- Glasgow-haskell-users

FFI and Libraries using GMP
by Benedikt Huber 10 Sep '07

10 Sep '07

Hello, I've been struggling using FFI bindings to libraries which rely on the GNU Mp Bignum library (gmp) - this is apparently a well known problem (http://hackage.haskell.org/trac/ghc/ticket/311) I do want to use some of those libraries however and so I started to get them work on ghc-6.6.1/darwin_8_i368. But as no solution was close to being satisfactory, I'd like to ask for some advice. Those two options worked to some extend: (1) Create or modify the library in question, so gmp is statically linked and its symbols are hidden. When source code is available, this is relatively easy, altough it requires modification of the build process (which can be a hassle). If a static "ar" archive is available, it is cumbersome (at least on Mac Os X I ran into a lot of troubles using nmedit), but possible. Furthermore, the resulting libraries are bloated, as each of them contains a copy of the GMP; left alone portability issues. (2) As suggested in ticket#311, I tried switching the allocator functions when switching to FFI. It worked, but not in GHCi; also, doing it manually is a lot of work, because, as far as I could figure out, it is neccessary to write a wrapper function for every C-function (indirectly) using the gmp. Furthermore, most of the libraries expose gmp datatypes (mpz_t,mpq_t) in their API. I currently use a little haskell module working on GHC.Exts, but that's propably not a good option from a maintainer's point of view. There are certainly other possibilities, but I couldn't find one which is both maintainable and portable. I would be very grateful for any advice, or some information on plans for resolving ticket #311; I'm aware that there are long-term plans for replacing gmp, but I'd prefer a seperate short-term solution for the problems with the FFI. There are some great libraries (like the Parma Polyhedral Library, to pick an example) out there using gmp, and it would be nice if writing bindings to those libs could be simplified. Thanks, Benedikt

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capturing ghci command output; :redir/:grep/:find
by Claus Reinke 08 Sep '07

08 Sep '07

having only recently started to play with ghci's :def and :cmd, i'm still in the process of figuring out what is and what isn't possible, and i've been wondering what wonderful things other ghci users have in their .ghci files? to start with, here are my current favourites (definitions attached, this is using a recent ghc 6.7). i'm looking forward to seeing your gems and favourites:-) -- capturing command output in variables: *Main> :redir out :info Monad *Main> putStrLn out class Monad m where (>>=) :: m a -> (a -> m b) -> m b (>>) :: m a -> m b -> m b return :: a -> m a fail :: String -> m a -- Defined in GHC.Base instance Monad Maybe -- Defined in Data.Maybe instance Monad [] -- Defined in GHC.Base instance Monad IO -- Defined in GHC.IOBase -- filtering command output for lines matching pattern: *Main> :grep break :? :abandon at a breakpoint, abandon current computation :break [<mod>] <l> [<col>] set a breakpoint at the specified location :break <name> set a breakpoint on the specified function :continue resume after a breakpoint :delete <number> delete the specified breakpoint :delete * delete all breakpoints :step single-step after stopping at a breakpoint :trace trace after stopping at a breakpoint :trace <expr> trace into <expr> (remembers breakpoints for :history) :set stop <cmd> set the command to run when a breakpoint is hit :show breaks show the active breakpoints :show context show the breakpoint context *Main> :grep class :browse Control.Monad class Monad m where class Functor f where fmap :: (a -> b) -> f a -> f b class (Monad m) => MonadPlus m where -- Hugs' :find <id>, calling editor to open definition of <id> *Main> :find main probably, there should be a wiki page collecting such :definitions, and other ways of improving the ghci usage experience. but i'm unsure whether to add to the haskell wiki http://haskell.org/haskellwiki/GHC/GHCi or to the ghc developer's wiki http://hackage.haskell.org/trac/ghc opinions? suggestions? tips? tricks?-) claus

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docon-2.10
by Serge D. Mechveliani 06 Sep '07

06 Sep '07

Announcement: I have put docon-2.10 instead of 2.09. What is new: two bugs fixed in installation. One of the fixes is for MacOS X, for its feature concerning the letter case in file names. Regards, ----------------- Serge Mechveliani mechvel(a)botik.ru

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Re: Mac GHC binary
by Christian Maeder 06 Sep '07

06 Sep '07

Hi Jeff, I think, there's only a problem when the GNUreadline framework is only in your home directory and when you want to link your own binary. Correct me if you also have a problem if the framework is globally installed in /Library/Frameworks. Indeed a framework entry is missing in the package.conf. But I doubt if a generic entry using $HOME would work. So this entry could only be set at installation time for a single user (and I don't know how). In fact, for linking we use the additional ghc flags: -optl-F$HOME/Library/Frameworks -optl-framework -optlGNUreadline These flags could be put in top-level script for ghc (in bindir). Does anyone have a better idea? Cheers Christian P.S, I hope it's ok for you, if I forward this to glasgow-haskell-users(a)haskell.org, too Jeff Lewis wrote: > Hi Christian: > > A few people here have tried using your binary Mac OS X build of > GHC. There's one problem we've run into. The readline package doesn't > work out of the box. It seems to be necessary to add `-framework > GNUreadline'. This shouldn't be necessary. I'd guess that there's a > missing `frameworks' entry in the package description. > > --Jeff

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configure option --oldincludedir
by Wolfgang Jeltsch 05 Sep '07

05 Sep '07

Hello, what is the option --oldincludedir of the configure script in the current 6.7 nightly snapshot for? ./configure --help says that its default is /usr/include. Is this directory used to install files into or is it just used for reading files? Best wishes, Wolfgang

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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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