Calling Haskell from other languages?

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Colin Paul Adams

11 Nov 2008 11 Nov '08

11:45 a.m.

Is there a way to call Haskell code from other languages? I have looked on the wiki, and as far as I can see, it only talks about the other way round (when Haskell is the main program). -- Colin Adams Preston Lancashire

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Jake Mcarthur

11 Nov 11 Nov

11:51 a.m.

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Nov 11, 2008, at 10:45 AM, Colin Paul Adams wrote:

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Is there a way to call Haskell code from other languages? I have looked on the wiki, and as far as I can see, it only talks about the other way round (when Haskell is the main program).

http://www.haskell.org/haskellwiki/GHC/Using_the_FFI#Calling_Haskell_from_C -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.8 (Darwin) iEYEARECAAYFAkkZuCkACgkQye5hVyvIUKk1pwCfRbVnERADZPygCNX2wjNkdQOC FXMAoKodV1TitVzr5ZJF/AUSmCXuRuKY =BUkK -----END PGP SIGNATURE-----

Jake Mcarthur

11:53 a.m.

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Actually, that's not the whole story. I didn't realize until I sent it. There does exist good documentation for this, I promise. - - Jake -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.8 (Darwin) iEYEARECAAYFAkkZuHoACgkQye5hVyvIUKnGeACfZN+9nNy+nGvQHDsG1FrI4Puu Zw0AmgKK0WOYTjWWeQX93rrnSJApG0pa =Vazy -----END PGP SIGNATURE-----

Colin Paul Adams

12:09 p.m.

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"Jake" == Jake Mcarthur writes:

Jake> Actually, that's not the whole story. I didn't realize until Jake> I sent it. There does exist good documentation for this, I Jake> promise. Good. Let me know where it is when you track it down. The link you pointed me too doesn't seem to address my question directly. Also, it only talks about C. If I want to call Haskell (and I do, perhaps) from another garbage-collected language (Eiffel, in particular) using C as the mutually understood language, am I not going to run into big problems? -- Colin Adams Preston Lancashire

Bulat Ziganshin

12:21 p.m.

New subject: Re[2]: Calling Haskell from other languages?

Hello Colin, Tuesday, November 11, 2008, 8:09:09 PM, you wrote:

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If I want to call Haskell (and I do, perhaps) from another garbage-collected language (Eiffel, in particular) using C as the mutually understood language, am I not going to run into big problems?

of course not. there will be two independent heaps. of course you can't directly send pointers to gc-collected structures between two languages, they should be converted through buffers in C world (i.e. malloced ones) -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com

Derek Elkins

1:35 p.m.

On Tue, 2008-11-11 at 17:09 +0000, Colin Paul Adams wrote:

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"Jake" == Jake Mcarthur writes:

Jake> Actually, that's not the whole story. I didn't realize until Jake> I sent it. There does exist good documentation for this, I Jake> promise.

Good. Let me know where it is when you track it down.

The link you pointed me too doesn't seem to address my question directly. Also, it only talks about C.

If I want to call Haskell (and I do, perhaps) from another garbage-collected language (Eiffel, in particular) using C as the mutually understood language, am I not going to run into big problems?

Read the FFI Report. It is relatively readable and comprehensive. http://www.cse.unsw.edu.au/~chak/haskell/ffi/ And yes, you will have to use C as an intermediary, though you may not have to actually write any C. You simply expose the Haskell functions in whatever form the other language expects. You'll almost certainly have to write marshalling code of some sort.

John Goerzen

2:31 p.m.

On Tue, Nov 11, 2008 at 12:35:05PM -0600, Derek Elkins wrote:

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On Tue, 2008-11-11 at 17:09 +0000, Colin Paul Adams wrote:

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> "Jake" == Jake Mcarthur writes:

Jake> Actually, that's not the whole story. I didn't realize until Jake> I sent it. There does exist good documentation for this, I Jake> promise.

Good. Let me know where it is when you track it down.

The link you pointed me too doesn't seem to address my question directly. Also, it only talks about C.

If I want to call Haskell (and I do, perhaps) from another garbage-collected language (Eiffel, in particular) using C as the mutually understood language, am I not going to run into big problems?

Read the FFI Report. It is relatively readable and comprehensive. http://www.cse.unsw.edu.au/~chak/haskell/ffi/

And yes, you will have to use C as an intermediary, though you may not have to actually write any C. You simply expose the Haskell functions in whatever form the other language expects. You'll almost certainly have to write marshalling code of some sort.

I often like to look at these situations as an opportunity to introduce modularity and piping. Do you really need them running in the same address space?

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_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

Colin Paul Adams

3:07 p.m.

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"John" == John Goerzen writes:

>> Read the FFI Report. It is relatively readable and >> comprehensive. http://www.cse.unsw.edu.au/~chak/haskell/ffi/ >> >> And yes, you will have to use C as an intermediary, though you >> may not have to actually write any C. You simply expose the >> Haskell functions in whatever form the other language expects. >> You'll almost certainly have to write marshalling code of some >> sort. John> I often like to look at these situations as an opportunity John> to introduce modularity and piping. Do you really need them John> running in the same address space? Good point. And thanks everyone for your help. I have enough to go on now. -- Colin Adams Preston Lancashire

Colin Paul Adams

14 Nov 14 Nov

3:03 a.m.

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"Colin" == Colin Paul Adams writes:

Colin> And thanks everyone for your help. I have enough to go on Colin> now. I followed the example at http://www.haskell.org/haskellwiki/Calling_Haskell_from_C (and renamed the files from A* to fib1*, as I want to pursue this further). But I get: fib1.o: In function `main': fib1.c:(.text+0x0): multiple definition of `main' fib1.o:fib1.c:(.text+0x0): first defined here fib1_stub.o: In function `stginit_export_Safe_zdffibonaccizuhszuaDN': fib1_stub.c:(.text+0x5): undefined reference to `Safe_zdffibonaccizuhszuaDN_closure' fib1_stub.o: In function `fibonacci_hs': fib1_stub.c:(.text+0x32): undefined reference to `Safe_zdffibonaccizuhszuaDN_closure' collect2: ld returned 1 exit status -- Colin Adams Preston Lancashire

Don Stewart

3:06 a.m.

colin:

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"Colin" == Colin Paul Adams writes:

Colin> And thanks everyone for your help. I have enough to go on Colin> now.

I followed the example at http://www.haskell.org/haskellwiki/Calling_Haskell_from_C

(and renamed the files from A* to fib1*, as I want to pursue this further).

But I get:

fib1.o: In function `main': fib1.c:(.text+0x0): multiple definition of `main' fib1.o:fib1.c:(.text+0x0): first defined here fib1_stub.o: In function `stginit_export_Safe_zdffibonaccizuhszuaDN': fib1_stub.c:(.text+0x5): undefined reference to `Safe_zdffibonaccizuhszuaDN_closure' fib1_stub.o: In function `fibonacci_hs': fib1_stub.c:(.text+0x32): undefined reference to `Safe_zdffibonaccizuhszuaDN_closure' collect2: ld returned 1 exit status

Not linking in the 'Safe' module on the command line? -- Don

Colin Paul Adams

3:11 a.m.

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"Don" == Don Stewart writes:

Don> Not linking in the 'Safe' module on the command line? Could be - I don't know any of this stuff. I was just following the instructions on the wiki page. How should these be amended? -- Colin Adams Preston Lancashire

Colin Paul Adams

11:17 a.m.

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"Colin" == Colin Paul Adams writes:

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"Don" == Don Stewart writes: Don> Not linking in the 'Safe' module on the command line?

Colin> Could be - I don't know any of this stuff. I was just Colin> following the instructions on the wiki page. Got it working now. It seemed to be some case dependency on the file name. -- Colin Adams Preston Lancashire

Don Stewart

11 Nov 11 Nov

2:39 p.m.

colin:

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"Jake" == Jake Mcarthur writes:

Jake> Actually, that's not the whole story. I didn't realize until Jake> I sent it. There does exist good documentation for this, I Jake> promise.

Good. Let me know where it is when you track it down.

The link you pointed me too doesn't seem to address my question directly. Also, it only talks about C.

If I want to call Haskell (and I do, perhaps) from another garbage-collected language (Eiffel, in particular) using C as the mutually understood language, am I not going to run into big problems?

No, you can manage objects via e.g. ForeignPtr's. The community has a whole has done bridges between Haskell and pretty much anything you care to name, via the C FFI. Just depends on how well you understand the memory management models of both players. -- Don

Fraser Wilson

8:28 p.m.

I had a proof of concept lying around a couple of years ago in which a big complicated Ada program called a big complicated Haskell program and vice versa. The tricky bit from memory was making it link, and satisfying their rumtime initialisation requirements. No explicit C was required I think. Fraser On 11 nov 2008, at 18:09, Colin Paul Adams wrote:

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"Jake" == Jake Mcarthur writes:

Jake> Actually, that's not the whole story. I didn't realize until Jake> I sent it. There does exist good documentation for this, I Jake> promise.

Good. Let me know where it is when you track it down.

The link you pointed me too doesn't seem to address my question directly. Also, it only talks about C.

If I want to call Haskell (and I do, perhaps) from another garbage-collected language (Eiffel, in particular) using C as the mutually understood language, am I not going to run into big problems? -- Colin Adams Preston Lancashire _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

Don Stewart

2:38 p.m.

colin:

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Is there a way to call Haskell code from other languages? I have looked on the wiki, and as far as I can see, it only talks about the other way round (when Haskell is the main program).

http://haskell.org/haskellwiki/Calling_Haskell_from_C Cheers, Don

Dave Tapley

12 Nov 12 Nov

5:30 a.m.

Hi Colin As an alternative you may consider using Thrift: http://incubator.apache.org/thrift/ Cheers, Dave On Tue, 2008-11-11 at 16:45 +0000, Colin Paul Adams wrote:

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Is there a way to call Haskell code from other languages? I have looked on the wiki, and as far as I can see, it only talks about the other way round (when Haskell is the main program).

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participants (8)

Bulat Ziganshin
Colin Paul Adams
Dave Tapley
Derek Elkins
Don Stewart
Fraser Wilson
Jake Mcarthur
John Goerzen