Re: [Haskell-cafe] [haskell.org Google Summer of Code 2013] Approved Projects
Edward Kmett ekmett at gmail.com writes: * Haskell Qt Binding Generator by Zhengliang Feng, mentored by Carter Schonwald with help from Ian-Woo Kim Interesting, as this has been done at least twice before. Is there a public write-up of what's going to be different this time? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Install wx on Windows XP
On Tue, 26 Mar 2013 08:58:18 +0100, Eric Wong wsysdu at gmail.com wrote: The best way to do this, is to download from https://github.com/atzedijkstra/wxHaskell . (This is the most up to date repository online.) Then replace the wxcore\Setup.hs file with the one attached to this e-mail (this has not been tested on non-Windows platforms). Install all wxHaskell packages from this repository, in the following order: wxdirect wxc wxcore wx I tried that on the latest HP, and it insisted on downloading the old version of wxdirect to sovle some dependency in wxcore, then rebuild wxc against it, and got back to the old problems. Is there going to be a new release on hackage with the fixes? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [haskell.org Google Summer of Code 2013] Approved Projects
Edward Kmett ekmett at gmail.com writes: There should be a link from the google-melange website, but one slight shift in focus is on either getting SWIG bindings or possibly even using Ian-Woo Kim's C++FFI tools. Carter may be able to go into more detail. There's almost no information in the google project abstract. My concern is that the problem isn't generating the bindings (as I've said, that's been done twice before). It's that Qt's slots-and-signals are horrible to use from the Haskell side. If the student hasn't already got a good idea of how to solve this, I fear that this project will be just generate another unusable set of bindings. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: Haskell Platform 2013.2.0.0
Good to see it released! Was there a deliberate decision not to build a Windows x64 platform, or is it just that there wasn't anyone to do it? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Infrastructure for testing the impact of a Functor/Applicative/Monad hierarchy
Niklas Hambüchen mail at nh2.me writes: Reading the other thread (Adding Applicative/Functor instances to all Monads in GHC) I was wondering if there was infrastructure for testing what effect making the often-discussed Functor/Monad change would have: How many packages on hackage would break etc. Some patches for GHC/base are attached to http://hackage.haskell.org/trac/ghc/ticket/4834. They're a couple of years old, so they may not apply cleanly, but they might help you in assessing the impact of such a change. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Release Candidates for Haskell Platform 2013.2
Mark Lentczner mark.lentczner at gmail.com writes: Some of the release candidates for Haskell Platform 2013.2 are up.These are what I expect to simply re-brand as the release, unless anyone uncovers some issues. Will they go on http://trac.haskell.org/haskell-platform/wiki/ReleaseCandidates? (http://trac.haskell.org/haskell-platform/ has a few outdated links. Does anyone know what the current links are for the documentation sections?) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Interfacing Java/Haskell
Hans Georg Schaathun georg+haskell at schaathun.net writes: Does anyone have experience with integrating Haskell and Java? I have done some searching, finding a lot of pointers but hardly anything in terms of evaluation, successes, or caveats. From what I see Frege looks promising, arguably not haskell I suppose, but does it work? Other projects I have seen appear to have reached a stand-still for ages. EclipseFP uses Haskell and Java processes talking to each other in JSON. That's the route which successful multi-lingual projects generally seem to go. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why were datatype contexts removed instead of fixing them?
Dan Doel dan.doel at gmail.com writes: However, another thing to consider is that getting rid of data type contexts was accepted into the language standard. ... which means that implementers should be free to fix data type contexts however they like, as they are now complier extensions which won't conflict with standard Haskell. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Why were datatype contexts removed instead of fixing them?
If I understand correctly, the problem with datatype contexts is that if we have e.g. data Eq a = Foo a = Foo a the constraint Eq a is thrown away after a Foo is constructed, and any method using Foos must repeat Eq a in its type signature. Why were these contexts removed from the language, instead of fixing them? PS This is following up on a discussion on haskell-beginners, How to avoid repeating a type restriction from a data constructor. I'm interested in knowing whether there's a good reason not to allow this, or if it's just a consequence of the way type classes are implemented by compilers. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why were datatype contexts removed instead of fixing them?
Kim-Ee Yeoh ky3 at atamo.com writes: data Foo a where Foo :: Eq a = a - Foo a is equivalent to data Foo a = Eq a = Foo a but is different from data Eq a = Foo a = Foo a ... and nothing in GADTs does what one would naively expect the last declaration to do. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why were datatype contexts removed instead of fixing them?
Brandon Allbery allbery.b at gmail.com writes: As I understand it, it's because fixing them involves passing around a dictionary along with the data, and you can't do that with a standard declaration (it amounts to an extra chunk of data that's only *sometimes* wanted, and that sometimes complicates things). GADTs already have to pass around extra data in order to support their constructors and destructors; and, being new and not part of the standard, they don't have backward compatibility or standards compatibility issues, so they can get away with including the extra dictionary without breaking existing programs. But you can't do this with GADTs either? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is there a generic way to detect mzero?
Jeff, I don't think your code works in general, since it is not guaranteed that x' == mzero is allowed unless (m b) is an instance of Eq. I'm unsure if you are able to test for mzero in general. Harry On Mon, Mar 26, 2012 at 3:11 PM, Jeff Shaw shawj...@msu.edu wrote: can :: (MonadPlus m) = (a - m b) - a - Bool can f x = case f x of mzero - False _ - True I got a warning: __testError.hs:31:11: Warning: Pattern match(es) are overlapped In a case alternative: _ - ... Ok, modules loaded: Main. The problem here is that when you match on f x, your first match is an identifier that matches anything at all, and binds it to mzero. I think what you're looking for is can f x = case f x of x' | x' == mzero - False _ - True Jeff __**_ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/**mailman/listinfo/haskell-cafehttp://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] Comparing programs
This is more of an algorithm question than a language question, but any insights would be much appreciated. The problem is to input a series of programs and find previous occurrences of the same algorithm. The programs consist of a set of input parameters (a, b, c, ...), and a set of side-effect-free functions (f, g, h, ...). Since the functions are side-effect-free, they can be reordered without changing the algorithm (f(a), g(b) is the same as g(b), f(a)). Subsequent calls of the same function with the same parameters have no effect (f(a), f(a) is the same as f(a)); in fact, you can assume duplicates have been removed in earlier processing. But here's the thing that makes it hard (at least for me): two programs are considered the same if they can be made to match by rearranging the order of the input parameters. I.e., f(a), g(b) is the same as f(b), g(a). Although parameters can be reordered, they cannot be substituted (f(a), g(b) is _not_ the same as f(a), g(a)). Example: f(a), g(b), h(a, b) is the same as f(b), g(a), h(b, a) but _not_ the same as f(a), g(b), h(b, a). I need a way to compare the input programs, and preferably to order them. In Haskell terms, given the programs are represented by a type Prog, I want Prog to be a member of class Ord, letting me use tools like Data.Map to look up information about previous instances. I can do a brute-force compare by trying all the parameter permutations, but that only gives me Eq, not Ord, and seems terribly inelegant as well. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
