- Haskell-Cafe - Haskell.org

FW: Random
by Simon Peyton-Jones 18 Dec '02

18 Dec '02

I'm behind the times... Thanks Volker Simon -----Original Message----- From: Simon Marlow Sent: 17 December 2002 15:51 To: Simon Peyton-Jones Subject: RE: Random Volker Stolz already did this (and for a bunch of other H98 libraries), but I didn't merge it into the branch, sorry. Cheers, Simon > -----Original Message----- > From: Simon Peyton-Jones [mailto:simonpj@microsoft.com] > Sent: 17 December 2002 15:08 > To: Mark Carroll; haskell-cafe(a)haskell.org > Subject: RE: Random > > > | Ah - I was never sure what to make of that - I normally just use the > GHC > | online Haddockised stuff which tells me no more than the type > signatures, > | but I suppose "split" must be more than (\x->(x,x))! (-: (I'll be > happy to > | help with adding documentation once I'm sure of the > semantics myself.) > > The Random library is carefully documented in the Haskell Report. It > would be an excellent and wonderful thing if someone could Haddock-ise > the Haskell Report documentation and put it in the library > documentation. > > Volunteers get CVS write access! > > Simon > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >

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RE: Random
by Simon Peyton-Jones 17 Dec '02

17 Dec '02

| Ah - I was never sure what to make of that - I normally just use the GHC | online Haddockised stuff which tells me no more than the type signatures, | but I suppose "split" must be more than (\x->(x,x))! (-: (I'll be happy to | help with adding documentation once I'm sure of the semantics myself.) The Random library is carefully documented in the Haskell Report. It would be an excellent and wonderful thing if someone could Haddock-ise the Haskell Report documentation and put it in the library documentation. Volunteers get CVS write access! Simon

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Library for concurrent threads running
by Dusan Kolar 17 Dec '02

17 Dec '02

Hello, My question/wish is maybe naive, but anyway: Is there a library (not a language extension, like Concurrent Haskell, Glasgow Parallel Haskell, ...) enabling to run two functions in parallel, possibly in cascade? Something like: > testAll (threadStart f1 (threadStart f2 f3)) > > where threadStart :: a -> b -> (WillBe a, WillBe b) > where type WillBe is something like Maybe, but > changing within a time (mutable values) ~ Processing, Just a, Nothing > > testAll (Nothing,p) = putStr "No result for f1" >> testPair p > testAll (l,(Nothing,r)) = putStr "Noresult for f2" >> testPair (l,r) > testAll (l,(ll,Nothing)) = putStr "No result for f3" >> testPair (l,ll) > testAll (Just a,p) = putStr ("res of f1: " ++ show a) >> testPair p > ... > > testPair ~ about the same like testAll Probably the explanation is not too clear and what I wish is out of the language scope (not really functional), but I would appreciate something like that. Is there something like that for Haskell/Hugs? Thx for any ref. Dusan

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Re: Haskell run-time tutorial
by Jonathan Holt 16 Dec '02

16 Dec '02

Matt Hellige wrote: > I found the book: > > Simon Peyton-Jones and David Lester > "Implementing Functional Languages: A Tutorial" > Prentice Hall, 1992 Thanks for the detailed and helpful reply. I've already downloaded the book, and from what I've seen thus far, it seems to be exactly what I need! Thanks! -Jony __________________________________________________ Do you Yahoo!? Yahoo! Mail Plus - Powerful. Affordable. Sign up now. http://mailplus.yahoo.com

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Haskell run-time tutorial
by Jonathan Holt 15 Dec '02

15 Dec '02

Hi guys, Having completed a simple parser project using Haskell, I'm getting more and more "hooked" on functional-programming in general and Haskell in particular. And learning the language has been a real treat as well, using the tutorial with occasional peeks at the report. However, when I'm considering undertaking more complex projects, I realize that there is one important erea of the Haskell language that is still pretty much a "black-hole" for me: the run-time environment. I honestly can't say that I completely understand how the actual control and data flows work when a Haskel program is executed, and I seem to be constantly surprised by the garbage-collection, which sometimes seems as if it doesn't work at all, and at other times seems to do magic. I've tried reading some of the articles related to the design of GHC's run-time. But they don't seem to be much help. They either assume that the reader has prior knowledge of functional-programming run-time environments, or get into very low-level details. And at the end of the day, this is very confusing, and I find terms like thunks, entries, partial-function-applications, etc. floating in my head hoplessly seeking anchor. So, where can one find a good introductory book / article on the subject? Thanks, -Jony __________________________________________________ Do you Yahoo!? Yahoo! Mail Plus - Powerful. Affordable. Sign up now. http://mailplus.yahoo.com

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Error Handling
by Thomas L. Bevan 13 Dec '02

13 Dec '02

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi, I'm writing a little command line app, but I have a question about error handling. The code will go something like, main = do (a:b:cs) <- getArgs i <- return (read a :: Int) j <- return (read b :: Int) putStr $ i + j How can I catch any possible cast exception? Ideally, I think I would like to use the ErrorT monad as a means of handling a potentially fairly complex set of inputs, but I can see no way of handling these errors neatly within that monad. Tom -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux) iD8DBQE98+VqGse0w80KF2gRAqnMAJ9CMiOWFS+3y2ELu7851MyvTb1aCgCgru+z EtW/mO+WZ0lqtYUECcHyTDE= =r1DY -----END PGP SIGNATURE-----

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Monads [beginner]
by maas＠cin.ufpe.br 13 Dec '02

13 Dec '02

What are Monads? Where can I read about then? I read that there´s some mathematical foundation under this concept, where can read about these theories? +---------------------------------+ | Marcos Aurélio Almeida da Silva | | E-mail: maas(a)cin.ufpe.br | +---------------------------------+

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RE: Haskell related Debian packages
by Simon Marlow 13 Dec '02

13 Dec '02

> Please excuse me if anyone feels that this email isn't > appropriate for this mailing list. Though these are somewhat > Debian-specific questions, I thought that some Haskell folks > could lent their insight. You would be the users after all. Also see the recent discussion on glasgow-haskell-users about a library building/packaging system (which didn't really reach a conclusion). > There aren't many examples of libraries (without any > binaries) that are packaged thus far. I noticed that > ctklight installs stuff in /usr/share/hugs98/extentions, but > it can be used with GHC also, so I am not sure why its done > this way. I don't use hugs too much though, also I don't know > anything about nhc. > > So I'm considering sticking the *.lhs files for HUnit, for > example, in /usr/share/hunit. Then people can alter their > Makefiles to include that directory in either hugs or ghc, > but I see one problem with that: GHC would want to compile > the source files, and stick them in /usr/share/hunit, but > would be unable to (because of permissions problems when > users compile). > > The package could install binary files, but then it would > build-depend on ghc which doesn't exist for several Debian > platforms. So I guess it could check to see if ghc is > installed on the building computer and stick binaries in /usr/lib. I think I would have two versions of each package: one that builds & installs a package for GHC, and one that installs source files for use with Hugs (GHCi can use the GHC package). These really are entirely different beasts, and in most cases will have zero files in common, so I think it makes sense to separate them altogether. That way you don't have to require GHC in order to install the Hugs version of the package, and vice-versa. Cheers, Simon

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Re: ffi
by Martin Huschenbett 13 Dec '02

13 Dec '02

> > $ ghc -ffi -o myprog Main.hs cfile.o > When I try this I also get an error: martin:~/work/prograemmelchen> ghc -ffi -o myprog Main.hs cfile.o ghc-5.02.2: unrecognised flag: -ffi Usage: For basic information, try the `--help' option. Do I use a wrong GHC version? THX, Martin.

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Re: Monads [beginner]
by Benderjgdefault＠aol.com 13 Dec '02

13 Dec '02

In a message dated 12/12/2002 2:45:31 PM Eastern Standard Time, maas(a)cin.ufpe.br writes: > What are Monads? > Where can I read about then? > > I read that there´s some mathematical foundation under this > concept, where > can read about these theories? A large set of articles on monads in the context of Haskell are collected on my bibliography web site: http://haskell.readscheme.org/monads.html There are also a few, more tutorial, articles available at http://haskell.org/bookshelf/ that are not included on my monads page. For more theoretical works-- while still being programming language related--I suggest Eugenio Moggi's site: http://www.disi.unige.it/person/MoggiE/publications.html. Jim Bender

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