February 2009 - Haskell-Cafe

RE: can't figure out a type
by Brian Bloniarz 11 Feb '09

11 Feb '09

Hi John, > In the class I wrote, c has kind * (e.g. [a]), but then I don't see > how to write a suitable map function. For that, I would want c to > have kind * -> *. Unfortunately then I don't know to write the > others. > > Would I have to do something with c having kind (* -> *) ? > > class Chunkable2 c el where > cLength :: c el -> Int > cHead :: c el -> Maybe el > cMap :: (el -> el') -> c el -> c el' When c is (* -> *), why do you need el to be a parameter of the typeclass at all? I.e., would this work for your purposes: > class Chunkable3 c where > cLength :: c el -> Int > cHead :: c el -> Maybe el > cMap :: (a -> b) -> c a -> c b > instance Chunkable3 [] where > cLength = length > cMap = map > cHead = ... Using Functor as a superclass of Chunkable3 works too. Thanks, -Brian _________________________________________________________________ More than messages–check out the rest of the Windows Live™. http://www.microsoft.com/windows/windowslive/

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More DPH Questions
by James Swaine 11 Feb '09

11 Feb '09

I apologize - I forgot to include this in my previous posting. I also couldn't seem to find an implementation of the foldP function, which is included in several of Roman's papers on DPH and ndp in general. Is this not implemented yet? Thanks, James Swaine

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Haskell Users in the West Michigan Area?
by John Van Enk 11 Feb '09

11 Feb '09

I'm wondering if there are people in the West Michigan, USA area who'd be interested in forming WMHUG (West Michigan Haskell Users Group). Any one on here from that area? /jve

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DPH Prelude
by James Swaine 11 Feb '09

11 Feb '09

I was wondering if anyone could point me to a more in-depth explanation of why we are (currently) restricted to using a special-purpose standard Prelude when writing vectorised code with DPH. We're prototyping using several data-parallel languages for a research project here at Northwestern University, and wanted to get a better idea how we might go about adding vectorisation support for addtional types/operations. There are certain simple operations which don't appear to be supported for primitive types yet (e.g. the ^ and ** operators for an Int type). These are the kinds of things we'd like to look into as a first step. Much thanks, James Swaine

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GHC development
by Andrew Coppin 11 Feb '09

11 Feb '09

OK, so I have a small question. I was just wondering what the current state of development with GHC is. So, I had a look at the developer wiki. Unfortunately, as best as I can tell, most of the status pages haven't been updated in many months. (Most of them still talk about what will or won't be in 6.10.1, which has been *released* for a while now.) What's the best way to find out what the "real" state of affairs is? What are the developers really working on? What's on hold? How far have people got with things? Etc. (Yes, I know. I'm nosey...)

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How outdated is Hugs?
by Rafael Gustavo da Cunha Pereira Pinto 11 Feb '09

11 Feb '09

Hi, I see Hugs last source code snapshot dates back to 2006. Was there any updates? Regards -- Rafael Gustavo da Cunha Pereira Pinto Electronic Engineer, MSc.

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Re: [Gtk2hs-users] Gtk2HS 0.10.0 Released
by Peter Verswyvelen 11 Feb '09

11 Feb '09

Nice. The demos are now included only in the source distri right? On Wed, Feb 11, 2009 at 1:40 PM, Axel Simon <Axel.Simon(a)ens.fr> wrote: > On Wed, 2009-02-11 at 13:36 +0100, Peter Verswyvelen wrote: > > Great job! I have been using the RC1 version for a while and it works > > well. > > > > > > - Full switch to the new model-view implementation using a Haskell > > model > > > > > > This is very interesting. Do demos exist to show this? > > > > Yes, all the demos under demo/treeList have been converted to use the > new ModelView (the directory name is stale, it should probably be > renamed to modelView since TreeList was the old interface). > > There's also a combo box demo in demo/menu. > > Cheers, > Axel. > > > On Wed, Feb 11, 2009 at 5:32 AM, Peter Gavin <pgavin(a)gmail.com> wrote: > > Hi everyone, > > > > I'd like to release the announcement of Gtk2HS 0.10.0. A lot > > of new > > stuff has gone into this release, including: > > > > - Support for GHC 6.10 > > - Bindings to GIO and GtkSourceView-2.0 > > - Full switch to the new model-view implementation using a > > Haskell model > > - Support for many more model-based widgets such as IconView > > and an > > updated binding for ComboBox > > - Full Drag-and-Drop support > > - Better support for Attributes in Pango > > - Replaced Event for EventM monad, thereby improving > > efficiency and > > convenience > > - Functions for interaction between Cairo and Pixbuf drawing > > - Lots of bug fixes, code cleanups, and portability > > improvements > > > > With this release, the bindings to GnomeVFS and > > GtkSourceView-1.0 have > > been deprecated. The TreeList modules have been deprecated > > from the > > Gtk+ bindings. > > > > Source and Win32 binaries are available at: > > > > > > > https://sourceforge.net/project/showfiles.php?group_id=49207&package_id=424… > > > > Thanks to everyone who submitted bug fixes and features this > > time around! > > > > Thanks, > > Peter Gavin > > Gtk2HS Release Manager > > > > > > > ------------------------------------------------------------------------------ > > Create and Deploy Rich Internet Apps outside the browser with > > Adobe(R)AIR(TM) > > software. With Adobe AIR, Ajax developers can use existing > > skills and code to > > build responsive, highly engaging applications that combine > > the power of local > > resources and data with the reach of the web. Download the > > Adobe AIR SDK and > > Ajax docs to start building applications > > today-http://p.sf.net/sfu/adobe-com > > _______________________________________________ > > Gtk2hs-users mailing list > > Gtk2hs-users(a)lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/gtk2hs-users > > > > > > > ------------------------------------------------------------------------------ > > Create and Deploy Rich Internet Apps outside the browser with > Adobe(R)AIR(TM) > > software. With Adobe AIR, Ajax developers can use existing skills and > code to > > build responsive, highly engaging applications that combine the power of > local > > resources and data with the reach of the web. Download the Adobe AIR SDK > and > > Ajax docs to start building applications today- > http://p.sf.net/sfu/adobe-com > > _______________________________________________ Gtk2hs-users mailing list > Gtk2hs-users(a)lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/gtk2hs-users > >

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Re: [Gtk2hs-users] Gtk2HS 0.10.0 Released
by Peter Verswyvelen 11 Feb '09

11 Feb '09

Great job! I have been using the RC1 version for a while and it works well. - Full switch to the new model-view implementation using a Haskell model This is very interesting. Do demos exist to show this? On Wed, Feb 11, 2009 at 5:32 AM, Peter Gavin <pgavin(a)gmail.com> wrote: > Hi everyone, > > I'd like to release the announcement of Gtk2HS 0.10.0. A lot of new > stuff has gone into this release, including: > > - Support for GHC 6.10 > - Bindings to GIO and GtkSourceView-2.0 > - Full switch to the new model-view implementation using a Haskell model > - Support for many more model-based widgets such as IconView and an > updated binding for ComboBox > - Full Drag-and-Drop support > - Better support for Attributes in Pango > - Replaced Event for EventM monad, thereby improving efficiency and > convenience > - Functions for interaction between Cairo and Pixbuf drawing > - Lots of bug fixes, code cleanups, and portability improvements > > With this release, the bindings to GnomeVFS and GtkSourceView-1.0 have > been deprecated. The TreeList modules have been deprecated from the > Gtk+ bindings. > > Source and Win32 binaries are available at: > > > > https://sourceforge.net/project/showfiles.php?group_id=49207&package_id=424… > > Thanks to everyone who submitted bug fixes and features this time around! > > Thanks, > Peter Gavin > Gtk2HS Release Manager > > > > ------------------------------------------------------------------------------ > Create and Deploy Rich Internet Apps outside the browser with > Adobe(R)AIR(TM) > software. With Adobe AIR, Ajax developers can use existing skills and code > to > build responsive, highly engaging applications that combine the power of > local > resources and data with the reach of the web. Download the Adobe AIR SDK > and > Ajax docs to start building applications today- > http://p.sf.net/sfu/adobe-com > _______________________________________________ > Gtk2hs-users mailing list > Gtk2hs-users(a)lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/gtk2hs-users >

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ANN: Data.Stream 0.3
by Wouter Swierstra 11 Feb '09

11 Feb '09

I've released a new version of the Data.Stream package, a modest library for manipulating infinite lists. Changes include: * Support for lazy SmallCheck; * Improved Show instance; * Stricter scans; * Various documentation fixes; * Several new functions from Data.List. Many of these features were based on patches by Bas van Dijk - thank you Bas! Haddock: http://www.cs.nott.ac.uk/~wss/repos/Stream/dist/doc/html/Stream/ Hackage: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Stream/ darcs: darcs get http://www.cs.nott.ac.uk/~wss/repos/Stream All the best, Wouter

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Re: [Haskell-cafe] evaluation semantics of bind
by Alberto G. Corona 11 Feb '09

11 Feb '09

forwarded: Yes! if no state is passed, the optimization makes sense and the term is not executed, like any lazy evaluation. For example, I used the debugger (that is, without optimizations) to verify it with the Maybe monad: op x= x+x print $ Just (op 1) >>= \y-> return (Just 2) does not evaluate op 1 but print $ Just (op 1) >>= \y-> return y does execute it. The trace of the first: [1 of 1] Compiling Main ( test.hs, interpreted ) Ok, modules loaded: Main. *Main> :set stop :list *Main> :step main Stopped at test.hs:4:6-43 _result :: IO () = _ 3 4 main= print $ Just (op 1) >>= \y-> return 2 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 5 [test.hs:4:6-43] *Main> :step Stopped at test.hs:4:14-43 _result :: Maybe Integer = _ 3 4 main= print $ Just (op 1) >>= \y-> return 2 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 5 [test.hs:4:14-43] *Main> :step Stopped at test.hs:4:14-24 _result :: Maybe Integer = _ 3 4 main= print $ Just (op 1) >>= \y-> return 2 ^^^^^^^^^^^ 5 [test.hs:4:14-24] *Main> :step Stopped at test.hs:4:35-43 _result :: Maybe Integer = _ 3 4 main= print $ Just (op 1) >>= \y-> return 2 ^^^^^^^^^ 5 [test.hs:4:35-43] *Main> :step Just 2 But in the second case op is executed: *Main> :step main Stopped at test.hs:4:6-43 _result :: IO () = _ 3 4 main= print $ Just (op 1) >>= \y-> return y ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 5 [test.hs:4:6-43] *Main> :step Stopped at test.hs:4:14-43 _result :: Maybe Integer = _ 3 4 main= print $ Just (op 1) >>= \y-> return y ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 5 [test.hs:4:14-43] *Main> :step Stopped at test.hs:4:14-24 _result :: Maybe Integer = _ 3 4 main= print $ Just (op 1) >>= \y-> return y ^^^^^^^^^^^ 5 [test.hs:4:14-24] *Main> :step Stopped at test.hs:4:35-43 _result :: Maybe Integer = _ y :: Integer = _ 3 4 main= print $ Just (op 1) >>= \y-> return y ^^^^^^^^^ 5 [test.hs:4:35-43] *Main> :step Just Stopped at test.hs:4:20-23 _result :: Integer = _ 3 4 main= print $ Just (op 1) >>= \y-> return y ^^^^ 5 [test.hs:4:20-23] *Main> :step Stopped at test.hs:6:0-8 _result :: Integer = _ 5 6 op x= x+x ^^^^^^^^^ 7 [test.hs:6:0-8] *Main> :step Stopped at test.hs:6:6-8 _result :: Integer = _ x :: Integer = _ 5 6 op x= x+x ^^^ 7 [test.hs:6:6-8] *Main> :step Just 2 2009/2/5 Gregg Reynolds <dev(a)mobileink.com>- Ocultar texto citado - > > On Thu, Feb 5, 2009 at 9:27 AM, Bulat Ziganshin <bulat.ziganshin(a)gmail.com> wrote: >> >> Hello Gregg, >> >> Thursday, February 5, 2009, 6:20:06 PM, you wrote: >> >> > An optimizer can see that the result of the first getChar is >> > discarded and replace the entire expression with one getChar without >> > changing the formal semantics. >> >> this is prohibited by using pseudo-value of type RealWorld which is >> passed through entire action stream. actually, order of execution is >> controlled by dependencies on this values >> >> http://haskell.org/haskellwiki/IO_inside >> > Thanks. I actually read that a few weeks ago and forgot all about it. So the gist is that type IO has special magic semantics. Formal, but hidden. Which means monad semantics are built in to the language, at least for that type. The Haskell Report doesn't seem to say anything about this, which seems odd. > > But then for non-IO monads, the optimization would be allowed, no? Of course; only the IO monad has external world behavior. > > Thanks, > > gregg > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >

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