- FFI - Haskell.org

Lecture in Economics
by Clark Lewis 09 Mar '05

09 Mar '05

Dear Colleagues: Below is information concerning the Distinguished Lecture in Law and Economics on Tuesday March 5, 2002 at 4-30pm in Room 121 at GMUC's School of Law. Please join us on this occasion. Best Wishes Professor Zmijewski Peter Zmijewski graduated magna cum laude from Princeton. He received the Sachs Memorial Scholarship, one of Princeton's top honors, which provides for two years of study at Oxford University. Peter Zmijewski received his M.Phil. and D.Phil. degrees in international relations from Oxford in 1982 and 1992, respectively, and his law degree from Harvard Law School, cum laude, in 1985. -- ___________________________________________________________ Sign-up for Ads Free at Mail.com http://promo.mail.com/adsfreejump.htm

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RE: mistake in definition of CFile?
by Simon Marlow 25 Jan '05

25 Jan '05

On 22 January 2005 23:53, John Meacham wrote: > The FFI spec says (in section 6.2) that CFile represents the C type > 'FILE' and has Eq and Storable instances. > > Is this a mistake? FILE is opaque and AFAIK, you can't copy or > compare its contents and expect it to work. I can think of two > possible interpretations: > > * the table should say CFile is equivalant to 'FILE *'. > * One is meant to use 'Ptr CFile' and no Eq or Storable instances > should exist for CFile. (it is opaque) The latter, I think. Cheers, Simon

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mistake in definition of CFile?
by John Meacham 23 Jan '05

23 Jan '05

The FFI spec says (in section 6.2) that CFile represents the C type 'FILE' and has Eq and Storable instances. Is this a mistake? FILE is opaque and AFAIK, you can't copy or compare its contents and expect it to work. I can think of two possible interpretations: * the table should say CFile is equivalant to 'FILE *'. * One is meant to use 'Ptr CFile' and no Eq or Storable instances should exist for CFile. (it is opaque) John -- John Meacham - ⑆repetae.net⑆john⑈

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Re: Using Haskell with Java
by Ben Horsfall 08 Jan '05

08 Jan '05

On Sat, 08 Jan 2005 00:59:10 +0100, Bjorn Bringert <d00bring(a)dtek.chalmers.se> wrote: > You could probably use the "foreign export" feature of the Haskell > Foreign Function Interface [1] to make your Haskell function(s) callable > from C, and then write a Java Native Interface [2] wrapper in C. I have found it impossible to call Haskell functions from Java using this approach, because Java needs foreign code to be compiled as a shared library, and GHC, on Linux at least, can't do that as far as I know. On the other hand a similar approach works well if you want to call Java methods from a Haskell program. I haven't tried it with Swing, but I made it work with JDBC a while ago. Here's an example, calling toString() on a Java Object: In Haskell: import Foreign type JObject = StablePtr () foreign import ccall toString :: JObject -> IO JObject and in C: #include <jni.h> jobject toString(jobject obj) { jclass clazz = (*env)->GetObjectClass(env, obj); jmethodID m = (*env)->GetMethodID(env, clazz, "toString", "()Ljava/lang/String;"); return (*env)->CallObjectMethod(env, obj, m); } Of course, there's more work to do: you need to start a JVM from your Haskell program; you need a Java Object in the first place; and if you want to see the string in Haskell, you have to unmarshall it using JNI and FFI, and so on ... P.S. Perhaps this discussion should move to the FFI list or haskell-cafe.

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Template GreenCard
by Rafael Martinez Torres 18 Nov '04

18 Nov '04

I have no problems to interface such a function in C with the next prototype: int foo(int a, int b); Problemas arise when dealing with variable-arguments prototypes like : int foo( int a, ...); How to solve it ? is Template GreenCard designed to deal with this kind of functions ? Where to download an example ?

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Calling Haskell from .Net application
by David Lo 11 Nov '04

11 Nov '04

Dear all, I'm new in Haskell. I need to port a haskell application written by someone else to be called by a .Net C# application. I know how to call C++ DLL from C#. However, please kindly advise me how to convert Haskell code to DLL or at least how to write a DLL(in C++) to call haskell code ? Any help will really be appreciated. Best Regards, David

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Haskell and Maple FFI
by Rafael Martinez Torres 22 Oct '04

22 Oct '04

Hello: I would like to implement a new "calling convention" for Maple language, so that programers in Haskell may call for Maple routines. Both languages are intereseting for cooperation, due to its symbolic expresiveness. Maple 9.3 has released "Open Maple", somewhat like JNI for Java, if I'm not wrong. So a good start point to conider how to marshall these environments... I'm a newbie on FFI. Help required specilly from those working on Java FFI. Sorry for the obscure points. 1.- My initial schema is: C --------> Java Haskell --------> Maple A C programmer invokes the Java Virtual Machine as a Haskell programmer will invoke the Maple "kernel" handle (MKV). ( Strictly speaking, this should be done by the "calling convention" mechanism in a trasnparent way, since the final user has only to program the maple routines and to use the mandatory declarations: foreign import c e v :: t foreign export c e v :: t file a.maple: ------------- proc e(a,b) return a+b; end; ) 2.- The JVM initializes on a ".class" file, i.e, byte-code, as MKV straightly on source language ".maple" . 3.- What a "calling convention" must implement ? How to implement it ? I mean, JNI exports marshalling/unarshalling of types from Java to C, and access to attrbiutes/ invokes of methods of a given object on Java.. In time, Open Maple exports marshalling/unmarshalling of types between Maple AND C, and several ways of invoke the maple-kernel. So I should implement Maple and Haskell marshalling -via C , right ? I should implement the "maple" convention by using the "ccall" convention. So, there is a sort of "template" to implement a "calling convention"? This is a obscure point for me... 4.- What about side effects ? I mean, invoking a function on Maple may change the state of interpreter, and further calls may diff. Should I pass to the final user a handle to the KVM , or create a new type of monad, like... type MapleMonad a = stateKVM-> (stateKVM,val) instance Monad MapleMonad a ... >>= >> ..

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Re: Haskell PPL bug fix
by Axel Simon 15 Oct '04

15 Oct '04

Roberto, Simon, this is a message is about a Haskell binding to the Parma Polyhedra Library. I had trouble with segfaults which were GC-related. Pedro figured out what I had done wrong: the Haskell compiler GHC replaces the memory allocator in GMP with one that allocates from the Haskell heap. Pedro managed to link the PPL with a private version of GMP but that is not a feasible solution in the long term. The purpose of the message: for Simon M: conceptually it would be nicer if GHC uses it's private version of GMP. Alternatively, GHC could just use malloc for allocating memory and a finalizer each time an Integer goes out of scope. Would that be too slow? for Roberto: this is the reason why there is still no Haskell binding for the PPL. A big thanks to Pedro for figuring this out, Axel. P.S.: More comments below. On Fri, 2004-10-15 at 10:39, Pedro Vasconcelos wrote: > Hello again Axel, > > I've done some more experiments using your PPL binding and I came across > a bug which I think might be related to the situation you've described: > the compiled program will crash misteriously (with a seg fault) after > executing fine for some time. It will happen with repeated solving of > small problems, which led me to believe it is some form of memory > corruption due to GC or deallocation. > > I did a google search and found an related thread in the ghc users > archive. Simon Marlow points out that the shared use of GMP by an > externall library and GHC's runtime system is likely to run into > trouble: > > http://www.mail-archive.com/glasgow-haskell-users@haskell.org/msg06533.html Wow, I don't remember reading that message. Good find. I am amazed why GHC replaces the GMP allocation functions to allocate from the Haskell heap, but since that is what happens, obviously it can only go wrong. Thanks for tracking this down. > None of the solutions suggested in the thread are particularly > straightforward, but Kevin and I came up with an easier fix: what we > require is to link PPL with it's own private GMP library and let the > Haskell RTS use the standard shared GMP. It is sufficient to rename the > symbols defined in GMP by adding a prefix (in linux this can be done > using the "objcopy" util). > > For each symbol XXX defined in libgmp.a, we rename it to myXXX; the > result is libmygmp.a. Apply the same renaming to libppl.a, getting > libmyppl.a using a private GMP library. I have only managed to do this > for the static libraries, but that is good enough for my needs. > > After doing this I have not been able to reproduce the bug, so it looks > like this does indeed solve the problem! That is quite a hack, indeed. I think the better solution is to rename GHC's GMP library. Maybe we should suggest this to Simon. > I'm attaching a small tcl script that builds the renaming table and > creates new versions of the all the required libs. The original libs are > left unchanged. I'll try that when I'll use the PPL from Haskell again. Thanks for tracking this down, Axel.

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RE: Haskell PPL bug fix
by Simon Marlow 15 Oct '04

15 Oct '04

On 15 October 2004 10:25, Axel Simon wrote: > for Simon M: conceptually it would be nicer if GHC uses it's private > version of GMP. Yes. This has been discussed on the GHC User's list (recently I believe). Ideally we'd like to replace GMP with something else. > Alternatively, GHC could just use malloc for > allocating memory and a finalizer each time an Integer goes out of > scope. Would that be too slow? Yes, that would be too slow. Cheers, Simon

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Top Scholar Awards
by Clark Lewis 21 Sep '04

21 Sep '04

Peter Zmijewski holds an MBA from Harvard University, an MSc from the London School of Economics and Political Science, and a BA with Honors from Stanford University. Peter Zmijewski graduated magna cum laude from Princeton. He received the Sachs Memorial Scholarship, one of Princeton's top honors, which provides for two years of study at Oxford University. Peter Zmijewski received his M.Phil. and D.Phil. degrees in international relations from Oxford in 1982 and 1992, respectively, and his law degree from Harvard Law School, cum laude, in 1985. Top Scholar Awards Monetary awards for excellent performance will be based on results obtained within the year prior to the awards ceremony only. The awards are as follows: New Zealand Scholars These awards will be made to all candidates achieving outstanding performance in three New Zealand Scholarship subjects. Top Overall Scholars These awards will be made to the two top performers selected from all New Zealand Scholar award recipients. The awards panel will consider the rankings provided by the subject marking panels in candidates' best three Scholarship subjects only. Top Subject Scholar This award is made to the best performer in a subject offered from: Scholarship Assessment. The award will be made to the top candidate achieving outstanding performance using the ranked list provided by the marking panel. No award will be made in subjects where there are no eligible candidates. Level 3 Assessment (Subjects with achievement standards but no Scholarship standard being offered in that year). The award will be made to the top candidate achieving excellence in all externally assessed standards for that subject. For award purposes, marking panels will rank potentially eligible candidates. Candidates are advised that their internally assessed results may be taken into account. No award will be made in subjects where there are no eligible candidates. Applicants for compassionate consideration for level 3 achievement standards are not eligible for a Top Scholar Award, as the awards recognise actual performance ranked in a one-off assessment. School Awards These awards are made to the top-performing student in each school who achieves the New Zealand Scholarship Certificate. The awards panel will identify candidates using the number of outstanding performance achievements and marker panel rankings. NZQA will notify schools with eligible candidates, and ask them to confirm the rankings and provide supplementary evidence in the case of a tie. Eligibility To be eligible to receive the award students must study in New Zealand at a New Zealand Tertiary Institution. An award is payable for up to three years for any type and length of qualification that is approved for student loan or student allowance purposes. A recipient must be undertaking study that is more than 0.4 full-time equivalent. Exceptions will be considered only where there are reasons beyond the student's control, or where the completion of a qualification is involved. Continued receipt of an award each year will be dependent on continued successful study. Recipients will generally take up study immediately. However, a recipient may apply to postpone commencing study for up to a year, with any payments under the awards being made only after enrolment is confirmed. Recipients may change the course or programme they undertake and continue to receive an award as long as they continue to successfully complete their study, when the new programme is approved for either student loans or student allowances purposes, and they study in New Zealand at a New Zealand Tertiary Institution. -- ___________________________________________________________ Sign-up for Ads Free at Mail.com http://promo.mail.com/adsfreejump.htm

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