- Haskell-Cafe - Haskell.org

name of this monadic combinator?
by Michael Vanier 01 Jun '10

01 Jun '10

I stumbled across this monadic combinator: mcombine :: Monad m => (a -> a -> a) -> m a -> m a -> m a mcombine f mx my = do x <- mx y <- my return (f x y) I used it to chain the outputs of two Parsec String parsers together using this operator: (<++>) :: Monad m => m String -> m String -> m String (<++>) = mcombine (++) mcombine seems like such a basic operation that it should be a library function, but I couldn't find one matching it on hoogle. Is there one? - Mike

7 8

ANN: list-extras 0.4.0
by wren ng thornton 01 Jun '10

01 Jun '10

-------------------------------------------- -- list-extras 0.4.0 -------------------------------------------- A minor (but interface-changing) release for common not-so-common functions for lists. -------------------------------------------- -- Changes (since 0.3.0) -------------------------------------------- * (by Tom Lokhorst) Added Data.List.Extras.list: a function for non-recursive case matching on lists. In the spirit of `maybe` and `either` (if we don't interpret them as catamorphisms). * Changed the type of Data.List.Extras.Pair.zipBy to be correct. I have no idea where the old more restrictive type came from. -------------------------------------------- -- Links -------------------------------------------- Homepage: http://code.haskell.org/~wren/ Hackage: http://hackage.haskell.org/package/list-extras Darcs: http://code.haskell.org/~wren/list-extras/ Haddock (Darcs version): http://code.haskell.org/~wren/list-extras/dist/doc/html/list-extras/ -- Live well, ~wren

1 0

yet another functional reactive programming tutorial :)
by Jinjing Wang 31 May '10

31 May '10

Dear list, As I'm learning frp and reading the wonderful tutorial at http://www.formicite.com/dopage.php?frp/frp.html , I'm putting up some more basic cheatsheet style tutorial for myself. http://github.com/nfjinjing/frp-guide Feel free to take advantage of it. -- jinjing

3 2

LLVM -> Haskell
by Tom Hawkins 31 May '10

31 May '10

Is there any work being done to read LLVM object code into Haskell? I've looked through the llvm library [1], but it appears focused on code generation. -Tom [1] http://hackage.haskell.org/package/llvm

3 4

Third Ghent Functional Programming Group Meeting: Tuesday, June 29 at 19h
by Jeroen Janssen 31 May '10

31 May '10

(apologies if you receive multiple copies) Dear all, We would like to announce that the third Ghent Functional Programming Group Meeting will take place on Tuesday, June 29, in the Technicum Building (Sint-Pietersnieuwstraat 41, 9000 Gent) of Ghent University at 19h. If you are interested in giving a talk, please do not hesitate to drop us a note! The final program will be announced shortly. For more information you can follow us at twitter (@ghentfpg) or sign up for our google group (http://groups.google.com/group/ghent-fpg) Hope to see you all then, Bart Coppens (Bart.Coppens(a)elis.ugent.be; Twitter: @bartcopp) Jasper Van der Jeugt (jaspervdj(a)gmail.com; Twitter: @jaspervdj) Jeroen Janssen (jejansse(a)gmail.com; Twitter: @jejansse) Note: if you do not want to receive any more e-mails from Ghent FPG, just send an e-mail to Jeroen Janssen (jejansse(a)gmail.com) and we will remove you from our mailinglist.

1 0

Improving Haskell on Windows by adding it to TakeoffGW
by MH 31 May '10

31 May '10

That's a great idea and I would love to help but I have no idea where and how to start. I would love to work on making Haskell installer work on TakeofGW. Would it be possible to write down some notes describing what needs to be done? Thanks, MH

1 0

Announce: berp, an implementation of Python 3, in Haskell
by Bernie Pope 31 May '10

31 May '10

I'm pleased to announce the first public release of berp, version 0.0.2. Berp is (the beginnings of) an implementation of Python 3, written in Haskell. It provides a compiler and an interpreter. In both cases the input Python program is translated into Haskell code. The compiler turns the Haskell code into machine code. The interpreter runs the Haskell code immediately via the GHCi interpreter. The user interface of the interpreter imitates the one provided by CPython. A cabal package is available: http://hackage.haskell.org/package/berp The source code is hosted on github: http://github.com/bjpop/berp Documentation is available on a github wiki: http://wiki.github.com/bjpop/berp/ Note: berp is known to work with GHC 6.10.4, but it may not work with 6.12.x, due to issues with GHC's memory usage when compiling the language-python package (ticket #3972 on the GHC trac). As you can see by the very low version number (0.0.2), berp is still young; there is lots of room for improvement. However, it does support a fairly wide variety of Python's features, and some extensions such as callCC and tail call optimisation. Read more about it on the github wiki mentioned above. Cheers, Bernie.

1 0

ANNOUNCE: MonadCatchIO-foreign
by Antoine Latter 31 May '10

31 May '10

Hello Haskell, I'd like to announce a very small library in two flavors. The problem I'm trying to solve is that we have some capabilities for writing functions which are polymorphic over monad but still use IO capabilities - liftIO :: (IO a -> m a) from the packages transformers and mtl. The packages[1,2] MonadCatchIO offer similar polymorphism for the exception capabilities of the IO monad. The package MonadCatchIO-foreign offers similar polymorphism for the following functions: alloca, allocaBytes, allocaArray, allocaArray0 and withForeignPtr. It's a small thing, but I don't see why it should be written twice. Links on hackage: http://hackage.haskell.org/package/MonadCatchIO-mtl-foreign http://hackage.haskell.org/package/MonadCatchIO-transformers-foreign GitHub link: http://github.com/aslatter/MonadCatchIO-foreign Feedback, praise and adulation welcome. Antoine

3 2

www.haskell.org web server down?
by Sean Leather 31 May '10

31 May '10

It responds to pings but not http. http://downforeveryoneorjustme.com/www.haskell.org Sean

1 0

Why Either = Left | Right instead of something like Result = Success | Failure
by Ionut G. Stan 31 May '10

31 May '10

Hi, I was just wondering if there's any particular reason for which the two constructors of the Either data type are named Left and Right. I'm thinking that something like Success | Failure or Right | Wrong would have been a little better. I've recently seen that Scala uses a similar convention for some error notifications so I'm starting to believe there's more background behind it than just an unfortunate naming. Thanks, -- Ionuț G. Stan | http://igstan.ro

18 24