RE: [Haskell-cafe] global variables
| I see no need two answer this again I believe I have already made my | views perfectly clear already and provided ample evidence to justify | them. Surely I don't need to do it again? Is there a Wiki page about this somewhere? Often email gets into a loop because not everyone reads everything on Haskell Cafe. (There's just too much of it.) When that happens, a good thing do to is to summarise the various positions on a Wiki page, so the debate can progress by refining text rather than by repeating it. There is the additional advantage that someone coming along later can still make sense of the debate. Simon ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Profiling, GUIs and libraries
On 20-mei-2007, at 17:39, Anthony Chaumas-Pellet wrote: Hello, I'm currently hacking away a wxhaskell program that uses up 100% CPU even when it should be idle. So, rather than doing blind guesswork, I've thought about using profiling to spot the zealous function. I do not need a very accurate result, though. ghc with -prof -auto(-all) produces the following error message, however: Could not find module `Graphics.UI.WX': Perhaps you haven't installed the profiling libraries for package wx-0.10.1? Use -v to see a list of the files searched for. So, I guess I need to rebuild wx with profiling, but I'm not sure how to do that exactly; search engine and the Wiki did not turn up any pointers, and there are no ready-made options to build wx with profiling. It seems Cabal can build a library with profiling automatically, but I don't think there exists a Cabalized version of wx yet. That, and I'm not sure if recompiling libraries to add profiling is a great idea, as wx itself may depend on other external libraries. So, is there a better way than profiling in my case, or am I missing something obvious here? You are not missing anything obvious. The process is in fact somewhat tricky. What you have to do is the following: - compile wxHaskell with profiling (by editing the makefiles to include the -prof -auto-all argument to GHC) - *install* the profiled wxHaskell - manually move the profiled object libraries to ones including the _p string before the .a, e.g. move /usr/local/wxhaskell/lib/libwx.a to /usr/local/wxhaskell/lib/libwx_p.a - manually move the profiled .hi files to .p_hi files, e.g. move /usr/local/wxhaskell/lib/imports/Graphics/UI/WX.hi to /usr/local/wxhaskell/lib/imports/Graphics/UI/WX.p_hi - compile wxHaskell without profiling - install the non-profiled wxHaskell - enjoy the ability to use wxHaskell in both profiled and unprofiled versions Note: this assumes you are on a Unix-like system. I have no clue how to do this on Windows, but I'm told it is similar. Oh, and this is tested and works. The external libraries that wx relies on are either truly external, as in called through the FFI, or GHC standard libs that normally already have a profiling version available. With regards, Arthur van Leeuwen. -- /\/ | [EMAIL PROTECTED] | Work like you don't need the money /__\ / | A friend is someone with whom | Love like you have never been hurt /\/__ | you can dare to be yourself | Dance like there's nobody watching ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] global variables
On 21-mei-2007, at 9:31, Simon Peyton-Jones wrote: | I see no need two answer this again I believe I have already made my | views perfectly clear already and provided ample evidence to justify | them. Surely I don't need to do it again? Is there a Wiki page about this somewhere? Often email gets into a loop because not everyone reads everything on Haskell Cafe. (There's just too much of it.) When that happens, a good thing do to is to summarise the various positions on a Wiki page, so the debate can progress by refining text rather than by repeating it. There is the additional advantage that someone coming along later can still make sense of the debate. As I am sure Adrian would tell you were he awake: http://www.haskell.org/haskellwiki/Top_level_mutable_state With regards, Arthur van Leeuwen -- /\/ | [EMAIL PROTECTED] | Work like you don't need the money /__\ / | A friend is someone with whom | Love like you have never been hurt /\/__ | you can dare to be yourself | Dance like there's nobody watching ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] SWIG with Haskell ?
Hello, Has anyone got any pointers on using SWIG with Haskell to integrate a C++ library? For the library there other language bindings, so I am in a position to leverage off these. In general what are the particular issues with C++ and Haskell. One obvious one is management of object lifecycle - making sure the object stays around long enough but doesn't out stay its welcome. Is using ForeignPtr sufficient? Cheers Mark ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] Scope of type variables in associated types
| The following doesn't seem to work. Is this a limitation of the current | implementation or will it never work? Are there any work arounds without | introducing extra type params into the data type E? | | class G a b | a - b where | data E a :: * | wrap :: b - E a | unwrap :: E a - b | | instance G a b where | data E a = EC b -- this line - the b is not in scope. | wrap = EC | unwrap (EC b) = b | | I get Not in scope: type variable `b'. That's a bug. b should be in scope However, your program is very suspicious! Associated data types *replace* functional dependencies, so you should not use both. Your probably want something like class G a where data E a :: * wrap :: a - E a unwrap :: E a - a Simon ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How Albus Dumbledore would sell Haskell
On Wed, 18 Apr 2007, Dan Weston wrote: You have already won over the scientists. I only know few mathematicians using Haskell, most of the (applied) mathematician colleagues I know prefer MatLab. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A wish for relaxed layout syntax
On Wed, 28 Mar 2007, Benjamin Franksen wrote: Hi, I often run into the following issue: I want to write a list of lengthy items like this mylist = [ quite_lengthy_list_item_number_one, quite_lengthy_list_item_number_two, quite_lengthy_list_item_number_three ] http://haskell.org/haskellwiki/List_notation ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Follow up on 'GroupBy behavior'
On Sat, 28 Apr 2007, Hans van Thiel wrote: Thanks again for the help, and, to follow up, this now does what I need.. -- partitions a list according to an equivalence relation partition1 :: (a - a - Bool) - [a] - ([a],[a]) partition1 eq ls = partition ((head ls) `eq`) ls -- partitionBy :: (a - a - Bool) - [a] - [[a]] partitionBy eq [] = [] partitionBy eq ls = (fst x):(partitionBy eq (snd x)) where x = partition1 eq ls partitionBy is essentially a List.unfoldr ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Behavior of groupBy
On Sat, 28 Apr 2007, Hans van Thiel wrote: Hello All, The standard function groupBy of List.hs doesn't work as I expect in this case: groupBy (\x y - (last x) == (last y)) [abc, bd,cac] results in: [[abc],[bd],[cac]] where I want: [[abc,cac], [bd]] I think you must roll your own one. How about repeated 'partition' to extract all elements that have the same trailing character like the head word of the list? I have done this in a more complex setting and called it 'slice': http://darcs.haskell.org/haskore/src/Haskore/Basic/TimeOrderedList.lhs slice :: (Eq a, Num time) = (body - a) - T time body - [(a, T time body)] slice f perf = let splitByHeadKey pf = fmap (\ev - let i = f (eventBody ev) (pf0, pf1) = partition ((i==) . f) 0 0 pf in ((i,pf0), pf1)) (listToMaybe pf) in List.unfoldr splitByHeadKey perf ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Unresolved overloading error
On Sat, 31 Mar 2007, Jacques Carette wrote: Bryan Burgers wrote: On 3/31/07, Scott Brown [EMAIL PROTECTED] wrote: It's working now, thank you. I changed the definition to binom n j = div (fac n) ((fac j)*(fac (n - j))) bernoulli n p j = fromIntegral(binom n j)*(p ^ j) * ((1 - p)^(n - j)) As a matter of style suggestion, it might make 'binom' more clear if you use 'div' as an infix operator: binom n j = (fac n) `div` ( fac j * fac (n - j) ) And as a matter of efficiency, no one would write binom using factorial, but would rather write at least binom u k = (product [(u-i+1) | i - [1..k]]) `div` (product [1..k]) and even better would be to do it this way -- bb u k = toInteger $ product [ (u-i+1) / i | i - [1..k]] but that does not type (for a good reason). How about binomialSeq :: Integral a = a - [a] binomialSeq n = scanl (\acc (num,den) - div (acc*num) den) 1 (zip [n, pred n ..] [1..n]) and the use of (!!) ? http://darcs.haskell.org/htam/src/Combinatorics.hs ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Scope of type variables in associated types
On Mon, May 21, 2007 at 10:36:00AM +0100, Simon Peyton-Jones wrote: | The following doesn't seem to work. Is this a limitation of the current | implementation or will it never work? Are there any work arounds without | introducing extra type params into the data type E? | | class G a b | a - b where | data E a :: * | wrap :: b - E a | unwrap :: E a - b | | instance G a b where | data E a = EC b -- this line - the b is not in scope. | wrap = EC | unwrap (EC b) = b | | I get Not in scope: type variable `b'. That's a bug. b should be in scope Ahh, cool. I which case I wonder if this too is a bug? : data Nil = Nil data Cons :: * - * - * where Cons :: val - tail - Cons val tail class F c v t | c - v t where data FD c t :: * instance F (Cons v t) v t where -- this blows up with conflicting definitions for `t' data FD (Cons v t) t = FDC v However, your program is very suspicious! Associated data types *replace* functional dependencies, so you should not use both. Your probably want something like class G a where data E a :: * wrap :: a - E a unwrap :: E a - a I'm afraid not. I really need wrap to take a 'b' and unwrap to return a 'b'. Talking on #haskell to sjanssen last night, he came up with: class F a b where data F a :: * instance F a b where data F a = F b cast :: (F a b, F a c) = b - c cast x = case F x of (F y) - y as evidence as to why it's unsafe. But with the fundep, I would have thought it would have been safe. The associated type way would be to drop the b and then have data F a :: * - * - just like in the papers. But I really need the b to be part of the class in order to match the b against other class constraints in other functions. In particular I need to be able to write something like: instance (G a b) = F a b where ... Somehow I doubt it, but is the following any less suspicious? class F a b where type BThing a :: * data FD a :: * wrap :: b - FD a unwrap :: FD a - b instance F a b where type BThing a = b data FD a = FDC (BThing a) wrap b = FDC b unwrap (FDC b) = b Incidentally, that type BThing a = b line also blows up with Not in scope: type variable `b'. Thanks, Matthew -- Matthew Sackman http://www.wellquite.org/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Editor
I have a dream. It's not a little dream. It's a big dream. I have a dream that someday I can find a UNIX/Linux text editor for Haskell hacking (and possibly two or three hundred other programming languages, although that's optional) that can give me all of the following: 1. A real GUI environment that takes into account some of the HID advances made in the past 30 years. (Emacs and Vim don't count, in other words.) 2. Good quality syntax highlighting for Haskell that includes all of the usual syntax highlighting goodies, plus: * the ability to seamlessly handle raw Haskell and both common forms of Literate Haskell; * the ability to properly highlight Haddock comments; * the ability to highlight functions and types from libraries (user-expandable) differently from local functions and types. 3. Line folding to hide and show blocks of code. 4. Code completion (user-expandable, ideally) for common library functions, type declarations, etc. 5. Easy, quick access to online documentation for said functions and declarations. 6. Good (ideally scriptable) access to external utilities for compilation, debugging, profiling, type inference, project management, etc. 7. A good plug-in system (ideally written in Haskell?) for expansion. Is there such a beast available out there somewhere? If not, is such a beast lurking in the background ready to pounce in the near future? -- Michael T. Richter [EMAIL PROTECTED] (GoogleTalk: [EMAIL PROTECTED]) I have to wonder why people think that when they can't manage local personnel within easy strangling and shooting distance, then they can manage personnel thousands of miles away that have different languages, cultures, and business rules. (Joe Celko) 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 can I select all the 3-element-combination out of a list efficiently
What I meant is this: http://en.wikipedia.org/wiki/Combinatorics#Combination_without_repetition the order does not matter and each object can be chosen only once. But thank all those who have offered help, it helps a lot ;) -- View this message in context: http://www.nabble.com/how-can-I-select-all-the-3-element-combination-out-of-a-list-efficiently-tf3776055.html#a10716285 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] Editor
Michael T. Richter wrote: I have a dream. It's not a little dream. It's a big dream. I have a dream that someday I can find a UNIX/Linux text editor for Haskell hacking (and possibly two or three hundred other programming languages, although that's optional) that can give me all of the following: 1. A real GUI environment that takes into account some of the HID advances made in the past 30 years. (Emacs and Vim don't count, in other words.) That particular part is trolling. Both emacs and vim take into account many of the HID advances made in the past 30 years. You're going to have to be more explicit about what you find unacceptable about them to get useful answers, in my opinion. I can't speak for vim, but emacs certainly satisfies 2.3, 2.4, 3, 4, 5, 6, and 7. (I'm not sure if 5 is 100% out-of-the-box but it would be very easy to sort it out if not). 2.5 I'd not really thought about before as an interesting requirement. Could be useful. 2. Good quality syntax highlighting for Haskell that includes all of the usual syntax highlighting goodies, plus: 3. the ability to seamlessly handle raw Haskell and both common forms of Literate Haskell; 4. the ability to properly highlight Haddock comments; 5. the ability to highlight functions and types from libraries (user-expandable) differently from local functions and types. 3. Line folding to hide and show blocks of code. 4. Code completion (user-expandable, ideally) for common library functions, type declarations, etc. 5. Easy, quick access to online documentation for said functions and declarations. 6. Good (ideally scriptable) access to external utilities for compilation, debugging, profiling, type inference, project management, etc. 7. A good plug-in system (ideally written in Haskell?) for expansion. Is there such a beast available out there somewhere? If not, is such a beast lurking in the background ready to pounce in the near future? -- *Michael T. Richter* [EMAIL PROTECTED] mailto:[EMAIL PROTECTED] (*GoogleTalk:* [EMAIL PROTECTED]) /I have to wonder why people think that when they can't manage local personnel within easy strangling and shooting distance, then they can manage personnel thousands of miles away that have different languages, cultures, and business rules. (Joe Celko)/ ___ 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] Profiling, GUIs and libraries
You are not missing anything obvious. The process is in fact somewhat tricky. What you have to do is the following snip Thanks! I've followed your instructions and got a profiler-enabled binary up and running. I'd figured out how to modify the Makefile (silly me searching for *G*HC), but I had no idea about the manual renaming of files. Anthony ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] Scope of type variables in associated types
| | instance G a b where | | data E a = EC b -- this line - the b is not in scope. | | wrap = EC | | unwrap (EC b) = b | | | | I get Not in scope: type variable `b'. | | That's a bug. b should be in scope I was wrong. It's not a bug. E is supposed to be a type *function*, so it can't mention anything on the RHS that is not bound on the LHS. We'll improve the documentation. | Ahh, cool. I which case I wonder if this too is a bug? : | | data Nil = Nil | data Cons :: * - * - * where | Cons :: val - tail - Cons val tail | | class F c v t | c - v t where | data FD c t :: * | | instance F (Cons v t) v t where | -- this blows up with conflicting definitions for `t' | data FD (Cons v t) t = FDC v As I said, associated types are an *alternative* to fundeps. We have not even begun to think about what happens if you use both of them together. You should not need to do so. | Somehow I doubt it, but is the following any less suspicious? | | class F a b where | type BThing a :: * | data FD a :: * | wrap :: b - FD a | unwrap :: FD a - b | | instance F a b where | type BThing a = b | data FD a = FDC (BThing a) | wrap b = FDC b | unwrap (FDC b) = b | | Incidentally, that type BThing a = b line also blows up with | Not in scope: type variable `b'. No, that is wrong in the same way as before. BThing is a *function* so its results must depend only on its arguments. S ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] how can I select all the 3-element-combination out of a list efficiently
geniusfat wrote: What I meant is this: http://en.wikipedia.org/wiki/Combinatorics#Combination_without_repetition the order does not matter and each object can be chosen only once. But thank all those who have offered help, it helps a lot ;) Then you want triples1 from the code below. The idea for triples1, triples2, and triples3 is that each pickOne returns a list of pairs. The first element of each pair is the chosen element and the second element of each pair is the list of choices for the next element (given the current choice). import Data.List -- Order does not matter, no repetition -- preserves sorting triples1 xs = do (x,ys) - pickOne xs (y,zs) - pickOne ys z - zs return (x,y,z) where pickOne [] = [] pickOne (x:xs) = (x,xs) : pickOne xs -- Alternative -- pickOne xs = map helper . init . tails $ xs -- helper (x:xs) = (x,xs) -- Order does matter, no repetition -- does not preserve sorting triples2 xs = do (x,ys) - pickOne xs (y,zs) - pickOne ys z - zs return (x,y,z) where pickOne xs = helper [] xs helper bs [] = [] helper bs (x:xs) = (x,bs++xs) : helper (x:bs) xs -- Alternative (produces results in different order -- and preserves sorting) -- pickOne xs = zipWith helper (inits xs) (init (tails xs)) -- helper pre (x:post) = (x,pre++post) -- Order does not matter, repetition allowed -- preserves sorting triples3 xs = do (x,ys) - pickOne xs (y,zs) - pickOne ys z - zs return (x,y,z) where pickOne [] = [] pickOne a@(x:xs) = (x,a) : pickOne xs -- Alternative -- pickOne xs = map helper . init . tails $ xs -- helper xs@(x:_) = (x,xs) -- Order does matter, repetition allowed -- preserves sorting triples4 xs = do x - xs y - xs z - xs return (x,y,z) temp = map ($ [1..4]) $ [triples1,triples2,triples3,triples4] preservesSorting = map (\xs - xs == sort xs) temp test1 = putStr . unlines . map show $ temp test2 = putStr . unlines . map show . map length $ temp ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] how can I select all the 3-element-combination out of a list efficiently
[EMAIL PROTECTED] wrote: Then you want triples1 from the code below. The idea for triples1, triples2, and triples3 is that each pickOne returns a list of pairs. The first element of each pair is the chosen element and the second element of each pair is the list of choices for the next element (given the current choice). In the spirit of multiple implementations; another approach is to note that you're really asking for all 3-element sublists: power [] = [[]] power (x:xs) = power xs ++ map (x:) (power xs) triples1' l = [ t | t - power l, length t == 3] (this implementation also preserves sorting) Jules ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Editor
On Mon, 2007-21-05 at 11:47 +0100, Jules Bean wrote: Michael T. Richter wrote: 1. A real GUI environment that takes into account some of the HID advances made in the past 30 years. (Emacs and Vim don't count, in other words.) That particular part is trolling. Both emacs and vim take into account many of the HID advances made in the past 30 years. You're going to have to be more explicit about what you find unacceptable about them to get useful answers, in my opinion. Vim is eliminated before it reaches the gate because it's a modal editor. Even with GVim in place, it still has that modal stench to it that leaps up and bites at awkward moments. And HID advances (the modal issue aside)? Go to an underpowered little editor like Gedit (what I use currently for raw Haskell, but which sadly isn't applicable to .lhs files of either stripe) and adjust your editing preferences. It's not a particularly good programmer's editor, but look at the lovely tabbed dialog box with all those lovely HID bits like checkboxes, radio buttons, spin buttons, dropdown lists, lists, etc. Now do the same in GVim and get ... a text file with some editing tricks to make things slightly easier. (It's not immediately obvious how to get rid of it either.) Where is the accounting for HID advances there? (Raw Vim is even worse.) Hell, even comparing the out-of-the-box syntax highlighting support in Gedit vs. (G)Vim is instructive. Code like makeRandomValueST :: StdGen - (MyType, StdGen) (which, incidentally, was far easier to copy from in Gedit than GVim to paste into this message) only differentiates :: and - from the text and delimiters in GVim while in Gedit (keeping in mind that Gedit isn't a very good editor!) differentiates those plus makeRandomValueST vs. StdGen and MyType. And the parentheses. (G)Vim is losing to freakin' GEDIT here! The Notepad of the GNOME world. Emacs is its own set of nightmares. I'm not even going to start going down the path of that particular holy war (and bucky-bit Hell). I'll acknowledge freely that it's an incredibly powerful programming environment. It just really doesn't play well with others at almost any level and quite definitely doesn't have anything resembling modern HID thought behind it. (To be fair to it, it does predate most modern HID work by a couple of decades.) -- Michael T. Richter [EMAIL PROTECTED] (GoogleTalk: [EMAIL PROTECTED]) All really first class designers are both artists, engineers, and men of a powerful and intolerant temper, quick to resist the least modification of the plans, energetic in fighting the least infringement upon what they regard as their own sphere of action. (Nevil Shute) 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] Scope of type variables in associated types
On Mon, May 21, 2007 at 12:39:20PM +0100, Simon Peyton-Jones wrote: | | instance G a b where | | data E a = EC b -- this line - the b is not in scope. | | wrap = EC | | unwrap (EC b) = b | | | | I get Not in scope: type variable `b'. | | That's a bug. b should be in scope I was wrong. It's not a bug. E is supposed to be a type *function*, so it can't mention anything on the RHS that is not bound on the LHS. We'll improve the documentation. Ok, thanks for the clarification. One final question then, how could I rewrite the following in associated types: class OneStep a b | a - b instance OneStep (Cons v t) t class TwoStep a b | a - b instance (OneStep a b, OneStep b c) = TwoStep a c If the fundep and b is dropped then I get: class OneStep a data OS a :: * instance OneStep (Cons v t) data OS (Cons v t) = t class TwoStep a data TS a :: * instance (OneStep a, OneStep b) = TwoStep a This last one can't be right, as I can't express the fact that the OS in OneStep a provides the link with OneStep b. So is there a way to achieve this sort of chaining with associated types? Sure, the fundep version requires undecidable instances, but I've been writing quite a lot of code lately that requires that! Many thanks, Matthew -- Matthew Sackman http://www.wellquite.org/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Editor
My friend read your email and remarked: How is this guy not embarrassed posting on the internet about not liking vim because he doesn't like editing config files? On 21/05/07, Michael T. Richter [EMAIL PROTECTED] wrote: On Mon, 2007-21-05 at 11:47 +0100, Jules Bean wrote: Michael T. Richter wrote:1. A real GUI environment that takes into account some of the HID advances made in the past 30 years. (Emacs and Vim don't count, in other words.) That particular part is trolling. Both emacs and vim take into account many of the HID advances made in the past 30 years. You're going to have to be more explicit about what you find unacceptable about them to get useful answers, in my opinion. Vim is eliminated before it reaches the gate because it's a modal editor. Even with GVim in place, it still has that modal stench to it that leaps up and bites at awkward moments. And HID advances (the modal issue aside)? Go to an underpowered little editor like Gedit (what I use currently for raw Haskell, but which sadly isn't applicable to .lhs files of either stripe) and adjust your editing preferences. It's not a particularly good programmer's editor, but look at the lovely tabbed dialog box with all those lovely HID bits like checkboxes, radio buttons, spin buttons, dropdown lists, lists, etc. Now do the same in GVim and get ... a text file with some editing tricks to make things slightly easier. (It's not immediately obvious how to get rid of it either.) Where is the accounting for HID advances there? (Raw Vim is even worse.) Hell, even comparing the out-of-the-box syntax highlighting support in Gedit vs. (G)Vim is instructive. Code like makeRandomValueST :: StdGen - (MyType, StdGen) (which, incidentally, was far easier to copy from in Gedit than GVim to paste into this message) only differentiates :: and - from the text and delimiters in GVim while in Gedit (keeping in mind that Gedit isn't a very good editor!) differentiates those *plus* makeRandomValueST vs. StdGen and MyType. And the parentheses. (G)Vim is losing to freakin' GEDIT here! The Notepad of the GNOME world. Emacs is its own set of nightmares. I'm not even going to start going down the path of that particular holy war (and bucky-bit Hell). I'll acknowledge freely that it's an incredibly powerful programming environment. It just really doesn't play well with others at almost any level and quite definitely doesn't have anything resembling modern HID thought behind it. (To be fair to it, it does predate most modern HID work by a couple of decades.) -- *Michael T. Richter* [EMAIL PROTECTED] (*GoogleTalk:* [EMAIL PROTECTED]) *All really first class designers are both artists, engineers, and men of a powerful and intolerant temper, quick to resist the least modification of the plans, energetic in fighting the least infringement upon what they regard as their own sphere of action. (Nevil Shute)* ___ 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] Editor
On 21 May 2007, at 13:04, Rodrigo Queiro wrote: My friend read your email and remarked: How is this guy not embarrassed posting on the internet about not liking vim because he doesn't like editing config files? Two points 1) This guy doesn't like editing config files -- that's his preference. He's stated he doesn't like either of vim or emacs, and whether you agree or not, you maybe should respect that and try to be useful and answer his question. 2) Believe it or not, a computer is a tool, it's there to get things done in the fastest and easiest way possible -- I should be able to edit my preferences in three clicks of a mouse button, rather than opening the preferences, finding the right place to edit (possibly looking up the manual to find the relevant things to insert in the config), typing a load in, and then having my preferences edited! Yes, I really do think that's an advantage, and no, I don't think snarky comments about not liking editing config files are either relevant or useful. Bob ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] how can I select all the 3-element-combination out of a list efficiently
Jules Bean wrote: In the spirit of multiple implementations; another approach is to note that you're really asking for all 3-element sublists: power [] = [[]] power (x:xs) = power xs ++ map (x:) (power xs) triples1' l = [ t | t - power l, length t == 3] (this implementation also preserves sorting) ...but is exponentially slower than necessary, and fails on infinite lists. Try this one: sublistsN 0 _ = [[]] sublistsN n (x:xs) = map (x:) (sublistsN (n-1) xs) ++ sublistsN n xs sublistsN _ _ = [] triples = sublistsN 3 BR, -- -- Mirko Rahn -- Tel +49-721 608 7504 -- --- http://liinwww.ira.uka.de/~rahn/ --- ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Editor
On Mon, 2007-21-05 at 13:04 +0100, Rodrigo Queiro wrote: My friend read your email and remarked: How is this guy not embarrassed posting on the internet about not liking vim because he doesn't like editing config files? Because, unlike your friend, I actually have seen the advances in HID over the past 30 years. Editing text files is not the be-all/end-all of user interfaces. Indeed there is astonishingly high volumes of evidence showing that it's a pretty miserable user interface -- a misery amplified by the fact that every two-bit program has its own entirely unique syntax (usually broken in many exciting ways!) full of cryptic commands and settings. Don't believe it? Go to your home directory and compare all the .files you find. You really think it's a good thing to maintain each of those manually? Oh, and of course it wasn't just the config files I showed problems with, now, was it? I seem to remember something about modality and bad syntax highlighting. Maybe I was tripping. It happens. For your friend's reference, here's a good outline of what principles underlie HID: http://www.asktog.com/basics/firstPrinciples.html. For even more modern outlooks, I'm sure a quick search at Amazon.com (or his bookseller of choice) can give him other ideas. So am I embarrassed for asking for something resembling a 21st-century user interface instead of a 1970s vintage one? Not in the slightest. -- Michael T. Richter [EMAIL PROTECTED] (GoogleTalk: [EMAIL PROTECTED]) It's OK to figure out murder mysteries, but you shouldn't need to figure out code. You should be able to read it. (Steve McConnell) 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 can I select all the 3-element-combination out of a list efficiently
geniusfat [EMAIL PROTECTED] writes: (snip) the order does not matter and each object can be chosen only once. (snip) In that case, with the help of Data.List.tails, one can do: threeOf :: [a] - [(a,a,a)] threeOf xs = [ (p,q,r) | (p:ps) - tails xs, (q:qs) - tails ps, r - qs ] (the r - qs is a simpler version of (r:rs) - tails qs) or maybe, nOf :: Int - [a] - [[a]] nOf _[] = [] nOf 1xs = map return xs nOf n (x:xs) = map (x:) (nOf (n-1) xs) ++ nOf n xs (These are fairly naive versions that just took me a few minutes, but perhaps they'll do.) -- Mark ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Editor
Hallo, On 5/21/07, Michael T. Richter [EMAIL PROTECTED] wrote: Oh, and of course it wasn't just the config files I showed problems with, now, was it? I seem to remember something about modality and bad syntax highlighting. Maybe I was tripping. It happens. You may not like modality, it's entirely within your rights, but it is *not* a problem. Fortunately it's still there for the millions of us who like it. -- -alex http://www.ventonegro.org/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Ann: Emping 0.2
Hello All, Version 0.2 of Emping, a utility to derive heuristic rules from a table of nominal data, is available. In addition to a reduced normal form in .csv format, which can be read by Open Office Calc, it now also displays observed implications and equivalences in the reduced rules (if present) and ambiguities in original rules (if present). A bug in the response to a user typing error has been fixed and some code has been simplified, compared to 0.1. An online user guide is at: http://j-van-thiel.speedlinq.nl/emp/empug.html and the Cabal package can be downloaded from there, or from the HackageDB. Thanks, Hans van Thiel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Editor
Your rant accomplishes nothing. Just note that programmers can generally be considered more open towards harder-to-learn but eventually more efficient to use interfaces. Yes, to a large part they lack visibility, consistency, integration, or other such properties; then again, once you learn to use them you're so much more efficient than before. And you loose the incentive to improve things. So instead of insulting people and complaining that nothing fits your needs you have at least two options: 1. Implement it. Of course, this is a _major_ effort and many many things are completely unsolved research issues. 2. Take what's there, learn to use it. Yes, it will lack so many things but one way or another you'll eventually get things done. On 5/21/07, Michael T. Richter [EMAIL PROTECTED] wrote: On Mon, 2007-21-05 at 13:04 +0100, Rodrigo Queiro wrote: My friend read your email and remarked: How is this guy not embarrassed posting on the internet about not liking vim because he doesn't like editing config files? Because, unlike your friend, I actually have seen the advances in HID over the past 30 years. Editing text files is not the be-all/end-all of user interfaces. Indeed there is astonishingly high volumes of evidence showing that it's a pretty miserable user interface -- a misery amplified by the fact that every two-bit program has its own entirely unique syntax (usually broken in many exciting ways!) full of cryptic commands and settings. Don't believe it? Go to your home directory and compare all the .files you find. You really think it's a good thing to maintain each of those manually? Oh, and of course it wasn't just the config files I showed problems with, now, was it? I seem to remember something about modality and bad syntax highlighting. Maybe I was tripping. It happens. For your friend's reference, here's a good outline of what principles underlie HID: http://www.asktog.com/basics/firstPrinciples.html. For even more modern outlooks, I'm sure a quick search at Amazon.com (or his bookseller of choice) can give him other ideas. So am I embarrassed for asking for something resembling a 21st-century user interface instead of a 1970s vintage one? Not in the slightest. -- Michael T. Richter [EMAIL PROTECTED] (GoogleTalk: [EMAIL PROTECTED]) It's OK to figure out murder mysteries, but you shouldn't need to figure out code. You should be able to read it. (Steve McConnell) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Remember! Everytime you say 'Web 2.0' God kills a startup! - userfriendly.org, Jul 31, 2006 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Scope of type variables in associated types
Ok, thanks for the clarification. One final question then, how could I rewrite the following in associated types: class OneStep a b | a - b instance OneStep (Cons v t) t class TwoStep a b | a - b instance (OneStep a b, OneStep b c) = TwoStep a c If the fundep and b is dropped then I get: class OneStep a data OS a :: * instance OneStep (Cons v t) data OS (Cons v t) = t data constructor missing !!! class TwoStep a data TS a :: * instance (OneStep a, OneStep b) = TwoStep a This last one can't be right, as I can't express the fact that the OS in OneStep a provides the link with OneStep b. So is there a way to achieve this sort of chaining with associated types? You'd have to write class OneStep a data OS a :: * instance OneStep (Cons v t) data OS (Cons v t) = OSC t class TwoStep a data TS a :: * instance (OneStep a, OneStep (OS a)) = TwoStep a where type TS a = TSC (OS (OS a)) which seems rather awkward with all these additional data type constructors. You'd be better off with associated type synonyms: class OneStep a type OS a :: * instance OneStep (Cons v t) type OS (Cons v t) = t class TwoStep a type TS a :: * instance (OneStep a, OneStep (OS a)) = TwoStep a type TS a = OS (OS a) which are currently under development. -- Tom Schrijvers Department of Computer Science K.U. Leuven Celestijnenlaan 200A B-3001 Heverlee Belgium tel: +32 16 327544 e-mail: [EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] how can I select all the 3-element-combination out of a list efficiently
Mark T.B. Carroll wrote: nOf _[] = [] nOf 1xs = map return xs nOf n (x:xs) = map (x:) (nOf (n-1) xs) ++ nOf n xs No! With this implementation we have nOf 0 _ == [] but it should be nOf 0 _ == [[]]: The list of all sublists of length 0 is not empty, it contains the empty list! Correct (and more natural): nOf 0 _ = [[]] nOf n (x:xs) = map (x:) (nOf (n-1) xs) ++ nOf n xs nOf _ [] = [] BR, -- -- Mirko Rahn -- Tel +49-721 608 7504 -- --- http://liinwww.ira.uka.de/~rahn/ --- ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Scope of type variables in associated types
Andres Loeh [EMAIL PROTECTED] wrote:
class OneStep a
data OS a :: *
instance OneStep (Cons v t)
data OS (Cons v t) = t
class TwoStep a
data TS a :: *
instance (OneStep a, OneStep b) = TwoStep a
instance (OneStep a, OneStep (OS a)) = TwoStep a
?
Doesn't seem to work. Ok, my original was wrong as I had no constructor
on the associated type. So below are 2 versions, one with fundeps, which
works, one with associated type synonynms which doesn't work, which
made me remember the warnings about how type synonynms aren't fully
implemented yet, and so I wrote a third version with indexed types, but
whilst I can make it work, wrapping up values in indexed types gets
really really messy.
{-# OPTIONS_GHC -fglasgow-exts -fallow-undecidable-instances #-}
module TestProb where
data Nil = Nil
data Cons v t = Cons v t
class OneStep a b | a - b
instance OneStep (Cons v t) t
class TwoStep a b | a - b
instance (OneStep a b, OneStep b c) = TwoStep a c
class OneStep' a where
type OS' a :: *
instance OneStep' (Cons v t) where
type OS' (Cons v t) = t
class TwoStep' a where
type TS' a :: *
instance (OneStep' a, OneStep' (OS' a)) = TwoStep' a where
type TS' a = (OS' (OS' a))
foo :: (TwoStep a b) = a - b - Bool
foo _ _ = True
foo' :: (TwoStep' a) = a - TS' a - Bool
foo' _ _ = True
*TestProb foo (Cons True (Cons 'b' (Cons hello Nil))) (Cons boo Nil)
True
*TestProb :t foo (Cons True (Cons 'b' (Cons hello Nil)))
foo (Cons True (Cons 'b' (Cons hello Nil))) :: Cons [Char] Nil - Bool
*TestProb :t foo' (Cons True (Cons 'b' (Cons hello Nil)))
interactive:1:0:
No instance for (OneStep'
(OS' (Cons Bool (Cons Char (Cons [Char] Nil)
arising from a use of `foo'' at interactive:1:0-45
Possible fix:
add an instance declaration for
(OneStep' (OS' (Cons Bool (Cons Char (Cons [Char] Nil)
Mmm. This is as a result of the instance (OneStep' a, OneStep' (OS' a))
constraint. Is it just me or does this look like the type synonynm isn't
being applied? So how about adding:
instance (OneStep' a) = OneStep' (OS' a) where
type OS' (OS' a) = a
*TestProb :t foo' (Cons True (Cons 'c' (Cons 5.3 (Cons hello Nil
foo' (Cons True (Cons 'c' (Cons 5.3 (Cons hello Nil :: (Fractional t) =
TS' (Cons Bool
(Cons Char (Cons t (Cons [Char] Nil
- Bool
Okay, but how do I inhabit that type?
*TestProb :t foo' (Cons True (Cons 'c' (Cons 5.3 (Cons hello Nil (Cons
5.3 (Cons hello Nil))
interactive:1:59:
Couldn't match expected type `TS'
(Cons Bool (Cons Char (Cons t (Cons [Char]
Nil'
against inferred type `Cons t1 (Cons [Char] Nil)'
In the second argument of `foo'', namely
`(Cons 5.3 (Cons hello Nil))'
So now, the third (and final!) version using indexed types:
class OneStep'' a where
data OS'' a :: *
mkOS'' :: a - OS'' a
instance OneStep'' (Cons v t) where
data OS'' (Cons v t) = OSC'' t
mkOS'' (Cons v t) = OSC'' t
instance (OneStep'' a) = OneStep'' (OS'' a) where
data OS'' (OS'' a) = OSC''w a
class TwoStep'' a where
data TS'' a :: *
mkTS'' :: a - TS'' a
instance (OneStep'' a, OneStep'' (OS'' a)) = TwoStep'' a where
data TS'' a = TSC'' (OS'' (OS'' a))
mkTS'' = TSC'' . mkOS'' . mkOS''
foo'' :: (TwoStep'' a) = a - TS'' a - Bool
foo'' _ _ = True
This, sort of works:
*TestProb let ts = mkTS'' (Cons True (Cons 'c' (Cons 5.3 (Cons hello Nil
in foo'' (Cons True (Cons 'c' (Cons 5.3 (Cons hello Nil ts
True
But of course, the wrapping into the indexed type demands the use of
mkTS''.
You can't even write:
*TestProb let ts = mkOS'' (Cons 'c' (Cons 5.3 (Cons hello Nil))) in foo''
(Cons True (Cons 'c' (Cons 5.3 (Cons hello Nil ts
interactive:1:119:
Couldn't match expected type `TS''
(Cons Bool (Cons Char (Cons t (Cons [Char]
Nil'
against inferred type `OS''
(Cons Char (Cons t1 (Cons [Char] Nil)))'
In the second argument of `foo''', namely `ts'
In the expression:
let ts = mkOS'' (Cons 'c' (Cons 5.3 (Cons hello Nil)))
in foo'' (Cons True (Cons 'c' (Cons 5.3 (Cons hello Nil ts
In the definition of `it':
it = let ts = mkOS'' (Cons 'c' (Cons 5.3 (Cons hello Nil)))
in foo'' (Cons True (Cons 'c' (Cons 5.3 (Cons hello Nil ts
Further, it is *impossible* to define mkTS'' for the extra
instance instance (OneStep'' a) = OneStep'' (OS'' a) where as to do
so would demand unwrapping the supplied (OS'' a) which can't be done -
if you try to add unwrop :: OS'' a - a to the class OneStep'' then try
to define it for the Cons instance - I've thrown away v so how are you
going to get it back? undefined?
Matthew
--
Matthew
Re: [Haskell-cafe] Lazy HTML parsing with HXT, HaXML/polyparse, what else?
On Mon, 14 May 2007, Malcolm Wallace wrote: Henning Thielemann [EMAIL PROTECTED] wrote: *Text.ParserCombinators.PolyLazy runParser (exactly 4 (satisfy Char.isAlpha)) (abc104++undefined) (*** Exception: Parse.satisfy: failed How can I rewrite the above example that it returns (abc*** Exception: Parse.satisfy: failed The problem in your example is that the 'exactly' combinator forces parsing of 'n' items before returning any of them. If you roll your own, then you can return partial results: let one = return (:) `apply` satisfy (Char.isAlpha) in runParser (one `apply` (one `apply` (one `apply` (one `apply` return [] (abc104++undefined) (abc*** Exception: Parse.satisfy: failed Equivalently: let one f = ((return (:)) `apply` satisfy (Char.isAlpha)) `apply` f in runParser (one (one (one (one (return []) (abc104++undefined) (abc*** Exception: Parse.satisfy: failed I wonder whether 'apply' merges two separate ideas: Applying a generated function to some parser generated value and forcing some parser to always succeed. From the documentation of 'apply' I assumed that 'apply f x' fails if 'f' or 'x' fails. In contrast to that it seems to succeed if only 'f' succeeds. Wouldn't it be better to have an explicit 'force' which declares a parser to never fail - and to return 'undefined' if this assumption is wrong. I have seen this 'force' in the MIDI loader of Haskore: http://darcs.haskell.org/haskore/src/Haskore/General/Parser.hs It would hold: apply f x == do g - f; fmap g (force x) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Behavior of groupBy
Thanks for the help! Strangely, I just now received your messages from April 28, hence the late reply... Hans van Thiel On Sat, 2007-04-28 at 18:09 +0200, Henning Thielemann wrote: On Sat, 28 Apr 2007, Hans van Thiel wrote: Hello All, The standard function groupBy of List.hs doesn't work as I expect in this case: groupBy (\x y - (last x) == (last y)) [abc, bd,cac] results in: [[abc],[bd],[cac]] where I want: [[abc,cac], [bd]] I think you must roll your own one. How about repeated 'partition' to extract all elements that have the same trailing character like the head word of the list? I have done this in a more complex setting and called it 'slice': http://darcs.haskell.org/haskore/src/Haskore/Basic/TimeOrderedList.lhs slice :: (Eq a, Num time) = (body - a) - T time body - [(a, T time body)] slice f perf = let splitByHeadKey pf = fmap (\ev - let i = f (eventBody ev) (pf0, pf1) = partition ((i==) . f) 0 0 pf in ((i,pf0), pf1)) (listToMaybe pf) in List.unfoldr splitByHeadKey perf ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Editor
I have a dream. It's not a little dream. It's a big dream. I have a dream that someday I can find a UNIX/Linux text editor for Haskell hacking (and possibly two or three hundred other programming languages, although that's optional) that can give me all of the following: 'find / -type dream | xargs rm' is not a good way to go about that that search, is it?-) by excluding the editors that fullfill most of your criteria, without any good reason, you're guaranteed to come up empty. i have a dream that there is an answer to life the universe and everything, and it isn't 42? you might not like the answer most people give, but there is a reason why that answer is so popular. of course, just because it is one valid answer, it need not be the right answer for you. you just need to be specific about why that particular answer doesn't suit you. 1. A real GUI environment that takes into account some of the HID advances made in the past 30 years. (Emacs and Vim don't count, in other words.) be specific, please! emacs and vim are often the first to integrate and experiment with whatever new ideas come into view (some even originated there). only few of those experiments find enough followers to make it into the main distributions, though. whatever it is you're missing, if you can't even name it, it can't be good enough reason to discard either emacs or vim). in my experience, most people complain about vim or emacs because they aren't aware of what these can do. it is not just that there is so much functionality and variation available that one has to invest time to learn even parts of that, one new feature a day. it is that much of what people don't like is deliberately not fixed, but configurable. some people don't like the complexity of emacs interactions, and prefer vim's brief and efficient modeskey-strokes, some don't like vim modes and prefer emacs-style commands, some prefer plain text, some prefer gui, some ... you might prefer either vim or emacs, but you shouldn't complain about anything that you can configure yourself (such as modes vs long commands, gui vs text, os-style or vim-style copypaste, colours and specifics of syntax highlighting, available menus, and so on). vim has a good integrated manual, and tutorials, but if i want that much functionality, i have to learn about it, and spend a lot of time in that documentation. the more my personal needs deviate from default settings, the more i have to learn and configure; the more specific functionality i need the more i have to delve into the details of what is available. if i don't want to learn how to use such powers, i have to make do with a less powerful, out-of-the-box environment. some people are happy with textpad, but i know nobody who has studied all of current vim or emacs. most users start out with the textpad equivalent of functionality in vim or emacs, then add to their knowledge and toolbox as and when they need to do so. looking at your requirements, for vim, to the extent i know it: 2. Good quality syntax highlighting for Haskell that includes all of the usual syntax highlighting goodies, plus: yes * the ability to seamlessly handle raw Haskell and both common forms of Literate Haskell; i stopped using literate haskell long ago, so i can't really say. (i always wanted literate haskell _sessions_, not programs, with definitions, redefinitions, evaluations, explanations, but all with a quite different structure than is useful for the programs being explored/described in such a session) * the ability to properly highlight Haddock comments; seem to be highlighted only as comments, by default, but you could change that, if you really wanted to. if the change looks useful, it should make it into the next vim release - that's how the current haskell highlighting got there and keeps developing. * the ability to highlight functions and types from libraries (user-expandable) differently from local functions and types. that sounds potentially useful, and some of the information is available (my vim settings have tables of local and library definitions for completion). however, vim doesn't know about haskell scopes, so the easiest solution would be unaware of renaming/hiding/etc. 3. Line folding to hide and show blocks of code. yes, along with other folding modes 4. Code completion (user-expandable, ideally) for common library functions, type declarations, etc. several completions, including two user-expandable ones. in my setup, completion can be based on source, tag files, haddock indices, ghci :browse,.. 5. Easy, quick access to online documentation for said functions and declarations. yes. open your favourite browser on the haddocks for the id under cursor. 6. Good (ideally scriptable) access to external utilities for compilation, debugging, profiling,
Re: [Haskell-cafe] Scope of type variables in associated types
On Mon, May 21, 2007 at 02:08:13PM +0100, Matthew Sackman wrote: Further, it is *impossible* to define mkTS'' for the extra -- should be mkOS'' But actually, in that code, the data declaration was never even used either - all that is needed is: instance (OneStep'' a) = OneStep'' (OS'' a) But it does rather leave a mess in the code. Matthew -- Matthew Sackman http://www.wellquite.org/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] how can I select all the 3-element-combination out of a list efficiently
Mirko Rahn [EMAIL PROTECTED] writes: (snip) Correct (and more natural): nOf 0 _ = [[]] nOf n (x:xs) = map (x:) (nOf (n-1) xs) ++ nOf n xs nOf _ [] = [] Thanks very much - in both claims you're indeed correct. -- Mark ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Editor
With a slightly less flippant response, have you ever tried TextMate? I haven't, but I've heard many wax lyrical about its combination of the UNIXy power of Vim et al with the intuitive and simple UI that OS X has a reputation for. Unfortunately, it's not free and is only for Mac OS X, but it seems that it was created by someone who shared your dream (although a less Haskell-centric version, no doubt). On 21/05/07, Michael T. Richter [EMAIL PROTECTED] wrote: I have a dream. It's not a little dream. It's a big dream. I have a dream that someday I can find a UNIX/Linux text editor for Haskell hacking (and possibly two or three hundred other programming languages, although that's optional) that can give me all of the following: 1. A real GUI environment that takes into account some of the HID advances made in the past 30 years. (Emacs and Vim don't count, in other words.) 2. Good quality syntax highlighting for Haskell that includes all of the usual syntax highlighting goodies, plus: 3. the ability to seamlessly handle raw Haskell and both common forms of Literate Haskell; 4. the ability to properly highlight Haddock comments; 5. the ability to highlight functions and types from libraries (user-expandable) differently from local functions and types. 6. Line folding to hide and show blocks of code. 7. Code completion (user-expandable, ideally) for common library functions, type declarations, etc. 8. Easy, quick access to online documentation for said functions and declarations. 9. Good (ideally scriptable) access to external utilities for compilation, debugging, profiling, type inference, project management, etc. 10. A good plug-in system (ideally written in Haskell?) for expansion. Is there such a beast available out there somewhere? If not, is such a beast lurking in the background ready to pounce in the near future? -- *Michael T. Richter* [EMAIL PROTECTED] (*GoogleTalk:* [EMAIL PROTECTED]) *I have to wonder why people think that when they can't manage local personnel within easy strangling and shooting distance, then they can manage personnel thousands of miles away that have different languages, cultures, and business rules. (Joe Celko)* ___ 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] Editor
On Mon, 2007-21-05 at 13:41 +0100, Neil Mitchell wrote: Michael is asking is there something more GUI like? - to which the answer is yes - Visual Haskell - Sadly what I was asking was is there anything more GUI like for Linux. ;) It doesn't surprise me that Macs and Windows boxes have something like what I'm looking for. Usability testing isn't alien to those platforms' mindsets. Unfortunately Macs are basically unavailable where I live. (I guess I could travel 24 hours round-trip to the nearest Apple store I know of and pay five months' spending money for a MacBook, not to mention the ticket prices, but that's not going to happen, I'm afraid.) And Windows as a platform lacks certain features I like (including stability, security and an absence of Trusted Computing) that made me turn away from it in the first place. It's one of those trade-off situations, but sometimes I really wish this particular trade-off weren't necessary. -- Michael T. Richter [EMAIL PROTECTED] (GoogleTalk: [EMAIL PROTECTED]) Theory is knowledge that doesn't work. Practice is when everything works and you don't know why. (Hermann Hesse) attachment: smiley-4.png 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] Editor
1.A real GUI 2.Good quality syntax highlighting for Haskell..., plus: 3. raw Haskell both forms of Literate Haskell; 4. properly highlight Haddock comments; 5. highlight functions and types from libraries differently from local 3.Line folding to hide and show blocks of code. 4.Code completion 5.Easy, quick access to online documentation 6.access to external utilities for compilation, debugging, profiling, type inference, project management, etc. 7.A good plug-in system Having dismissed Visual Haskell for being Windows-only, have you considered EclipseFP? It doesn't tick all of your boxes, but maybe it goes far enough in the right direction. AFAICT it fulfills 1, 2.3, 2.5 (but I'm not sure about this), 3, 6, and 7 (ish - plugins would be written in Java). Alistair * Confidentiality Note: The information contained in this message, and any attachments, may contain confidential and/or privileged material. It is intended solely for the person(s) or entity to which it is addressed. Any review, retransmission, dissemination, or taking of any action in reliance upon this information by persons or entities other than the intended recipient(s) is prohibited. If you received this in error, please contact the sender and delete the material from any computer. * ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Editor
On 21-mei-2007, at 13:56, Michael T. Richter wrote: Hell, even comparing the out-of-the-box syntax highlighting support in Gedit vs. (G)Vim is instructive. Code like makeRandomValueST :: StdGen - (MyType, StdGen) (which, incidentally, was far easier to copy from in Gedit than GVim to paste into this message) only differentiates :: and - from the text and delimiters in GVim while in Gedit (keeping in mind that Gedit isn't a very good editor!) differentiates those plus makeRandomValueST vs. StdGen and MyType. And the parentheses. This is an interesting take on things. What to highlight and why is decidedly non-trivial. Personally, I strongly *dislike* highlighting of user-defined identifiers. And honestly, in Haskell, most identifiers are user-defined. Furthermore, the haskell vim highlighter actually allows you to highlight delimiters, True and False, the names of a number of types, and the names of debugging functions. It requires settings to turn that on though, as the highlighter should be as minimally visually intrusive in its default setting as possible. Or at least, that's what I think, and I was the last person to get his grubby paws on vim's highlighter for Haskell. It does highlight literate Haskell code quite nicely however, both in bird track style and in TeX style. It does expect literate Haskell to be in .lhs files though... Note that it is somewhat tricky to distinguish between the occurences of the a's before and after the semicolon in the following: map :: ( a - b ) - [a] - [b]; map f (a:as) = f a : (map f as) I'd like to see what GEdit does to that. :) Doei, Arthur van Leeuwen. -- /\/ | [EMAIL PROTECTED] | Work like you don't need the money /__\ / | A friend is someone with whom | Love like you have never been hurt /\/__ | you can dare to be yourself | Dance like there's nobody watching ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Behavior of groupBy
On Mon, 21 May 2007, Hans van Thiel wrote: Thanks for the help! Strangely, I just now received your messages from April 28, hence the late reply... Our mail server does now send a bunch of mails I thought that were sent long ago. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Editor
Bayley, Alistair wrote: 1. A real GUI 2. Good quality syntax highlighting for Haskell..., plus: 3. raw Haskell both forms of Literate Haskell; 4. properly highlight Haddock comments; 5. highlight functions and types from libraries differently from local 3. Line folding to hide and show blocks of code. 4. Code completion 5. Easy, quick access to online documentation 6. access to external utilities for compilation, debugging, profiling, type inference, project management, etc. 7. A good plug-in system Having dismissed Visual Haskell for being Windows-only, have you considered EclipseFP? It doesn't tick all of your boxes, but maybe it goes far enough in the right direction. AFAICT it fulfills 1, 2.3, 2.5 (but I'm not sure about this), 3, 6, and 7 (ish - plugins would be written in Java). There is also some experimentation under way to implement plugins in Haskell: http://leiffrenzel.de/eclipse/cohatoe/ The Haskell code is plugged into Eclipse via hs-plugins. However, the ultimate entry point to the IDE is still Eclipse's, so there will be some Java/XML boilerplate necessary for getting a plugin hooked. Thanks ciao, Leif Alistair * Confidentiality Note: The information contained in this message, and any attachments, may contain confidential and/or privileged material. It is intended solely for the person(s) or entity to which it is addressed. Any review, retransmission, dissemination, or taking of any action in reliance upon this information by persons or entities other than the intended recipient(s) is prohibited. If you received this in error, please contact the sender and delete the material from any computer. * ___ 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] AngloHaskell 2007
I'd like to announce AngloHaskell 2007, or at least the start of the process of organising it! Last year there was a get-together organised around the interviews for the job of GHC maintainer. There were talks, with a largely pragmatic flavour, and there was plenty of socialising. It was fun, and doing it again seems a good idea. In the vein of last year's process, organising an event this year shall take place on the Haskell Wiki page at: http://www.haskell.org/haskellwiki/AngloHaskell and on IRC, in #anglohaskell on irc.freenode.net So far this is almost all the detail available, as neither date nor venue have been set - a summer date seems good though, and by the time we're organised I imagine late July or August looks most likely. Simon Peyton-Jones has offered to ask Microsoft Research for space to give talks in. This worked well last year, but if anyone else wants to offer a venue that's fine! -- [EMAIL PROTECTED] The task of the academic is not to scale great intellectual mountains, but to flatten them. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Editor
On 21/05/07, Michael T. Richter [EMAIL PROTECTED] wrote: Easy, quick access to online documentation for said functions and declarations. I'm writing this for Emacs right now. At the moment both Emacs and Vim can access everything that GHCi has to offer on a function, which means where it's defined, it's type and so on, but not Haddock documentation. I'm extending haskell-mode's inf-haskell.el to take this into account. -- -David House, [EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Profiling, GUIs and libraries
Just in case anyone was wondering how to do this with the other major Haskell GUI lib Gtk2Hs... ./configure --enable-profiling some day when Gtk2Hs is cabalised it'll be even easier. Duncan On Sun, 2007-05-20 at 17:39 +0200, Anthony Chaumas-Pellet wrote: Hello, I'm currently hacking away a wxhaskell program that uses up 100% CPU even when it should be idle. So, rather than doing blind guesswork, I've thought about using profiling to spot the zealous function. I do not need a very accurate result, though. ghc with -prof -auto(-all) produces the following error message, however: Could not find module `Graphics.UI.WX': Perhaps you haven't installed the profiling libraries for package wx-0.10.1? Use -v to see a list of the files searched for. So, I guess I need to rebuild wx with profiling, but I'm not sure how to do that exactly; search engine and the Wiki did not turn up any pointers, and there are no ready-made options to build wx with profiling. It seems Cabal can build a library with profiling automatically, but I don't think there exists a Cabalized version of wx yet. That, and I'm not sure if recompiling libraries to add profiling is a great idea, as wx itself may depend on other external libraries. So, is there a better way than profiling in my case, or am I missing something obvious here? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Scope of type variables in associated types
Matthew Sackman wrote: class G a where data E a :: * wrap :: a - E a unwrap :: E a - a I'm afraid not. I really need wrap to take a 'b' and unwrap to return a 'b'. Talking on #haskell to sjanssen last night, he came up with: How does class F a where data B a :: * data E a :: * wrap :: B a - E a unwrap :: E a - B a sound? 'B a' would represent the 'b' in your previous attempt, class F a b | a - b where ... Bertram ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell: the Craft of Functional Programming
I'm not sure what you mean by a lot of transcription work. It's an excellent book, aimed at beginners. transcribe :: Print - Etext Mike PR Stanley wrote: Hi I've acquired a copy of the above title but it requires a lot of transcription work. So, I thought I'd first ensure it's worth the time and effort. This edition was published in 1999. All Opinions on the text, good or bad, would be very welcome. Thanks, Paul ___ 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 Albus Dumbledore would sell Haskell
Henning Thielemann wrote: On Wed, 18 Apr 2007, Dan Weston wrote: You have already won over the scientists. I only know few mathematicians using Haskell, most of the (applied) mathematician colleagues I know prefer MatLab. Blehr! _ I hate MatLab... it's horrid! (OTOH, I'm not a real mathematition, so...) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How Albus Dumbledore would sell Haskell
On May 21, 2007, at 14:15 , Andrew Coppin wrote: Henning Thielemann wrote: I only know few mathematicians using Haskell, most of the (applied) mathematician colleagues I know prefer MatLab. I hate MatLab... it's horrid! Everyone hates Matlab. Problem is, it's hard to find anything like its toolkits -- brandon s. allbery [linux,solaris,freebsd,perl] [EMAIL PROTECTED] system administrator [openafs,heimdal,too many hats] [EMAIL PROTECTED] electrical and computer engineering, carnegie mellon university KF8NH ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How do I insert an element in HaXml?
At Sun, 20 May 2007 10:55:26 +0100, Malcolm Wallace wrote: Jeremy Shaw [EMAIL PROTECTED] writes: How do I create a HaXml filter that adds a new element as a child of an existing element. For example, let's say I have the XML document: a b/ c/ /a How do I add a new element under a / so that I have the document: a newElement/ b/ c/ /a Using the combinators, it goes something like this: mkElem a [ mkElem newElement [] , children ] `o` tag a Having matched the outer tag, you then rebuild it with some extra stuff added. Obviously you would abstract the common pattern if you do this frequently: insertAtStart :: String - String - CFilter insertAtStart outer newelem = mkElem outer [ mkElem newElem [] , children ] `o` tag outer Thanks! I should probably mention that I don't actually have a specific problem I am trying to solve here. I am trying to write a tutorial on how to use the combinators, and there is a certain class of problems I can't seem to handle. I am not sure if it is because there is a hole in my understanding, or if there is an hole in what the combinators can express. The hole is related to operations that want to edit the children of a element in some sort of aggregate manner. The current example is inserting a new element. Another example is sorting the children. Going back to the example at hand, what if I don't know the name and attributes of the parent? For example, if I have the document: top section attr=value1 b / b / /section section2 attr=value3 b / /section2 othersection attr=\value2\/ /top And a I want to add single newElement / to any child of top that already has one or more b / element, so I get this output: top section attr=value1 newElement / b / b / /section section2 attr=value3 newElement / b / /section2 othersection attr=value2/ /top A solution that comes close is this filter: chip ((chip (mkElem newElement [] `union` keep)) `when` (elm / tag b)) Except that it will produce a newElement / for *every* b /, whereas I only want a single newElement / per parent. If I introduce a new (poorly named) primitive: editElem :: CFilter - CFilter editElem f c@(CElem (Elem name as _)) = [ CElem (Elem name as (f c)) ] Then I can express the filter like this: chip (editElem (mkElem newElement [] `union` children) `when` (keep / tag b)) But, I don't see an obvious way to implement 'editElem' using the existing combinators. On the other hand, 'chip' can be implemented in terms of 'editElem': chip' = editElem children but, I am not sure what implications that has, if any. thanks! j. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Editor
You mentioned a dream Have you looked at Yi? might be worth a peek if you're prepared to work towards your dream. http://www.haskell.org/haskellwiki/Yi ...a long way to go - but it certainly nails #7! --Ben On 21 May 2007, at 15:44, Leif Frenzel wrote: Bayley, Alistair wrote: 1. A real GUI 2. Good quality syntax highlighting for Haskell..., plus: 3. raw Haskell both forms of Literate Haskell; 4. properly highlight Haddock comments; 5. highlight functions and types from libraries differently from local 3. Line folding to hide and show blocks of code. 4. Code completion 5. Easy, quick access to online documentation 6. access to external utilities for compilation, debugging, profiling, type inference, project management, etc. 7. A good plug-in system Having dismissed Visual Haskell for being Windows-only, have you considered EclipseFP? It doesn't tick all of your boxes, but maybe it goes far enough in the right direction. AFAICT it fulfills 1, 2.3, 2.5 (but I'm not sure about this), 3, 6, and 7 (ish - plugins would be written in Java). There is also some experimentation under way to implement plugins in Haskell: http://leiffrenzel.de/eclipse/cohatoe/ The Haskell code is plugged into Eclipse via hs-plugins. However, the ultimate entry point to the IDE is still Eclipse's, so there will be some Java/XML boilerplate necessary for getting a plugin hooked. Thanks ciao, Leif Alistair * Confidentiality Note: The information contained in this message, and any attachments, may contain confidential and/or privileged material. It is intended solely for the person(s) or entity to which it is addressed. Any review, retransmission, dissemination, or taking of any action in reliance upon this information by persons or entities other than the intended recipient(s) is prohibited. If you received this in error, please contact the sender and delete the material from any computer. * ___ 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 mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How Albus Dumbledore would sell Haskell
(aside to Dylan T: I hope you don't mind me advertising your (well, public) web pages here. In my opinion a lot more people should know about the stuff that both you and Ken are doing!) Here's an example of some great math being done in haskell: http://www.math.columbia.edu/~dpt/genus2fiber/ (the code for this paper): http://arxiv.org/abs/math.GT/0510129 On Mon, 21 May 2007, Brandon S. Allbery KF8NH wrote: On May 21, 2007, at 14:15 , Andrew Coppin wrote: Henning Thielemann wrote: I only know few mathematicians using Haskell, most of the (applied) mathematician colleagues I know prefer MatLab. I hate MatLab... it's horrid! Everyone hates Matlab. Problem is, it's hard to find anything like its toolkits -- brandon s. allbery [linux,solaris,freebsd,perl] [EMAIL PROTECTED] system administrator [openafs,heimdal,too many hats] [EMAIL PROTECTED] electrical and computer engineering, carnegie mellon university KF8NH ___ 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] List algorithm
Hello, is there an efficient algorithm that takes two positive numbers n and m and that computes all lists l of numbers 0x=n such that sum l = m? For instance alg 5 1 = [[1]] alg 5 2 = [[1,1],[2]] alg 5 3 = [[1,1,1],[1,2],[2,1],[3]] ... I know that filter (\l-sum l == m) (powerSet [1..n]) would do the job, however I am looking for a more efficient approach. Help is greatly appreciated, even a google search term would be fine :-) I really hope for a polynomial algorithm although I am not very optimistic about this. Ciao, Steffen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Editor
Michael T. Richter wrote: 1. A real GUI environment that takes into account some of the HID advances made in the past 30 years. (Emacs and Vim don't count, in other words.) I for my life think HID refers to human input devices: keyboard, mouse, joystick, gamepad, pedal, microphone, touchscreen... When this HID statement is brought up, the first and only thing I think of is the recent Mathematica 6: It supports the gamepad for rotating 3D plots. Apart from that, absolutely no programming environment takes into account much of the HID advances in the past 30 years; they only go up to keyboard and mouse. GUI, menu, modal, modeless... those would be HCI. But that inspires some real fantasy for the next century. I want to watch a function definition as a 3D thunk, and rotate it with the gamepad. It is even better than a parse tree, because I want let x2=x*x in x2+x2 to be displayed as: * / \ x2 x2 | | --- + / \ \ / x or any topological equivalence. At my selection, some nodes stick out blurbs containing their types or haddocks. No more 20th century dark age dogma of vertical serialization of horizontal serialization of characters euphemized as plain text file, the least problem of which is the sorry kludge of operator precedences and parenthesizing. In this thread I ask, can programming be liberated from the plain text file, now that it is liberated from the von Neumann style? Module dependency graphs receive the same treatment. Modules in a project are shown as a 3D graph. Using the gamepad, I rotate the graph, bring a module to the forefront, and press the circle button to open it. Debugging has never been more enticing! All CAFs and thunks are displayed in 3D. (As usual, you can use the gamepad to change perspective at will.) A small virtual organism, dubbed the bug, walks the thunks and does the graph reductions. You can of course interrupt the bug and give explorative instructions. You may want to rename this activity to bugging. Imperative communities may boast the best debuggers, but only in Haskell you find the best buggers! (On second thought, dubbing the virtual organism the alligator may bug you less.) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] List algorithm
Steffen Mazanek [EMAIL PROTECTED] writes: alg 5 1 = [[1]] alg 5 2 = [[1,1],[2]] alg 5 3 = [[1,1,1],[1,2],[2,1],[3]] Would this be better? alg n m = case signum m of -1 - [] 0 - [[]] 1 - [ x : xs | x - [1..n], xs - alg n (m - x) ] -- Mark ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] efficient and/or lazy partitions of a multiset
HC-er's,
Find below some simple-minded code from a naive Haskeller for generating all
partitions of a multiset about which i have two questions.
mSplit :: [a] - [([a], [a])]
mSplit [x] = [([x],[])]
mSplit (x:xs) = (zip (map (x:) lxs) rxs)
++ (zip lxs (map (x:) rxs))
where (lxs,rxs) = unzip (mSplit xs)
1. Is there a clever way to reduce the horrid complexity of the naive
approach?
2. How lazy is this code? Is there a lazier way?
i ask this in the context of checking statements of the form \phi * \psi |=
e_1 * ... * e_n where
- [| \phi * \psi |] = { a \in U : a === b_1 * b_2, b_1 \in [| \phi |],
b_2 \in [| \psi |] }
- === is some congruence generated from a set of relations
A nice implementation for checking such statements will iterate through the
partitions, generating them as needed, checking subconditions and stopping
at the first one that works (possibly saving remainder for a rainy day when
the client of the check decides that wasn't the partition they meant).
Best wishes,
--greg
--
L.G. Meredith
Managing Partner
Biosimilarity LLC
505 N 72nd St
Seattle, WA 98103
+1 206.650.3740
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Re: [Haskell-cafe] List algorithm
[EMAIL PROTECTED] (Mark T.B. Carroll) writes: alg n m = case signum m of -1 - [] 0 - [[]] 1 - [ x : xs | x - [1..n], xs - alg n (m - x) ] FWIW it's faster if you do some memoising: algMemo n m = lookupMemo m where memo = [[]] : map helper [1..m] lookupMemo m = if m 0 then [] else memo !! m helper m' = [ x : xs | x - [1..n], xs - lookupMemo (m' - x) ] -- Mark ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] List algorithm
[EMAIL PROTECTED] (Mark T.B. Carroll) writes: (snip) algMemo n m = lookupMemo m where memo = [[]] : map helper [1..m] lookupMemo m = if m 0 then [] else memo !! m helper m' = [ x : xs | x - [1..n], xs - lookupMemo (m' - x) ] which, I suppose, is rather like, algMemo n m = last memo where memo = [[]] : map helper [1 .. m] helper m' = [ x : xs | x - [1 .. min m' n], xs - memo !! (m' - x) ] -- Mark ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Editor
On Tuesday 22 May 2007 02:30, Claus Reinke wrote: Vim is eliminated before it reaches the gate because it's a modal editor. Even with GVim in place, it still has that modal stench to it that leaps up and bites at awkward moments. that's a bit more specific, at least. but as far as i recall, modes were considered bad for specific reasons, such as 'users can't see where they are, modewise', 'functionality becomes unavailable in a mode', 'users have no way to get out of a mode', etc. and most of these specific issues have actually been addressed in vim. Since no-one else has done so, i thought i should mention Cream: http://cream.sourceforge.net/featurelist.html Cream is a customisation of Vim/gVim, providing a more contemporary GUI style and single-mode editing (although modal editing is available if one wants it) - with all the power of Vim under the hood. :-) Alexis. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] type class question
I think this must almost be a FAQ, or at least a PAQ (Previously AQ)... If I have a type class for conversion to a type X: class XType a where toX :: a - X I can define instances for instance XType Int where toX = ... instance XType Double where toX = ... instance XType Tuple where toX = ... but not for Strings, given that they are a synonym for [Char]. Hence: instance XType String where toX = ... results in: Illegal instance declaration for `XType String' (The instance type must be of form (T a b c) where T is not a synonym, and a,b,c are distinct type variables) In the instance declaration for `XType String' Is there some type class cleverness that can make this work in haskell 98? I can create a new wrapper type for strings: newtype StringWrap = StringWrap String and write an instance for that, but then I'll have to litter my code with calls to this constructor. I'm aware of the approach taken by class Show in the prelude, which adds a extra method to the class: class XType a where toX :: a - X listToX :: [a] - X but I believe this says that whenever we can convert a to an X we can also convert [a] to an X, whereas I only want [Char] to be acceptable. Thanks for any pointers. Tim ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] type class question
Tim Docker wrote: I think this must almost be a FAQ, or at least a PAQ (Previously AQ)... If I have a type class for conversion to a type X: class XType a where toX :: a - X I can define instances for instance XType Int where toX = ... instance XType Double where toX = ... instance XType Tuple where toX = ... but not for Strings, given that they are a synonym for [Char]. Hence: instance XType String where toX = ... results in: Illegal instance declaration for `XType String' (The instance type must be of form (T a b c) where T is not a synonym, and a,b,c are distinct type variables) In the instance declaration for `XType String' Is there some type class cleverness that can make this work in haskell 98? I can create a new wrapper type for strings: newtype StringWrap = StringWrap String and write an instance for that, but then I'll have to litter my code with calls to this constructor. I'm aware of the approach taken by class Show in the prelude, which adds a extra method to the class: class XType a where toX :: a - X listToX :: [a] - X but I believe this says that whenever we can convert a to an X we can also convert [a] to an X, whereas I only want [Char] to be acceptable. I believe there is a trick where essentially you end up with, instance IsChar a = XType [a] where ... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Editor OT: streamofconciousness
On Mon, May 21, 2007 at 06:37:22PM +0800, Michael T. Richter wrote: 1. A real GUI environment that takes into account some of the HID advances made in the past 30 years. (Emacs and Vim don't count, in other words.) heh. find me a new GUI editor that takes into account the HID advances that were well established 30 years ago and I will be happy. I am all for innovation, but not at the cost of needed and useful functionality. I recently had a discussion with a coworker where he went off for a long time about his new 'refactoring' editor, telling me cool stuff he could do with it. Excited and interested, I went to see what it was about (I always am interested in new stuff, especially if it can make my life easier). I watched as he used pop-up windows and dialogs to happily indent and unindent methods and rename variables, after which he turned to me and said proudly now this is refactoring.. To which, I, puzzled, responded, Really? to me it just looked like you were editing. It is a perhaps sad fact that a lot of innovation when it comes to editing interfaces is simply one of terminology. Inventing names for well established practices, imbuing them with the magical power of buzzwords to sway opinion in the face of rationality and then dismiss every feature that one cannot list on a features FAQ as irrelevant. It is somewhat depressing that immutable pre-packaged macros[1] and the simple brute-force inclusion of separate tools[2] into the editor are hailed as innovation, when new innovations, whether they are simple refinements of old ideas[3], excercises in orthoginality[4], or truely new research[5] are left to the wayside. But such is the power of the bullet point. John [1] many (but not all) refactoring features i have seen. [2] http://en.wikipedia.org/wiki/Cscope [3] http://en.wikipedia.org/wiki/Sam_(text_editor) [4] http://en.wikipedia.org/wiki/Acme_%28Plan_9%29 [5] http://tlau.org/research/smartedit/ -- John Meacham - ⑆repetae.net⑆john⑈ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Scope of type variables in associated types
Bertram Felgenhauer: How does class F a where data B a :: * data E a :: * wrap :: B a - E a unwrap :: E a - B a sound? 'B a' would represent the 'b' in your previous attempt, class F a b | a - b where ... I'm with Simon in thinking that this code is suspicious. For any given call to wrap or unwrap, how is the compiler supposed to determine which instance to use, given that a cannot be uniquely determined from the type of the function? The same question also applies to Matthew's original formulation using functional dependencies: class G a b | a - b where data E a :: * wrap :: b - E a unwrap :: E a - b Simon's reformulation doesn't have this problem: class G a where data E a :: * wrap :: a - E a unwrap :: E a - a ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] type class question
Derek Elkins wrote: I believe there is a trick where essentially you end up with, instance IsChar a = XType [a] where ... That is simple enough, and works fine. Thanks! Tim ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Wanted: extended static checking for xmonad
When working on xmonad, we're trying to produce very clean, correct code -- a window manager that just works. To do this, we're looking to employ more static checking tools to the code base. Currently we use: * QuickCheck (checks high level window manager behaviour) * Catch (Neil's pattern match verifier, caught a couple of bugs) * ghc -Wall One other tool we're considering: * HPC. check program coverage of the test suite. But I suspect that there's an awful lot of other small checkers of various kinds out there. So: * Do you know of some other cool code checking tool for Haskell? * That could be used on xmonad (xmonad.org) to reduce code smell? If so, let us know! :-) -- Don P.S. Perhaps it is time for a wiki page documenting the available extended static checking tools for Haskell. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
