[Haskell-cafe] RE: No warning in GHC
[Redirecting to haskell-cafe] Try http://www.haskell.org/ghc/docs/latest/html/users_guide/flag-reference.html#id2959068 With -Wall I get bash-3.2$ ghc -c -Wall Foo.hs Foo.hs:3:0: Warning: Definition but no type signature for `func' Inferred type: func :: forall t t1. (Num t1) = t - t1 Foo.hs:3:5: Warning: Defined but not used: `x' Foo.hs:4:10: Warning: This binding for `x' shadows the existing binding bound at Foo.hs:3:5 | -Original Message- | From: cvs-ghc-boun...@haskell.org [mailto:cvs-ghc-boun...@haskell.org] On Behalf Of | Grigory Sarnitskiy | Sent: 21 March 2010 19:37 | To: cvs-...@haskell.org | Subject: No warning in GHC | | Hello! I wonder, why GHC shows no warning in situations like | | func x = x | where x = 5 | | Sometimes I forget about argument names used, and use the same names in let or where. | And it can take me quite a lot time to understand what is wrong. I think it would be | nice to warn users if the argument is redefined in let/where clause. Shall I report | a bug/feature request? I'm using ghc 6.10.4. | | btw, I couldn't post to IRC: #ghc :Cannot send to channel | | ___ | Cvs-ghc mailing list | cvs-...@haskell.org | http://www.haskell.org/mailman/listinfo/cvs-ghc ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Occurs check error, help!
-Ursprüngliche Nachricht- Von: adamtheturtle kill2thr...@hotmail.com Gesendet: 22.03.2010 04:52:19 An: haskell-cafe@haskell.org Betreff: [Haskell-cafe] Re: Occurs check error, help! Ivan Miljenovic ivan.miljenovic [ gmail.com writes: Since my answer before to your question obviously wasn't clear enough, let me highlight the lines of the error message that summarise what you have to do: On 22 March 2010 14:31, adamtheturtle kill2thrill [ hotmail.com wrote: Possible fix: add (Eq a) to the context of the type signature for `shuffle' Alternatively, use the random-shuffle package rather than coding your own. So sorry to keep on going on about this but I have been set to start with shuffle :: Int - [a] - [a] so I have to do that and can't use the given code and I really don't know where to put (Eq a) shuffle :: Eq a = Int - [a] - [a] Another option is to remove the call to delete, after all, what you want isn't to remove the first occurrence of an element equal to (cards !! i) from cards, but you want to remove element No. i from cards. You can simply achieve that without any type-class constraint. Take a look at take, drop and splitAt. Those should help you. Thank you so much for replying :) ___ 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] Re: Strange typing?
Ozgur Akgun wrote: Is there any way to limit a functions type, not by a data type but by a group of constructors of a data type? If not, what would be the *right* thing to do to achieve this level of type safety? data DT1 = X | Y | Z data DT2 = A | B | C | D func1 :: DT1 - DT2 -- instead of this func1' :: (X|Y) - (B|C) -- i want sth. like this. (| means or) OCaml has a feature called 'polymorphic variants' that allows exactly this. You may want to google 'polymorphic variants in haskell'. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] breadth first search one-liner?
Dear all, there is this neat one-line BFS implementation bfs :: Eq a = ( a - [a] ) - a - [a] bfs next start = let xs = nub $ start : ( xs = next ) in xs but it has a problem: it only works for infinite graphs. This is fine: take 20 $ bfs ( \ x - [2*x, x+1] ) 1 but this is not: take 20 $ bfs ( \ x - filter (0) [ div x 2, x - 1 ] ) 10 Is there a nice way to repair this? (I know how to code a BFS but here I'm asking for a one-liner.) J. W. signature.asc Description: OpenPGP digital signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] breadth first search one-liner?
On Mon, Mar 22, 2010 at 11:02:32AM +0100, Johannes Waldmann wrote: Dear all, there is this neat one-line BFS implementation bfs :: Eq a = ( a - [a] ) - a - [a] bfs next start = let xs = nub $ start : ( xs = next ) in xs but it has a problem: it only works for infinite graphs. This is fine: take 20 $ bfs ( \ x - [2*x, x+1] ) 1 but this is not: take 20 $ bfs ( \ x - filter (0) [ div x 2, x - 1 ] ) 10 Is there a nice way to repair this? bfs :: (a - [a]) - a - [a] bfs f s = concat $ takeWhile (not . null) $ iterate (= f) [s] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: breadth first search one-liner?
Nice! - Where's the 'nub'? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANNOUNCE: AusHac2010
Dreading the end of ZuriHac? Wish the Haskellian camaraderie could continue? Well, if you're able to make your way to Sydney, Australia between the 16th and 18th of July, then AusHac2010 is for _you_! It will be held at the School of Computer Science and Engineering at the University of New South Wales (thanks to Manuel Chakravarty and Ben Lippmeier for offering to organise the rooms!). If you are wanting to attend the inaugural Australian Hackathon, please register at http://axman6.wufoo.com/forms/aushac-2010-sign-up/ . For more information, see http://www.haskell.org/haskellwiki/AusHac2010 We will shortly be adding an extended version of the Who table; please also add your details there as well as which projects you would be interested in hacking in. Hoping to see you there! -- 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] Re: breadth first search one-liner?
On Mon, Mar 22, 2010 at 10:30:32AM +, Johannes Waldmann wrote: Nice! - Where's the 'nub'? A bit longer: bfs :: Eq a = (a - [a]) - a - [a] bfs f s = concat $ takeWhile (not . null) $ map snd $ iterate step ([], [s]) where step (seen, xs) = let seen' = xs++seen in (seen', nub $ [y | x - xs, y - f x, notElem y seen']) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: breadth first search one-liner?
A bit closer to the original: bfs :: Eq a = (a - [a]) - a - [a] bfs f s = concat $ takeWhile (not . null) levels where levels = foldr trim [] $ [s] : map (nub . (= f)) levels trim xs xss = xs : map (\\ xs) xss ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: breadth first search one-liner?
Ross Paterson wrote: On Mon, Mar 22, 2010 at 10:30:32AM +, Johannes Waldmann wrote: Nice! - Where's the 'nub'? A bit longer: bfs :: Eq a = (a - [a]) - a - [a] bfs f s = concat $ takeWhile (not . null) $ map snd $ iterate step ([], [s]) where step (seen, xs) = let seen' = xs++seen in (seen', nub $ [y | x - xs, y - f x, notElem y seen']) Basically the same idea: bfs next start = let go _ [] = [] go xs ys = let zs = nub (ys = next) \\ xs in ys ++ go (zs ++ xs) zs in go [start] [start] A slightly different approach is to add stage markers to the produced streams, say bfs next start = let xs = nub $ Left 0 : Right s : (xs = next') next' (Left n) = [Left (n + 1)] next' (Right s) = map Right (next s) stop (Left _ : Left _ : _) = [] stop (Left x : xs) = stop xs stop (Right x : xs) = x : stop xs in stop xs or bfs next start = lefts . takeWhile (not . null) . unfoldr (Just . span (either (const False) (const True)) . tail) $ fix (nub . (Left 0 :) . (Right start :) . (= either ((:[]) . Left . succ) (map Right . next))) This has the advantage that nub can be used directly. But it's far from beautiful. regards, Bertram ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Bytestrings and [Char]
Hello, I was recentyl playing with Haskell (GHC that is) IO and text processing. Bytestrings and Lazy Bytestrings allow for fast and memory eficient string (well, bytestring) handling, yet a lot of libraries do not support them (yet) Given the incredibly inneficient memory representation of [Char] (16 bytes? per cell) I wonder wheather String should default to lazy batestring altogether instead of [Char]. The levenshtein distance as is on hackage uses e.g. String ([Char]) and as such is unneccessarily slow. My question or discussion point: Why not depreciate [Char] altogether and favour of lazy Bytestrings? Regards, Johann ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bytestrings and [Char]
Johann Höchtl johann.hoec...@gmail.com writes: Bytestrings and Lazy Bytestrings allow for fast and memory eficient string (well, bytestring) handling, yet a lot of libraries do not support them (yet) WHat do you mean? A lot of libraries need to use String because it's easier to deal with and doesn't rely on knowing which encoding is being used. Bytestring is often nicer for IO, but for internal library stuff (e.g. parsing) it may still be easier to use String. Given the incredibly inneficient memory representation of [Char] (16 bytes? per cell) I wonder wheather String should default to lazy batestring altogether instead of [Char]. Well, then all pattern matching, etc. fails. String and ByteStrings have their own separate places and uses. The levenshtein distance as is on hackage uses e.g. String ([Char]) and as such is unneccessarily slow. Have you ported a version to ByteString and demonstrated that it is noticeably faster? Are you sure that it isn't the fault of the algorithm being used? Do you know that people only care about the levenshtein distance of ByteStrings and not of normal Strings? (Disclaimer: I've never even looked at the package.) Providing a ByteString version as well might be a viable option; replacing the current one is quite likely not. My question or discussion point: Why not depreciate [Char] altogether and favour of lazy Bytestrings? I believe I've answered this above. -- 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] Bytestrings and [Char]
On Mon, Mar 22, 2010 at 1:16 PM, Johann Höchtl johann.hoec...@gmail.com wrote: My question or discussion point: Why not depreciate [Char] altogether and favour of lazy Bytestrings? A sequence of bytes is not the same thing as a sequence of Unicode code points. If you want to replace String by something more efficient have a look at Data.Text. -- Johan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bytestrings and [Char]
On 23 March 2010 00:10, Johan Tibell johan.tib...@gmail.com wrote: A sequence of bytes is not the same thing as a sequence of Unicode code points. If you want to replace String by something more efficient have a look at Data.Text. Though Data.Text still has the disadvantage of not being as nice to deal with as String, since you can't pattern match on it, etc. Whilst it may degrade performance, treating String as a list of characters rather than an array provides you with greater flexibility of how to deal with it. -- 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] which version is in the platform
On the page: http://hackage.haskell.org/platform/ I am told that the platform includes ghc-6.10.4, but if I click there on the Haskell:batteries included link to get to the page: http://hackage.haskell.org/platform/contents.html its states there that I get 6.12.1? Doaitse ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] which version is in the platform
doaitse: On the page: http://hackage.haskell.org/platform/ I am told that the platform includes ghc-6.10.4, but if I click there on the Haskell:batteries included link to get to the page: http://hackage.haskell.org/platform/contents.html its states there that I get 6.12.1? The beta of the 2010.2.0.0 release is now up, which is based on GHC 6.12. The last stable Haskell Platform release is 2009.2.0.0, which used GHC 6.10.4. (And the windows installer currently up provides this version). -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] which version is in the platform
It seems that I am being served old pages by my web browser from the cache on my machine. By reloading the platform page, I suddenly am asked what system I do have, from weher I am referred to the 6.12 version of the platform, Doaitse On 22 mrt 2010, at 14:25, Don Stewart wrote: doaitse: On the page: http://hackage.haskell.org/platform/ I am told that the platform includes ghc-6.10.4, but if I click there on the Haskell:batteries included link to get to the page: http://hackage.haskell.org/platform/contents.html its states there that I get 6.12.1? The beta of the 2010.2.0.0 release is now up, which is based on GHC 6.12. The last stable Haskell Platform release is 2009.2.0.0, which used GHC 6.10.4. (And the windows installer currently up provides this version). -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] which version is in the platform
doaitse: It seems that I am being served old pages by my web browser from the cache on my machine. By reloading the platform page, I suddenly am asked what system I do have, from weher I am referred to the 6.12 version of the platform, Great! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANN: Three package announcements
There are three new packages on Hackage: - monad-parallel 0.5 (http://hackage.haskell.org/package/monad-parallel) - monad-coroutine 0.5 (http://hackage.haskell.org/package/monad-coroutine) - Streaming Component Combinators 0.5 (http://hackage.haskell.org/package/scc) The first two packages are completely new. Their functionality has been present in SCC 0.4, but I thought they might be useful on their own. I'm keeping all the version numbers in sync for now, and the source code for all three packages is in a single Darcs repository at http://code.haskell.org/SCC/. The monad-parallel library defines two Monad subclasses, MonadParallel and MonadFork, that enable monadic computations to be executed in parallel and their results combined. The library also exports a subset of the Control.Monad interface (ap, sequence, and related functions), adjusted to exploit the parallelism. The only currently defined MonadParallel instances are IO, Maybe, [], and Identity. More instances could be added, but I didn't want the package to depend on MTL or transformers. The library design was heavily influenced by the discussion in this Cafe thread: http://www.mail-archive.com/haskell-cafe@haskell.org/msg68581.html The monad-coroutine package exports a generic monad transformer Coroutine: Functor s = MonadTrans (Coroutine s). A Coroutine-transformed monad can suspend at any point, returning its resumption wrapped in the functor s. There are also some functions for manipulating and running coroutines, as well as a couple of useful suspension functors such as Yield and Await. Finally, version 0.5 of Streaming Component Combinators (a.k.a. SCC) comes with some significant code refactoring (as the two aforementioned packages prove), simplifications, and performance enhancements. No new features have been added since the 0.4 release. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] CUFP mailing list
Hi everyone, is there a mailing list for CUFP-lers? I have some questions that are related to commercial software development (in Haskell) which I don't think fit well on this list. Günther ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bytestrings and [Char]
On Mon, Mar 22, 2010 at 6:10 AM, Johan Tibell johan.tib...@gmail.comwrote: On Mon, Mar 22, 2010 at 1:16 PM, Johann Höchtl johann.hoec...@gmail.com wrote: My question or discussion point: Why not depreciate [Char] altogether and favour of lazy Bytestrings? A sequence of bytes is not the same thing as a sequence of Unicode code points. If you want to replace String by something more efficient have a look at Data.Text. Slight correction. A sequence of bytes is exactly the same thing as a sequence of Unicode bytes when you use UTF8. -- Johan ___ 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] Syntax programming with lexemes rather than trees?
Hello All Modern functional programming languages give you algebraic data types that are mighty convenient for programming with syntax trees. However, I'm working in a domain (music typesetting) where modelling syntax with trees can be problematic and I'm wondering whether I should work at a lower level - essentially a list / stream of lexemes and some notion of a context stack for processing, tracking when I'm inside a tuplet and the metrical calculation is scaled, for example. Does anyone know of any previous work that takes a lexical view of syntax rather than an abstract syntax tree view? Any domain is good - I can't imagine there's any prior work on music typesetting. Pointers to papers would be more digestible than code but either is fine. Similarly, implementation in any functional language is fine. Thanks Stephen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bytestrings and [Char]
David Leimbach wrote: On Mon, Mar 22, 2010 at 6:10 AM, Johan Tibell johan.tib...@gmail.com mailto:johan.tib...@gmail.com wrote: On Mon, Mar 22, 2010 at 1:16 PM, Johann Höchtl johann.hoec...@gmail.com mailto:johann.hoec...@gmail.com wrote: My question or discussion point: Why not depreciate [Char] altogether and favour of lazy Bytestrings? A sequence of bytes is not the same thing as a sequence of Unicode code points. If you want to replace String by something more efficient have a look at Data.Text. Slight correction. A sequence of bytes is exactly the same thing as a sequence of Unicode bytes when you use UTF8. What is a Unicode byte? Cheers, Jochem -- Jochem Berndsen | joc...@functor.nl ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] haskell platform questions
wren ng thornton w...@freegeek.org writes: I'm still on 10.5.8. I don't have cabal-install installed yet, but I just installed GHC-6.12.1/HP-2010.1.0.0. I can verify that ghci works fine so far. I'll check out cabal-install in the next couple days. If there is an issue here it'd be with the binaries that ship with the platform, not GHC; can you check /usr/local/bin/cabal to see if yours has the same issue? I'm betting I probably have to re-link the binaries with some magic don't break on Leopard linker flag. G -- Gregory Collins g...@gregorycollins.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: breadth first search one-liner?
Bertram Felgenhauer wrote: or bfs next start = lefts . takeWhile (not . null) I copied the wrong version. This should be bfs next start = rights . concat . takeWhile (not . null) -- rest unchanged . unfoldr (Just . span (either (const False) (const True)) . tail) $ fix (nub . (Left 0 :) . (Right start :) . (= either ((:[]) . Left . succ) (map Right . next))) Bertram ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Announce: Haskell Platform 2010.1.0.0 (beta) release
Live from (post-) Zurihac, I'm pleased to announce the 2010.1.0.0 (beta branch) release of the Haskell Platform, supporting GHC 6.12. http://hackage.haskell.org/platform/ The Haskell Platform is a comprehensive, robust development environment for programming in Haskell. For new users the platform makes it trivial to get up and running with a full Haskell development environment. For experienced developers, the platform provides a comprehensive, standard base for commercial and open source Haskell development that maximises interoperability and stability of your code. The 2010.1.0.0 release is a beta release for the GHC 6.12 series of compilers. It currently doesn't provide a Windows installer (which defaults to GHC 6.10.4 for now). We expect to make the stable branch with GHC 6.12.2 in soon. This release includes a binary installer for Mac OS X Snow Leopard, as well as source bundles for an Unix system, and a new design. The Haskell Platform would not have been possible without the hard work of the Cabal development team, the Hackage developers and maintainers, the individual compiler, tool and library authors who contributed to the suite, and the distro maintainers who build and distribute the Haskell Platform. Thanks! -- Don (for The Platform Infrastructure Team) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] RFC: only-read-or-write-vars
I wonder if this would be a place to add a function returning the pair
of the read and write capabilities (for the lack of a better word) of a
value.
something like:
rwPair:: v α - (ReadOnly v α , WriteOnly v α)
rwPair a = (readOnly a, writeOnly a)
sorry for the lame name, but my name game is off today.
This particular function comes handy when playing with passing channels
or pointers around. It might be worth it to have a dedicated type for
that as well.
What would this dedicated type look like?
Something along the lines of
* a type alias:
type ReadWrite v α = (ReadOnly v α , WriteOnly v α)
* or a data type:
data ReadWrite v α = ReadWrite {reader:: ReadOnly v α, writer::
WriteOnly v α }
The intent is to be able to recognise the available capabilities.
Then we could write a Link type, which is the sum of all four
possibilities and allowing pattern matching on capabilities. This is
similar to links in pi-calculus. I'm not sure if a link type should be
in your library though. My gut feeling is it should be in a separate
library, which implements a trusted kernel, which guarantees linearity -
i.e ReadOnly and WriteOnly to be used only once - either shallow,
guaranteeing that the projection can be taken only once, or deep
providing guarantees for 'proper' linearity. Sorry, I digress, that is a
pet subject I've been playing with on and off.
BTW thanks for pointing me to pointers! Of course a Ptr is also a
mutable variable so I've added instances for them.
Pleasure to be of help, even if it was by accident
Cheers,
Vlado
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Re: [Haskell-cafe] Syntax programming with lexemes rather than trees?
I'm working in a domain (music typesetting) where modelling syntax with trees can be problematic and I'm wondering whether I should work at a lower level - essentially a list / stream of lexemes and some notion of a context stack for processing, tracking when I'm inside a tuplet and the metrical calculation is scaled, for example. It sounds like your domain is generation of syntax, rather than parsing. It also sounds rather similar to the difference between the high-level language accepted by a compiler (represented by an AST) and the target language produced by a compiler (generally a flat list of almost-atomic instructions and labels). So maybe techniques for dealing with low-level assembly-like languages would be worth investigating. Regards, Malcolm ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Syntax programming with lexemes rather than trees?
Hi Malcolm Thanks - particularly I don't want to go to an AST because its I'm finding it too convoluted 'shape wise' - processing beam groups inside tuplets etc. is a nightmare - music representations have had at least eight centuries of ad hoc extension. I know Norman Ramsey and colleagues papers on low-level representations - I'll give them a re-reading. Thanks again Stephen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Strange typing?
Thank you all very much for the pointers. Best, On 22 March 2010 09:32, Gleb Alexeyev gleb.alex...@gmail.com wrote: Ozgur Akgun wrote: Is there any way to limit a functions type, not by a data type but by a group of constructors of a data type? If not, what would be the *right* thing to do to achieve this level of type safety? data DT1 = X | Y | Z data DT2 = A | B | C | D func1 :: DT1 - DT2 -- instead of this func1' :: (X|Y) - (B|C) -- i want sth. like this. (| means or) OCaml has a feature called 'polymorphic variants' that allows exactly this. You may want to google 'polymorphic variants in haskell'. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ozgur Akgun ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Hackape package lackage
Hackage seems to be down again. $ cabal update Downloading package list from server 'http://hackage.haskell.org/packages/archive' ^Ccabal: interrupted $ ping -c3 hackage.haskell.org PING abbot.galois.com (69.30.63.204) 56(84) bytes of data. --- abbot.galois.com ping statistics --- 3 packets transmitted, 0 received, 100% packet loss, time 2012ms ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bytestrings and [Char]
Turn on OverloadedStrings and you can pattern match on any type you like that is in the IsString class. Which means that Data.Text can use string literals just like regular strings (but you can't use Char literals in the match). On Mon, Mar 22, 2010 at 1:15 PM, Ivan Miljenovic ivan.miljeno...@gmail.com wrote: On 23 March 2010 00:10, Johan Tibell johan.tib...@gmail.com wrote: A sequence of bytes is not the same thing as a sequence of Unicode code points. If you want to replace String by something more efficient have a look at Data.Text. Though Data.Text still has the disadvantage of not being as nice to deal with as String, since you can't pattern match on it, etc. Whilst it may degrade performance, treating String as a list of characters rather than an array provides you with greater flexibility of how to deal with it. -- 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 mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hackape package lackage
We're watching *massive* traffic right now due to HP release. It's not down, just very very busy. For fun, here's a map of who's downloading Haskell: http://imgur.com/flwPF.png 74 countries in 12 hours, and counting. - Don dougal: Hackage seems to be down again. $ cabal update Downloading package list from server 'http://hackage.haskell.org/packages/archive' ^Ccabal: interrupted $ ping -c3 hackage.haskell.org PING abbot.galois.com (69.30.63.204) 56(84) bytes of data. --- abbot.galois.com ping statistics --- 3 packets transmitted, 0 received, 100% packet loss, time 2012ms ___ 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] Hackape package lackage
I'd love to see that map normalised by the population of the country – would be interesting to see where Haskell is popular. Bob On 22 Mar 2010, at 16:22, Don Stewart wrote: We're watching *massive* traffic right now due to HP release. It's not down, just very very busy. For fun, here's a map of who's downloading Haskell: http://imgur.com/flwPF.png 74 countries in 12 hours, and counting. - Don dougal: Hackage seems to be down again. $ cabal update Downloading package list from server 'http://hackage.haskell.org/packages/archive' ^Ccabal: interrupted $ ping -c3 hackage.haskell.org PING abbot.galois.com (69.30.63.204) 56(84) bytes of data. --- abbot.galois.com ping statistics --- 3 packets transmitted, 0 received, 100% packet loss, time 2012ms ___ 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
[Haskell-cafe] ANN: data-category, restricted categories
Hi everybody, At ZuriHac I released data-category. It is an implementation of several category-theoretical constructions. I started this library to learn about both category theory and type level programming, so I wanted to implement the CT concepts as directly as possible. This in contrast to the excellent category-extras library, which (I think) also tries to be as useful as possible. CT is about studying categories, so for data-category I wanted to implement all kinds of categories. The Control.Category module unfortunately requires you to implement id :: cat a a (for all a), which means it only supports categories that have exactly the same objects as Hask. So Data.Category contains an implementation of restricted categories, using inspiration from Oleg's restricted monads. It is well known that the Functor class also is a bit limited, as it only supports endofunctors in Hask. But there's another problem, if you want to define the identity functor, or the composition of 2 functors, then you have to use newtype wrappers, which can get in the way. Data.Category has an implementation of functors which solves this by using type families. Functors are represented by labels, and the type family F turns the label into the actual functor. F.e. type instance F List a = [a], type instance F Id a = a. The current version contains: - categories - Void, Unit, Pair (discrete categories with 0, 1 and 2 objects respectively) - Boolean - Omega, the natural numbers as an ordered set (ω) - Monoid - Functor, the category of functors from one category to another - Hask - Kleisli - Alg, the category of F-Algebras - functors - the identity functor - functor composition - the constant functor - the co- and contravariant Hom-functors - the diagonal functor - natural transformations - universal arrows - limits and colimits (as universal arrows from/to the diagonal functor) - using Void as index category this gives initial and terminal objects - f.e. in Alg the arrows from the initial object are catamorphisms - using Pair as index category this gives products and coproducts - f.e. in Omega they are the minimum and maximum and in Boolean and and or. - adjunctions Of course the are still a lot of things missing, especially in the details. And I'm a category theory beginner, so there will probably be some mistakes in there as well. F.e. Edward Kmett doesn't like () being the terminal object in Hask, which I thought I understood, but after thinking about it a bit more I don't. You can find data-category on hackage and on github: http://hackage.haskell.org/package/data-category http://github.com/sjoerdvisscher/data-category greetings, Sjoerd Visscher ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Zarathustra
Hi Cliff, here is a link which might interest you http://en.wikipedia.org/wiki/Zoroastrianism Love Günther ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: ANN: data-category, restricted categories
Hmm. What are benefits of data-category over category-extras? 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] Re: ANN: data-category, restricted categories
Mainly that category-extras doesn't have restricted categories, so most of the categories in data-category cannot be defined with category-extras. This also means that in category-extras many constructions are built from the ground up, instead of being built with a few basic building blocks, because that often requires a restricted category. But data-category certainly isn't meant as a replacement of category-extras. It is a totally different way of working with CT. On Mar 22, 2010, at 6:10 PM, Maciej Piechotka wrote: Hmm. What are benefits of data-category over category-extras? Regards ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Sjoerd Visscher http://w3future.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] haskell platform questions
BTW, I started to try the macports method (thinking that maybe building on my machine would resolve the linker problem), but the package up there seems to be the old one: $ port info haskell-platform haskell-platform @2009.2.0.2 (devel, haskell) Description: This is the the Haskell Platform: a single, standard Haskell distribution for every system. The Haskell Platform is a blessed library and tool suite for Haskell distilled from Hackage. Homepage: http://hackage.haskell.org/platform/ Runtime Dependencies: ghc, hs-platform-cgi, hs-platform-fgl, hs- platform-editline, hs-platform-GLUT, hs-platform-haskell-src, hs- platform-html, hs-platform-HUnit, hs-platform-mtl, hs-platform-network, hs-platform-OpenGL, hs-platform-parallel, hs- platform-parsec, hs-platform-QuickCheck, hs-platform-regex-base, hs- platform-regex-compat, hs-platform-regex-posix, hs-platform-stm, hs-platform-time, hs-platform-xhtml, hs- platform-zlib, hs-platform-HTTP, hs-platform-alex, hs-platform-happy, hs-platform-cabal Platforms:darwin License: unknown Maintainers: gwri...@macports.org Maybe the dependencies haven't changed? Also, not a big deal, but the instructions for the dmg version here http://hackage.haskell.org/platform/new/mac.html page say to follow the instructions, but there aren't any packaged with it. I mistakenly ran the Haskell Platform 2010.1.0.0 installer first thinking that maybe it would install ghc as a dependency, but this crashed. Then I uninstalled everything, installed GHC-6.12.1- i386.pkg, then Haskell Platform 2010.1.0.0, and rebooted... and then experienced the cabal problem. BTW, there's some description of linker flags here: http://discussions.apple.com/thread.jspa?threadID=2151112 but the developer claims 10.5.8 solved his problems (that's what I'm on). Warren On Mar 22, 2010, at 7:45 AM, Gregory Collins wrote: wren ng thornton w...@freegeek.org writes: I'm still on 10.5.8. I don't have cabal-install installed yet, but I just installed GHC-6.12.1/HP-2010.1.0.0. I can verify that ghci works fine so far. I'll check out cabal-install in the next couple days. If there is an issue here it'd be with the binaries that ship with the platform, not GHC; can you check /usr/local/bin/cabal to see if yours has the same issue? I'm betting I probably have to re-link the binaries with some magic don't break on Leopard linker flag. G -- Gregory Collins g...@gregorycollins.net ___ 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] haskell platform questions
Warren Harris warrensomeb...@gmail.com writes: Then I uninstalled everything, installed GHC-6.12.1- i386.pkg, then Haskell Platform 2010.1.0.0, and rebooted... and then experienced the cabal problem. BTW, there's some description of linker flags here: http://discussions.apple.com/thread.jspa?threadID=2151112 but the developer claims 10.5.8 solved his problems (that's what I'm on). Thanks, that's helpful. I'll cut a new release shortly. G -- Gregory Collins g...@gregorycollins.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] which version is in the platform
Don Stewart d...@galois.com writes: The beta of the 2010.2.0.0 release is now up, which is based on GHC 6.12. Hang on, you just announced 2010.1.0.0... have you suddenly released _another_ major version? :p -- 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] CUFP mailing list
Günther Schmidt wrote: I have some questions that are related to commercial software development (in Haskell) which I don't think fit well on this list. Really? This is haskell-cafe. If its even tangentially haskell related I'm sure this this list would be fine. According to http://www.haskell.org/haskellwiki/Mailing_Lists haskell-cafe@haskell.org (archives) General Haskell questions; extended discussions. In Simon Peyton Jones' words: forum in which it's acceptable to ask anything, no matter how naive, and get polite replies. 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] Bytestrings and [Char]
Hi David Leimbach wrote: On Mon, Mar 22, 2010 at 6:10 AM, Johan Tibell johan.tib...@gmail.com wrote: On Mon, Mar 22, 2010 at 1:16 PM, Johann Höchtl johann.hoec...@gmail.com wrote: My question or discussion point: Why not depreciate [Char] altogether and favour of lazy Bytestrings? A sequence of bytes is not the same thing as a sequence of Unicode code points. If you want to replace String by something more efficient have a look at Data.Text. Slight correction. A sequence of bytes is exactly the same thing as a sequence of Unicode bytes when you use UTF8. And a sequence of bytes is exactly the same thing as a UTF-32 string, when the sequence is encoded as UTF-32. But that is not the point. The point is that when some function is handed a ByteString, the ByteString can be encoded in many ways. It do not even have to be text. So you need a UTF-8 String type. /Mads -- Johan ___ 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 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
[Haskell-cafe] Software Deployment and Distribution - WAS Re: CUFP mailing list
Hello Erik, all right then. I've written a commercial Desktop application in Haskell for the Win32 platform. The one thing missing is Software Copy Protection, ie. a software licensing mechanism. When I google for Software Copy Protection I get a lot of results, commercial products themselves, which is fine, but I can't tell which ones are any good or worth their money. I've never seriously done C#, VB or whatever people mainly write Win32 apps in, so I don't know any mailing lista or forums where I could ask this question. This list has pretty much been the only list I used for more than 2 years now. I've never seen a similar issued raised here before so I thought the CUFP mailing list is a better place for this. Can anybody here recommend a good software for this then? I do not want to code it myself and would prefer a ready to use solution, it it's not free that fine too. Best regards Günther Am 22.03.10 22:23, schrieb Erik de Castro Lopo: Günther Schmidt wrote: I have some questions that are related to commercial software development (in Haskell) which I don't think fit well on this list. Really? This is haskell-cafe. If its even tangentially haskell related I'm sure this this list would be fine. According to http://www.haskell.org/haskellwiki/Mailing_Lists haskell-cafe@haskell.org (archives) General Haskell questions; extended discussions. In Simon Peyton Jones' words: forum in which it's acceptable to ask anything, no matter how naive, and get polite replies. Cheers, Erik ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Software Deployment and Distribution - WAS Re: CUFP mailing list
Günther Schmidt wrote: I've written a commercial Desktop application in Haskell for the Win32 platform. The one thing missing is Software Copy Protection, ie. a software licensing mechanism. When I google for Software Copy Protection I get a lot of results, commercial products themselves, which is fine, but I can't tell which ones are any good or worth their money. I've never seriously done C#, VB or whatever people mainly write Win32 apps in, so I don't know any mailing lista or forums where I could ask this question. This list has pretty much been the only list I used for more than 2 years now. I've never seen a similar issued raised here before so I thought the CUFP mailing list is a better place for this. Can anybody here recommend a good software for this then? I do not want to code it myself and would prefer a ready to use solution, it it's not free that fine too. Well that certainly is an unusual question. There are large companies like Apple, the RIAA and the MPAA who have put large amounts of time, money and effort into copy protection schemes only to have them broken, sometimes in as little as a day or two. In addition, by the time you have a copy control mechanism that is partially effective your users may find the experience so painful that using cracked copies is easier. There is a common theme here: http://i.imgur.com/GxzeV.jpg http://www.bradcolbow.com/archive.php/?p=205 http://xkcd.com/488/ 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] Software Deployment and Distribution - WAS Re: CUFP mailing list
Fundamentally, Software Copy Protection (as well as DRM) is an unsolvable problem. It's basically like saying that you want to give someone something and not give it to them at the same time. With physical products there are physical properties that you can use to accomplish some aspects of this. But with information products and the possibility of essentially zero-cost copying you don't have these physical constraints to help you. Copy Protection (CP) and DRM advocates have tried to use cryptography to solve this problem. The idea being that cryptography lets you hide information from people, so it should be able to help with this problem. Encryption allows Alice and Bob to communicate secretly without Eve, Mallet, etc from being able to read their communication. This is all predicated on the idea that Alice and Bob trust each other. (I'm only going to reveal my secrets to you if I trust that you're not going to publish them for others to read.) The problem that CP (Alice) is up against is that Bob and Eve are the same person! If you can't trust the person to whom you're sending something, then the only secure solution is not to send it to them. This can be done by delivering software that simply doesn't have certain capabilities. You typically can't just disable the capabilities in your software. You have to ensure that the code implementing those capabilities is not present. Software as a service is another solution to this problem. On Mon, Mar 22, 2010 at 6:09 PM, Erik de Castro Lopo mle...@mega-nerd.com wrote: Günther Schmidt wrote: I've written a commercial Desktop application in Haskell for the Win32 platform. The one thing missing is Software Copy Protection, ie. a software licensing mechanism. When I google for Software Copy Protection I get a lot of results, commercial products themselves, which is fine, but I can't tell which ones are any good or worth their money. I've never seriously done C#, VB or whatever people mainly write Win32 apps in, so I don't know any mailing lista or forums where I could ask this question. This list has pretty much been the only list I used for more than 2 years now. I've never seen a similar issued raised here before so I thought the CUFP mailing list is a better place for this. Can anybody here recommend a good software for this then? I do not want to code it myself and would prefer a ready to use solution, it it's not free that fine too. Well that certainly is an unusual question. There are large companies like Apple, the RIAA and the MPAA who have put large amounts of time, money and effort into copy protection schemes only to have them broken, sometimes in as little as a day or two. In addition, by the time you have a copy control mechanism that is partially effective your users may find the experience so painful that using cracked copies is easier. There is a common theme here: http://i.imgur.com/GxzeV.jpg http://www.bradcolbow.com/archive.php/?p=205 http://xkcd.com/488/ 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] Software Deployment and Distribution - WAS Re: CUFP mailing list
Hi Günther Congratulations! You might find this article useful. Though it only mentions one particular system Armadillo, there are a number of good tips like releasing updates frequently so the binaries change, and the author is well regarded in micro software circles. http://www.kalzumeus.com/2006/09/05/everything-you-need-to-know-about-registration-systems/ GHC binaries do contain quite a lot of textual information. Where functions work with registration codes you ought to cloak their names and maybe add a dummy API to throw crackers off the scent. Best wishes Stephen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Graphical representation of Haskell code
Hello, I’m relatively new to Haskell. I’m wondering if it exist a tool to graphically represent Haskell code. Look at the little graphics at: http://www.haskell.org/arrows/index.html (and following pages) from Ross Paterson. http://www.haskell.org/arrows/index.htm If found these very useful to understand the Arrow monad. Why not automatise this in a tool? Such a tool could draw a graphic from the code of a program. This could be done entirely automatically from the types of the functions. Let’s try to do it on a simple example, as an exercise: f = Map (+1) How does this function could be represented? It contains the (+) function. This function has the type (+) :: Num a = a - a - a. From this type we could deduce the graphic: [image: Haskell schematic_html_m20060f13.gif] Or a curried version: [image: Haskell schematic_html_5155f0eb.gif] The function (+1) then is: [image: Haskell schematic_html_m68795eb7.gif] The function map could be drawn like this : [image: Haskell schematic_html_m28c92a58.gif] Or like this: [image: Haskell schematic_html_m6ae433ea.gif] And the entire function map (+1) could be represented as: [image: Haskell schematic_html_macb1643.gif] Thanks to the advanced type system of Haskell, everything could be deduced from the type signatures. Such a tool would be recreational and educational. One could zoom in and out in a program, to display more or less details. This could help understand a program, globally or locally. We could even imagine a constructive version of the tool, where the programmer would draw functions from a toolbox, and stick them into the graphic! Does a tool approaching this already exist? If not, would it be a good project? Cheers, Corentin Haskell schematic_html_m28c92a58.gifHaskell schematic_html_m6ae433ea.gifHaskell schematic_html_m68795eb7.gifHaskell schematic_html_macb1643.gifHaskell schematic_html_m20060f13.gifHaskell schematic_html_5155f0eb.gif___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Graphical representation of Haskell code
On 23 March 2010 10:02, Dupont Corentin corentin.dup...@gmail.com wrote: I’m relatively new to Haskell. Welcome! I’m wondering if it exist a tool to graphically represent Haskell code. Look at the little graphics at: http://www.haskell.org/arrows/index.html (and following pages) from Ross Paterson. If found these very useful to understand the Arrow monad. Why not automatise this in a tool? Such a tool could draw a graphic from the code of a program. 1) Because no-one has written such a tool yet (though someone has suggested doing one as a GSoC project). 2) I'm of the opinion that unless you just use it on small snippets, the generated images will be too large and unweildy. This could be done entirely automatically from the types of the functions. Except not everyone provides type signatures for their functions; whilst it may be possible to use the GHC API to infer these type signatures, my understanding is that it's preferable to use other parsers such as haskell-src-exts as the GHC API is unstable. [shameless plug] My SourceGraph (http://hackage.haskell.org/package/SourceGraph) tool does function call visualisation as part of its analyses. [/shameless plug] -- 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] Re: Software Deployment and Distribution - WAS Re: CUFP mailing list
Hello Erik, the software I wrote and am about to sell was developed for use by German Hospitals only. It's being used to calculate a departments share of the revenues paid by the insurance companies for a case and needed every 6 months by the hospitals when it enters budget negotiations with the insurance companies. It could for instance not be used by Hospitals outside of Germany. I think it is unlikely that the Hospitals would try to hack my application but thanks for the concern. But I do need something in place, something that will check if the hospital is using a licensed version. It is also expected on the customers side otherwise the customer would not even consider using the software but reject it outright. Best regards Günther ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Software Deployment and Distribution - WAS Re: CUFP mailing list
Günther Schmidt wrote: Hello Erik, the software I wrote and am about to sell was developed for use by German Hospitals only. It's being used to calculate a departments share of the revenues paid by the insurance companies for a case and needed every 6 months by the hospitals when it enters budget negotiations with the insurance companies. It could for instance not be used by Hospitals outside of Germany. I think it is unlikely that the Hospitals would try to hack my application but thanks for the concern. Since the number of people wanting to use your application is small, even the most primitve copy protection mechanisms would probably suffice. 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] Graphical representation of Haskell code
Reminds me of To Dissect a Mockingbird [http://dkeenan.com/Lambda/]. On Tue, Mar 23, 2010 at 7:12 AM, Ivan Miljenovic ivan.miljeno...@gmail.com wrote: On 23 March 2010 10:02, Dupont Corentin corentin.dup...@gmail.com wrote: I’m relatively new to Haskell. Welcome! I’m wondering if it exist a tool to graphically represent Haskell code. Look at the little graphics at: http://www.haskell.org/arrows/index.html (and following pages) from Ross Paterson. If found these very useful to understand the Arrow monad. Why not automatise this in a tool? Such a tool could draw a graphic from the code of a program. 1) Because no-one has written such a tool yet (though someone has suggested doing one as a GSoC project). 2) I'm of the opinion that unless you just use it on small snippets, the generated images will be too large and unweildy. This could be done entirely automatically from the types of the functions. Except not everyone provides type signatures for their functions; whilst it may be possible to use the GHC API to infer these type signatures, my understanding is that it's preferable to use other parsers such as haskell-src-exts as the GHC API is unstable. [shameless plug] My SourceGraph (http://hackage.haskell.org/package/SourceGraph) tool does function call visualisation as part of its analyses. [/shameless plug] -- 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 mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] haskell platform questions
Gregory Collins wrote: wren ng thornton w...@freegeek.org writes: I'm still on 10.5.8. I don't have cabal-install installed yet, but I just installed GHC-6.12.1/HP-2010.1.0.0. I can verify that ghci works fine so far. I'll check out cabal-install in the next couple days. If there is an issue here it'd be with the binaries that ship with the platform, not GHC; can you check /usr/local/bin/cabal to see if yours has the same issue? w...@semiramis:~ $ ls /usr/local ls: /usr/local: No such file or directory w...@semiramis:~ $ ls /usr/bin/cabal ls: /usr/bin/cabal: No such file or directory But http://hackage.haskell.org/platform/new/contents.html tells me cabal-install is supposed to ship with the platform... -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] haskell platform questions
On 23 March 2010 14:25, wren ng thornton w...@freegeek.org wrote: w...@semiramis:~ $ ls /usr/local ls: /usr/local: No such file or directory w...@semiramis:~ $ ls /usr/bin/cabal ls: /usr/bin/cabal: No such file or directory But http://hackage.haskell.org/platform/new/contents.html tells me cabal-install is supposed to ship with the platform... It is; where did you install it to though? Does whereis cabal say anything? -- 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] Graphical representation of Haskell code
I've proposed to do it at this GSOC. More exactly, it is still in the feedback phase, I'll integrate all feedback in another blog post and in an application for GSOC tomorrow. If you want to read about it in this stage, you can visit my blog [0]. Feedback on reddit can be seen here[1]. The pictures from Ross Paterson were one of the reasons for my idea. [0]: http://pgraycode.wordpress.com/2010/03/20/haskell-project-idea/ [1]: http://www.reddit.com/r/haskell/comments/bg3bx/i_need_feedback_on_a_haskell_project_idea_maybe/ -- Mihai Maruseac On Tue, Mar 23, 2010 at 1:02 AM, Dupont Corentin corentin.dup...@gmail.comwrote: Hello, I’m relatively new to Haskell. I’m wondering if it exist a tool to graphically represent Haskell code. Look at the little graphics at: http://www.haskell.org/arrows/index.html (and following pages) from Ross Paterson. http://www.haskell.org/arrows/index.htm If found these very useful to understand the Arrow monad. Why not automatise this in a tool? Such a tool could draw a graphic from the code of a program. This could be done entirely automatically from the types of the functions. Let’s try to do it on a simple example, as an exercise: f = Map (+1) How does this function could be represented? It contains the (+) function. This function has the type (+) :: Num a = a - a - a. From this type we could deduce the graphic: [image: Haskell schematic_html_m20060f13.gif] Or a curried version: [image: Haskell schematic_html_5155f0eb.gif] The function (+1) then is: [image: Haskell schematic_html_m68795eb7.gif] The function map could be drawn like this : [image: Haskell schematic_html_m28c92a58.gif] Or like this: [image: Haskell schematic_html_m6ae433ea.gif] And the entire function map (+1) could be represented as: [image: Haskell schematic_html_macb1643.gif] Thanks to the advanced type system of Haskell, everything could be deduced from the type signatures. Such a tool would be recreational and educational. One could zoom in and out in a program, to display more or less details. This could help understand a program, globally or locally. We could even imagine a constructive version of the tool, where the programmer would draw functions from a toolbox, and stick them into the graphic! Does a tool approaching this already exist? If not, would it be a good project? Cheers, Corentin ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe Haskell schematic_html_m6ae433ea.gifHaskell schematic_html_5155f0eb.gifHaskell schematic_html_m68795eb7.gifHaskell schematic_html_macb1643.gifHaskell schematic_html_m28c92a58.gifHaskell schematic_html_m20060f13.gif___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Graphical representation of Haskell code
On Mon, Mar 22, 2010 at 7:02 PM, Dupont Corentin corentin.dup...@gmail.com wrote: Hello, I’m relatively new to Haskell. I’m wondering if it exist a tool to graphically represent Haskell code. ... Let’s try to do it on a simple example, as an exercise: f = Map (+1) Your graphic for f = map (+1) seems much more complex than the corresponding code. I would agree with Ivan Miljenovic: I'm of the opinion that unless you just use it on small snippets, the generated images will be too large and unwieldy. The first question I would ask is /why/ would you like to visualize some Haskell code? If you want to see the high-level structure of a complex program, try SourceGraph. (I have never used it though.) On the other hand, if you are trying to visualize Haskell as part of your efforts to learn the language, then I believe it would be best to draw diagrams by hand, rather than relying on an automated tool. The kinds of things that you'll want to depict are probably going to vary considerably, depending on what you're trying to understand. Consider a few different implementations of the map function: -- version 1: recursion map1 :: (a - b) - [a] - [b] map1 f [] = [] map1 f (x:xs) = (f x) : map1 f xs -- version 2: fold map2 :: (a - b) - [a] - [b] map2 f = foldr ((:) . f) [] -- version 3: continuation passing style map3 :: (a - b) - [a] - [b] map3 f xs = map' (\x y - f x : y) xs where map' k [] = [] map' k (y:ys) = k y (map' k ys) -- version 4: list comprehension map4 :: (a - b) - [a] - [b] map4 f xs = [f x | x - xs] -- version 5: list monad map5 :: (a - b) - [a] - [b] map5 f xs = xs = (return . f) These all do exactly the same thing, but each one uses different techniques. If I'm trying to learn (or teach) Haskell, I would probably need a slightly different visual language for each one in order to capture the most relevant concepts in a useful way. How would you visualize them? @Mihai Maruseac: I think a visual debugger would be a wonderful idea. You may want to consider how a visual debugger would work with each of these versions of map. :-) You might also consider several versions of factorial :-) http://www.willamette.edu/~fruehr/haskell/evolution.html -- Ron ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] which version is in the platform
ivan.miljenovic: Don Stewart d...@galois.com writes: The beta of the 2010.2.0.0 release is now up, which is based on GHC 6.12. Hang on, you just announced 2010.1.0.0... have you suddenly released _another_ major version? :p 2010.1.0.0 is definited as a 'beta' for 2010.2 http://trac.haskell.org/haskell-platform/wiki/VersionNumbers ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
