Re: [Haskell-cafe] Newbie Question: Using Haskell Functions in a C Program
On Thu, May 8, 2008 at 5:09 PM, Philip Müller [EMAIL PROTECTED] wrote: Thanks for all the answers. I'm testing this right now and simples cases work as expected. However from what I've read it seems it'll get ugly once I try to pass a C array to a Haskell function. Well, maybe arrays in C have been ugly before trying to pass them to Haskell functions ;) To elaborate a bit about the C program, it's a small game using OpenGL for output and mouse and keyboard for input. The SDL package (http://hackage.haskell.org/cgi-bin/hackage-scripts/package/SDL) is quite nice for input handling and window making and whatnot. I have heard it is a bitch to get working on Windows, though. The OpenGL package (http://hackage.haskell.org/cgi-bin/hackage-scripts/package/OpenGL) is good, but can be a real pain to get going because the documentation layout is terrible. To toot my own horn, if your graphics are simple enough (specifically, 2D), you can use graphics-drawingcombinators (http://hackage.haskell.org/cgi-bin/hackage-scripts/package/graphics-drawingcombinators), which has a simple interface, for output. It depends on SDL, so above caveat applies. But once you learn the pattern, I/O is basically a transliteration from C. The reason I struggle with such C-like libraries in Haskell is that I spend all my time trying to clean them up and make them more Haskell-like. I definitely consider FFI more of a pain (when you want to do anything sophisticated) than the OpenGL package, though. Luke ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Newbie Question: Using Haskell Functions in a C Program
Hello Philip, Friday, May 9, 2008, 2:17:41 AM, you wrote: Is there a way to write some of the functions in Haskell and then use them in my C code via some kind of interface? http://haskell.org/haskellwiki/IO_inside#Interfacing_with_foreign_evil_.28under_development.29 and then entries 1,6,7 in http://haskell.org/haskellwiki/IO_inside#Further_reading -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Newbie Question: Using Haskell Functions in a C Program
mail:
Is there a way to write some of the functions in Haskell and then use
them in my C code via some kind of interface?
Using C just for IO is a bit weird -- perhaps you could illustrate
the kind of IO you're doing? Learning how to do IO in Haskell is
a much safer solution that linking the Haskell runtime into your
C program.
That said, this is done by using 'foreign export' declarations
in your Haskell code, then linking the compiled Haskell objects
into your C code, as follows:
We define the fibonacci function in Haskell:
{-# LANGUAGE ForeignFunctionInterface #-}
module Safe where
import Foreign.C.Types
fibonacci :: Int - Int
fibonacci n = fibs !! n
where fibs = 0 : 1 : zipWith (+) fibs (tail fibs)
fibonacci_hs :: CInt - CInt
fibonacci_hs = fromIntegral . fibonacci . fromIntegral
foreign export ccall fibonacci_hs :: CInt - CInt
And call it from C:
#include A_stub.h
#include stdio.h
int main(int argc, char *argv[]) {
int i;
hs_init(argc, argv);
i = fibonacci_hs(42);
printf(Fibonacci: %d\n, i);
hs_exit();
return 0;
}
Now, first compile the Haskell file:
$ ghc -c -O A.hs
Which creates some *.c and *.h headers, which you import into
your C program. Now compile your C code with ghc (!), passing
the Haskell objects on the command line:
$ ghc -optc-O test.c A.o A_stub.o -o test
How run your C code:
$ ./test
Fibonacci: 267914296
And that's it.
-- Don
P.S. Its easier to learn how to do IO in Haskell :)
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Re: [Haskell-cafe] Newbie Question: Using Haskell Functions in a C Program
Thanks for all the answers. I'm testing this right now and simples cases work as expected. However from what I've read it seems it'll get ugly once I try to pass a C array to a Haskell function. Well, maybe arrays in C have been ugly before trying to pass them to Haskell functions ;) To elaborate a bit about the C program, it's a small game using OpenGL for output and mouse and keyboard for input. I just don't know how to do that in Haskell - my knowledge is quite basic in nature ;) Regards Philip ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Newbie Question: Using Haskell Functions in a C Program
mail: Thanks for all the answers. I'm testing this right now and simples cases work as expected. However from what I've read it seems it'll get ugly once I try to pass a C array to a Haskell function. Right, passing arrays back and forth is going to get tiring. Well, maybe arrays in C have been ugly before trying to pass them to Haskell functions ;) To elaborate a bit about the C program, it's a small game using OpenGL for output and mouse and keyboard for input. I just don't know how to do that in Haskell - my knowledge is quite basic in nature ;) Oh, then you'll want to use the Haskell OpenGL bindings. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/OpenGL There's a few OpenGL-based games in Haskell, here: http://haskell.org/haskellwiki/Applications_and_libraries/Games and a section of blog articles on using the OpenGL bindings: http://haskell.org/haskellwiki/Blog_articles/Graphics#OpenGL -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
