July 2009 - Haskell-Cafe

Hackage and version control
by Vasili I. Galchin 03 Aug '09

03 Aug '09

Hello, It seems to me that Hackage doesn't provide version control, e.g. check out and check in. Am I incorrect? Kind regards, Vasili

8 8

ANN: atom 0.1.0
by Tom Hawkins 02 Aug '09

02 Aug '09

Atom is a Haskell DSL for hard realtime applications. This release includes support for assertions and functional coverage to aid simulation and testing. The rev of the minor version indicates a bit of library stability. This is the version we're using for our application, which officially went into production and hit the road last month -- literally. http://hackage.haskell.org/package/atom -Tom

3 3

Retrieving inner state from outside the transformer
by Phil 01 Aug '09

01 Aug '09

Hi, I've hit a brick wall trying to work out, what should be (and probably is!) a simple problem. I have a StateT stack (1 State monad, 2 StateT transformers) which works fine and returns the result of the outer monad. I thought I understood this fine, but perhaps not. My understanding is that the result returned by the inner-most monad is always 'transformed' by the outer monads and thus the result you get is that computed in the outer transformer. The problem I have is now I'd like not only to get the final state of the outer most transformer, but I'd also like to know the final states of the the inner StateT and the inner State at the end of the computation (so that at a later point in time I can reinitialize a similar stack and continue with the same set of states I finished with). So I figured I could have a separate (parent) State Monad (not part of this stack) that would store the final state of the sequence below. I figured it couldn't be part of this stack, as one computation on the stack does not lead to one result in the parent State Monad; it is only the end states of the sequence I care about. Anyway, currently I just have the stack evaluated as below. Is there anyway from outside of the computation that I can interrogate the states of the inner layers? The only way I can see to do this is inside the outer monad itself. As I'm not using the result I could use 'lift get' and 'lift lift get' to make the outer transformer return the two inner states as it's result. I could ignore this result for the first (iterations-1) and bind a final iteration which uses replicateM instead of replicateM_. This strikes me as pretty horrible tho! So, in the example below if I want to modify the 'result' function so it returns no only the outer state, but also the two inners states as a tuple (Double,Double,Double) is there an easier way of doing this? result :: RngClass a => NormalClass b => a -> b -> MonteCarloUserData -> Double result initRngState initNormState userData = evalState a initRngState where a = evalStateT b initNormState b = execStateT ( do replicateM_ (iterations userData) (mc userData)) 0 Any advice greatly appreciated! Thanks, Phil.

4 4

Re: Strange memory usage problem
by John Lato 01 Aug '09

01 Aug '09

> From: Ketil Malde <ketil(a)malde.org> > > Hi, > > I'm observing something I find quite strange. I have a program that > normally streams through a file, and it runs in the expected constant > space, consuming about 5MB, according to 'top'. When I uncomment a > certain block of code in the library it uses, space consumption > appears to grow linearly with the input size. > > This is a bit surprising to me, since the code in question isn't used > by the program at all, and yesterday, Cale confirmed this behavior on > a recent GHC (6.10.3, I think - mine is 6.8.2 as shipped with Ubuntu > 9.04). > I can confirm this behavior on GHC 6.10.4 on OSX 10.5.7. Try adding {-# INLINE getRB #-} above the getRB definition. That fixes it for me. I think that when the rest of the code is commented out, getRB is only called in one location, so GHC inlines it automatically. Since getRB is also called in the commented-out code, it probably isn't automatically inlined when that code is available. I suspect that the inlining allows GHC to infer some strictness property it otherwise can't. Cheers, John Lato

2 1

Re: [Haskell] ANNOUNCE: OpenGL 2.3.0.0
by Felipe Lessa 01 Aug '09

01 Aug '09

On Wed, Jul 29, 2009 at 06:26:30PM +0200, Sven Panne wrote: > Apart from that, a bug in vertexAttribPointer has been fixed. ...and the new ObjectName, StateVar and Tensor packages are being used, and this is great! Thanks for the release. -- Felipe.

4 9

ANN: tkhs-0.1.* Presentation Utility
by Yusaku Hashimoto 31 Jul '09

31 Jul '09

Hi, I'm pleased to announce the release of tkhs-0.1.*, Simple presentation utility. If you are thinking PowerPoint is overkill for your presentation, Tkhs may fit the purpose. See screenshot of running tkhs in my terminal: http://nonowarn.tumblr.com/post/152324109 When you invoke tkhs with slide file written in simple format text, tkhs displays the first slide. And you can operate a presentation by some keys. Details like slide file format and keybinds for operating slide are available at README[1] file included by the package. Project is hosted at patch-tag[2], Feel free to send me patch. Finally, I'm very grateful Evan Klizke and Brian Lewis. Evan is the author of hspresent[3] which inspired me to write tkhs. Brian sent me patch improving English. [1]: http://patch-tag.com/r/tkhs/snapshot/current/content/pretty/README [2]: http://patch-tag.com/r/tkhs/pullrepo [3]: http://hackage.haskell.org/package/hspresent Thanks, nwn

2 1

Need feedback on my Haskell code
by CK Kashyap 31 Jul '09

31 Jul '09

Hi Everyone, I managed to write up the line drawing function using the following links - http://www.cs.helsinki.fi/group/goa/mallinnus/lines/bresenh.html http://rosettacode.org/wiki/Bresenham%27s_line_algorithm#Haskell line :: Point -> Point -> [Point] line (xa,ya) (xb,yb) = line' (x1,y1) (x2,y2) deltax deltay ystep isSteep 0 where isSteep = abs (yb - ya) > abs (xb - xa) (xa',ya',xb',yb') = if isSteep then (ya,xa,yb,xb) else (xa,ya,xb,yb) (x1,y1,x2,y2) = if xa' > xb' then (xb',yb',xa',ya') else (xa',ya',xb',yb') deltax = x2 - x1 deltay = abs (y2 - y1) ystep = if y1 < y2 then 1 else -1 line' :: Point -> Point -> Integer -> Integer -> Integer -> Bool -> Integer -> [Point] line' (x1,y1) (x2,y2) deltax deltay ystep isSteep error = if x1 == x2 then if isSteep then [(y1,x1)] else [(x1,y1)] else if isSteep then [(y1,x1)] ++ line' (newX,newY) (x2,y2) deltax deltay ystep isSteep newError else [(x1,y1)] ++ line' (newX,newY) (x2,y2) deltax deltay ystep isSteep newError where newX = x1 + 1 tempError = error + deltay (newY, newError) = if (2*tempError) >= deltax then (y1+ystep,tempError-deltax) else (y1,tempError) Can someone please provide feedback on this? In terms of, how do I get more Haskell'ism into it. Regards, Kashyap

8 14

Strange memory usage problem
by Ketil Malde 31 Jul '09

31 Jul '09

Hi, I'm observing something I find quite strange. I have a program that normally streams through a file, and it runs in the expected constant space, consuming about 5MB, according to 'top'. When I uncomment a certain block of code in the library it uses, space consumption appears to grow linearly with the input size. This is a bit surprising to me, since the code in question isn't used by the program at all, and yesterday, Cale confirmed this behavior on a recent GHC (6.10.3, I think - mine is 6.8.2 as shipped with Ubuntu 9.04). Since this appears to be reproducible, I put together a test case. The steps are: darcs get http://malde.org/~ketil/biohaskell/biolib-unstable darcs get http://malde.org/~ketil/biohaskell/flower Build them using the usual incantations (./Setup.hs configure/build/install). Download the test input file: wget http://malde.org/~ketil/test.sff Run for instance this command line: fselect "And (Func GT len 100) (Func GT k2 0.5)" test.sff This should now run in constant space. To observe the linear growth space, unpull the last patch from biolib, i.e. this one: Fri Jul 31 00:14:09 CEST 2009 Ketil Malde <ketil(a)malde.org> * comment out recover functionality - otherwise FSelect leaks memory! M ./Bio/Sequence/SFF.hs -1 +7 This uncomments some otherwise unused code, which apparently triggers this behavior. I'm unable to see what causes this, so any suggestions welcome. -k -- If I haven't seen further, it is by standing in the footprints of giants

1 0

gtksourceview link problem with leksah on windows
by Bart De Vylder 31 Jul '09

31 Jul '09

Dear Haskellers, i'm having troubles linking Leksah against gtksourceview on windows (XP). I've installed gtk2hs (using the windows installer) but am not sure whether/where to specify the library search path for ld. Here is the output I get: C:\Documents and Settings\bartdv>cabal install leksah Resolving dependencies... Configuring leksah-0.6.1... Preprocessing executables for leksah-0.6.1... Building leksah-0.6.1... [ 1 of 55] Compiling DeepSeq ( src\DeepSeq.hs, > dist\build\leksah\leksah-tmp\DeepSeq.o ) > ... > [55 of 55] Compiling Main ( src\Main.hs, > dist\build\leksah\leksah-tmp\Main.o ) Linking dist\build\leksah\leksah.exe ... C:\app\Haskell_Platform\2009.2.0.1\gcc-lib\ld.exe: cannot find > -lgtksourceview-2.0 collect2: ld returned 1 exit status cabal: Error: some packages failed to install: leksah-0.6.1 failed during the building phase. The exception was: exit: ExitFailure 1 any help/ tips are very welcome, I'm eager to leave emacs... Bart

1 0

Deepest polymorphic functor
by Eduard Sergeev 31 Jul '09

31 Jul '09

I was wondering if it is possible to somehow change "deep" f_map from http://okmij.org/ftp/Haskell/deepest-functor.lhs article in a such a way that it would work not only for monotypes like in the provided example: test1 = f_map (+1) [[[1::Int,2,3]]] But for polymorphic types as well (e.g. behaves like simple map) so the following line would compile as well: test1 = f_map (+1) [[[1,2,3]]] ? -- View this message in context: http://www.nabble.com/Deepest-polymorphic-functor-tp24709303p24709303.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

3 7