Re: [Haskell-cafe] Inputs to classic FRP: unsafeInterleaveIO/unsafePerformIO
Edward Amsden wrote: As far as I can tell, with classic FRP implementations (those which use behaviors as a first-class abstraction), the only way to create a behavior or event based on some external input (for instance keypresses or microphone input) is to do something with unsafePerformIO or unsafeInterleaveIO. A behavior is a value, which when evaluated at a specific time would have to either block its evaluation until input could be read, or check the input at that particular time. Is there any other way of implementing external behaviors besides that? Yes, there are other ways, see for example the implementation here: http://tinyurl.com/frp-automaton . This is essentially a pure variant of Ryan's implementation. My implementation has a serious problem, namely that sharing is lost. I think this is the case for Ryan's implementation as well. The state of a behavior will be duplicated and updates multiple times. This can be fixed by observing sharing, of course. I'm currently working on a push-driven FRP implementation. (Though I'm getting second thoughts as to whether the small increase in efficiency is worth the implementation cost.) See also http://apfelmus.nfshost.com/blog/2011/04/24-frp-push-driven-sharing.html Best regards, Heinrich Apfelmus -- http://apfelmus.nfshost.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] -- Extension for Pearls of Functional Algorithm Design by Richard Bird, 2010, page 25 #Haskell
Do you have a question for the group or something you want to discuss? On Mon, Apr 25, 2011 at 8:50 PM, cas...@istar.ca wrote: -- Extension for Pearls of Functional Algorithm Design by Richard Bird, -- 2010, page 25 #Haskell -- This version assumes 3 disjoint ordered sets represented as lists. -- So either: xy XOR xy -- Since it uses lists it is no faster than the divide and conquer approach. -- I might try to convert this version to sorted arrays for -- O(log|X|+log|Y|+log|Z|) performance -- If I can figure out how to do it without suffering from indexitis. smallest3'' :: Ord a = Int - ([a], [a], [a]) - a smallest3'' k ([],[],ts) = ts !! k smallest3'' k (zs,[],[]) = zs !! k smallest3'' k ([],ws,[]) = ws !! k smallest3'' k ([],ws,ts) = smallest'' k (ws,ts) smallest3'' k (zs,[],ts) = smallest'' k (zs,ts) smallest3'' k (zs,ws,[]) = smallest'' k (zs,ws) smallest3'' k (zs,ws,ts) = case (ab, bc, ac) of ~~(True, True, True)- smallest3h'' k ((zs,p,ys),(ws,q),(ts,o,rs)) -- abc ~~(True, False, True) - smallest3h'' k ((zs,p,ys),(ts,o),(ws,q,us)) -- acb ~~(False, True, True) - smallest3h'' k ((ws,q,vs),(zs,p),(ts,o,rs)) -- bac ~~(False, True, False) - smallest3h'' k ((ws,q,vs),(ts,o),(zs,p,xs)) -- bca ~~(True, False, False) - smallest3h'' k ((ts,o,ss),(zs,p),(ws,q,us)) -- cab ~~(False, False, False) - smallest3h'' k ((ts,o,ss),(ws,q),(zs,p,xs)) -- cba where ~~p = (length zs) `div` 2 ~~q = (length ws) `div` 2 ~~o = (length ts) `div` 2 ~~(xs, a : ys) = splitAt p zs ~~(us, b : vs) = splitAt q ws ~~(rs, c : ss) = splitAt o ts ~~smallest3h'' k ((zs,p,ys),(ws,q),(ts,o,rs)) = case (k=p+q+o) of ~~(True)- smallest3'' k (zs,ws,rs) ~~(False) - smallest3'' (k-p-1) (ys,ws,ts) smallest'' :: Ord a = Int - ([a], [a]) - a smallest'' k ([],ws) = ws !! k smallest'' k (zs,[]) = zs !! k smallest'' k (zs,ws) = case (ab, k=p+q) of ~~(True, True) - smallest'' k (zs,us) ~~(True, False) - smallest''(k-p-1) (ys,ws) ~~(False, True) - smallest'' k (xs,ws) ~~(False, False)- smallest''(k-q-1) (zs,vs) where ~~p = (length zs) `div` 2 ~~q = (length ws) `div` 2 ~~(xs, a : ys) = splitAt p zs ~~(us, b : vs) = splitAt q ws ___ 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] HipmunkPlayground compile error
$ system_profiler SPSoftwareDataType | grep System Version System Version: Mac OS X 10.6.7 (10J869) $ ghc --version The Glorious Glasgow Haskell Compilation System, version 7.0.2 $ cabal --version cabal-install version 0.10.2 using version 1.10.1.0 of the Cabal library $ cabal install hipmunkplayground ... Updating documentation index /Users/andrew/Library/Haskell/doc/index.html cabal: Error: some packages failed to install: GLFW-0.4.2 failed during the building phase. The exception was: ExitFailure 1 HipmunkPlayground-5.2.0.3 depends on GLFW-0.4.2 which failed to install. Cheers, Andrew Pennebaker www.yellosoft.us ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] HipmunkPlayground compile error
On Tue, Apr 26, 2011 at 1:38 AM, Andrew Pennebaker andrew.penneba...@gmail.com wrote: $ system_profiler SPSoftwareDataType | grep System Version System Version: Mac OS X 10.6.7 (10J869) $ ghc --version The Glorious Glasgow Haskell Compilation System, version 7.0.2 $ cabal --version cabal-install version 0.10.2 using version 1.10.1.0 of the Cabal library $ cabal install hipmunkplayground ... Updating documentation index /Users/andrew/Library/Haskell/doc/index.html cabal: Error: some packages failed to install: GLFW-0.4.2 failed during the building phase. The exception was: ExitFailure 1 HipmunkPlayground-5.2.0.3 depends on GLFW-0.4.2 which failed to install. GLFW is the package that failed to install. The reason for that should be in the scroll back somewhere but it can often be hard to find when it's buried in a huge list of compilation messages. If you try with just GLFW, eg., cabal install GLFW, then it should be easier to spot the error. Since you're on a mac, I would highly recommend getting the latest haskell platform. You're on 7.0.2 which has bug fixes that are relevant to build failures on OSX, as I understand it. Jason ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to keep cabal and ghci package versions in sync?
Henning Thielemann schlepptop at henning-thielemann.de writes: You can manually select packages for GHCi with '-package' option. However I do not know a way to automatically syncronise this with the dependencies from the Cabal file. I kind of expected 'cabal-dev ghci' to do this for me. Thanks for help, I'm cleaning my packages for now. -- Gracjan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] How to update the RNG per call (State monad) when generating QuickCheck arbitraries?
Maybe this is a beginners question... But here my problems description: import Random import Control.Monad import qualified Control.Monad.State as S import Test.QuickCheck.Gen import Test.QuickCheck.Arbitrary Each thing can have one of three types: data Ontology = Thing1 Bool | ThingK Bool deriving (Show, Eq) instance Arbitrary Ontology where arbitrary = oneof [ return $ Thing1 True , return $ ThingK True , return $ Thing1 False , return $ ThingK False ] Liked to have a state monad runner for my arbitrary things as in Real World Haskell, Chapter 14. Monads (Random values in the state monad). [RWH]: -- file: ch14/Random.hs type RandomState a = S.State StdGen a [RWH]: -- file: ch14/Random.hs getRandom :: Random a = RandomState a getRandom = S.get = \gen - let (val, gen') = random gen in S.put gen' return val [RWH]: -- file: ch14/Random.hs getTwoRandoms :: Random a = RandomState (a, a) getTwoRandoms = liftM2 (,) getRandom getRandom [RWH]: -- file: ch14/Random.hs runTwoRandoms :: IO (Int, Int) runTwoRandoms = do oldState - getStdGen let (result, newState) = S.runState getTwoRandoms oldState setStdGen newState return result Thought getRandom function would be the best place to inject my unGen function call, but cannot get it to type-check: getRandom :: Random a = RandomState [a] getRandom = S.get = \gen - let (val, gen') = liftM2 (,) (unGen arbitrary gen 12) (random gen) in S.put gen' return val A function not almost fulfilling my needs but the Random Number Generator isn't updated... I liked to have different [Ontology] occasions per call: genArray :: [Ontology] genArray = unGen arbitrary (mkStdGen 42) 12 :: [Ontology] Does anyone have the patience to help me out at least one step further? Cheers Daniel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Why does Cabal not choose the latest package?
Hello! I've had some of the usual problems with packages depending on multiple versions of another package. It seems the root of the hole problem was that I once attempted to run cabal install cabal-install This brought in a number of older packages (Cabal-1.8.0.6, containers-0.3.0.0, directory-1.0.1.2, filepath-1.1.0.4, process-1.0.1.5) to my local package DB, which led to inconsistencies when trying to install new packages. However, if I run cabal install cabal-install-0.10.2 things work just fine. So the problem is that it wants to install an older version of cabal-install. A session demonstrating the problem is found below. Why doesn't cabal always install the latest packages? Thanks! / Emil [emax@laptop:~] ghc --version The Glorious Glasgow Haskell Compilation System, version 7.0.2 [emax@laptop:~] cabal --version cabal-install version 0.10.2 using version 1.10.1.0 of the Cabal library [emax@laptop:~] cabal install cabal-install Resolving dependencies... Downloading containers-0.3.0.0... ... [emax@laptop:~] cabal install cabal-install-0.10.2 Resolving dependencies... Configuring cabal-install-0.10.2... Preprocessing executables for cabal-install-0.10.2... Building cabal-install-0.10.2... ... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why does Cabal not choose the latest package?
On Tue, Apr 26, 2011 at 3:22 AM, Emil Axelsson e...@chalmers.se wrote: Hello! I've had some of the usual problems with packages depending on multiple versions of another package. It seems the root of the hole problem was that I once attempted to run cabal install cabal-install This brought in a number of older packages (Cabal-1.8.0.6, containers-0.3.0.0, directory-1.0.1.2, filepath-1.1.0.4, process-1.0.1.5) to my local package DB, which led to inconsistencies when trying to install new packages. However, if I run cabal install cabal-install-0.10.2 things work just fine. So the problem is that it wants to install an older version of cabal-install. A session demonstrating the problem is found below. Why doesn't cabal always install the latest packages? I consider this a bug but it's actually an intentional feature by the cabal developers. I explained it in the past here: http://osdir.com/ml/haskell-cafe@haskell.org/2010-09/msg00758.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] converting prefixes of CString - String
On 25 Apr 2011, at 08:16, Eric Stansifer wrote:
Let 'c2h' convert CStrings to Haskell Strings, and 'h2c' convert
Haskell Strings to CStrings. (If I understand correctly, c2h . h2c
=== id, but h2c . c2h is not the identity on all inputs;
That is correct. CStrings are 8-bits, and Haskell Strings are 32-bits.
Converting from Haskell to C loses information, unless you use a multi-byte
encoding on the C side (for instance, UTF8).
or perhaps c2h is not defined for all CStrings.
Rather, h2c is not necessarily well-defined for all Haskell Strings. In
particular, the marshalling functions in Foreign.C.String simply truncate any
character larger than one byte, to its lowest byte.
I suggest you look at the utf8-string package, for instance
Codec.Binary.UTF8.String.{encode,decode}, which convert Haskell strings to/from
a list of Word8, which can then be transferred via the FFI to wherever you like.
Regards,
Malcolm
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Re: [Haskell-cafe] A small Darcs anomoly
On 25 Apr 2011, at 11:13, Andrew Coppin wrote: On 24/04/2011 06:33 PM, Jason Dagit wrote: This is because of a deliberate choice that was made by David Roundy. In darcs, you never have multiple branches within a single darcs repository directory tree. Yes, this seems clear. I'm just wondering whether or not it's the best design choice. It seems to me to be a considerable insight. Branches and repositories are the same thing. There is no need for two separate concepts. The main reason other VCSes have two concepts is because one of them is often more efficiently implemented (internally) than the other. But that's silly - how much better to abstract over the mental clutter, and let the implementation decide how its internals look! So in darcs, two repositories on the same machine share the same files (like a branch), but if they are on different machines, they have separate copies of the files. The difference is a detail that you really don't need to know or care about. It does mean that you duplicate information. You have [nearly] the same set of patches stored twice, No, if on the same machine, the patches only appear once, it is just the index that duplicates some information (I think). In fact just as if it were a branch in another VCS. Regards, Malcolm ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] plugins and cabal build
On 26 April 2011 04:57, Michael Snoyman mich...@snoyman.com wrote: Hi all, I'm experimenting with using the plugins package for yesod devel server. The basic approach is to use cabal for building the object files, and then load them with plugins. I can get everything to work when I compile with ghc --make, but I believe name mangling is getting in the way with the cabal build route. Can someone give some guidance on how to properly mangle the function names so that plugins can load them? I'm not sure if he reads this list, but Andy Stewart might know (and I've CC'd him to this). -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Wai and http-enumerator not as lazy as I'd like
Hi all, I'm using Wai and http-enumerator to build a http proxy. The core of the code looks like this: import qualified Network.HTTP.Enumerator as HE import qualified Network.Wai as Wai serveRequest :: forall (m :: * - *). (MonadControlIO m, Failure HE.HttpException m) = HE.Request m - m Wai.Response serveRequest request = do HE.Response sc rh bs - HE.withManager $ HE.httpLbsRedirect request return $ Wai.responseLBS (mkStatus sc) rh bs This works but does not run in constant space as I would have hoped. The thing is, HE.httpLbsRedirect returns a lazy ByteString and Wai.responseLBS writes a lazy ByteString, so why isn't the whole thing lazy? I'd appreciate any clues. Cheers, Erik -- -- Erik de Castro Lopo http://www.mega-nerd.com/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] converting prefixes of CString - String
Let 'c2h' convert CStrings to Haskell Strings, and 'h2c' convert
Haskell Strings to CStrings. (If I understand correctly, c2h . h2c
=== id, but h2c . c2h is not the identity on all inputs;
That is correct. CStrings are 8-bits, and Haskell Strings are 32-bits.
Converting from Haskell to C loses information, unless you use a multi-byte
encoding on the C side (for instance, UTF8).
So actually I am incorrect, and h2c . c2h is the identity but c2h . h2c is not?
I suggest you look at the utf8-string package, for instance
Codec.Binary.UTF8.String.{encode,decode}, which convert Haskell strings
to/from a list of Word8, which can then be transferred via the FFI to
wherever you like.
This package was very helpful; I looked at the source to see how the
utf8 encoding was done. It looks as if the functionality I want is
technically feasible but not implemented yet; it shouldn't be too
much trouble to implement it myself, by imitating the existing
'decode' function but changing its behavior when it runs out of input
in the middle of a utf8-character. Also key is the property
s1 ++ s2 == decode (encode s1)) ++ decode (encode s2))
holds.
Thanks,
Eric
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Re: [Haskell-cafe] Wai and http-enumerator not as lazy as I'd like
On Tue, Apr 26, 2011 at 7:27 AM, Erik de Castro Lopo mle...@mega-nerd.com wrote: Hi all, I'm using Wai and http-enumerator to build a http proxy. The core of the code looks like this: import qualified Network.HTTP.Enumerator as HE import qualified Network.Wai as Wai serveRequest :: forall (m :: * - *). (MonadControlIO m, Failure HE.HttpException m) = HE.Request m - m Wai.Response serveRequest request = do HE.Response sc rh bs - HE.withManager $ HE.httpLbsRedirect request return $ Wai.responseLBS (mkStatus sc) rh bs This works but does not run in constant space as I would have hoped. The thing is, HE.httpLbsRedirect returns a lazy ByteString and Wai.responseLBS writes a lazy ByteString, so why isn't the whole thing lazy? None of the lbs functions in http-enumerator can operate in constant space - they are all built on top of the utility function lbsIter which provides a warning: Convert the HTTP response into a Response value. Even though a Response contains a lazy bytestring, this function does not utilize lazy I/O, and therefore the entire response body will live in memory. If you want constant memory usage, you'll need to write your own iteratee and use http or httpRedirect directly. See: http://hackage.haskell.org/packages/archive/http-enumerator/0.6.0.2/doc/html/Network-HTTP-Enumerator.html#g:4 It might be good to have this warning on the functions that use lbsIter, or have them use ByteStrings instead of Lazy ByteStrings. Antoine I'd appreciate any clues. Cheers, Erik -- -- Erik de Castro Lopo http://www.mega-nerd.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 small Darcs anomoly
This is because of a deliberate choice that was made by David Roundy. In darcs, you never have multiple branches within a single darcs repository directory tree. Yes, this seems clear. I'm just wondering whether or not it's the best design choice. It seems to me to be a considerable insight. Presumably David thought the same. I won't deny that there is a certain simplifying elegance to it. It does mean that you duplicate information. You have [nearly] the same set of patches stored twice, No, if on the same machine, the patches only appear once, it is just the index that duplicates some information (I think). In fact just as if it were a branch in another VCS. 1. Conceptually, you have the same information twice. 2. I have no idea how to make Darcs do the thing with hard links (is that even supported under Windows?) I just copy the whole folder using the normal OS file tools. Either way, you lose the ability to see how branches are related to each other, which might be useful in some cases. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: Leksah 0.10.0
On Tuesday 26 April 2011 02:00:32, jutaro wrote: Well, it is a bit more intricate to invert the sides. After * swapping LeftP and RightP in Edit Prefs - Initial Pane positions * Close all panes and pane groups. (You may leave an editor window open, so that you better see what happens in the next steps). * Collapse all (Hit Ctrl-1 - 2 times) * Split vertical (Hit Ctrl-2), put the focus to the left, split horizontal (Hit Ctrl-3) * Go to Panes Menu and reopen the Log and the Browser and an editor Window * Configure tabs as you like * Save the session or restart Leksah Intricate indeed. If some day you have too much time, consider adding configuration options for that. Until then, how about putting that in the docs? How do I configure autocompletion to only begin after three or four letters have been typed? Go to Edit Prefs - GUI Options, and select Complete only on Hotkey, then hit Ctrl-Space if you want completion. Not ideal (for me), but good enough I think. Although, I find kate's configuration option to start autocompletion after n letters *very* nice. Daniel Fischer wrote: Decreasing indentation via backspace goes one column per backspace, how can I configure it to go to the next (previous) tab position on backspace in the leading whitespace of a line? You can't do this currently, but you can post a wish for enhancement to our issue tracker. Pity. Quoth Hamish: shifttab works, but it is a bit dumb. Changing backspace is on my wish list too. I think we should make it look at the text above to find the correct indentation points. So there's initial support for it, good sign. Please try to run Leksah with the default config (~/.leksah-0.10/packageSources) Will do. Unfortunately I had to wipe the old OS from disk and now have to rebuild a couple of GHCs and a load of libraries (different gmp version), that'll take a while. Indeed leksah may use more memory on the first run That's natural, collecting the data isn't free. (actually it is ghc, which uses it). I'm not sure about that. According to top, leksah-server used that much memory long after ghc ran last. And on the second start, it didn't invoke ghc (at least, no ghc was reported by top). Looks a bit as though it doesn't write the data soon enough. Or it could have been the first sign of my OS crashing. But on consecutive starts it may use about/up to 150MB, but not the numbers you give. That's more reasonable. We'll see. So please try to run Leksah with the default config, and see if the problem remains. Yes, but as mentioned above, that'll not be immediately. Jürgen Thanks, Daniel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A small Darcs anomoly
On 26 April 2011 13:16, Andrew Coppin andrewcop...@btinternet.com wrote: 2. I have no idea how to make Darcs do the thing with hard links (is that even supported under Windows?) I just copy the whole folder using the normal OS file tools. darcs get path/to/other/local/repo Either way, you lose the ability to see how branches are related to each other, which might be useful in some cases. How do you see how git branches are related to each other? -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] converting prefixes of CString - String
On 26 Apr 2011, at 13:31, Eric Stansifer wrote: Let 'c2h' convert CStrings to Haskell Strings, and 'h2c' convert Haskell Strings to CStrings. (If I understand correctly, c2h . h2c === id, but h2c . c2h is not the identity on all inputs; That is correct. CStrings are 8-bits, and Haskell Strings are 32-bits. Converting from Haskell to C loses information, unless you use a multi-byte encoding on the C side (for instance, UTF8). So actually I am incorrect, and h2c . c2h is the identity but c2h . h2c is not? Ah, my bad. In reading the composition from right to left, I inadvertently read h2c and c2h from right to left as well! So, starting from C, converting to Haskell, and back to C is the identity, yes. Starting from Haskell, no. Regards, Malcolm ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A small Darcs anomoly
On Tue, Apr 26, 2011 at 6:35 AM, Ivan Lazar Miljenovic ivan.miljeno...@gmail.com wrote: On 26 April 2011 13:16, Andrew Coppin andrewcop...@btinternet.com wrote: 2. I have no idea how to make Darcs do the thing with hard links (is that even supported under Windows?) I just copy the whole folder using the normal OS file tools. darcs get path/to/other/local/repo More specifically than that. This is the workflow I follow with darcs repos. Say, that I want to get the Foo repo: mkdir ~/repos/Foo cd ~/repos/Foo darcs get http://example.com/Foo HEAD darcs get HEAD feature-branch Then I can send the patches from feature-branch to the official Foo repo at any time. I can also merge them back into HEAD doing a darcs pull from feature-branch to HEAD. I think this is quite comparable to the git workflow. Either way, you lose the ability to see how branches are related to each other, which might be useful in some cases. How do you see how git branches are related to each other? You can use gitk to see how the histories have interacted. Jason ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] There is no null; Maybe/Option types
wren ng thornton w...@freegeek.org wrote: But the greatest thing about Maybe is that you don't *have* to write code in monadic style. Because Maybe makes explicit the null-pointer shenanigans in other languages, you can simply unwrap the Maybe and pass around the raw value instead of letting Nothing permeate your whole program. Spending all your time in the Maybe monad is just as bad as spending all your time in the IO monad. Unless you're saying that I'm one of the worst Haskell programmers in the world, you are totally wrong. Monads are an abstraction for convenience and beauty in expression, not for encapsulating bad habits. Particularly there is nothing wrong with writing 90% of your code in monadic style, which is what I do, often combining three or more monads. And even if I don't use Maybe in monadic style, I often use combinators like 'maybe'. Monadic style to avoid explicit wrapping, and combinators to avoid explicit unwrapping. What exactly is wrong with that? Why would you /not/ use (=) to calculate the fourth root from a monadic square root function? fourthRoot :: (Alternative f, Integral i, Monad f) = i - f i fourthRoot = mSqrt = mSqrt Purity begets clarity! All Haskell code is pure (in the sense of referential transparency), including monadic code, even in the IO monad. Greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife = sex) http://ertes.de/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A small Darcs anomoly
On Tuesday 26 April 2011 15:35:42, Ivan Lazar Miljenovic wrote: How do you see how git branches are related to each other? To some extent, you can see such a relation in gitk. For mercurial, hg glog also shows a bit. I suppose there's also something to visualise branches in bazaar, but I've never used that, so I don't know. So, with gitk/glog, you can see that foo branched off bar after commit 0de8793fa1bc..., then checkout/update to that commit [or bar's head], checkout/update to foo's head/tip and compare. Or there could be some feature I've never heard of yet. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] plugins and cabal build
Ivan Lazar Miljenovic ivan.miljeno...@gmail.com writes: On 26 April 2011 04:57, Michael Snoyman mich...@snoyman.com wrote: Hi all, I'm experimenting with using the plugins package for yesod devel server. The basic approach is to use cabal for building the object files, and then load them with plugins. I can get everything to work when I compile with ghc --make, but I believe name mangling is getting in the way with the cabal build route. Can someone give some guidance on how to properly mangle the function names so that plugins can load them? I'm not sure if he reads this list, but Andy Stewart might know (and I've CC'd him to this). Hi Ivan, sorry for late, too busy on Linux job. Yes, i have got hot-swap code work for Manatee (http://hackage.haskell.org/package/manatee) I used to use plugins, but i found it's buggy. So i use GHC-API wrote my own code at: https://patch-tag.com/r/AndyStewart/manatee-core/snapshot/current/content/pretty/Manatee/Core/Dynload.hs Michael, from your need, you just need read function `dynload`, other functions is write for Manatee framework. Let me explain function `dynload`: dynload :: (String, String, [(String, HValue - IO ())]) - IO () dynload (filepath, moduleName, loadList) = ... First argument is FilePath that contain module. Second argument is moduleName you need scan. Third argument is tuple list that contain symbol you need load and callback function for symbol's HValue. Once function `dynload` find symbol in target module, it will use below code dynamic load new value: (do hValue - compileExpr (moduleName ++ . ++ symbolName) liftIO $ loadFun hValue) function `compileExpr` will get the HValue of symbol, then use loadFun update HVaule in running program. The key is `HValue - IO ()`, you need build TVar/IORef in your running program, once you got new HValue, you should write writeTVar/writeIORef in function `HValue - IO ()` to update the value of TVar/IORef, then you can dynamic loading new value and don't need reboot. I have draw some picture to explain above framework: http://www.flickr.com/photos/48809572@N02/5304662424/in/photostream/lightbox/ Michael, hope above will help you, good luck! :) -- Andy ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A small Darcs anomoly
On 2011-04-26 15:51 +0200, Daniel Fischer wrote: On Tuesday 26 April 2011 15:35:42, Ivan Lazar Miljenovic wrote: How do you see how git branches are related to each other? To some extent, you can see such a relation in gitk. For mercurial, hg glog also shows a bit. I suppose there's also something to visualise branches in bazaar, but I've never used that, so I don't know. So, with gitk/glog, you can see that foo branched off bar after commit 0de8793fa1bc..., then checkout/update to that commit [or bar's head], checkout/update to foo's head/tip and compare. No need to do a checkout; gitk can visualize any or all branches of the repository simultaneously. -- Nick Bowler, Elliptic Technologies (http://www.elliptictech.com/) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Question about the Monad instance for Iteratee (from the enumerator package)
Joining slightly late... From: John Millikin jmilli...@gmail.com John Lato's iteratee package is based on IterateeMCPS.hs[1]. I used IterateeM.hs for enumerator, because when I benchmarked them the non-CPS version was something like 10% faster on most operations. Based on tests I did before iteratee-0.4, the fastest implementation was Oleg's alternate design which is in the comments of IterateeM.hs. I don't think any current packages use that however, with good reason. I'd be interested to see the results of a shootout between iteratee and enumerator. I would expect them to be basically equivalent most of the time, with maybe two or three operations with a small (but consistent) difference one way or the other. John L. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A small Darcs anomoly
On Tuesday 26 April 2011 16:04:55, Nick Bowler wrote: On 2011-04-26 15:51 +0200, Daniel Fischer wrote: On Tuesday 26 April 2011 15:35:42, Ivan Lazar Miljenovic wrote: How do you see how git branches are related to each other? To some extent, you can see such a relation in gitk. For mercurial, hg glog also shows a bit. I suppose there's also something to visualise branches in bazaar, but I've never used that, so I don't know. So, with gitk/glog, you can see that foo branched off bar after commit 0de8793fa1bc..., then checkout/update to that commit [or bar's head], checkout/update to foo's head/tip and compare. No need to do a checkout; gitk can visualize any or all branches of the repository simultaneously. Yes, at least if you're only interested in the genealogy. When I think about how branches are related, I think of contents at least as much as of genealogy. Can gitk show the code next to each other? I wouldn't be surprised, but I haven't yet found a way to do it (but I've only taken a couple of short looks, so that doesn't say much). ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A small Darcs anomoly
On Tue, Apr 26, 2011 at 3:16 PM, Andrew Coppin andrewcop...@btinternet.com wrote: Presumably David thought the same. I won't deny that there is a certain simplifying elegance to it. It does mean that you duplicate information. You have [nearly] the same set of patches stored twice, No, if on the same machine, the patches only appear once, it is just the index that duplicates some information (I think). In fact just as if it were a branch in another VCS. 1. Conceptually, you have the same information twice. 2. I have no idea how to make Darcs do the thing with hard links (is that even supported under Windows?) I just copy the whole folder using the normal OS file tools. Either way, you lose the ability to see how branches are related to each other, which might be useful in some cases. http://wiki.darcs.net/Ideas/Branches I would like to have in-place Darcs branches too but not for wasting space reason. It is nice to keep complete history of the project and with current loose coupling of branches it requires more discipline from me :) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] typing hmatrix expressions
hello alberto, i've had some funny issues with using the cmap function, and i'd like understand what i'm doing wrong namely it wont correctly instantiate for vectors or matrices and I don't understand why. basically my question is: what is the correct type for the hmatrix expression mapMat f =liftMatrix $! cmap f I'd like to just give it a type like Storable a = (a-a)- Matrix a - Matrix a but i get an error message like Electrical.lhs:89:29: No instance for (Container Vector e0) arising from a use of `cmap' Possible fix: add an instance declaration for (Container Vector e0) In the second argument of `($!)', namely `cmap f' In the expression: liftMatrix $! cmap f In an equation for `mapMat': mapMat f = liftMatrix $! cmap f which i feel shouldn't be happening. is the type of cmap in some way too polymorphic, or am I just not turning on the right ghc type extensions for this to work, or is this something that would have been well typed prior to ghc 7? Or am i just not correctly understanding this type error and i'm making a simple mistake? thanks! -Carter ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to update the RNG per call (State monad) when generating QuickCheck arbitraries?
On Tue, Apr 26, 2011 at 3:04 AM, Daniel Kahlenberg d.kahlenb...@googlemail.com wrote: Thought getRandom function would be the best place to inject my unGen function call, but cannot get it to type-check: You haven't described what it is you're actually trying to do, and I'm afraid your code doesn't help to understand that. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A small Darcs anomoly
On Tue, 2011-04-26 at 16:34 +0200, Daniel Fischer wrote: On Tuesday 26 April 2011 16:04:55, Nick Bowler wrote: On 2011-04-26 15:51 +0200, Daniel Fischer wrote: On Tuesday 26 April 2011 15:35:42, Ivan Lazar Miljenovic wrote: How do you see how git branches are related to each other? To some extent, you can see such a relation in gitk. For mercurial, hg glog also shows a bit. I suppose there's also something to visualise branches in bazaar, but I've never used that, so I don't know. So, with gitk/glog, you can see that foo branched off bar after commit 0de8793fa1bc..., then checkout/update to that commit [or bar's head], checkout/update to foo's head/tip and compare. No need to do a checkout; gitk can visualize any or all branches of the repository simultaneously. Yes, at least if you're only interested in the genealogy. When I think about how branches are related, I think of contents at least as much as of genealogy. Can gitk show the code next to each other? I wouldn't be surprised, but I haven't yet found a way to do it (but I've only taken a couple of short looks, so that doesn't say much). I cannot say for gitk but gitview does it does it for sure: gitview --all --date-order Regards 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] How to update the RNG per call (State monad) when generating QuickCheck arbitraries?
On Tue, Apr 26, 2011 at 9:16 AM, Daniel Kahlenberg d.kahlenb...@gmail.comwrote: hold on I'd like to have the genArray call generating distinctive results in one IO execution The problem you're seeing is due to the fact that you're not taking the final RNG state from the first execution of your code and passing it as the initial state to the second. Since you're initialising each one with the same RNG state, you're getting the same results in each case. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to keep cabal and ghci package versions in sync?
On Tue, Apr 26, 2011 at 2:10 AM, Gracjan Polak gracjanpo...@gmail.com wrote: I kind of expected 'cabal-dev ghci' to do this for me. At the moment, cabal-dev ghci just uses the -package-conf and -no-user-package-conf flags to restrict ghci to the sandboxed and global package dbs. It's difficult to do more without parsing the content of the project's cabal file, and that parser isn't exposed through a library api (it's in cabal-install), which makes it a little difficult to use. --Rogan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Question about the Monad instance for Iteratee (from the enumerator package)
On Tuesday, April 26, 2011 7:19:25 AM UTC-7, John Lato wrote: I'd be interested to see the results of a shootout between iteratee and enumerator. I would expect them to be basically equivalent most of the time, with maybe two or three operations with a small (but consistent) difference one way or the other. I did some basic benchmarks a few months ago; if I remember correctly, it depends almost entirely on how well GHC optimizes CPS on a particular platform. The relative performace was very similar to Lennart Kolmodin's benchmarks of binary at http://lennartkolmodin.blogspot.com/2011/02/binary-by-numbers.html . In particular, CPS/iteratee is faster on 32-bit, while state passing/enumerator is faster on 64-bit. This difference exists for almost all operations, and was on the order of 5-15% depending on the shape of the input. I couldn't figure out a good way to benchmark the libraries themselves when there's so much noise from the compiler. I'm waiting for GHC7 to stabilise a bit before doing another benchmark -- the LLVM backend and new CPS handling should make both implementations faster, once they're a bit more mature. I really hope CPS becomes as fast on 64-bit as it is on 32-bit, because it's a much cleaner implementation. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANNOUNCE: cereal-0.3.3.0
Hot on the heels of the last release, cereal-0.3.3.0 [1] adds support for parsing and rendering lazy ByteStrings. Most running functions in Data.Serialize.Get and Data.Serialize.Put now have lazy analogues, and Data.Serialize has gained encodeLazy and decodeLazy. This new functionality was made possible by the incremental parsing support added in cereal-0.3.1.0 by Lemmih. [1] http://hackage.haskell.org/package/cereal-0.3.3.0 smime.p7s Description: S/MIME Cryptographic Signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Haskell User Group starter kit
Hi all, We may be coming to a time where we start to see Haskell User Groups or Functional Programming clubs popping up all the over the place. Maybe it's a good time to put our heads together and figure out what we can do to nurture these groups, to keep them going strong rather than fizzling out. One idea might be create some sort of Haskell User Group starter kit so that individual groups can hit the ground running with some concrete ideas. http://www.haskell.org/haskellwiki/Haskell_User_Group My hope is that it would provide just enough material for a group to reach critical mass. So just enough stuff to account for the different kinds of activities a HUG may want to do (eg. Coding Dojos vs Talks vs Reading Group), but not so much that HUGs feel intimidated or stifled. Have you started a HUG recently? Or are you thinking of starting one? Maybe you could contribute just one idea to the kit? More welcome, of course :-) -- Eric Kow http://www.nltg.brighton.ac.uk/home/Eric.Kow For a faster response, try +44 (0)1273 64 2905 or xmpp:ko...@jabber.fr (Jabber or Google Talk only) pgpuG7vIxZHIv.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell User Group starter kit
Yes! This is a great idea. I'm a Haskell enthusiast in St. Louis, MO, USA and have given numerous talks on Haskell locally at Lambda Lounge[1], a catch-all groups for functional programmers, and the St.Louis Perl Mongers[2]. I would love to have a dedicated Haskell User Group, but unfortunately this town appears to run on the JVM and I haven't been able to drum up too much interest by myself. I've also never started or run a user group before and I am also not the greatest salesman so some pointers on how to create a buzz would be helpful. -deech [1] lambdalounge.org [2] http://stlouis.pm.org/ On Tue, Apr 26, 2011 at 12:47 PM, Eric Y. Kow eric@gmail.com wrote: Hi all, We may be coming to a time where we start to see Haskell User Groups or Functional Programming clubs popping up all the over the place. Maybe it's a good time to put our heads together and figure out what we can do to nurture these groups, to keep them going strong rather than fizzling out. One idea might be create some sort of Haskell User Group starter kit so that individual groups can hit the ground running with some concrete ideas. http://www.haskell.org/haskellwiki/Haskell_User_Group My hope is that it would provide just enough material for a group to reach critical mass. So just enough stuff to account for the different kinds of activities a HUG may want to do (eg. Coding Dojos vs Talks vs Reading Group), but not so much that HUGs feel intimidated or stifled. Have you started a HUG recently? Or are you thinking of starting one? Maybe you could contribute just one idea to the kit? More welcome, of course :-) -- Eric Kow http://www.nltg.brighton.ac.uk/home/Eric.Kow For a faster response, try +44 (0)1273 64 2905 or xmpp:ko...@jabber.fr (Jabber or Google Talk only) ___ 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] Question about the Monad instance for Iteratee (from the enumerator package)
On Tue, Apr 26, 2011 at 6:32 PM, John Millikin jmilli...@gmail.com wrote: On Tuesday, April 26, 2011 7:19:25 AM UTC-7, John Lato wrote: I'd be interested to see the results of a shootout between iteratee and enumerator. I would expect them to be basically equivalent most of the time, with maybe two or three operations with a small (but consistent) difference one way or the other. I did some basic benchmarks a few months ago; if I remember correctly, it depends almost entirely on how well GHC optimizes CPS on a particular platform. The relative performace was very similar to Lennart Kolmodin's benchmarks of binary at http://lennartkolmodin.blogspot.com/2011/02/binary-by-numbers.html . In particular, CPS/iteratee is faster on 32-bit, while state passing/enumerator is faster on 64-bit. This difference exists for almost all operations, and was on the order of 5-15% depending on the shape of the input. I couldn't figure out a good way to benchmark the libraries themselves when there's so much noise from the compiler. That figures. Thanks for sharing this. John L. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Inputs to classic FRP: unsafeInterleaveIO/unsafePerformIO
Apfelmus, I hope you don't abandon your efforts, at least for the selfish reason that I enjoy reading your blog entries about trying to implement it! I was looking at your last entry and trying to understand if/how you solve the order-dependency problem for events. In particular: source events e1, e2 e3 = e1 union e2 e4 = e2 union e1 e5 = e3 union e4 The graph from your description would look something like e1 e2 | \-A / \ A-\ e3e3 e4e4 | | || e5e5 e5e5 When I was looking at the FRP problem before, it felt a lot like the 'adaptive' problem, so I was looking at Umut Acar's papers and trying to build something along those lines. But perhaps your API is simple enough that you don't need that degree of complexity. -- ryan On Tue, Apr 26, 2011 at 12:29 AM, Heinrich Apfelmus apfel...@quantentunnel.de wrote: Edward Amsden wrote: As far as I can tell, with classic FRP implementations (those which use behaviors as a first-class abstraction), the only way to create a behavior or event based on some external input (for instance keypresses or microphone input) is to do something with unsafePerformIO or unsafeInterleaveIO. A behavior is a value, which when evaluated at a specific time would have to either block its evaluation until input could be read, or check the input at that particular time. Is there any other way of implementing external behaviors besides that? Yes, there are other ways, see for example the implementation here: http://tinyurl.com/frp-automaton . This is essentially a pure variant of Ryan's implementation. My implementation has a serious problem, namely that sharing is lost. I think this is the case for Ryan's implementation as well. The state of a behavior will be duplicated and updates multiple times. This can be fixed by observing sharing, of course. I'm currently working on a push-driven FRP implementation. (Though I'm getting second thoughts as to whether the small increase in efficiency is worth the implementation cost.) See also http://apfelmus.nfshost.com/blog/2011/04/24-frp-push-driven-sharing.html Best regards, Heinrich Apfelmus -- http://apfelmus.nfshost.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 small Darcs anomoly
2. I have no idea how to make Darcs do the thing with hard links (is that even supported under Windows?) I just copy the whole folder using the normal OS file tools. darcs get path/to/other/local/repo Either way, you lose the ability to see how branches are related to each other, which might be useful in some cases. How do you see how git branches are related to each other? git show-branch [branches] It was one of nicest things in git for me when I stared to use it. xmms2-devel $ git show-branch ! [error-on-implicit] OTHER: wscript: make implicit function declarations an error in C code * [master] FEATURE(2184): Update pre-generated cython files. ! [missing-protos] OTHER: one more me in AUTHORS --- + [error-on-implicit] OTHER: wscript: make implicit function declarations an error in C code + [missing-protos] OTHER: one more me in AUTHORS + [missing-protos^] OTHER: explicitely declare g_sprintf() + [missing-protos~2] OTHER: explicitely declare semtimedop() +*+ [master] FEATURE(2184): Update pre-generated cython files. The simpler things are: git [log|diff] from..to git [log|diff] from...to Set of [commits|changes] to be added to another branch. -- Sergei signature.asc Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANNOUNCE: iteratee-compress 0.2.0.0
On Mon, 2011-04-25 at 15:47 +0900, Conrad Parker wrote: On 23 April 2011 19:29, Maciej Piechotka uzytkown...@gmail.com wrote: Iteratee-compress provides compressing and decompressing enumerators including flushing (using John Lato's implementation). Currently only gzip and bzip is provided but LZMA is planned. Changes from previous version: - Add BZip support Cool :) I notice the haddocks on hackage have not been generated; would this be due to libbz2-dev missing on the hackage server? Conrad. No - you need to wait as it is a batch process. Currently it is up-to-date. Regards 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] HipmunkPlayground compile error
Thanks for the tip. GHC 7.0.3 does seem to fix a couple bugs, and maybe even run faster than GHC 7.0.2. But it doesn't solve the problem. $ ghc --version The Glorious Glasgow Haskell Compilation System, version 7.0.3 $ cabal --version cabal-install version 0.10.2 using version 1.10.1.0 of the Cabal library $ cabal install hipmunk (works) $ cabal install hipmunkplayground (dozens of GLFW warnings) ... Updating documentation index /Users/andrew/Library/Haskell/doc/index.html cabal: Error: some packages failed to install: GLFW-0.4.2 failed during the building phase. The exception was: ExitFailure 1 HipmunkPlayground-5.2.0.3 depends on GLFW-0.4.2 which failed to install. $ cabal install glfw (dozens of GLFW warnings) ... cabal: Error: some packages failed to install: GLFW-0.4.2 failed during the building phase. The exception was: ExitFailure 1 Cheers, Andrew Pennebaker www.yellosoft.us On Tue, Apr 26, 2011 at 4:49 AM, Jason Dagit dag...@gmail.com wrote: On Tue, Apr 26, 2011 at 1:38 AM, Andrew Pennebaker andrew.penneba...@gmail.com wrote: $ system_profiler SPSoftwareDataType | grep System Version System Version: Mac OS X 10.6.7 (10J869) $ ghc --version The Glorious Glasgow Haskell Compilation System, version 7.0.2 $ cabal --version cabal-install version 0.10.2 using version 1.10.1.0 of the Cabal library $ cabal install hipmunkplayground ... Updating documentation index /Users/andrew/Library/Haskell/doc/index.html cabal: Error: some packages failed to install: GLFW-0.4.2 failed during the building phase. The exception was: ExitFailure 1 HipmunkPlayground-5.2.0.3 depends on GLFW-0.4.2 which failed to install. GLFW is the package that failed to install. The reason for that should be in the scroll back somewhere but it can often be hard to find when it's buried in a huge list of compilation messages. If you try with just GLFW, eg., cabal install GLFW, then it should be easier to spot the error. Since you're on a mac, I would highly recommend getting the latest haskell platform. You're on 7.0.2 which has bug fixes that are relevant to build failures on OSX, as I understand it. Jason ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Can't install haskellnet with ghc7
Hi -cafe, Did anybody managed to install haskellnet from hackage with ghc7? I tried on windows and mac and I get the following type error: [ 4 of 11] Compiling Network.HaskellNet.SMTP ( Network/HaskellNet/SMTP.hs, dist/build/Network/HaskellNet/SMTP.o ) Network/HaskellNet/SMTP.hs:269:25: Couldn't match expected type `Data.Text.Internal.Text' with actual type `[Char]' Expected type: Data.Text.Internal.Text Actual type: String In the first argument of `simpleMail', namely `to' In a stmt of a 'do' expression: myMail - simpleMail to from subject plainBody htmlBody attachments Am I missing something? -- Cp ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Good reads?
[I originally posted this over in haskell-beginners. However, since this list has a lot more traffic, and I am not sure how many people read both lists, I thought I would post here as well. I apologize for the doublepost! Just want to make sure I can get some replies from the great people here who might not read the beginners list] Hey all, I have mostly been brought in imperative/OOP languages. In connection with my college studies, however, I have taken great interest in the functional paradigm, and would very much like to dig deeper into it. I am currently reading through Peyton-Jones Haskell: The Craft of Functional Programming (2nd ed.), as well as a great paper published by one of my professors (http://www.cse.chalmers.se/~rjmh/Papers/whyfp.html). However, what other works, in your opinions, should I look into to get a more complete understanding of functional programming? Thanks in advance! Chris ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Creating polygons in qtHaskell
Hi! I'm using qtHaskell and I'm trying to create a QGraphicsPolygonItem object. From what I see I need to create a QPolygonF item that I can supply to the constructor, but to populate the QPolygonF I need to use methods of the QVector class that QPolygonF inherits and I can't figure out how to do that. It seems that QVector is not part of the qtHaskell library. What I would like to do is something like this (where mypoints is a list of QPointF): makePolygon = do polygon - qPolygonF () mapM (pushBack polygon) mypoints qGraphicsPolygonItem_nf polygon However, pushBack doesn't seem to be available. Does anyone know a way to do this? -- Mvh Øystein Kolsrud ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Can't install haskellnet with ghc7
On 04/26/2011 10:17 PM, Charles-Pierre Astolfi wrote: Hi -cafe, Did anybody managed to install haskellnet from hackage with ghc7? I tried on windows and mac and I get the following type error: [ 4 of 11] Compiling Network.HaskellNet.SMTP ( Network/HaskellNet/SMTP.hs, dist/build/Network/HaskellNet/SMTP.o ) Network/HaskellNet/SMTP.hs:269:25: Couldn't match expected type `Data.Text.Internal.Text' with actual type `[Char]' Expected type: Data.Text.Internal.Text Actual type: String In the first argument of `simpleMail', namely `to' In a stmt of a 'do' expression: myMail- simpleMail to from subject plainBody htmlBody attachments Am I missing something? your mime-mail library is too recent. the upper version in the cabal file of haskellnet is not limited, so it's picking up the 0.3.0 version which is incompatible with the 0.2.x. Otherwise it was working for me with the previous version for both ghc6 and ghc7. -- Vincent ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Good reads?
On Tue, Apr 26, 2011 at 5:48 PM, Christopher Svanefalk christopher.svanef...@gmail.com wrote: I am currently reading through Peyton-Jones Haskell: The Craft of Functional Programming (2nd ed.), as well as a great paper published by one of my professors (http://www.cse.chalmers.se/~rjmh/Papers/whyfp.html). However, what other works, in your opinions, should I look into to get a more complete understanding of functional programming? You might consult the Typeclassopedia (Brent Yorgey). Understanding these typeclasses helped me start understand the power of abstraction that Haskell (and FP in general) gives a programmer. quoth the abstract: The standard Haskell libraries feature a number of type classes with algebraic or category-theoretic underpinnings. Becoming a fluent Haskell hacker requires intimate familiarity with them all, yet acquiring this familiarity often involves combing through a mountain of tutorials, blog posts, mailing list archives, and IRC logs. The goal of this article is to serve as a starting point for the student of Haskell wishing to gain a firm grasp of its standard type classes. The essentials of each type class are introduced, with examples, commentary, and extensive references for further reading. http://www.haskell.org/wikiupload/8/85/TMR-Issue13.pdf, page 13 And from a fellow student: have fun! -- Edward Amsden Student Computer Science Rochester Institute of Technology www.edwardamsden.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: Leksah 0.10.0
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 On 4/26/11 09:15 , Daniel Fischer wrote: On Tuesday 26 April 2011 02:00:32, jutaro wrote: Well, it is a bit more intricate to invert the sides. After * swapping LeftP and RightP in Edit Prefs - Initial Pane positions * Close all panes and pane groups. (You may leave an editor window open, so that you better see what happens in the next steps). * Collapse all (Hit Ctrl-1 - 2 times) * Split vertical (Hit Ctrl-2), put the focus to the left, split horizontal (Hit Ctrl-3) * Go to Panes Menu and reopen the Log and the Browser and an editor Window * Configure tabs as you like * Save the session or restart Leksah Intricate indeed. If some day you have too much time, consider adding configuration options for that. Until then, how about putting that in the docs? How about a layout editor mode where you can drag panes around, double-click somewhere to split at that point (hold shift for horizontal split, maybe?), and a window palette to drag windows into panes? - -- brandon s. allbery [linux,solaris,freebsd,perl]allber...@gmail.com system administrator [openafs,heimdal,too many hats]kf8nh -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.11 (Darwin) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAk23VXoACgkQIn7hlCsL25X/0gCgpKLaNqOeHbgO8D4ZQ38y1EQV ZisAnik6XZHVPGs3k50xGZ+MEJCaAfZC =P0vf -END PGP SIGNATURE- ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Good reads?
I'm currently reading Real World Haskell ( http://book.realworldhaskell.org/read/), and it's an excellent book. It goes into detail on quite a few interesting and practical uses of the language. Also, in the spirit of this discussion, is there a resource that attempts to compare libraries for common tasks so developers can make informed decisions without having to research each library or approach on their own? As an example, in other languages you might read about CSV parsing from a few different sources and see a general consensus on how to approach it. After hours of digging through code on Hackage and reading up on different approaches, I can't seem to find a consensus in Haskell. If anyone knows of a book/resource that breaks down different approaches to common problems and when/why you might choose one over the other, I'm very interested. -Eric Rasmussen On Tue, Apr 26, 2011 at 3:52 PM, Edward Amsden eca7...@cs.rit.edu wrote: On Tue, Apr 26, 2011 at 5:48 PM, Christopher Svanefalk christopher.svanef...@gmail.com wrote: I am currently reading through Peyton-Jones Haskell: The Craft of Functional Programming (2nd ed.), as well as a great paper published by one of my professors (http://www.cse.chalmers.se/~rjmh/Papers/whyfp.html). However, what other works, in your opinions, should I look into to get a more complete understanding of functional programming? You might consult the Typeclassopedia (Brent Yorgey). Understanding these typeclasses helped me start understand the power of abstraction that Haskell (and FP in general) gives a programmer. quoth the abstract: The standard Haskell libraries feature a number of type classes with algebraic or category-theoretic underpinnings. Becoming a fluent Haskell hacker requires intimate familiarity with them all, yet acquiring this familiarity often involves combing through a mountain of tutorials, blog posts, mailing list archives, and IRC logs. The goal of this article is to serve as a starting point for the student of Haskell wishing to gain a firm grasp of its standard type classes. The essentials of each type class are introduced, with examples, commentary, and extensive references for further reading. http://www.haskell.org/wikiupload/8/85/TMR-Issue13.pdf, page 13 And from a fellow student: have fun! -- Edward Amsden Student Computer Science Rochester Institute of Technology www.edwardamsden.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] How to keep cabal and ghci package versions in sync?
On 27/04/2011, at 3:04 AM, Rogan Creswick wrote: At the moment, cabal-dev ghci just uses the -package-conf and -no-user-package-conf flags to restrict ghci to the sandboxed and global package dbs. It's difficult to do more without parsing the content of the project's cabal file, and that parser isn't exposed through a library api (it's in cabal-install), which makes it a little difficult to use. Can't you use cabal as a library to do this? I had a crack at figuring out a ghci command line in TBC (testing by convention): https://github.com/peteg/TBC while waiting for this cabal feature to be implemented: http://hackage.haskell.org/trac/hackage/ticket/382 Apparently there's a GSoC project that will nail this. You can fire up TBC with the verbose flag and it will give you a very long ghc invocation line that is strongly similar to what cabal uses to compile your project. It doubtlessly is incomplete, and probably bit rotten. I will try to make it work with the latest Haskell Platform release in the coming weeks. I welcome patches, but you're better off fixing cabal itself. cheers peter -- http://peteg.org/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] plugins and cabal build
On Tue, Apr 26, 2011 at 4:56 PM, Andy Stewart lazycat.mana...@gmail.com wrote: Ivan Lazar Miljenovic ivan.miljeno...@gmail.com writes: On 26 April 2011 04:57, Michael Snoyman mich...@snoyman.com wrote: Hi all, I'm experimenting with using the plugins package for yesod devel server. The basic approach is to use cabal for building the object files, and then load them with plugins. I can get everything to work when I compile with ghc --make, but I believe name mangling is getting in the way with the cabal build route. Can someone give some guidance on how to properly mangle the function names so that plugins can load them? I'm not sure if he reads this list, but Andy Stewart might know (and I've CC'd him to this). Hi Ivan, sorry for late, too busy on Linux job. Yes, i have got hot-swap code work for Manatee (http://hackage.haskell.org/package/manatee) I used to use plugins, but i found it's buggy. So i use GHC-API wrote my own code at: https://patch-tag.com/r/AndyStewart/manatee-core/snapshot/current/content/pretty/Manatee/Core/Dynload.hs Michael, from your need, you just need read function `dynload`, other functions is write for Manatee framework. Let me explain function `dynload`: dynload :: (String, String, [(String, HValue - IO ())]) - IO () dynload (filepath, moduleName, loadList) = ... First argument is FilePath that contain module. Second argument is moduleName you need scan. Third argument is tuple list that contain symbol you need load and callback function for symbol's HValue. Once function `dynload` find symbol in target module, it will use below code dynamic load new value: (do hValue - compileExpr (moduleName ++ . ++ symbolName) liftIO $ loadFun hValue) function `compileExpr` will get the HValue of symbol, then use loadFun update HVaule in running program. The key is `HValue - IO ()`, you need build TVar/IORef in your running program, once you got new HValue, you should write writeTVar/writeIORef in function `HValue - IO ()` to update the value of TVar/IORef, then you can dynamic loading new value and don't need reboot. I have draw some picture to explain above framework: http://www.flickr.com/photos/48809572@N02/5304662424/in/photostream/lightbox/ Michael, hope above will help you, good luck! :) -- Andy Hi Andy, Thanks you for your very helpful reply. I still have your previous advice on this subject in my things to study list. Looks like taking the easy way out didn't work after all. Thanks for the great example to work from, hopefully it will work out properly. Michael ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
