if you'd normally be linking using g++, you'll need (IIRC) -lstdc++
added to linking-ghc's command line
Alfonso Acosta wrote:
Although you could use gcc to link the code I wouldn't recommend it
(mainly for the problems you are currently having)
SImply call GHC to compile both the C and Haskell code. It will take
care of finding the headers and supplying the necessary linker
arguments.
ghc -ffi -c foo.hs myfoo_c.c
BTW, you don't need to compile viaC
2008/4/17 Miguel Lordelo <[EMAIL PROTECTED]>:
Well Isaac...I became now a little bit smarter then yesterday!!!
I show you the example that I found and on which I´m working with.
File: foo.hs
module Foo where
foreign export ccall foo :: Int -> IO Int
foo :: Int -> IO Int
foo n = return (length (f n))
f :: Int -> [Int]
f 0 = []
f n = n:(f (n-1))
To get the C wrapper you insert the following command:
ghc -ffi -fvia-C -C foo.hs
After execution you will have these following additional files:
foo.hc
foo.hi
foo_stub.c
foo_stub.h
foo_stub.o
What I did next was to create a file named: myfoo_c.c, where I will call the
foo function (implemented in Haskell).
(you can see this example on
http://www.haskell.org/ghc/docs/latest/html/users_guide/ffi-ghc.html )
But the problem is to compile with gcc (must I put any flag or whatever set
something)
The gcc output is:
myfoo_c.c:2:19: error: HsFFI.h: No such file or directory
I downloaded this header file from: (I know that is not the correct way, but
it was the only idea that occurs at the moment)
http://www.koders.com/c/fidD0593B84C41CA71319BB079EFD0A2C80211C9337.aspx
I compiled again and the following return error appears:
myfoo_c.c:(.text+0x1c): undefined reference to `hs_init'
myfoo_c.c:(.text+0x31): undefined reference to `foo'
myfoo_c.c:(.text+0x50): undefined reference to `hs_exit'
collect2: ld returned 1 exit status
These functions are necessary to setup GHC runtime (see:
http://www.haskell.org/ghc/docs/latest/html/users_guide/ffi-ghc.html )
What I want to know is how to compile myfoo_c.c?! Is it with GCC or GHC?!
Chears,
Miguel Lordelo.
On Wed, Apr 16, 2008 at 9:16 PM, Isaac Dupree <[EMAIL PROTECTED]>
wrote:
perhaps
haskell:
foreign export "foo_func" foo :: Int -> IO Int
-- I forget the rest of the syntax here
C++:
extern "C" {
int foo_func(int i);
}
int some_cplusplus_function() {
int bat = 3;
int blah = foo_func(bat);
return blah;
}
Is that all you need to do?
Miguel Lordelo wrote:
Hi all,
Well...somehow I'm a beginner in Haskell. But actually my interest in
Haskell will increase if it is possible to call a haskell function in
C++.
Something like GreenCard ( http://www.haskell.org/greencard/ )
simplifying
the task of interfacing Haskell programs to external libraries
(usually).
But is there also a task to interface a foreign language with Haskell,
but
calling Haskell functions. Or c2hs which is an interface generator that
simplifies the development of Haskell bindings to C libraries.
I want to know this, because in my company some guys are doing some
testing
with Frotran and MatLab and I want to show them the power of haskell and
the
software which we are using is implemented in C++ (there is the reason
to
make Haskel -> C++).
I read somewhere that the only way for C++ calling a haskell function is
to
create a binding between Haskell and C and from C to C++, but a easy
"Hello
World" example was not there.
Unfortunatelly I couldn't found anything usefull, like an complete
example,
or how to compile the code from haskell to C to C++.
Can sombody help me, please :P
Chears,
Miguel Lordelo.
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