- Glasgow-haskell-users

6.6.1 + DoCon on Mac OS
by Serge D. Mechveliani 06 Sep '07

06 Sep '07

People, please, who can advise about ghc-6.6.1 + DoCon on Mac OS ? There exists the public release of DoCon-2.09 computer algebra application, which works under ghc-6.6.1 (http://haskell.org/docon) It was tested only under Linux. I hope that it will work under Unix too. But what about Mac OS ? (`Mac' means Mackintosh ?) Can you look into the files install.txt, source/Makefile, source/docon.cabal in DoCon-2.09 and tell whether this installation is likely to work under Mac OS ? How DoCon-2.09 + ghc-6.6.1 can be ported to Mac OS ? Thank you in advance for your explanation. ----------------- Serge Mechveliani mechvel(a)botik.ru

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file name letters
by Serge D. Mechveliani 05 Sep '07

05 Sep '07

Dear GHC users and developers, there has occured a curious case with file name letters. One user has built the docon library application (in Haskell) on MacOS X 10.4 + ghc-6.6.1. And making the test program has failed due to the presence of the file linalg.hs in the directory of the testing modules for DoCon. This file is not needed for this docon release, it is a reserve. I set its name in the lower case letters in order for GHC to ignore it. I test DoCon only in Linux, and have not access to MacOS. Thanks to Christian Maeder <Christian.Maeder(a)dfki.de>, he noticed that MacOS ignores the letter case in the file names! When the commands cd demotest ghc ... --make Main run on MacOS, ghc suddenly touches the file linalg.hs -- for some reason (and there also exists LinAlg in the library built). All right, I shall readily fix this `bug'. But out of curiosity, who's bug is this: of GHC, DoCon, or MacOS ? Is the file name letters a matter of Haskell-98 ? Do the GHC docs mention the question of the letter case in the file names? Regards, ----------------- Serge Mechveliani mechvel(a)botik.ru

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6.6.1 + docon on MacOS X
by Serge D. Mechveliani 04 Sep '07

04 Sep '07

People, here is more detail to my last letter about ghc-6.6.1 + docon-2.09 on MacOS : the system is Mac OS X 10.4. Thank you in advance for your explanation. ----------------- Serge Mechveliani mechvel(a)botik.ru

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RULES and type classes
by Andreas Schropp 03 Sep '07

03 Sep '07

> // > In particular, it would be nice to be able to specialise based on the > instances, as we do for [a] --> [Int], e.g. > > RULES sum = sumInt :: [Int] -> Int > > is fine in the current system. So I could imagine some nice > specialisations based on say, the good old Ord: > > RULES nub = nubOrd :: (Eq a, Ord a) => [a] -> [a] > > which might use a Map, say. > > I don't know how costly this instance matching would be. > -- Don In principle I think you should be able to get constraint-specialized implementations right now, using Oleg's type-class overloaded (aka 2-polymorphic) functions (http://okmij.org/ftp/Haskell/poly2.txt) Some prototyping, not tested: import Poly2 {- -- from Poly2: (these can also be expressed as `TypeCls'-Membership-instance -> feasable with deriving machinery?) type Fractionals = Float :*: Double :*: HNil type Nums = Int :*: Integer :*: AllOf Fractionals :*: HNil type Ords = Bool :*: Char :*: AllOf Nums :*: HNil type Eqs = AllOf (TypeCl OpenEqs) :*: AllOfBut Ords Fractionals :*: HNil -} data NubLabel -- Ord-specialized instance, guarded by Membership-Predicate instance GFN Z NubLabel (Member Ords) instance (Ord a) => Apply (GFnA Z NubLabel) [a] [a] where -- we get here if Guard succeded apply _ = Map.tolist . Map.fromListWith const -- default instance instance TypeCast pred Otherwise => GFN n NubLabel pred instance (Eq a) => Apply (GFnA n NubLabel) [a] [a] where apply _ = List.nub nub_opt xs = apply (GFn NubLabel) xs But it probably needs some deriving-infrastructure for the `TypeCls' member-predicate to make it feasible. BTW: rewriting rules being turing-complete, I'm wondering if theres some "freaky hackery" to be discovered, or yet going on? :>

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Type Synonyms and termination checking
by Jim Apple 03 Sep '07

03 Sep '07

Regarding http://www.haskell.org/pipermail/cvs-ghc/2007-August/037655.html and Are type functions checked for termination? If so, where can I find the details? Jim

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:def and ghci command output
by Claus Reinke 31 Aug '07

31 Aug '07

ghci's :def takes a 'String -> IO String' and converts it into a ghci command. this makes it possible to pass a command parameter to a haskell function, and to interpret the result of the call as a ghci command. that is nice, but how do i get access to the command's output? that is, i'd like to run a ghci command, and capture its ouput as a haskell String, eg, to pass it on to another ghci command, or to a haskell function. perhaps something simple, like an additional ghci top-level binding: GHCi.cmd :: String -> IO String so that i could write things like let doSomething output = .. :def mymodules \_->GHCi.cmd ":show modules" >>= doSomething or a way to compose ghci commands, so that i could write :def doSomething \output->.. :def mymodules \_->return ":show modules :>>= :doSomething" would that be difficult to provide? claus

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Derived instances
by Fernand 31 Aug '07

31 Aug '07

Hi, I have just discovered Generics in Haskell and, writing some code with GHC, I wondered about the portability of my code. It is possible I overlooked something in the GHC documentation but I did not found a way to obtain, let say, the haskell code for the derived classes. I mean, having the following type declaration : > data Something = This | That deriving (Eq, Ord, Typeable, Data) I can use the -fgenerics to automatically derive instances for Something. But I could wish to have the generated source code for those instances (like, I suppose, the DrIft tool does), for instance, to compile my source with another compiler, which does not support Generics. Is that possible ? Thank you, Fernand

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Re: [Haskell] ghc as a library and profiling
by Simon Marlow 31 Aug '07

31 Aug '07

Sönke Hahn wrote: > I am working on a program that uses ghc as a library to typecheck code. I want > to profile the program (compiling with '-prof -auto-all' and running > with '+RTS -p'). Trying to compile, results in the following message: > > Could not find module `GHC': > Perhaps you haven't installed the profiling libraries for package > ghc-6.6.1? Yes, by default we don't build or supply the GHC package with profiling, because of the extra bloat it would add to the downloads and the time taken to build it. With the latest GHC sources from darcs you can add 'GhcCompilerWays=p' to your mk/build.mk and get the GHC package built for profiling too. > A second idea that comes to my mind is this: > The ghc package is hidden in the standard installation, so i unhided (unhid?) > it via 'ghc-pkg expose ghc'. Maybe it just exposed the non-profiling version > and kept the profiling version hidden? How would i expose both? You probably don't really want to expose the GHC package, because it doesn't use hierarchical modules and so pollutes the top-level module namespace. Cheers, Simon

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template haskell syntax
by Christian Maeder 25 Aug '07

25 Aug '07

Hi, for haskell prime I suggest to change the stolen syntax "[e|", "[p|", "[d|", "[t|" to [|<letter>| in order to avoid the confusion with list comprehensions. Cheers Christian

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Status of GHC runtime dependency on GNU multi precision arithmetic library
by Brian Hulley 23 Aug '07

23 Aug '07

Hi, I know this is a sensitive issue and I absolutely don't want to start any kind of discussion about the merits or otherwise of LGPL, but I was wondering if there are any plans to remove the GNU mp library from the runtime so that it would be possible to distribute native executables compiled with GHC without having to deal with the additional issues raised by the current inclusion of this LGPL component in the runtime. (Afaik everything else in ghc is under a BSD3 license.) It's less of an issue on Linux where libgmp is dynamically linked but when thinking about using Haskell ghc for creating Windows apps it is for me a real problem, because it would mean I'd have to distribute the code for my app as a library along with the code as an executable, thus doubling the download size for my apps as well as having to include a license that has to explain to a possibly non-technical user that although the program includes code that is libre/gratis free the program is not itself free etc etc... Regards, Brian.

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