June 2001 - Hugs-Users

ForeignObj Finalizer in Hugs
by KAKIHARA Norihiro 02 Jul '01

02 Jul '01

I want to use ForeignObj for large transient data, but Hugs ForeignObj implementation is quite mysterious... Three ForeignObj interfaces are described as such in exts/Foreign.hs. primitive makeForeignObj :: Addr{-x-} -> Addr{-free-} -> IO ForeignObj primitive writeForeignObj :: ForeignObj -> Addr -> IO () primitive eqForeignObj :: ForeignObj -> ForeignObj -> Bool The latter argument of makeForeignObj is a mystery. 1. I thought it is a pointer of function (with type of [void (*)(void *);] ?). foreign import "foo" "newFO" newFO :: IO Addr foreign import "foo" "delFO" delFO :: Addr -> IO () primitive unsafeCoerce "primUnsafeCoerce" :: a -> b newFO >>= (\fo -> makeForeignObj fo (unsafeCoerce delFO)) This code causes an unexpected signal (probably the implementation of Addr -> IO () is different from C form). 2. `foreign label' is valid? foreign import "foo" "newFO" newFO :: IO Addr foreign label "foo" "delFO" delFO :: Addr newFO >>= (\fo -> makeForeignObj fo delFO) No, it isn't. 3. Then I try to get the pointer of delFO directly (Fortunately lcc-win32 3.1 allows internal global variables viewable, however, I suppose other C compilers do not...). foreign import "foo" "newFO" newFO :: IO Addr foreign import "foo" "delFO" delFO :: Addr -> IO () foreign import "foo" "getDelFO" getDelFO :: IO Addr getDelFO >>= (\del -> newFO >>= (\fo -> makeForeignObj fo del)) It works as expected. But I think such description is not appropriate! Variables in DLL are not always viewable by another program. How I should use ForeignObj finalizer in Hugs? -- KAKIHARA Norihiro [The following code was workable in my environment...] ********** main.c ********** #include <windows.h> #include <stdio.h> BOOL WINAPI LibMain(HINSTANCE hInstance, DWORD fdwReason, LPVOID lpReserved) { return TRUE; } extern int *newObj(void) { int *i; i = (int*)malloc(sizeof(int)); *i = 5; printf("CREATED %d\n", *i); return i; } static void delObj(int *i) { printf("DELETED %d\n", *i); free(i); } extern void *getDelObj(void) { return (void*)delObj; } ******** foreignObj.hs ********** import Foreign foreign import "foreignObj" "newObj" newObj :: IO Addr foreign import "foreignObj" "getDelObj" getDelObj :: IO Addr test :: IO () test = getDelObj >>=(\del -> newObj >>= (\obj -> makeForeignObj obj del) >>= (\_ -> putStr "End Program"))

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add functions to a class
by Christopher Sharpe 29 Jun '01

29 Jun '01

Hello, Can you help me understand how to make something more quantified than just (a -> b) a member of a class? Thanks in advance! ============================================================================== This is a "literate" program and may be saved as "t.lhs" (say) then loaded into Haskell. I am using O'Hugs version 0.5 under Windows 98. We want to make ((Int,Float) -> String) a Show. Try the direct approach: ------------------------------------------- instance Show ((Int,Float) -> String) where showsPrec _ f _ = f (3,5.4) ------------------------------------------- It fails with 'Type variable expected in instance type'. Try defining a type synonym: ------------------------------------------- >type MyF = ((Int,Float) -> String) instance Show MyF where showsPrec _ f _ = f (3,5.4) ------------------------------------------- It fails with 'Type synonym "MyF" not permitted in instance of "Show" '. Try defining a newtype: ------------------------------------------- >newtype MyNewtype = MyDataConstructor ((Int,Float) -> String) >instance Show MyNewtype where > showsPrec _ (MyDataConstructor f) _ = f (3,5.4) >--We never really made MyF a Show, but function "show'" is a workaround. >show' myF = show (MyDataConstructor myF) ------------------------------------------- Testing: ------------------------------------------- >f :: MyF >f x | x == (3,5.4) = "This shows the value of my function applied to a certain argument." > | otherwise = "OK" >test = show' f -------------------------------------------

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export lists
by Michael Ackerman 28 Jun '01

28 Jun '01

Hello, I've just started to study the Haskell module system, and I find that export lists for modules in Hugs do not seem to work. For example, if I write module Foo (a) where a = 0 b = 1 and then load Foo, both a and b are visible. What am I doing wrong? Any help will be appreciated. Michael

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Help!!!
by Nicole Gabler 18 Jun '01

18 Jun '01

Hi all, I have a problem: I need the library Directory.hs. But there is no Directory.hs in {Hugs}/lib/ !! All standard libraries are there expect of this one. I downloaded Hugs from http://www.haskell.org/hugs/. Is there any alternative?? Or did I understand something wrong?? I hope you can help me! Best regards, Nicole

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I'VE MISPOSTED!
by KAKIHARA Norihiro 16 Jun '01

16 Jun '01

I've misposted my message To compile H/Direct 0.17 with GHC 4.08.2 at Hugs-User (correctly at glasgow-haskell-user). Please excuse me...

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To compile H/Direct 0.17 with GHC 4.08.2
by KAKIHARA Norihiro 16 Jun '01

16 Jun '01

> Sorry to hear this. I found that make boot doesn't work for me either, > but if I just type "make all" after it stops, everything seems to work. > You can certainly not just use the ihc.exe from H/Direct 0.16 binary > release. I see. Trying again and again, I could compile H/Direct `without no trouble' -- rather than successfully. This is how I compiled H/Direct 0.17 with GHC 4.08.2 (Windows Installer Release), 1. Install some more Cygnus tools into ghc/bin. * sh.exe in ash ... to make GHC compilable (probably the leak of package). * date.exe in sh-utils ... used in `make boot'. * dlltool.exe, dllwrap.exe in binutils ... used in `make lib' for compiling Hugs libraries (optional?). 2. Edit line 156 in lib/WideStringSrc.c as such. (Otherwise, a confliction error will occur.) extern int wcslen (const WCHAR* wstr); into extern size_t wcslen (const WCHAR* wstr); 3. Type them in the following order at the H/Direct toplevel: $ make boot $ make all $ make lib 4. Copy hdirect/lib/libHScom.a into ghc/lib. (Otherwise, ghc cannot find -lHScom.) Then I tried to compile examples/string, and get the following output: Hello world Thanks! > >

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Problem on Using Hugs with Fran
by Yeo Gek Hui 09 Jun '01

09 Jun '01

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