getChars will get 'f' 'o' 'o' and '\n'. it is not haskell that is treating enter as specially, it is your terminal, getChar just returns exactly what was passed to it. hSetBuffering stdin NoBuffering will have the desired effect, but is there another way? this will cause getChar to return right away as soon as they type the first character. which is probably what you want. of course, if they press an enter, you will see an enter. but you don't have to wait until they press one. John -- John Meacham - ⑆repetae.net⑆john⑈ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Read a single char
On 10/25/06, Neil Mitchell [EMAIL PROTECTED] wrote: How can I input EOF symbol in WinHugs?No possible way. If you could type the NUL character that mightpossibly work, but even then 1) you can't, 2) it might not.Do you have a particular need for typing the end of getContents in WinHugs? If so, I can open a bug and might be able to fix it for thenext release.Thank you!Surely I can get along without getContents in WinHugs: last time I thought aboutit I just wanted to show getContents function to my students (and using hGetContents on a file handle seems to be better example). Another function thatcould be useful when teaching IO is 'interact', and it seems that it's alsoimpossible to use it without typing EOF (am I right?).So it would be nice to have a way to type EOF in WinHugs, but surely it's a feature one can live without.And thank you for WinHugs, it is really useful!-- Dimitri ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Read a single char
On Wed, Oct 25, 2006 at 01:06:28AM +0400, Dimitri Timofeev wrote: Sorry if it is a bit off-topic in this thread. How can I input EOF symbol in WinHugs? Ctrl-Z and Ctrl-D don't work for me, so I can't use getContents function. Maybe there is a piece of documentation that I should read? does F6 work? it used to back with DOS something or another. John -- John Meacham - ⑆repetae.net⑆john⑈ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Read a single char
On 10/25/06, John Meacham [EMAIL PROTECTED] wrote: does F6 work? it used to back with DOS something or another.It works in console Hugs, as well as Ctrl-Z, but does not work in WinHugs.-- Dimitri ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Read a single char
Hi Surely I can get along without getContents in WinHugs: last time I thought about it I just wanted to show getContents function to my students (and using hGetContents on a file handle seems to be better example). Another function that could be useful when teaching IO is 'interact', and it seems that it's also impossible to use it without typing EOF (am I right?). You can use interact, you just have to hit the stop button to break out of it. Interestingly Ctrl+C is captured by interact, as is Ctrl+Z/Ctrl+D, so fixing it up to return -1 in these cases should be pretty easy - i'll try and get that done tomorrow. And thank you for WinHugs, it is really useful! Thank you :) - its nice to know that it is being used. Neil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Configurations proposal
On 10/24/06, Duncan Coutts [EMAIL PROTECTED] wrote: On the other hand, in Gtk2Hs I know one case where we do this. We have aGraphics.UI.Gtk.Cairo api module that is only included if Gtk was builtagainst Cairo. In any case it could be faked by using cpp to just not export anything rather than not having the module exposed at all. Soit's not clear that it's worth banning. Or maybe making it slightlyharder is worth it so that people don't get in the habit. Couldn't you split this into Gtk and Gtk-Cairo packages, where the latter is only built if Cairo is available? Similarly, in your GUI example, couldn't you have seperate foo and foo-gui packages, and only build the foo-gui package if the GUI libraries are available? Otherwise, how can you say I depend on the Gtk package being built with Cairo support and I depend on the GUI portion of the foo package?In general, optional groups of modules should be split off into separate packages, and there should be a way of building a bundle of related packages together (just like one can build a group of related executables together already). Regards,Brian ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Haskell custom search engine
Google now lets us create our own custom search engine pages, so I whipped one up for Haskell, http://www.google.com/coop/cse?cx=015832023690232952875%3Acunmubfghzq also, as a demo, embedded http://www.cse.unsw.edu.au/~dons/search.html Seems to do a reasonable job of targetting just Haskell sites. Feel free to add more Haskell material, or refine the search. In fact, search for mailing list items seems rather easy this way. Neil, I wonder if we could integrate this with Hoogle somehow? -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
