July 2009 - Haskell-Cafe

List spine traversal
by Tony Morris 01 Jul '09

01 Jul '09

Is there a canonical function for traversing the spine of a list? I could use e.g. (seq . length) but this feels dirty, so I have foldl' (const . const $ ()) () which still doesn't feel right. What's the typical means of doing this? -- Tony Morris http://tmorris.net/

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gtk2hs tray icon disappears when using GHCi
by Deniz Dogan 01 Jul '09

01 Jul '09

Hi I'm just trying out gtk2hs for the first time and I quite like it. However, for some reason my tray icon (...Gtk.Display.StatusIcon) disappears after a split second when I run my program using GHCi. What's the reason for this? Perhaps this is even a bug? It works just fine if I compile an .exe. I'm using Windows XP with GHC 6.10.3 and gtk2hs 0.10.1. import Graphics.UI.Gtk import Graphics.UI.Gtk.Display.StatusIcon main :: IO () main = do initGUI window <- windowNew tray <- statusIconNewFromFile "c:/Program Files/TortoiseHg/icons/commit.png" window `onDestroy` mainQuit widgetShowAll window mainGUI -- Deniz Dogan

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Haskell on JVM
by Greg Meredith 30 Jun '09

30 Jun '09

Simon, et al, It might be interesting to look at CAL<http://labs.businessobjects.com/cal/>as a non-blank-slate beginning for Haskell on the JVM. To my mind there are three things that this needs to make it a real winner: - Much, much better Java interop. Basically, the bar to meet here is Scala/Java interop. - Better support for "std" Haskell syntax - and better support for some of the basic (semantic and syntactic) extensions - Figuring out what of Hackage it is reasonable to support Best wishes, --greg Date: Tue, 23 Jun 2009 15:16:03 +0100 > From: Simon Peyton-Jones <simonpj(a)microsoft.com> > Subject: RE: [Haskell-cafe] Haskell on the iPhone > To: Rick R <rick.richardson(a)gmail.com>, Haskell Cafe > <haskell-cafe(a)haskell.org> > Message-ID: > < > 638ABD0A29C8884A91BC5FB5C349B1C33F4BAAFA41(a)EA-EXMSG-C334.europe.corp.microsoft.com > > > > Content-Type: text/plain; charset="us-ascii" > > Good news about the iPhone port! > > There seems to be quite a bit more interest now in supporting platforms > other than win/*nix on x86 these days*. Maybe now there will be sufficient > motivation to make the fundamental changes required. Caveat: I have > absolutely no idea of the scope or complexity of said changes. I will look > through the LambdaVM code (and iPwn when available) to get an idea. > > There is definitely an opportunity here for someone to make an impact. > There is no reason in principle why Haskell can't run on a JVM or .net or > other platform. But it's not just a simple matter of absorbing some patch > or other. Here's a summary I wrote a little while ago: > > http://haskell.org/haskellwiki/GHC:FAQ#Why_isn.27t_GHC_available_for_.NET_o… > > The short summary is: > > * There is interesting design work to do; and then interesting > engineering work to make it a reality. > > * We (at GHC HQ) would love to see that happen, but are not likely > to drive it. > > * If someone, or a small group, wanted to take up the cudgels and > work on it, we'd be happy to advise. > > * We'd certainly consider folding the results into the HEAD, > provided the author(s) are willing to maintain it, and we feel that the > result is comprehensible and maintainable. > > * But another viable route might well be to use the GHC API, which > means that the result wouldn't be part of GHC at all, just a client of the > API. That would make it much easier to distribute upgrades etc, just as a > Cabal package. > > Simon > -- L.G. Meredith Managing Partner Biosimilarity LLC 1219 NW 83rd St Seattle, WA 98117 +1 206.650.3740 http://biosimilarity.blogspot.com

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