- Haskell-Cafe - Haskell.org

Benchmarks for graph algorithms
by damodar kulkarni 06 Oct '12

06 Oct '12

Hi cafe, Where do Haskell and DPH stand in comparison to C/OpenMP w.r.t. graph algorithms? Are benchmarks for graph algorithms available for Haskell like the ones we find at http://www.graphanalysis.org/benchmark/? - Damodar

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referential transparency? (for fixity of local operators)
by Johannes Waldmann 06 Oct '12

06 Oct '12

I was really surprised at the following: *Main> 1 + 2 * 3 7 *Main> ( \ (+) (*) -> 1 + 2 * 3 ) (+) (*) 9 because I was somehow assuming that either a) the Prelude fixities of the operators are kept b) or they are undefined, so the parser rejects. but the Haskell standard says "Any operator lacking a fixity declaration is assumed to be infixl 9". This really should be "infix 9"?

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does try force evaluation of IO value
by s9gf4ult＠gmail.com 05 Oct '12

05 Oct '12

if i have some lazy io action, assuming (maction :: IO a) which may raise exceptions while running, will "try" force evaluation of "a" to determine is exception raised or not ? Sorry for my broken english.

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Windows - Creating FreeGLUT DLL
by Thiago Negri 05 Oct '12

05 Oct '12

I'm trying OpenGL on Haskell and couldn't create the FreeGLUT DLL myself. I did follow this tutorial: http://netsuperbrain.com/blog/posts/freeglut-windows-hopengl-hglut/ But when I put my DLL on the folder of the binary, it complains about "initGlut". Using the DLL pointed by FreeGLUT official site, created by other person, works fine. I don't know what I did wrong. Anyone had this problem? Thanks.

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Re: [Haskell-cafe] ANNOUNCE: test-framework-golden-1.1
by Roman Cheplyaka 05 Oct '12

05 Oct '12

* Janek S. <fremenzone(a)poczta.onet.pl> [2012-10-05 11:50:53+0200] > > Cool, looking forward to reading it! > Well, the post is already finished: > http://ics.p.lodz.pl/~stolarek/blog/2012/10/code-testing-in-haskell/ > I was just going to publish it and then your email came up on the list. > > > I hope you won't forget to cover SmallCheck in your article as well. > > Being also the maintainer of SmallCheck, I want it to steal some fame > > from QuickCheck :) > Sorry to disappoint you, but I did not mention SmallCheck. So far I'm relying on QuickCheck and > didn't feel like I need to look for other testing library. I might be wrong of course. There are some technical advantages to SmallCheck (determinism, no need to shrink etc.), but the main reason I prefer it is because it gives me more confidence. With quickcheck, I know that it generated 100 tests, but I've no idea what those tests are, and whether the RNG missed some important corner cases. With SmallCheck I know that it tried *all* cases up to certain depth, so it's much more reassuring. (Except for cases when the notion of depth isn't that informative, like floating-point numbers.) Roman

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Re: [Haskell-cafe] ANNOUNCE: test-framework-golden-1.1
by Roman Cheplyaka 05 Oct '12

05 Oct '12

* Tim Docker <tim(a)dockerz.net> [2012-10-05 12:19:40+1000] > Hi Roman, > > This sounds like a great idea. As you suggest, I've put this kind of > thing together in scripts many times, without a consistent framework. > > I haven't tried it yet, but have one question. When you call a > function like > > goldenVsString > > I assume one generally provides a relative path. what is the file > path relative to? How does one arrange a package of haskell code and > associated golden files, and reference the golden files from within > the haskell so that the tree works from any location? The paths are naturally relative to the working directory of the test executable. In my projects, I typically have ./test.hs ./tests/case1.golden ./tests/case2.golden ./tests/case3.golden And so test.hs refers to test cases by relative paths like "tests/case1.golden". Of course, that'll only work if you run test.hs from its directory, but it is the case most of the time anyway. Also, since paths are relative to the directory containing the project.cabal file, "cabal test" works, too. If, for some reason, you want to be able to run tests from any location, you could provide the path to golden paths e.g. via an environment variable. Roman > On 05/10/12 07:55, Roman Cheplyaka wrote: > >I am glad to announce the first public release of test-framework-golden — a > >golden testing library. > > > >Hackage: http://hackage.haskell.org/package/test-framework-golden > >GitHub: https://github.com/feuerbach/test-framework-golden > > > >Golden tests are similar to unit tests (as implemented in HUnit), but the idea > >is to store the expected result in files (called «golden» files). > > > >I was introduced to the idea of golden testing by Bohdan Vlasyuk at ZuriHac in > >2010. Since then I've discovered that this is a nice approach and it is already > >used in variety of projects (e.g. ghc, haddock). > > > >Surprisingly, not much is written about golden testing, and I've been unable to > >find any golden testing libraries for Haskell or any other programming language. > >Every project has its own ad-hoc implementation in Haskell/Python/Shell/etc. > > > >The closest match on the market is Simon Michael's shelltestrunner. But to use > >it you have to expose the tested functionality via command line, which may be > >inconvenient. > > > >So this is my attempt at a general golden testing library. > > > >It consists of two modules. > >Test.Golden has a simple interface that helps you get started very quickly. > >Test.Golden.Advanced provides a very generic testing function that you can use > >to implement the testing system you dream about. > > > >The library is integrated with test-framework, so you can use golden tests in > >addition to SmallCheck/QuickCheck/HUnit tests. > > > >In future there's a plan to support some golden test management capabilities. > > > >Roman > > > >_______________________________________________ > >Haskell-Cafe mailing list > >Haskell-Cafe(a)haskell.org > >http://www.haskell.org/mailman/listinfo/haskell-cafe >

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Which advanced Haskell topics interest you
by Manuel M T Chakravarty 04 Oct '12

04 Oct '12

Most existing Haskell books and similar teaching material is aimed at programmers who are new to Haskell. This survey is to assess the community interest in teaching material covering advanced topics beyond the commonly taught introductory material. https://docs.google.com/spreadsheet/viewform?formkey=dE1QZFNRLTFMdkllYWIyR2… Manuel

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Re: [Haskell-cafe] Creating Repa arrays from unboxed vectors
by Janek S. 04 Oct '12

04 Oct '12

Thanks! > This makes it look like you've got two versions of vector installed, This is true, I have vector-0.9.1 and vector-0.10, but > with Repa built against the version that _isn't_ 0.9.1. this, I think, is not exactly correct: [root@GLaDOS : /dane/download] ghc-pkg field repa depends depends: QuickCheck-2.4.2-41cb2884cc20cd78948de62849bd9667 base-4.5.0.0-6db966b4cf8c1a91188e66d354ba065e bytestring-0.9.2.1-18f26186028d7c0e92e78edc9071d376 ghc-prim-0.2.0.0-c2ff696e5b8ec4d4b2bc2e42085fe471 template-haskell-2.7.0.0-133c0fdb189e05de22bd926d39f99fe3 vector-0.9.1-04dd5c58c224b03a4dc90091cf93a01d So Repa is build againts 0.9.1. Everything works when I do "ghc-pkg hide vector-0.10.0". Is there a way to tell GHCi which version of library it should load? I tried -XPackageImports but it doesn't allow to specify version of a package, only its name (or I don't know how to specify version). Jan

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What is a functional approach to linear algebra routines? I see REPA warns that one must use fusion or risk slow routines.
by KC 04 Oct '12

04 Oct '12

Apparently using STUarrays in an imperative fashion is fraught with peril (and the performance of molasses). Casey -- -- Regards, KC

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HaskellDB Convertible Exception: incompatible types
by Andras Gyomrey 04 Oct '12

04 Oct '12

Hi, I get *** Exception: Convertible: error converting source data SqlLocalTime 2012-04-27 10:22:15 of type SqlValue to type Data.Time.LocalTime.LocalTime.ZonedTime: incompatible types when i try to show a record with a field of type CalendarTime (automatically generated by Database.HaskellDB.DBDirect, Mysql database type is "timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP" I already looked forhttp:// haskell.1045720.n5.nabble.com/programmatic-DB-interface-td3120759.html. But the problem there is about a regexp (not a type). And the incompatible type problem was caused because of a concatenation. Here, as you can see, i have no idea what's going on. Can someone please help me? Andras

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