[Haskell-cafe] Interfacing C++ iterators does not work as expected

[Huynh Huu Long]

Hi,

I tried to access C++ iterators from Haskell via the FFI. There are two
example programs attached, in Haskell as well as in C++. Both utilise the
same iterator wrapper example.cpp, but when running the Haskell program it
prints an empty list, where it should print the contents of some vector. The
C++ program meanwhile runs fine though. What does not seem to work is this
part:

bool
finished (std::vectorint::iterator *begin, std::vectorint::iterator
*end)
{
return *begin == *end;
}

In Haskellland, finished :: Ptr Iterator - Ptr Iterator - IO Bool always
returns IO True. Is this a bug lurking in my program or is it a GHC issue?

Long


ffi_and_iterators.tar.gz
Description: GNU Zip compressed data
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Re: [Haskell-cafe] Interfacing C++ iterators does not work as expected

[Huynh Huu Long]

Big thanks, that works for me as well. Doesn't GHC check whether a
type is allowed (like CInt,...) or not (like Bool,...)?

2011/5/2 Gábor Lehel illiss...@gmail.com:
 It works if I replace the 'bool' return type of 'finished' with int
 and CInt on the C++ and Haskell side, respectively, and test for (/=
 0).

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