RE: Calling Haskell from Python / C++
| So here is what I envision: I write the main | application in Python. I write a (hopefully) small | Haskell module that: | a) Calls back to the main Python app for reading the | text to be parsed, preferably using laziness. | b) Parses the text, and maybe processes a bit. | c) Returns the parsed data-structure. (This may be | tricky, but I think I know how to do it). If Python uses C's calling convention, it might be easy; just use 'foreign import' and 'foreign export' (see the FFI spec at haskell.org). If it doesn't, someone would have to add the Python calling convention to the various implementations. Simon
Simon Peyton-Jones writes:
If Python uses C's calling convention, it might be easy; just use 'foreign import' and 'foreign export' (see the FFI spec at haskell.org).
I remember reading that the main program, that wants to call Haskell code, would have to be compiled with a special Haskell main() routine, though? Is that true? And if, why is that necessary? -peter
--- Simon Peyton-Jones
| So here is what I envision: I write the main | application in Python. I write a (hopefully) small | Haskell module that: | a) Calls back to the main Python app for reading the | text to be parsed, preferably using laziness. | b) Parses the text, and maybe processes a bit. | c) Returns the parsed data-structure. (This may be | tricky, but I think I know how to do it).
If Python uses C's calling convention, it might be easy; just use 'foreign import' and 'foreign export' (see the FFI spec at haskell.org).
If it doesn't, someone would have to add the Python calling convention to the various implementations.
Unfortunately, Python does not support calling arbitrary C functions. In order to call C functions from Python, you have to write a �Python extension module�. (This restriction is actually a direct result of Python being interpreted, rather than compiled.) But I do have another idea: If I was working only on Windows, I could have used HaskellDirect to wrap the Haskell code as a COM component, and since Python seems to have good COM support (though I never used it) this would have solved my problem neatly. However, I need Linux portability, which rules out using COM. But there is a good COM alternative for Linux: XPCOM from the Mozilla project. This is a cross-platform and somewhat improved COM, which has C++, Java, JavaScript, Perl, and Python bindings. And this brings me to my next question: How difficult would it be to extend HaskellDirect to support XPCOM? Thanks, -JH __________________________________________________ Do you Yahoo!? U2 on LAUNCH - Exclusive greatest hits videos http://launch.yahoo.com/u2
participants (3)
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Jonathan Holt -
Peter Simons -
Simon Peyton-Jones