September 2007 - Glasgow-haskell-users

6.6.1 + DoCon on Mac OS
by Serge D. Mechveliani 05 Sep '07

05 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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