October 2000 - Glasgow-haskell-users

ppr for Haskell Abstract Syntax
by Kate S. Golder 07 Nov '00

07 Nov '00

Hi - I was wondering if anyone knows if there is a pretty printer for Haskell Abstract Syntax anywhere? I've been asking around, but haven't located one yet. If you know of one that I could use, it would be really helpful! Thanks in advance, *Kate ********************** Kate S. Golder Wellesley College Class of 2002 Freeman Hall Wellesley College Wellesley, Ma 02481

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AW: Using Haskell code in VBA (MS Access)?
by Lescher Christian 26 Oct '00

26 Oct '00

I tried to compile this small example with ghc-4.08.1, but it didn't work (compiling ok., but DLL does not run), while with ghc-4.05 everything is okay. What can be wrong with this? Christian Lescher > -----Urspr> üngliche Nachricht----- > Von: Sigbjorn Finne [SMTP:sof@microsoft.com] > Gesendet am: Donnerstag, 17. August 2000 20:18 > An: 'Christian Lescher' > Cc: glasgow-haskell-users(a)haskell.org > Betreff: RE: Using Haskell code in VBA (MS Access)? > > > The support libraries for HaskellDirect provide > functions for converting between BSTRs and Haskell' > String (Com.marshallBSTR, Com.unmarshallBSTR) -- > http://www.dcs.gla.ac.uk/fp/software/hdirect/user-32.html > > has the overview. However, the binaries available for > that library is for ghc-4.045, so you'd have to compile > them up yourself for ghc-4.08. > > To build a 'static' DLL, here's what you need to do: > > - compile up all your Haskell code using -static. > - write a .def file containing the entry points you > want to expose. In my example, the .def file would > just contain: > > EXPORTS > adder@8 > > - link the static DLL: > > ghc-4.05 -static --mk-dll -optdll--def=adder.def \ > -o adder.dll adder.o dllMain.o -lHSrts > > I heard some rumours that -static might disappear. If that's > the case, I think that would be unfortunate. > > --sigbjorn > > Christian Lescher <christian(a)lescher.de> writes: > > > > Thank you for your detailed answer - it's really great, it works! :-) > > > > However, I have got one more problem: the function I want to > > call from VBA is of > > type String -> String -> String > > Is there a (simple) method to convert VBA strings (BSTR) to > > Haskell's [Char] and > > vice versa? > > > > By the way: Is it possible to build DLLs that do not depend > > on GHC's runtime DLLs? > > I tried out the "-static" option like for compiling EXEs, but > > it didn't work. > > > > CL > > > > >

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RE: Compiling mutually recursive modules involving instances
by Simon Peyton-Jones 26 Oct '00

26 Oct '00

| The manual also says a new, better, higher level way for | dealing with mutually recursive modules is in the works. | Is there any chance it will be ready for the next release? I don't think so. The upcoming GHCi will be the next release and it indeed gives a much better chance of doing this stuff properly. Making recursive modules possible is a high priority. But making them easy isn't as high priority as lots of other things, I'm afraid. Simon

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RE: getContents
by Simon Marlow 26 Oct '00

26 Oct '00

> I don't really understand getContents. (Does anyone?) I > have some code here > (far too large to submit). If I do (on Linux, ghc4.08.1, > both with and without optimisation) > ------------------ > contents <- hGetContents handle > seq (last contents) (hClose handle) > ------------------ > the code works. However I looked at the manual and it seems > that hClose should > force the whole of contents to be read anyway. So I changed it to > ------------------ > contents <- hGetContents handle > hClose handle > ------------------ > and then the code doesn't work. If these are meant to be the > same, then we have a GHC > bug. If not, could someone explain in words of one syllable why not? > > PS - if you want the source code you'll have to download and > compile the whole of UniForM!! Using hClose on a semi-closed handle is a Bad Thing. The Haskell Report says: "Once a semi-closed handle becomes closed, the contents of the associated stream becomes fixed, and is the list of those items which were succesfully read from that handle". So I take this to mean that when you hClose a semi-closed handle, you get a random amount of data in the handle which depends on how good your compiler's strictness analyser is. yesno? Cheers, Simon

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getContents
by George Russell 26 Oct '00

26 Oct '00

I don't really understand getContents. (Does anyone?) I have some code here (far too large to submit). If I do (on Linux, ghc4.08.1, both with and without optimisation) ------------------ contents <- hGetContents handle seq (last contents) (hClose handle) ------------------ the code works. However I looked at the manual and it seems that hClose should force the whole of contents to be read anyway. So I changed it to ------------------ contents <- hGetContents handle hClose handle ------------------ and then the code doesn't work. If these are meant to be the same, then we have a GHC bug. If not, could someone explain in words of one syllable why not? PS - if you want the source code you'll have to download and compile the whole of UniForM!!

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RE: Compiling mutually recursive modules involving instances
by Simon Peyton-Jones 26 Oct '00

26 Oct '00

The best thing to do is never to put an instance declaration in an hi-boot file. I don't think you ever really need to. In contrast, mutual recursion of type declarations is often unavoidable. The manual should really say this Simon | -----Original Message----- | From: José Romildo Malaquias [mailto:romildo@urano.iceb.ufop.br] | Sent: 24 October 2000 16:00 | To: glasgow-haskell-users(a)haskell.org | Subject: Compiling mutually recursive modules involving instances | | | Hello. | | I am having difficulties in compiling mutually recursive | modules involving classes and instances in GHC 4.08.1. | Basicaly I am not finding how to write a .hi-boot where | I want to put classes and instances. | | Consider a program with 3 modules: M1, M2 and Main. The | sources are attached to the message. What should go | into M2.hi-boot? Would anyone write M2.hi-boot for me | so that I can learn it. | | Thanks. | | Romildo | -- | Prof. José Romildo Malaquias <romildo(a)iceb.ufop.br> | Departamento de Computação | Universidade Federal de Ouro Preto | Brasil |

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Compiling mutually recursive modules involving instances
by José Romildo Malaquias 24 Oct '00

24 Oct '00

Hello. I am having difficulties in compiling mutually recursive modules involving classes and instances in GHC 4.08.1. Basicaly I am not finding how to write a .hi-boot where I want to put classes and instances. Consider a program with 3 modules: M1, M2 and Main. The sources are attached to the message. What should go into M2.hi-boot? Would anyone write M2.hi-boot for me so that I can learn it. Thanks. Romildo -- Prof. José Romildo Malaquias <romildo(a)iceb.ufop.br> Departamento de Computação Universidade Federal de Ouro Preto Brasil

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Overloaded function and implicit parameter passing
by José Romildo Malaquias 23 Oct '00

23 Oct '00

Hi. While experimenting with the implicit parameter extension to Haskell 98, implemented in GHC 4.08.1 and latest Hugs, I came accross a difference among those implementations regarding overloading functions with implicit parameters. As a test consider the program ------------------------- cut here module Main where class C a where f :: (?env :: Integer) => a -> Integer instance C Integer where f x = ?env + x main = putStrLn (show (f (45::Integer) with ?env = 100)) ------------------------- cut here Hugs accepts this program and outputs 145, as expected. But GHC 4.08.1 refuses to compile it, emitting the message $ ghc -fglasgow-exts Test1.hs -o test1 Test1.hs:7: Unbound implicit parameter `env_rJX :: Integer' arising from use of `env_rJX' at Test1.hs:7 In the first argument of `+', namely `env_rJX' In the right-hand side of an equation for `f': env_rJX + x Compilation had errors Would anybody comment on what is going on with GHC? I am willing to use implicit parameters in the software I am developing, but I have the need to overload functions with implicit parameters. While Hugs is good for development, its performance may rule it out when the final product is ready. So I will need a good Haskell compiler to compile my system. Any comments? Romildo -- Prof. José Romildo Malaquias <romildo(a)iceb.ufop.br> Departamento de Computação Universidade Federal de Ouro Preto Brasil

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RE: Interface Files _ HOWTO?
by Simon Peyton-Jones 23 Oct '00

23 Oct '00

Compile the module from bottom to top, with -c. Then link. THus ghc -c MyList.hs ghc -c ListFun.hs ...etc... ghc -c Main.hs ghc -o MyApp MyList.o ListFun.o ... Main.o Simon | -----Original Message----- | From: Ingo Sander [mailto:ingo@ele.kth.se] | Sent: 20 October 2000 17:09 | To: glasgow-haskell-users(a)haskell.org | Subject: Interface Files _ HOWTO? | | | After working a lot with Hugs I tried to compile my Haskell | code with GHC. | But it does not work, I am not able to figure out how to work with the | interface files (.hi). My program is build out of several | modules, like | this (much simpler, but facing the same problem...) | | File MyList.hs | ============== | | module MyList(MkList(Empty, (:-))) where | | infixr 5 :- | | data MkList a = Empty | | a :- (MkList a) deriving (Eq, Show) | | | File ListFun.hs | =============== | | module ListFun(mapL) where | | import MyList | | mapL f Empty = Empty | mapL f (x:-xs) = f x :- mapL f xs | | | | File ListLib | ============ | | module ListLib(module MyList, module ListFun) where | | import MyList | import ListFun | | | File Main.hs | ============ | | module Main(main) where | | import ListLib | | main = putStr (show (mapL (+1) (1:-2:-Empty))) | | | | As I said the code works with hugs, and I want to have the | hierarchy in | the library structure. | | So, how do I compile this in GHC? I hoped, that it would be enough to | compile all files with the -c option (generating .hi and .o files) and | then compiling Main.hs to get an executable program. Howeve, I get the | following: | | > ghc Main.hs | ghc: module version unchanged at 7 | Undefined first referenced | symbol in file | MyList_ZCzm_con_info Main.o | MyList_zdfShowMkList_closure Main.o | ListFun_mapL_closure Main.o | MyList_Empty_static_closure Main.o | ld: fatal: Symbol referencing errors. No output written to a.out | | So, what's wrong, and am I totally on the wrong track... (I | studied the | GHC User Guide, but could not find the answer to my problem). | | Thanks in advance! | | Ingo Sander | | | | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users(a)haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users |

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Interface Files _ HOWTO?
by Ingo Sander 20 Oct '00

20 Oct '00

After working a lot with Hugs I tried to compile my Haskell code with GHC. But it does not work, I am not able to figure out how to work with the interface files (.hi). My program is build out of several modules, like this (much simpler, but facing the same problem...) File MyList.hs ============== module MyList(MkList(Empty, (:-))) where infixr 5 :- data MkList a = Empty | a :- (MkList a) deriving (Eq, Show) File ListFun.hs =============== module ListFun(mapL) where import MyList mapL f Empty = Empty mapL f (x:-xs) = f x :- mapL f xs File ListLib ============ module ListLib(module MyList, module ListFun) where import MyList import ListFun File Main.hs ============ module Main(main) where import ListLib main = putStr (show (mapL (+1) (1:-2:-Empty))) As I said the code works with hugs, and I want to have the hierarchy in the library structure. So, how do I compile this in GHC? I hoped, that it would be enough to compile all files with the -c option (generating .hi and .o files) and then compiling Main.hs to get an executable program. Howeve, I get the following: > ghc Main.hs ghc: module version unchanged at 7 Undefined first referenced symbol in file MyList_ZCzm_con_info Main.o MyList_zdfShowMkList_closure Main.o ListFun_mapL_closure Main.o MyList_Empty_static_closure Main.o ld: fatal: Symbol referencing errors. No output written to a.out So, what's wrong, and am I totally on the wrong track... (I studied the GHC User Guide, but could not find the answer to my problem). Thanks in advance! Ingo Sander

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